We thank Marie Persson Vejg&#229;rden for technical assistance. The research leading to these results has received funding from the New York Stem Cell Foundation, the European Research Council under the European Union&#39;s Seventh Framework Programme: FP/2007-2013 Neuro Stem Cell Repair (no. 602278) and ERC Grant Agreement no. 30971, the Swedish Research Council (grant agreement 521-2012-5624, 2016-00873 and 70862601/ Bagadilico), Swedish Parkinson Foundation (Parkinsonfonden), and the Strategic Research Area at Lund University Multipark (multidisciplinary research in Parkinson&#39;s disease). Janelle Drouin-Ouellet is supported by a Canadian Institutes of Health Research (CIHR) fellowship (#358492), and Roger Barker is supported by an NIHR Biomedical Research Centre grant to the University of Cambridge/Addenbrooke&#39;s Hospital. Malin Parmar is a New York Stem Cell Foundation Robertson Investigator. Shelby Shrigley is funded by the European Union Horizon 2020 Programme (H2020-MSCA-ITN-2015) under the Marie Sk&#322;odowska-Curie Innovative Training Network and Grant Agreement No. 676408.

Adult dermal fibroblasts were obtained from the Parkinson&#39;s Disease Research and Huntington&#39;s disease clinics at the John van Geest Centre for Brain Repair (Cambridge, UK) and used under local ethical approval (REC 09/H0311/88). For details on the skin biopsy sampling procedure, see reference8.
1. Preparation of Skin Fibroblasts for Reprogramming
<ol>
	<li>Using an automated cell thawing system or a 37 &#176;C water bath, thaw the adult human dermal fibroblasts (aHDFs) and plate 200,000 per T75 flask (count with an automated cell counter) in 10 mL of fibroblast medium (see Table 1) at 37 &#176;C in 5% CO2.</li>
	<li>Perform a complete medium change with fibroblast medium on the next day.</li>
	<li>Change the fibroblast medium every 3&#8211;4 days until the cells reach 95% confluency. 
	NOTE: One confluent flask will contain approximately 1,000,000 cells. The aHDFs can be frozen to build a stock of the cell line (section 2) or directly re-plated ready for reprogramming (section 3).</li>
</ol>
2. Freezing of Skin Fibroblasts
<ol>
	<li>Place a controlled-rate freezing container in a box with ice or in the fridge at 4 &#176;C.</li>
	<li>Dissociate the cells with 0.05% trypsin (1.5 mL per T75 flask) at 37 &#176;C for 3&#8211;5 min.</li>
	<li>Add fibroblast medium (containing fetal bovine serum (FBS)) to neutralize the trypsin (3 mL per flush per T75 flask) and collect the detached cells in a 15 mL tube by flushing out the cells in the flask twice.</li>
	<li>Count the cells using the automated cell counter; (recommended) freeze approximately 500,000 aHDFs per vial.</li>
	<li>Spin down the cells at 400 x g for 5 min.</li>
	<li>Resuspend the cell pellet in 1 mL of freezing medium (see Table 1) and transfer into the cryogenic tube. Place the tubes directly into the controlled-rate freezing container.</li>
	<li>Store the controlled rate freezing apparatus at -80 &#176;C overnight. The following day, transfer the tubes to a -140 &#176;C freezer and store until needed.</li>
</ol>
3. Plating for Reprogramming (Day &#8722;1)
NOTE: It is recommended to use a gelatin coating for short term experiments (up to 30 days); alternatively, for long term experiments it is recommended to start on a poly-L-ornithine, fibronectin and laminin (PFL) coating.
<ol>
	<li>60 min before plating the aHDFs for reprogramming, coat a 24-well plate with 0.1% gelatin (250 &#181;L/well) and incubate at 37 &#176;C.</li>
	<li>Aspirate the fibroblast medium on the aHDFs. Wash once with DPBS. Dissociate the cells with 0.05% trypsin (1.5 mL per T75 flask) at 37 &#176;C for 3&#8211;5 min.</li>
	<li>Add fibroblast medium to neutralize the trypsin (3 mL per flush per T75 flask) and collect the detached cells in a 15 mL tube by flushing out the cells in the flask twice.</li>
	<li>Spin down the cells at 400 x g for 5 min. Discard supernatant, and resuspend the cell pellet in 1 mL of fibroblast medium.</li>
	<li>Count the cells using an automated cell counter (to ensure a good quality conversion check that the cell viability is above 90% with trypan blue staining).</li>
	<li>For a complete 24-well plate, prepare a suspension of 1,320,000 cells in 13.2 mL of fibroblast medium to achieve a suspension of 100,000 cells/mL of medium (or 55,000 cells/well in 550 &#181;L of fibroblast medium multiplied by the number of wells needed).</li>
	<li>Aspirate the gelatin from the plate and wash twice with DPBS. Add 500 &#181;L of the cell suspension to each well and incubate overnight at 37 &#176;C in 5% CO2.</li>
</ol>
4. Viral Transduction (Day 0)
NOTE: Working with lentiviral particles requires category 2 equipment and the use of an agent to neutralize the virus. Wearing double pairs of gloves is also strongly recommended.
<ol>
	<li>Warm up 13.2 mL of fibroblast medium to 37 &#176;C.</li>
	<li>Thaw a lentiviral vector containing the transcription factors Ascl1 and Brn2 with two short hairpin RNAs (shRNA) targeting REST at room temperature. 
	NOTE: Refer to reference8; the construct is available in a plasmid repository. For details on the procedure to produce lentiviruses please refer to reference9.</li>
	<li>Add the necessary volume of lentivirus to infect the aHDFs at multiplicity of infection (MOI) of 20 to the medium without any transduction enhancers. 
	<img alt="Equation" src="/files/ftp_upload/56904/56904eq1v2.jpg" /></li>
	<li>Replace the medium in the 24-well plate with fibroblast medium containing the lentiviral vector (500 &#181;L/well) and incubate overnight at 37 &#176;C in 5% CO2.</li>
	<li>The next day, replace the medium in the wells with fresh fibroblast medium without the lentiviral vector. 
	NOTE: The medium is considered infectious for 7 days and as such, adequate protection and handling procedures should be used during the first week following viral transduction.</li>
</ol>
5. Maintenance of the Converting Cells
NOTE: Once conversion begins cells are susceptible to lifting; take care to tip the plate up and use a 1,000 &#181;L pipette when removing media to avoid cells detaching.
<ol>
	<li>On day 3, remove the fibroblast medium and add 500 &#181;L of early neuronal conversion medium (see Table 1).</li>
	<li>Two to three times a week, take out 225 &#181;L of old medium from the well and add-in 250 &#181;L of fresh early neuronal conversion medium.</li>
	<li>On day 18, remove all of the medium from each well and replace with 500 &#181;L of late neuronal conversion medium (see Table 1).</li>
	<li>Continue to change half of the medium as above with late neuronal conversion medium every 2&#8211;3 days until day 25 or experiment endpoint (Figure 1A). 
	NOTE: If cells are not plated in every well for the experiment, fill empty wells with PBS or water to prevent overt evaporation of the medium and minimize variation between wells.</li>
</ol>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>Stock Concentration</td>
			<td>Working Concentration</td>
		</tr>
		<tr>
			<td colspan="3">Fibroblast medium</td>
		</tr>
		<tr>
			<td>Basal medium</td>
			<td>N/A</td>
			<td>N/A</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>10,000 U/mL</td>
			<td>100 mg/mL</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>N/A</td>
