Name: a rankl-based osteoclast culture assay of mouse bone marrow to investigate the role of mtorc1 in osteoclast formation
Uploaded: 2018-03-15T12:30:00
Description: Watch this Scientific Journal Video about A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation at JoVE.com

The authors thank Dr. Minghan Tong and S. Kato for kindly providing reagents and mice. We thank the members of the Zou lab for useful discussions. This work was supported in part by grants from 973 Program from the Chinese Ministry of Science and Technology (MOST) [2014CB964704 and 2015CB964503], Clinical Research Program of 9th People&#39;s Hospital, Shanghai Jiao Tong University School of Medicine. Thanks for the help of Core Facility for Cell Biology and Core Facility for Chemical Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences.

All procedures relating to the animals were performed according to the protocol approved by the Stanford Administrative Panel on Laboratory Animal Care (APLAC) and were approved by the Animal Care and Use Committee of the Shanghai Institute of Biochemistry and Cell Biology.
1. Preparation
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	<li>Generate osteoclast specific Raptor deletion mice (Raptorfl/fl; Ctsk-cre, hereafter RapCtsk) by mating Raptorfl/fl mic...

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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+characterization+of+osteoclast-like+cells+and+their+progenitors+in+cultures+of+feline+marrow+mononuclear+cells.">Identification and characterization of osteoclast-like cells and their progenitors in cultures of feline marrow mononuclear cells.</a> J Cell Biol. 99 (2), 471-480 (1984).</li><li>Lacey, D. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoprotegerin+ligand+is+a+cytokine+that+regulates+osteoclast+differentiation+and+activation.">Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation.</a> Cell. 93 (2), 165-176 (1998).</li><li>Wong, B. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TRANCE+is+a+novel+ligand+of+the+tumor+necrosis+factor+receptor+family+that+activates+c-Jun+N-terminal+kinase+in+T+cells.">TRANCE is a novel ligand of the tumor necrosis factor receptor family that activates c-Jun N-terminal kinase in T cells.</a> J Biol Chem. 272 (40), 25190-25194 (1997).</li><li>Zoncu, R., Efeyan, A., Sabatini, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=mTOR:+from+growth+signal+integration+to+cancer,+diabetes+and+ageing.">mTOR: from growth signal integration to cancer, diabetes and ageing.</a> Nat Rev Mol Cell Biol. 12 (1), 21-35 (2011).</li><li>Bhaskar, P. T., Hay, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+two+TORCs+and+Akt.">The two TORCs and Akt.</a> Dev Cell. 12 (4), 487-502 (2007).</li><li>Dai, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inactivation+of+Regulatory-associated+Protein+of+mTOR+(Raptor)/Mammalian+Target+of+Rapamycin+Complex+1+(mTORC1)+Signaling+in+Osteoclasts+Increases+Bone+Mass+by+Inhibiting+Osteoclast+Differentiation+in+Mice.">Inactivation of Regulatory-associated Protein of mTOR (Raptor)/Mammalian Target of Rapamycin Complex 1 (mTORC1) Signaling in Osteoclasts Increases Bone Mass by Inhibiting Osteoclast Differentiation in Mice.</a> J Biol Chem. 292 (1), 196-204 (2017).</li><li>Sambrook, J., Fritsch, E. F., Maniatis, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular cloning: a laboratory manual. , (1989).</li><li>Weischenfeldt, J., Porse, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+Marrow-Derived+Macrophages+(BMM):+Isolation+and+Applications.">Bone Marrow-Derived Macrophages (BMM): Isolation and Applications.</a> CSH Protoc. 2008, (2008).</li><li>Bradley, E. W., Oursler, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoclast+culture+and+resorption+assays.">Osteoclast culture and resorption assays.</a> Methods Mol Biol. 455, 19-35 (2008).</li><li>Tevlin, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoclast+derivation+from+mouse+bone+marrow.">Osteoclast derivation from mouse bone marrow.</a> J Vis Exp. (93), e52056 (2014).</li><li>Xing, L., Boyce, B. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RANKL-based+osteoclastogenic+assays+from+murine+bone+marrow+cells.">RANKL-based osteoclastogenic assays from murine bone marrow cells.</a> Methods Mol Biol. 1130, 307-313 (2014).</li><li>Hsu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tumor+necrosis+factor+receptor+family+member+RANK+mediates+osteoclast+differentiation+and+activation+induced+by+osteoprotegerin+ligand.">Tumor necrosis factor receptor family member RANK mediates osteoclast differentiation and activation induced by osteoprotegerin ligand.</a> Proc Natl Acad Sci U S A. 96 (7), 3540-3545 (1999).</li><li>Underwood, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+where+comes+the+osteoclast?.">From where comes the osteoclast?.</a> J Pathol. 144 (4), 225-226 (1984).</li><li>Wein, M. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+bone+resorption+in+mice+by+Schnurri-3.">Control of bone resorption in mice by Schnurri-3.</a> Proc Natl Acad Sci U S A. 109 (21), 8173-8178 (2012).</li></ol>