			<td>10%</td>
		</tr>
		<tr>
			<td colspan="3">Freezing medium</td>
		</tr>
		<tr>
			<td>Fibroblast medium</td>
			<td>N/A</td>
			<td>45%</td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>N/A</td>
			<td>45%</td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>N/A</td>
			<td>10%</td>
		</tr>
		<tr>
			<td colspan="3">Early neuronal conversion medium (ENM)</td>
		</tr>
		<tr>
			<td>Neural differentiation medium&#160;</td>
			<td>N/A</td>
			<td>N/A</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>10,000 U/mL</td>
			<td>100 mg/mL</td>
		</tr>
		<tr>
			<td>CHIR99021</td>
			<td>10 mM</td>
			<td>2 &#181;M</td>
		</tr>
		<tr>
			<td>SB-431542</td>
			<td>20 mM</td>
			<td>10 &#181;M</td>
		</tr>
		<tr>
			<td>Noggin</td>
			<td>100 &#181;g/mL</td>
			<td>0.5 &#181;g/mL</td>
		</tr>
		<tr>
			<td>LDN-1931189</td>
			<td>10 mM</td>
			<td>0.5 &#181;M</td>
		</tr>
		<tr>
			<td>VPA</td>
			<td>1 M</td>
			<td>1 mM</td>
		</tr>
		<tr>
			<td>LM-22A4</td>
			<td>20 mM</td>
			<td>2 &#181;M</td>
		</tr>
		<tr>
			<td>GDNF</td>
			<td>20 &#181;g/mL</td>
			<td>2 ng/mL</td>
		</tr>
		<tr>
			<td>NT3</td>
			<td>10 &#181;g/mL</td>
			<td>10 ng/&#181;L</td>
		</tr>
		<tr>
			<td>db-cAMP</td>
			<td>50 mM</td>
			<td>0.5 mM</td>
		</tr>
		<tr>
			<td colspan="3">Late neuronal conversion medium (LNM)</td>
		</tr>
		<tr>
			<td>Neural differentiation medium&#160;</td>
			<td>N/A</td>
			<td>N/A</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>10,000 U/mL</td>
			<td>100 mg/mL</td>
		</tr>
		<tr>
			<td>LM-22A4</td>
			<td>20 mM</td>
			<td>2 &#181;M</td>
		</tr>
		<tr>
			<td>GDNF</td>
			<td>20 &#181;g/mL</td>
			<td>2 ng/mL</td>
		</tr>
		<tr>
			<td>NT3</td>
			<td>10 &#181;g/mL</td>
			<td>10 ng/&#181;L</td>
		</tr>
		<tr>
			<td>db-cAMP</td>
			<td>50 mM</td>
			<td>0.5 mM</td>
		</tr>
		<tr>
			<td colspan="3">FACS Buffer</td>
		</tr>
		<tr>
			<td>HBSS 1x [-calcium, -magnesium, - phenol red]</td>
			<td>N/A</td>
			<td>N/A</td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>N/A</td>
			<td>1%</td>
		</tr>
		<tr>
			<td>DNAase</td>
			<td>N/A</td>
			<td>0.05%</td>
		</tr>
	</tbody>
</table>
Table 1: Composition of the different media used. Full description of the composition for all media needed in this protocol including fibroblast medium, freezing medium, early neuronal conversion medium, late neuronal conversion medium, and FACS buffer.
6. Glass Coverslips for Electrophysiological Recordings
NOTE: It is recommended to wear a lab coat, goggles, double gloves, and complete all of the work in a fume hood. This protocol is adapted from 10.
<ol>
	<li>Place glass coverslips at the bottom of a glass dish without overlap.</li>
	<li>Add general lab cleaning detergent to submerge all of the coverslips without risking overflow during shaking (approximately 30 mL). Place onto an orbital shaker at slow speed for 2 h.</li>
	<li>Wash six times (30 min each) with autoclaved deionized water.</li>
	<li>Add 95% ethanol for 2 h.</li>
	<li>Remove the ethanol and wait until coverslips are dry.</li>
	<li>Once dry, transfer the coverslips into a glass beaker and add 70% nitric acid until the coverslips are submerged.</li>
	<li>Place the glass beaker into a sonicator bath for 60 min.</li>
	<li>Remove the nitric acid and wash three times with autoclaved deionized water. 
	Caution: Always add acid to water, never the other way around as this can lead to a violent reaction.</li>
	<li>Remove as much water from the beaker as possible and add concentrated hydrochloric acid (HCI) until the coverslips are submerged; swirl the beaker and cover with paraffin film.</li>
	<li>Sonicate for 60 min (50&#8211;60 Hz, 30 W).</li>
	<li>Remove as much HCI from coverslips as possible and place into an appropriate waste bin. Rinse with autoclaved deionized water twice.</li>
	<li>Take the coverslips out of the hood and rinse 20 times (or more) with autoclaved deionized water until all of the HCI is removed.</li>
	<li>Once dry, place coverslips into sterile 24-well plates.</li>
	<li>Place the plates under ultraviolet (UV) light overnight. The next day the coverslips are ready to use. 
	NOTE: If glass coverslips are being used, it is recommended to use the PFL coating. Simply place one coverslip into each well of a 24-well plate (using sterile forceps) and follow the protocol as below.</li>
</ol>
7. PFL Coating for Long Term Culture
<ol>
	<li>Coat the 24-well plate with poly-L-ornithine (500 &#181;L/well) and leave overnight at 37 &#176;C in 5% CO2.</li>
	<li>Aspirate the poly-L-ornithine and wait until it is dry enough to form drops on top.</li>
	<li>Make a drop (approximately 60 &#181;L) of laminin in the center of each well and spread to cover the entire surface of the coverslip. Leave for 2 h 45 min at 37 &#176;C in 5% CO2.</li>
	<li>Wash three times with DPBS.</li>
	<li>Add fibronectin (500 &#181;L/well) and leave overnight at 37 &#176;C in 5% CO2.</li>
	<li>Wash once with DPBS before adding cells. 
	NOTE: The PFL coating can be used for long term cultures of iNs (over 100 days), although progressive cell death is to be expected from day 30.</li>
</ol>
8. FACS
NOTE: To re-plate the cells after FACS sorting prepare a PFL-coated plate 48 h in advance. Cells can be sorted using a neural cell adhesion molecule (NCAM) antibody from day 20 onwards following transduction.
<ol>
	<li>Remove the media with a 1,000 &#181;L pipette (do not wash to avoid cells detaching).</li>
	<li>Add cell dissociating agent (250 &#181;L/well), leave for 10&#8211;20 min until the cells lift, and float as single cells.</li>
	<li>During this time prepare the FACS buffer.</li>
	<li>Triturate gently with a 1,000 &#181;L pipette. If some clumps remain, incubate a little bit longer.</li>
	<li>Once a single cell suspension is obtained, remove it from the well and place into a 1.5 mL tube.</li>
	<li>Flush out the well twice with late neuronal conversion medium and place into the same 1.5 mL tube.</li>
	<li>Spin down at 400 x g for 5 min and discard the supernatant.</li>
	<li>Resuspend the cell pellet in 200 &#181;L of FACS buffer.</li>
	<li>Spin down the cells at 400 x g for 5 min and discard the supernatant.</li>
	<li>Repeat steps 8.8 and 8.9 twice.</li>
	<li>Resuspend the cell pellet in 50 &#181;L of FACS buffer containing human CD56 (NCAM) antibody at a concentration of 1:50 for 15 min on ice. Protect from light.</li>
	<li>Spin down the cells at 400 x g for 5 min.</li>
	<li>Resuspend in 200 &#181;L FACS buffer to wash and spin down the cells at 400 x g for 5 min.</li>
	<li>Repeat step 8.13.</li>
	<li>Resuspend in 200 &#181;L of FACS buffer containing propidium iodide (PI; 10 &#181;g/mL). Sort the NCAM positive (iNs) and PI negative (live) cells using FACS by gating based on the fluorescence intensity level of control samples that were not stained with the NCAM antibody or PI.</li>
	<li>Collect the NCAM positive cells in a tube containing late neuronal conversion medium.</li>
	<li>Count the cells using an automated cell counter and re-plate the cells at a high density (50,000 cells/cm2) in late neuronal conversion medium in a PFL coated dish.</li>
	<li>Continue to change half of the medium 2&#8211;3 times a week with late neuronal conversion medium until the experiment endpoint (Figure 1A).</li>
</ol>

<ol><li>Takahashi, K., Yamanaka, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Induction+of+pluripotent+stem+cells+from+mouse+embryonic+and+adult+fibroblast+cultures+by+defined+factors%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.</a> Cell. 126, 663-676 (2006).</li>
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<li>Avior, Y., Sagi, I., Benvenisty, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pluripotent+stem+cells+in+disease+modelling+and+drug+discovery%5BTitle%5D)+AND+%22Nat+Rev+Mol+Cell+Biol%22%5BJournal%5D)">Pluripotent stem cells in disease modelling and drug discovery.</a> Nat Rev Mol Cell Biol. 17, 170-182 (2016).</li>
<li>Mertens, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Directly+Reprogrammed+Human+Neurons+Retain+Aging-Associated+Transcriptomic+Signatures+and+Reveal+Age-Related+Nucleocytoplasmic+Defects%5BTitle%5D)+AND+%22Cell+Stem+Cell%22%5BJournal%5D)">Directly Reprogrammed Human Neurons Retain Aging-Associated Transcriptomic Signatures and Reveal Age-Related Nucleocytoplasmic Defects.</a> Cell Stem Cell. 17, 705-718 (2015).</li>
<li>Hashizume, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Epigenetic+regulation+of+the+nuclear-coded+GCAT+and+SHMT2+genes+confers+human+age-associated+mitochondrial+respiration+defects%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">Epigenetic regulation of the nuclear-coded GCAT and SHMT2 genes confers human age-associated mitochondrial respiration defects.</a> Sci Rep. 5, 10434(2015).</li>
<li>Lapasset, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rejuvenating+senescent+and+centenarian+human+cells+by+reprogramming+through+the+pluripotent+state%5BTitle%5D)+AND+%22Genes+Dev%22%5BJournal%5D)">Rejuvenating senescent and centenarian human cells by reprogramming through the pluripotent state.</a> Genes Dev. 25, 2248-2253 (2011).</li>
<li>Huh, C. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Maintenance+of+age+in+human+neurons+generated+by+microRNA-based+neuronal+conversion+of+fibroblasts%5BTitle%5D)+AND+%22Elife%22%5BJournal%5D)">Maintenance of age in human neurons generated by microRNA-based neuronal conversion of fibroblasts.</a> Elife. 5, (2016).</li>
<li>Drouin-Ouellet, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((REST+suppression+mediates+neural+conversion+of+adult+human+fibroblasts+via+microRNA-dependent+and+-independent+pathways%5BTitle%5D)+AND+%22EMBO+Mol+Med%22%5BJournal%5D)">REST suppression mediates neural conversion of adult human fibroblasts via microRNA-dependent and -independent pathways.</a> EMBO Mol Med. , (2017).</li>
<li>Tiscornia, G., Singer, O., Verma, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Production+and+purification+of+lentiviral+vectors%5BTitle%5D)+AND+%22Nat+Protoc%22%5BJournal%5D)">Production and purification of lentiviral vectors.</a> Nat Protoc. 1, 241-245 (2006).</li>
<li>Richner, M., Victor, M. B., Liu, Y., Abernathy, D., Yoo, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((MicroRNA-based+conversion+of+human+fibroblasts+into+striatal+medium+spiny+neurons%5BTitle%5D)+AND+%22Nat+Protoc%22%5BJournal%5D)">MicroRNA-based conversion of human fibroblasts into striatal medium spiny neurons.</a> Nat Protoc. 10, 1543-1555 (2015).</li>
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</ol>

The authors have nothing to disclose.

This one-step/one vector reprogramming method provides an efficient way to obtain iNs from human adult fibroblasts. Human adult fibroblasts are normally much more difficult to covert than fetal fibroblasts, with limited studies previously reporting efficiencies of approximately 5-10%12,13. However, with this new protocol it is possible to achieve a neuronal yield (measured as MAP2+ cells) of approximately 50%8. Additionally, our protocol can be used on dermal fibroblasts that have been passaged multiple times without losing efficiency of conversion. Thus far we have used cells passaged up to 14 times without detecting any decrease in conversion efficiency. Also, there is no difference in reprogramming efficiency in our hands with fibroblasts from donors of age between 52 and 87. For more details on the age and disease of other cell lines tested with this construct see reference8. Other studies have also reported no difference in conversion efficiency using a lentiviral-based and small molecule-enhanced protocol with donors between 0 and 89 years4. Furthermore, consistent applicability with miRNA-based neuronal reprogramming has been reported in fibroblasts of all ages, with donors between 0 and 86 years7. Through this route, mature neurons can be obtained in approximately 12&#8211;15 weeks in vitro or approximately 8 weeks following transplantation in vivo8. This is advantageous because it gives access to both disease and patient specific human iNs from tissue that is easily accessible. Although this protocol is efficient, it will not produce a 100% neuronal yield, and as such a purification step using FACS for instance is required.
The most critical step within this protocol is viral transduction (protocol section 4). It is crucial that the virus titer is precise, in addition to having plated an accurate number of aHDFs for conversion. The recommended titer for use with this protocol is between 4 x 108 and 4 x 109. Using a titer of anything below 1 x 108 would not be recommended as adding large volumes of virus will be toxic to the cells. Moreover, as the fibroblasts begin to covert to iNs they will become more fragile and susceptible to lifting. It is essential to be gentle when changing the media as not to disturb the cells too much. This can be done by removing the fluid slowly with a 1,000 &#181;L pipette. Finally, when plating for reprogramming (protocol section 3) it is important to ensure a healthy fibroblast population before beginning an experiment; this is indicated by a cell viability of above 90% with trypan blue staining. The aHDFs should always be passaged before reaching 95% confluency.
If there is noticeable cell death before viral transduction, do not begin conversion: double check that the cell viability is above 90% and that there were no problems with coating of the plate. It is expected to have a small amount of cell death following viral transduction, however, this should not be significant. In this case, confirm accurate seeding of 50,000 aHDFs/well and check the virus titer. If there is noticeable inconsistency between wells during conversion, first check that every well contains an equal amount of media and overt evaporation is not occurring at the edges (if necessary extra media can be added to the edge wells). Alternatively, check step 4.4, and ensure appropriate mixing for a homogenous suspension when transducing. It is crucial to add the lentivirus to the medium first, before adding this into the wells. Directly adding lentivirus into the wells will increase well to well variability and is also likely to be toxic to the cells. Lastly, always check that the medium is warmed to 37 &#176;C before adding to cells.
This protocol includes optional sections for coating conditions for long term culture of iNs and FACS sorting to increase neuronal purity. For experiments wishing to investigate functional characterization of iNs, a protocol for preparation of glass coverslips for electrophysiology has also been included. The conversion protocol here is set up for use with a 24-well plate; if desired this can be modified to a 6-, 12-, 48-, 96-well plate or flasks. In this case, please adjust all volumes to the surface area of the plate or flask utilized.
This protocol uses the forced expression of Ascl1 and Brn2 in combination with a REST knockdown all packaged in one single vector8 to generate iNs of a pan-neuronal phenotype. The generation of any glial subtypes with this method, however, has not been assessed. This method would thus need to be modified for use with other reprogramming factors to obtain subtype specific neurons. Direct reprogramming has previously shown the possibility to generate motor neurons, sensory neurons, photoreceptors, striatal medium spiny neurons, and dopaminergic neurons10,14. This will be beneficial when investigating neurological diseases in which specific neuronal subtype are preferentially affected, for example Parkinson&#39;s disease and dopaminergic neurons.
Until very recently, direct neural reprogramming technology did not allow for the production of iNs in a standardized and efficient manner &#8212; to a level that is required for toxicology and drug screening assays on a large scale. This new method is very efficient and can be used on fibroblasts that have been passaged many times, such that it now removes these restrictions and opens up for a vast array of studies, not only in a human neural system, but also in a system that can be patient specific. The simplicity of this approach renders the iN technology accessible for any groups wanting to perform similar studies in-house and can be easily used not only for large scale biomedical applications, such as drug screening and toxicology assays, but also to support data derived from animal models and human post mortem tissue samples.