The osteoclastogenic assay is the most widely used method to isolate and culture osteoclasts in vitro12,13. While several RANKL-based osteoclast inductions have been described13,14,15, the present study described a protocol with some modifications based on the previous methods.
In the previous study, BMMs were plating immediately afte...

Bone is an ever-changing organ and is remodeled by osteoblasts and osteoclasts throughout life. Osteoclasts are responsible for mineralized matrix resorption and osteoblasts synthesize and secrete new bone matrices1. The balance between bone resorption and bone formation is crucial for bone health including maintenance of bone mass and response to stimulation and injury. If this balance is disrupted, a series of bone metabolic diseases may occur, including osteoporosis and periodontal diseases. In these diseases, bone mass loss resulting from osteoclastic bone resorption exceeds the bone forming capacity of osteoblasts2,3. Thus, in order to develop pharmaceutical targets to treat skeletal disorders such as osteoporosis, it is critical to understand the generation and biology of osteoclasts4.
Osteoclasts are unique giant multinucleated cells located at or near the bone surface, and belong to the monocyte/macrophage family1. Ibbotson K. J. et al. reported a method to generate osteoclast-like cells in vitro with medium containing 1,25-dihydroxy-vitamin D35. The identification of macrophage-colony stimulating factor (M-CSF) and receptor activator for nuclear factor-&#954; B ligand (RANKL) as essential factors of osteoclast formation has dramatically increased the efficiency of osteoclastogenesis in vitro1,6,7. The ability to culture osteoclasts in vitro has improved our understanding of the generation and regulation of osteoclasts.
The mammalian/mechanistic target of rapamycin (mTOR) functions in two structurally and functionally distinct complexes, namely mTORC1 and mTORC28,9. The two multi-protein complexes are distinct from each other due to their different components and downstream substrates. mTORC1 contains the unique regulatory-associated protein of mTOR (Raptor), while mTORC2 contains the rapamycin-insensitive companion of mTOR (Rictor)9. mTORC1 can integrate and transmit important signals to regulate cell growth, proliferation and differentiation. Recently, we demonstrated that mTORC1 plays a key role in the network of catabolic bone resorption by deletion of Raptor to inactivate mTORC1 in osteoclasts10. However, the underlying mechanisms require further study. In the present study, a RANKL-based osteoclastogenic method was used to generate osteoclasts from bone marrow-derived macrophages (BMMs) of wild-type (WT) and RapCtsk mice, and to study the influence of mTORC1 inactivation on osteoclast formation.