Development of efficacious treatments for neurological disorders have been hampered by the limited access to living human brain cells to perform mechanistic studies and functional assays. About a decade ago, this situation radically changed with the development of induced pluripotent stem cell (iPSCs) technology1,2. This, combined with a better understanding of the neural differentiation mechanisms occurring during normal human development, has allowed for the generation of defined and diverse neuronal subtypes from patient and disease specific material. With such material, it is now possible to study intracellular mechanisms underlying neurological diseases and the potential of different compounds to alleviate those pathological features3.
While iPSCs have been revolutionary to the field of neuroscience, one major drawback of these cells is that their ageing signature is erased during the reprogramming process in such a way that the rejuvenated neuron does not retain the vulnerability associated with aging4,5,6. This particular feature of the neurons that are produced may end up being critical for recapitulating many aspects of the intracellular pathogenic cascade, particularly in the case of diseases for which old age is an important risk factor.
Direct neural reprogramming is a technology where a somatic cell is directly converted into an iN without going through a pluripotent intermediate stage. This allows for rapid generation of human neurons in vitro that can be both patient and disease specific. One remarkable characteristic of direct reprogramming is that the starting age of the donor cell is maintained, and with that, its vulnerability to ageing processes such as increased production of oxidative stress4,7. As a result, iNs from patients with neurological diseases associated with ageing, such as Alzheimer&#39;s and Parkinson&#39;s disease, are well suited for a broad range of biomedical applications including disease modeling, drug screening assays, and toxicology studies.
The main caveat that has prevented iNs from patients with neurodegenerative disorders being widely used is that they are not easy to reprogram, and this becomes even more difficult with expansion of the fibroblasts. As a result, generation of iN cells in quantities required for these types of applications has not been achieved until only recently8. We have now developed a simple method to reprogram fibroblasts from donors of any age in a very efficient manner. This method combines the forced expression of the neuronal transcription factors Ascl1 and Brn2 with a knockdown of the repressor protein RE1-silencing transcription factor (REST) using a single vector. Here, we describe the different steps leading to the generation of iNs converted from skin fibroblasts biopsied from elderly donors.

<table><tbody><tr><td>&lt;strong&gt;Cell Lines&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Adult human dermal fibroblasts&amp;nbsp;</td><td></td><td></td><td>[C2 passage #7] Donor was a 67 year old female. Cells obtained from the Parkinson&amp;rsquo;s Disease Research and Huntington&amp;rsquo;s disease clinics at the John van Geest Centre for Brain Repair (Cambridge, UK).</td></tr><tr><td>&lt;strong&gt;Reagents for Fibroblast Culture, Transduction and Conversion&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Dulbecco&#039;s phosphate-buffered saline (DPBS) [-CaCl&lt;sub&gt;2&lt;/sub&gt;, -MgCl&lt;sub&gt;2&lt;/sub&gt;]</td><td>Gibco</td><td>14190094</td><td></td></tr><tr><td>Trypsin-EDTA [0.5%]</td><td>Gibco</td><td>15400-054</td><td>Dilute to 0.05% in DPBS.</td></tr><tr><td>Virkon (agent used to neutralize virus)</td><td>Viroderm</td><td>7511&amp;nbsp;</td><td>Dilute to 1% solution with warm water.</td></tr><tr><td>Milli-Q Water</td><td>Millipore</td><td></td><td></td></tr><tr><td>&lt;strong&gt;Basal medium&lt;/strong&gt; - Dulbecco&amp;rsquo;s Modified Eagle Medium (DMEM) + GlutaMax</td><td>Gibco</td><td>61965059</td><td></td></tr><tr><td>Penicillin/Streptomycin [10,000 U/mL]</td><td>Gibco</td><td>15140-122</td><td></td></tr><tr><td>Fetal Bovine Serum (FBS)</td><td>Gibco</td><td>10270-106</td><td></td></tr><tr><td>CryoMACS&amp;reg;&amp;nbsp;dimethyl sulfoxide (DMSO) 10</td><td>Miltenyi</td><td>170-076-303</td><td></td></tr><tr><td>&lt;strong&gt;Neural differentiation medium&lt;/strong&gt; - NDiff 227</td><td>Takara-Clontech</td><td>Y40002</td><td></td></tr><tr><td>LM-22A4&amp;nbsp;</td><td>Tocris</td><td>4607</td><td>Dilute 10 mg in 1450 &amp;micro;L DMSO. &lt;strong&gt;Stock concentration: 20 mM.&lt;/strong&gt;</td></tr><tr><td>Glial cell line-derived neurotrophic factor (GDNF) [recombinant human]</td><td>R&amp;amp;D systems</td><td>212-GD-010</td><td>Dilute 10 ug in 500 &amp;micro;L 0,1% BSA in DPBS. &lt;strong&gt;Stock concentration: 20 &amp;micro;g/mL.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>NT3 [recombinant human]</td><td>R&amp;amp;D systems</td><td>267-N3-025</td><td>Dilute 25 &amp;micro;g in 2,5 mL 0,1% BSA in DPBS. &lt;strong&gt;Stock concentration: 10 &amp;micro;g/mL.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>db-cAMP&amp;nbsp;</td><td>Sigma Aldrich</td><td>D0627</td><td>Dilute 1 g in 40,7 mL Milli-Q water. Filter and make 500 &amp;micro;L aliquots or stock tubes of 10 mL. &lt;strong&gt;Stock concentration: 50 mM.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>CHIR99021</td><td>Axon</td><td>1386</td><td>Dilute 2 &amp;micro;g in 429,8 &amp;micro;L DMSO. &lt;strong&gt;Stock concentration: 10 mM.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>SB-431542</td><td>Axon</td><td>1661</td><td>Dilute 5 mg in 595 &amp;micro;L DMSO. &lt;strong&gt;Stock concentration: 20 mM.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>Noggin [recombinant human]</td><td>Miltenyi</td><td>130-103-456</td><td>Dilute 100 &amp;micro;g in 100 &amp;micro;L of Milli-Q water + 900 &amp;micro;L 0,1% BSA in DPBS. &lt;strong&gt;Stock concentration: 100 &amp;micro;g/mL.&lt;/strong&gt;</td></tr><tr><td>LDN-193189</td><td>Axon</td><td>1509</td><td>Dilute 2 mg in 360 &amp;micro;L DMSO. &lt;strong&gt;Stock concentration: 10 mM.&lt;/strong&gt;</td></tr><tr><td>Valproic acid sodium salt (VPA)</td><td>Merck Millipore</td><td>676380</td><td>Dilute 5 g in Milli-Q water to acheive a &lt;strong&gt;stock concentration of 1 M. CAUTION:&lt;/strong&gt; Avoid ingestion, contact with skin, and breathing dust formation.</td></tr><tr><td>&lt;strong&gt;Reagents for Coatings&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Gelatin&amp;nbsp;</td><td>Sigma Aldrich</td><td>G2500</td><td>Dilute to 0.1% in Milli-Q water.</td></tr><tr><td>Poly-L-ornithine</td><td>Sigma Aldrich</td><td>P3655</td><td>Dissolve in Milli-Q water. &lt;strong&gt;Use at 15&amp;micro;g/mL.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>Fibronectin</td><td>ThermoFisher Scientific</td><td>33010-018</td><td>2 mL of Milli-Q water + 70 &amp;micro;L 0,25 M NaOH. &lt;strong&gt;Use at 5 &amp;micro;g/mL.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>Laminin</td><td>ThermoFisher Scientific</td><td>23017-015</td><td>Store at -80&amp;deg;C. Thaw on ice, keep cool and aliquot 30 &amp;micro;L. &lt;strong&gt;Use at 5 &amp;micro;g/mL.&amp;nbsp;&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Reagents for Fluorescence Activated Cell Sorting&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Cell dissociation agent - Accutase (Stem Pro)</td><td>ThermoFisher Scientific</td><td>A1110501</td><td></td></tr><tr><td>Hanks&#039; Balanced Salt Solution (HBSS) 1X [-calcium, -magnesium, - phenol red]</td><td>ThermoFisher Scientific</td><td>14175-046</td><td></td></tr><tr><td>Bovine Serum Albumin (BSA)</td><td>Sigma Aldrich</td><td>A2153</td><td>Use at 1% concentration for Anti-Human CD56 (NCAM).</td></tr><tr><td>DNAase</td><td>Sigma Aldrich</td><td>DN-25</td><td>Use at 0.05% concentration.</td></tr><tr><td>Anti-Human CD56 (NCAM) Antibody [Mouse]</td><td>BD Pharmingen</td><td>555518</td><td>Use at 1 : 50.</td></tr><tr><td>Propidium iodide</td><td>Sigma Aldrich</td><td>P4170</td><td>Dilute to 1mg/mL in PBS and keep sterile. &lt;strong&gt;Use at 1:1000 to achieve a concentration of 10&amp;micro;g/mL.&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Reagents for Glass Coverslips&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Autoclaved deionized water</td><td></td><td></td><td></td></tr><tr><td>Alconox detergent</td><td>Sigma Aldrich</td><td>Z273228</td><td></td></tr><tr><td>Ethanol 95%</td><td></td><td></td><td></td></tr><tr><td>Nitric Acid</td><td>Sigma Aldrich</td><td>438073-M</td><td>&lt;strong&gt;CAUTION:&lt;/strong&gt; Concentrated nitric acid is highly corrosive, and its vapours are potentially harmful.</td></tr><tr><td>Concentrated hydrochloric acid (HCI)</td><td></td><td></td><td>&lt;strong&gt;CAUTION:&lt;/strong&gt; Concentrated hydrochloric acid is highly corrosive, and its vapours are potentially harmful.</td></tr><tr><td>&lt;strong&gt;Reagents for Immunocytochemistry&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Paraformaldehyde (PFA)</td><td>Merck Millipore</td><td>1040051000</td><td>Use at a concentration of 4%. &lt;strong&gt;CAUTION:&lt;/strong&gt; PFA is a potent fixative. Avoid ingestion and contact with skin</td></tr><tr><td>Triton X-100</td><td>Fisher Scientific</td><td>10254640</td><td>Use at a concentration of 0.1%.</td></tr><tr><td>Serum [Donkey]</td><td>Merck Millipore</td><td>S30-100ML</td><td></td></tr><tr><td>Anti-MAP2 Antibody [Chicken]</td><td>Abcam</td><td>ab5392</td><td>Use at a concentration of 1 : 5,000.</td></tr><tr><td>Tau HT7 Monoclonal Antibody [Mouse]</td><td>ThermoFisher Scientific</td><td>MN1000</td><td>Use at a concentration of 1 : 500.</td></tr><tr><td>Cy3 Anti-Chicken Antibody [Donkey]</td><td>Jackson ImmunoResearch</td><td>703-165-155</td><td>Use at a concentration of 1 : 400.</td></tr><tr><td>Alexa Fluor488 Anti-Mouse Antibody [Donkey]</td><td>Jackson ImmunoResearch</td><td>715-545-150</td><td>Use at a concentration of 1 : 400.</td></tr><tr><td>4&amp;prime;,6-Diamidine-2&amp;prime;-phenylindole dihydrochloride (DAPI)</td><td>Sigma Aldrich</td><td>D9542</td><td>Reconstitute the powder in Milli-Q water to 1 mg/mL. Aliquot and store at -20&amp;deg;C, &lt;strong&gt;light sensitive&lt;/strong&gt;. Use at a concentration of 1 : 500.</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>T75 flask [Nunclon Delta Surface]</td><td>ThermoFisher Scientific</td><td>156499</td><td></td></tr><tr><td>24-well plate [Nunc]</td><td>ThermoFisher Scientific</td><td>142485</td><td></td></tr><tr><td>1.5 mL polypropylene tube</td><td>Sigma Aldrich</td><td>Z336769</td><td></td></tr><tr><td>15 mL falcon tube&amp;nbsp;</td><td>Sarstedt</td><td>62.554.502</td><td></td></tr><tr><td>50 mL falcon tube&amp;nbsp;</td><td>Sarstedt</td><td>62.547.254</td><td></td></tr><tr><td>CryoPure tube 1.6 mL</td><td>Sarstedt</td><td>72.380</td><td></td></tr><tr><td>Pippette controller</td><td></td><td></td><td>For pipetting volumes 1-25 mL.</td></tr><tr><td>Sterile serological pipettes: 5, 10 and 25 mL&amp;nbsp;</td><td>Sarstedt</td><td>86.1253.001, 86.1254.001, 86.1685.001</td><td></td></tr><tr><td>Adjustable volume pipettors: 5, 20, 200, and 1,000 &amp;micro;L&amp;nbsp;</td><td></td><td></td><td></td></tr><tr><td>Sterile pipette tips</td><td></td><td></td><td>For pipetting volumes of 0.5 - 1,000 &amp;micro;L.</td></tr><tr><td>Glass coverslips</td><td>NeuVitro</td><td>GG-12-1.5-oz</td><td>#1.5 thickness, 12mm diameter, 0.5oz, CE certified, fit 24 well plates.</td></tr><tr><td>Glass dish</td><td></td><td></td><td>Approximately 150mm diameter.</td></tr><tr><td>Glass beaker</td><td></td><td></td><td>Make sure to have an appropriate size beaker for the sonicator bath available. Water from the sonicator bath should not overflow into the glass beaker.</td></tr><tr><td>Parafilm M</td><td>VWR</td><td></td><td></td></tr><tr><td>ThawSTAR Automated Cell Thawing System</td><td>BioCision</td><td>BCS-601</td><td></td></tr><tr><td>Countess II Automated Cell Counter</td><td>ThermoFisher Scientific</td><td>AMQAX1000</td><td></td></tr><tr><td>Cell counting chambers [50 slides] and trypan blue [0.4%]</td><td>ThermoFisher Scientific</td><td>C10228</td><td>For use with Countess II Automated Cell Counter.</td></tr><tr><td>CoolCell Cell LX Controlled-rate Freezing Container</td><td>Biocision</td><td>BCS-405</td><td></td></tr><tr><td>Laminar flow hood</td><td></td><td></td><td></td></tr><tr><td>Humidified 5% CO&lt;sub&gt;2&lt;/sub&gt; 37 &amp;deg;C incubator</td><td></td><td></td><td></td></tr><tr><td>Centrifuge</td><td></td><td></td><td>Suitable for 1,5, 15 and 50 mL tubes.</td></tr><tr><td>Orbital shaker</td><td></td><td></td><td></td></tr><tr><td>Sonicator - Bransonic Model B200 cleaner</td><td>Sigma Aldrich</td><td>Z305359</td><td>Frequency = 50-60Hz, Amplitude = 30 Watts</td></tr><tr><td>FACS Aria III cell sorter</td><td>BD Pharmingen</td><td></td><td></td></tr><tr><td>Phase contrast microscope</td><td>Olympus</td><td>CKX31</td><td></td></tr><tr><td>Inverted fluorescence microscope</td><td>Leica</td><td>DMI6000 B</td><td></td></tr></tbody></table>

simple generation of a high yield culture of induced neurons from human adult skin fibroblasts