<table>
	<tbody>
		<tr>
			<td>Raptorfl/fl mice</td>
			<td>The Jackson Laboratory</td>
			<td>013188</td>
			<td></td>
		</tr>
		<tr>
			<td>Ctsk-cre mice</td>
			<td></td>
			<td></td>
			<td>a gift from S. Kato, University of Tokyo, Tokyo, Japan</td>
		</tr>
		<tr>
			<td>&#945;-MEM</td>
			<td>Corning</td>
			<td>10-022-CVR</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutamine</td>
			<td>Gibico</td>
			<td>25030081</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin streptomycin</td>
			<td>Gibico</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal calf serum</td>
			<td>BioInd</td>
			<td>04-001-1A</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant mouse M-CSF protein</td>
			<td>R&#38;D</td>
			<td>Q3U4F9</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant mouse RANKL protein</td>
			<td>R&#38;D</td>
			<td>Q3TWY5</td>
			<td></td>
		</tr>
		<tr>
			<td>RBC lysis buffer</td>
			<td>Beyotime</td>
			<td>C3702</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue</td>
			<td>Sigma-Aldrich</td>
			<td>302643</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Citrate solution</td>
			<td>Sigma-Aldrich</td>
			<td>915</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde solution</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acid Phosphatase, Leukocyte (TRAP) Kit</td>
			<td>Sigma-Aldrich</td>
			<td>387A-1KT</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast Garnet GBC Base solution</td>
			<td>Sigma-Aldrich</td>
			<td>3872</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Nitrite Solution</td>
			<td>Sigma-Aldrich</td>
			<td>914</td>
			<td></td>
		</tr>
		<tr>
			<td>Naphthol AS-BI Phosphate Solution</td>
			<td>Sigma-Aldrich</td>
			<td>3871</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetate solution</td>
			<td>Sigma-Aldrich</td>
			<td>3863</td>
			<td></td>
		</tr>
		<tr>
			<td>Tartrate solution</td>
			<td>Sigma-Aldrich</td>
			<td>3873</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate-buffered saline</td>
			<td>Corning</td>
			<td>21-031-CVR</td>
			<td></td>
		</tr>
		<tr>
			<td>L-tartaric acid</td>
			<td>Sigma-Aldrich</td>
			<td>251380</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium tartrate dibasic dehydrate</td>
			<td>Sigma-Aldrich</td>
			<td>s4797</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ZnCl2</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Shanghai Chemical Co. Ltd.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphatase substrate</td>
			<td>Sigma-Aldrich</td>
			<td>P4744</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Raptor</td>
			<td>Cell Signaling Technology</td>
			<td>2280</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-P-ribosomal protein S6 (S235/236)</td>
			<td>Cell Signaling Technology</td>
			<td>2317</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-ribosomal protein S6</td>
			<td>Cell Signaling Technology</td>
			<td>2211</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-&#946;-actin</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-130300</td>
			<td></td>
		</tr>
		<tr>
			<td>37% formaldehyde</td>
			<td>Xilong scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>polyvinylidene fluoride (PVDF) membrane</td>
			<td>Bio-Rad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Western Chemiluminescent HRP Substrate (ECL)</td>
			<td>Millipore</td>
			<td>00000367MSDS</td>
			<td></td>
		</tr>
		<tr>
			<td>IX71</td>
			<td>Olympus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Envision</td>
			<td>Perkin Elmer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>0.45-mm Syringe</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Scissor</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mosquito forcep</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

a rankl-based osteoclast culture assay of mouse bone marrow to investigate the role of mtorc1 in osteoclast formation

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result in a series of bone metabolic diseases, including osteoporosis. To develop pharmaceutical targets for the prevention of pathological bone mass loss, the mechanisms by which osteoclasts differentiate from precursors must be understood. The ability to isolate and culture a large number of osteoclasts in vitro is critical in order to determine the role of specific genes in osteoclast differentiation. Inactivation of the mammalian/mechanistic target of rapamycin complex 1 (TORC1) in osteoclasts can decrease osteoclast number and increase bone mass; however, the underlying mechanisms require further study. In the present study, a RANKL-based protocol to isolate and culture osteoclasts from mouse bone marrow and to study the influence of mTORC1 inactivation on osteoclast formation is described. This protocol successfully resulted in a large number of giant osteoclasts, typically within one week. Deletion of Raptor impaired osteoclast formation and decreased the activity of secretory tartrate-resistant acid phosphatase, indicating that mTORC1 is critical for osteoclast formation.

Using the present protocol, a large number of giant osteoclasts were seen on day 6; if giant osteoclasts are not seen, one more day of osteoclast differentiation may be needed (Figure 1). Successful osteoclast formation was confirmed by TRAP staining (Figure 2A). Osteoclasts were giant wine red/purple cells with more than 3 nuclei. More than 250 osteoclasts were obtained in each well of the 96-well plate in WT BMMs (<strong class...