Induced neurons (iNs), the product of somatic cells directly converted to neurons, are a way to obtain patient-derived neurons from tissue that is easily accessible. Through this route, mature neurons can be obtained in a matter of a few weeks. Here, we describe a straightforward and rapid one-step protocol to obtain iNs from dermal fibroblasts obtained through biopsy samples from adult human donors. We explain each step of the process, including the maintenance of the dermal fibroblasts, the freezing procedure to build a stock of the cell line, seeding of the cells for reprogramming, as well as the culture conditions during the conversion process. In addition, we describe the preparation of glass coverslips for electrophysiological recordings, long-term coating conditions, and fluorescence activated cell sorting (FACS). We also illustrate examples of the results to be expected. The protocol described here is easy to perform and can be applied to human fibroblasts derived from human skin biopsies from patients with various different diagnoses and ages. This protocol generates a sufficient amount of iNs which can be used for a wide array of biomedical applications, including disease modeling, drug screening, and target validation.

A clear change in cell morphology should be visible from day 5 onwards (Figure 1B). Some cell death is to be expected after viral transduction, although not overtly. From each well in a 24-well plate a total cell yield of 20,000-40,000 cells should be expected by day 25, of which about half should have become neurons. It is important to note that the yield and purity can vary across cell line, as well as with disease state and virus batches.
Cells will express most standard neuronal markers including MAP2 and TAU (Figure 1C) at day 25 in addition to exhibiting a mature neuronal morphology. It is possible to get a pure iN population by doing FACS based on the marker NCAM (see references8,11). Cells can thereafter be either re-plated onto PFL triple coating (see reference10) or directly frozen for biomolecular analyses.
If the cells are not sorted, immunofluorescence labeling with either MAP2 or TAU should be performed to identify the successfully converted cells and co-labeled with the protein of interest.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56904/56904fig1.jpg" /> 
Figure 1: Evolution of the iN conversion over time. (A) Timeline of the experiment and map of the construct packaged in a lentivirus used to reprogram the adult human dermal fibroblasts. Each black arrow represents a medium change. (B) Representative phase contrast images depicting the changes in morphology of cells during the conversion process between day 0 to day 22 (as indicated on the upper right corner of each panel). Images were taken on a phase contrast microscope using the 10X objective. (C) Immunofluorescence image of a TAU and MAP2 double staining at day 35 post-transduction. Cells were fixed in 4% paraformaldehyde and permeabilized with 0.1% Triton in DPBS for 10 min. Cells were blocked for 30 min in a 5% serum solution in DPBS. The antibodies were diluted in blocking solution and applied overnight at 4 &#176;C. Fluorophore-conjugated secondary antibodies were diluted in blocking solution and applied for 2 h. Cells were counterstained with DAPI for 15 min followed by 3 washes with DPBS. Images were taken on an inverted fluorescence microscope using the 20X objective. Scale bars = 100 &#181;m (B, C). Abbreviations: ENM: early neuronal medium; LNM: late neuronal medium. <a href="https://cloudflare.jove.com/files/ftp_upload/56904/56904fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Simple Generation of a High Yield Culture of Induced Neurons from Human Adult Skin Fibroblasts at JoVE.com

Simple Generation of a High Yield Culture of Induced Neurons from Human Adult Skin Fibroblasts

Direct neuronal reprogramming generates neurons that maintain the age of the starting somatic cell. Here, we describe a single vector-based method to generate induced neurons from dermal fibroblasts obtained from adult human donors.

Induced neurons (iNs), the product of somatic cells directly converted to neurons, are a way to obtain patient-derived neurons from tissue that is easily ...

simple-generation-high-yield-culture-induced-neurons-from-human-adult

Research

JoVE Journal

Neuroscience

10.3K Views.  Lund University. Directe neuronale herprogrammering genereert neuronen die de leeftijd van de begincel van somatische handhaven. Hier beschrijven we een enkele vector-gebaseerde methode voor het genereren van geïnduceerde neuronen van dermale fibroblasten van volwassen menselijke donors verlangde.

Video: Simple Generation of a High Yield Culture of Induced Neurons from Human Adult Skin Fibroblasts

Three-dimensional Quantification of Dendritic Spines from Pyramidal Neurons Derived from Human Induced Pluripotent Stem Cells

Dendritic spines are small protrusions that correspond to the post-synaptic compartments of excitatory synapses in the central nervous system. They are distributed along the dendrites. Their morphology is largely dependent on neuronal activity, and they are dynamic. Dendritic spines express glutamatergic receptors (AMPA and NMDA receptors) on their surface and at the levels of postsynaptic densities. Each spine allows the neuron to control its state and local activity independently. Spine morphologies have been extensively studied in glutamatergic pyramidal cells of the brain cortex, using both in vivo approaches and neuronal cultures obtained from rodent tissues. Neuropathological conditions can be associated to altered spine induction and maturation, as shown in rodent cultured neurons and one-dimensional quantitative analysis 1. The present study describes a protocol for the 3D quantitative analysis of spine morphologies using human cortical neurons derived from neural stem cells (late cortical progenitors). These cells were initially obtained from induced&#160;pluripotent stem cells. This protocol allows the analysis of spine morphologies at different culture periods, and with possible comparison between induced&#160;pluripotent stem cells obtained from control individuals with those obtained from patients with psychiatric diseases.

Dendritic spines of pyramidal neurons are the sites of most excitatory synapses in mammalian brain cortex. This method describes a 3D quantitative analysis of spine morphologies in human cortical pyramidal glutamatergic neurons derived from induced&#160;pluripotent stem cells.

Dendritic spines are small protrusions that correspond to the post-synaptic compartments of excitatory synapses in the central nervous system. They are ...

Developmental Biology

Generation of Neural Stem Cells from Discarded Human Fetal Cortical Tissue

Neural stem cells (NSCs) reside along the ventricular zone neuroepithelium during the development of the cortical plate. These early progenitors ultimately give rise to intermediate progenitors and later, the various neuronal and glial cell subtypes that form the cerebral cortex. The capacity to generate and expand human NSCs (so called neurospheres) from discarded normal fetal tissue provides a means with which to directly study the functional aspects of normal human NSC development 1-5. This approach can also be directed toward the generation of NSCs from known neurological disorders, thereby affording the opportunity to identify disease processes that alter progenitor proliferation, migration and differentiation 6-9. We have focused on identifying pathological mechanisms in human Down syndrome NSCs that might contribute to the accelerated Alzheimer's disease phenotype 10,11. Neither in vivo nor in vitro mouse models can replicate the identical repertoire of genes located on human chromosome 21. 
Here we use a simple and reliable method to isolate Down syndrome NSCs from aborted human fetal cortices and grow them in culture. The methodology provides specific aspects of harvesting the tissue, dissection with limited anatomical landmarks, cell sorting, plating and passaging of human NSCs. We also provide some basic protocols for inducing differentiation of human NSCs into more selective cell subtypes.

A simple and reliable method on isolation and culture of neural stem cells from discarded human fetal cortical tissue is described. Cultures derived from known human neurological disorders can be used for characterization of pathological cellular and molecular processes, as well as provide a platform to assess pharmacological efficacy.

Neural stem cells (NSCs) reside along the ventricular zone neuroepithelium during the development of the cortical plate. These early progenitors ...

Efficient Derivation of Human Neuronal Progenitors and Neurons from Pluripotent Human Embryonic Stem Cells with Small Molecule Induction

There is a large unfulfilled need for a clinically-suitable human neuronal cell source for repair or regeneration of the damaged central nervous system (CNS) structure and circuitry in today's healthcare industry. Cell-based therapies hold great promise to restore the lost nerve tissue and function for CNS disorders. However, cell therapies based on CNS-derived neural stem cells have encountered supply restriction and difficulty to use in the clinical setting due to their limited expansion ability in culture and failing plasticity after extensive passaging1-3. Despite some beneficial outcomes, the CNS-derived human neural stem cells (hNSCs) appear to exert their therapeutic effects primarily by their non-neuronal progenies through producing trophic and neuroprotective molecules to rescue the endogenous cells1-3. Alternatively, pluripotent human embryonic stem cells (hESCs) proffer cures for a wide range of neurological disorders by supplying the diversity of human neuronal cell types in the developing CNS for regeneration1,4-7. However, how to channel the wide differentiation potential of pluripotent hESCs efficiently and predictably to a desired phenotype has been a major challenge for both developmental study and clinical translation. Conventional approaches rely on multi-lineage inclination of pluripotent cells through spontaneous germ layer differentiation, resulting in inefficient and uncontrollable lineage-commitment that is often followed by phenotypic heterogeneity and instability, hence, a high risk of tumorigenicity7-10. In addition, undefined foreign/animal biological supplements and/or feeders that have typically been used for the isolation, expansion, and differentiation of hESCs may make direct use of such cell-specialized grafts in patients problematic11-13. To overcome these obstacles, we have resolved the elements of a defined culture system necessary and sufficient for sustaining the epiblast pluripotence of hESCs, serving as a platform for de novo derivation of clinically-suitable hESCs and effectively directing such hESCs uniformly towards clinically-relevant lineages by small molecules14 (please see a schematic in Fig. 1). Retinoic acid (RA) does not induce neuronal differentiation of undifferentiated hESCs maintained on feeders1, 14. And unlike mouse ESCs, treating hESC-differentiated embryoid bodies (EBs) only slightly increases the low yield of neurons1, 14, 15. However, after screening a variety of small molecules and growth factors, we found that such defined conditions rendered retinoic acid (RA) sufficient to induce the specification of neuroectoderm direct from pluripotent hESCs that further progressed to neuroblasts that generated human neuronal progenitors and neurons in the developing CNS with high efficiency (Fig. 2). We defined conditions for induction of neuroblasts direct from pluripotent hESCs without an intervening multi-lineage embryoid body stage, enabling well-controlled efficient derivation of a large supply of human neuronal cells across the spectrum of developmental stages for cell-based therapeutics.

We have established a protocol for induction of neuroblasts direct from pluripotent human embryonic stem cells maintained under defined conditions with small molecules, which enables derivation of a large supply of human neuronal progenitors and neuronal cell types in the developing CNS for neural repair.

There is a large unfulfilled need for a clinically-suitable human neuronal cell source for repair or regeneration of the damaged central nervous system ...

Integration Free Derivation of Human Induced Pluripotent Stem Cells Using Laminin 521 Matrix

Xeno-free and fully defined conditions are key parameters for robust and reproducible generation of homogenous human induced pluripotent stem (hiPS) cells. Maintenance of hiPS cells on feeder cells or undefined matrices are susceptible to batch variances, pathogenic contamination and risk of immunogenicity. Utilizing the defined recombinant human laminin 521 (LN-521) matrix in combination with xeno-free and defined media formulations reduces variability and allows for the consistent generation of hiPS cells. The Sendai virus (SeV) vector is a non-integrating RNA-based system, thus circumventing concerns associated with the potential disruptive effect on genome integrity integrating vectors can have. Furthermore, these vectors have demonstrated relatively high efficiency in the reprogramming of dermal fibroblasts. In addition, enzymatic single cell passaging of cells facilitates homogeneous maintenance of hiPS cells without substantial prior experience of stem cell culture. Here we describe a protocol that has been extensively tested and developed with a focus on reproducibility and ease of use, providing a robust and practical way to generate defined and xeno-free human hiPS cells from fibroblasts.

Robust derivation of human induced pluripotent stem (hiPS) cells was achieved by using non-integrating Sendai virus (SeV) vector mediated reprogramming of dermal fibroblasts. hiPS cell maintenance and clonal expansion was performed using xeno-free and chemically defined culture conditions with recombinant human laminin 521 (LN-521) matrix and Essential E8 (E8) Medium.

Xeno-free and fully defined conditions are key parameters for robust and reproducible generation of homogenous human induced pluripotent stem (hiPS) ...

Derivation of Adult Human Fibroblasts and their Direct Conversion into Expandable Neural Progenitor Cells

Generation of&#160;induced pluripotent stem cell (iPSCs) from adult skin fibroblasts and subsequent differentiation into somatic cells provides fascinating prospects for the derivation of autologous transplants that circumvent histocompatibility barriers. However, progression through a pluripotent state and subsequent complete differentiation into desired lineages remains a roadblock for the clinical translation of iPSC technology because of the associated neoplastic potential and genomic instability. Recently, we and others showed that somatic cells cannot only be converted into iPSCs but also into different types of multipotent somatic stem cells by using defined factors, thereby circumventing progression through the pluripotent state. In particular, the direct conversion of human fibroblasts into induced neural progenitor cells (iNPCs) heralds the possibility of a novel autologous cell source for various applications such as cell replacement, disease modeling and drug screening. Here, we describe the isolation of adult human primary fibroblasts by skin biopsy and their efficient direct conversion into iNPCs by timely restricted expression of Oct4, Sox2, Klf4, as well as c-Myc. Sox2-positive neuroepithelial colonies appear after 17 days of induction and iNPC lines can be established efficiently by monoclonal isolation and expansion. Precise adjustment of viral multiplicity of infection and supplementation of leukemia inhibitory factor during the induction phase represent critical factors to achieve conversion efficiencies of up to 0.2%. Thus far, patient-specific iNPC lines could be expanded for more than 12 passages and uniformly display morphological and molecular features of neural stem/progenitor cells, such as the expression of Nestin and Sox2. The iNPC lines can be differentiated into neurons and astrocytes as judged by staining against TUJ1 and GFAP, respectively. In conclusion, we report a robust protocol for the derivation and direct conversion of human fibroblasts into stably expandable neural progenitor cells that might provide a cellular source for biomedical applications such as autologous neural cell replacement and disease modeling.

Generation of induced pluripotent stem cells provides fascinating prospects for the derivation of autologous transplants. However, progression through a pluripotent state and laborious re-differentiation still hinders clinical translation. Here we describe the derivation of adult human fibroblasts and their direct conversion into induced neural progenitor cells and the subsequent differentiation into neural lineages.

Generation of&#160;induced pluripotent stem cell (iPSCs) from adult skin fibroblasts and subsequent differentiation into somatic cells provides ...

Isolation of Adult Human Dermal Fibroblasts from Abdominal Skin and Generation of Induced Pluripotent Stem Cells Using a Non-Integrating Method

Induced pluripotent stem cells (iPSCs) could be considered, to date, a promising source of pluripotent cells for the management of currently untreatable diseases, for the reconstitution and regeneration of injured tissues and for the development of new drugs. Despite all the advantages related to the use of iPSCs, such as the low risk of rejection, the lessened ethical issues, and the possibility to obtain them from both young and old patients without any difference in their reprogramming potential, problems to overcome are still numerous. In fact, cell reprogramming conducted with viral and integrating viruses can cause infections and the introduction of required genes can induce a genomic instability of the recipient cell, impairing their use in clinic. In particular, there are many concerns about the use of c-Myc gene, well-known from several studies for its mutation-inducing activity. Fibroblasts have emerged as the suitable cell population for cellular reprogramming as they are easy to isolate and culture and are harvested by a minimally invasive skin punch biopsy. The protocol described here provides a detailed step-by-step description of the whole procedure, from sample processing to obtain cell cultures, choice of reagents and supplies, cleaning and preparation, to cell reprogramming by the means of a commercial non-modified RNAs (NM-RNAs)-based reprogramming kit. The chosen reprogramming kit allows an effective reprogramming of human dermal fibroblast to iPSCs and small colonies can be seen as early as 24 h after the first transfection, even with modifications with the respect to the standard datasheet. The reprogramming procedure used in this protocol offers the advantage of a safe reprogramming, without the risk of infections caused by viral vector-based methods, reduces the cellular defense mechanisms, and allows the generation of xeno-free iPSCs, all critical features that are mandatory for further clinical applications.

Cell reprogramming requires the introduction of key genes, which regulate and maintain the pluripotent cell state. The protocol described enables the formation of induced pluripotent stem cells (iPSCs) colonies from human dermal fibroblasts without viral/integrating methods but using non-modified RNAs (NM-RNAs) combined with immune evasion factors reducing cellular defense mechanisms.

Induced pluripotent stem cells (iPSCs) could be considered, to date, a promising source of pluripotent cells for the management of currently untreatable ...

Bioengineering

Na&iuml;ve Adult Stem Cells Isolation from Primary Human Fibroblast Cultures

Over the last decade, several adult stem cell populations have been identified in human skin 1-4. The isolation of multipotent adult dermal precursors was first reported by Miller F. D laboratory 5, 6. These early studies described a multipotent precursor cell population from adult mammalian dermis 5. These cells--termed SKPs, for skin-derived precursors-- were isolated and expanded from rodent and human skin and differentiated into both neural and mesodermal progeny, including cell types never found in skin, such as neurons 5. Immunocytochemical studies on cultured SKPs revealed that cells expressed vimentin and nestin, an intermediate filament protein expressed in neural and skeletal muscle precursors, in addition to fibronectin and multipotent stem cell markers 6. Until now, the adult stem cells population SKPs have been isolated from freshly collected mammalian skin biopsies.
Recently, we have established and reported that a population of skin derived precursor cells could remain present in primary fibroblast cultures established from skin biopsies 7. The assumption that a few somatic stem cells might reside in primary fibroblast cultures at early population doublings was based upon the following observations: (1) SKPs and primary fibroblast cultures are derived from the dermis, and therefore a small number of SKP cells could remain present in primary dermal fibroblast cultures and (2) primary fibroblast cultures grown from frozen aliquots that have been subjected to unfavorable temperature during storage or transfer contained a small number of cells that remained viable 7. These rare cells were able to expand and could be passaged several times. This observation suggested that a small number of cells with high proliferation potency and resistance to stress were present in human fibroblast cultures 7.
We took advantage of these findings to establish a protocol for rapid isolation of adult stem cells from primary fibroblast cultures that are readily available from tissue banks around the world (Figure 1). This method has important significance as it allows the isolation of precursor cells when skin samples are not accessible while fibroblast cultures may be available from tissue banks, thus, opening new opportunities to dissect the molecular mechanisms underlying rare genetic diseases as well as modeling diseases in a dish.

Na&#239;ve Adult Stem Cells Isolation from Primary Human Fibroblast Cultures

We report a method to isolate na&#239;ve multipotent skin-derived precursor (SKP) cells from primary human fibroblast cultures. We show that these SKPs derived from fibroblast cultures share similar stem cell properties to the ones derived directly from human skin biopsies. These cells express the neural crest marker, nestin, in addition to the multipotent markers such as OCT4 and Nanog.

Over the last decade, several adult stem cell  populations have been identified in human skin 1-4.  The isolation of multipotent adult dermal precursors ...

Biology

In vitro Modeling for Neurological Diseases using Direct Conversion from Fibroblasts to Neuronal Progenitor Cells and Differentiation into Astrocytes

Research on neurological disorders focuses primarily on the impact of neurons on disease mechanisms. Limited availability of animal models severely impacts the study of cell type specific contributions to disease. Moreover, animal models usually do not reflect variability in mutations and disease courses seen in human patients. Reprogramming methods for generation of induced pluripotent stem cells (iPSCs) have revolutionized patient specific research and created valuable tools for studying disease mechanisms. However, iPSC technology has disadvantages such as time, labor commitment, clonal selectivity and loss of epigenetic markers. Recent modifications of these methods allow more direct generation of cell lineages or specific cell types, bypassing clonal isolation or a pluripotent stem cell state. We have developed a rapid direct conversion method to generate induced Neuronal Progenitor Cells (iNPCs) from skin fibroblasts utilizing retroviral vectors in combination with neuralizing media. The iNPCs can be differentiated into neurons (iNs) oligodendrocytes (iOs) and astrocytes (iAs). iAs production facilitates rapid drug and disease mechanism testing as differentiation from iNPCs only takes 5 days. Moreover, iAs are easy to work with and are generated in pure populations at large numbers. We developed a highly reproducible co-culture assay using mouse GFP+ neurons and patient derived iAs to evaluate potential therapeutic strategies for numerous neurological and neurodegenerative disorders. Importantly, the iA assays are scalable to 384-well format facilitating the evaluation of multiple small molecules in one plate. This approach allows simultaneous therapeutic evaluation of multiple patient cell lines with diverse genetic background. Easy production and storage of iAs and capacity to screen multiple compounds in one assay renders this methodology adaptable for personalized medicine.

We describe a protocol to reprogram human skin-derived fibroblasts into induced Neuronal Progenitor Cells (iNPCs), and their subsequent differentiation into induced Astrocytes (iAs). This method leads to fast and reproducible generation of iNPCs and iAs in large quantities.

Research on neurological disorders focuses primarily on the impact of neurons on disease mechanisms. Limited availability of animal models severely ...

Isolating Induced Neural Progenitor Cell Colonies Derived From Adult Human Fibroblasts

Source: Meyer, S. et al., <a href="https://app.jove.com/v/52831">Derivation of Adult Human Fibroblasts and their Direct Conversion into Expandable Neural Progenitor Cells.</a>&#160;J. Vis. Exp. (2015).
This video demonstrates a technique for isolating induced neural progenitor cells (iNPCs) derived from adult human fibroblasts. It outlines the steps involved in isolating the iNPC colonies and culturing them in laminin-coated multi-well plate wells in the presence of suitable culture media that facilitate the continued proliferation and expansion of the iNPC population.

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1. Isolation of Putative Induced ...

JoVE Encyclopedia of Experiments

Neuronal Culture Techniques

Primary Neuronal Culture

Generating Neurons by Reprogramming Human Dermal Fibroblast Cells

Source: Shrigley, S., et al. <a href="https://app.jove.com/v/56904">Simple Generation of a High Yield Culture of Induced Neurons from Human Adult Skin Fibroblasts.</a> J. Vis. Exp. (2018)
The video demonstrates the generation of neurons from adult human dermal fibroblasts (aHDFs). The aHDFs are reprogrammed using a lentiviral vector carrying genes for neuronal transcription factors and short hairpin RNAs (shRNAs). The shRNAs inhibit the expression of a neuronal transcriptional repressor, and the neuronal transcription factors activate genes to differentiate aHDFs into neurons. These reprogrammed aHDFs are cultured in an early and a late neuronal conversion medium to generate mature neurons.

1. Preparation of Skin Fibroblasts for Reprogramming

	Using an automated cell thawing system or a 37 &#176;C water bath, thaw the adult human dermal ...

Simple Generation of a High Yield Culture of Induced Neurons from Human Adult Skin Fibroblasts

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