Watch this Scientific Journal Video about A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation at JoVE.com

A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation

This manuscript describes a protocol to isolate and culture osteoclasts in vitro from mouse bone marrow, and to study the role of the mammalian/mechanistic target of rapamycin complex 1 in osteoclast formation.

Osteoclasts are unique bone-resorbing cells that differentiate from the monocyte/macrophage lineage of bone marrow. Dysfunction of osteoclasts may result ...

The overall goal of this protocol is to isolate and culture osteoclasts in vitro from mouse bone marrow and to study the role of the mammalian target of rapamycin complex one in osteoclast formation. This method can help answer key questions in the formation of osteoclasts, such as the role of mTORC1 in osteoclast differentiation. The main advantage of this technique is to result in a large number of giant osteoclasts within one week.The implications of this technique extend toward the therapy of osteoporosis because it is helpful to study the mechanism by which osteoclast differentiates from their precursors. To begin this procedure, make a vertical incision at the distal end of the tibia of a euthanized mouse, and dissect the skin along the hind limbs. Next, cut the articular ligament of the hip joints with scissors, and dislocate the hind limbs from the trunk.Cut the articular ligament of the knee joint, and carefully disassociate the tibia and femur from it. Gently remove the soft tissue with scissors. Place all of the bones of one mouse in each well of a six-well plate with two milliliters of alpha-MEM on ice.For isolation, fill one well of a six-well plate with 75%ethanol and the other five wells with alpha-MEM. Put all the bones of one mouse in the ethanol wash for 15 seconds, and then wash the bones five times with alpha-MEM for 10 seconds each time. Cut off the epiphyses with the scissor, and insert a 0.45-millimeter syringe needle into the bone cavity.Flush the marrow out with alpha-MEM into a 50-milliliter centrifuge tube. Next, flush the bone cavity using the same method from the other end of the bone. Repeat at least twice to wash the bone cavity thoroughly until the bone is pale.Subsequently, centrifuge the bone marrow to obtain a cell pellet at four degrees Celsius for five minutes. Afterward, aspirate the supernatant. Add three milliliters of red blood cell lysis buffer into the centrifuge tube, and pipette gently to resuspend the bone marrow.Then, keep the centrifuge tube on ice for eight minutes to lyse the red blood cells. After eight minutes, add six milliliters of alpha-MEM into the centrifuge tube to stop the cell lysis. Centrifuge at 800 g and four degrees Celsius for 10 minutes, and aspirate the supernatant.Then, resuspend in three milliliters of alpha-MEM culture medium, and place the cells into a six-well plate. Incubate at 37 degrees Celsius overnight. In this step, transfer the supernatant to a 15-milliliter centrifuge tube to collect the unattached cells in the next morning.Afterward, centrifuge at 800 g and four degrees Celsius for five minutes, and aspirate the supernatant. Then, resuspend the cells in four milliliters of alpha-MEM culture medium. Take 20 microliters of the cell solution and mix with 20 microliters of Trypan Blue.Subsequently, add 10 microliters of the mixture to the counting chamber, and obtain the cell count per milliliter of solution. Following that, add an appropriate volume of alpha-MEM culture medium to obtain a cell solution of 500, 000 cells per milliliter. Next, add 500 microliters and 50 microliters of bone marrow macrophage induction medium into each well of a 24-well plate and 96-well plate, respectively.Afterward, add 500 microliters and 50 microliters of cell solution into each well of a 24-well plate and 96-well plate, respectively. Incubate at 37 degrees Celsius for three days. Three days after plating, collect 50 microliters of medium from each well of the 96-well plate, and freeze it at negative 20 degrees Celsius.Then, aspirate the residual medium. Add one milliliter and 100 microliters of osteoclast induction medium into each well of a 24-well plate and a 96-well plate, respectively. Incubate at 37 degrees Celsius for two days.After two days, collect 50 microliters of medium from each well, and aspirate the residual medium. Then, add osteoclast induction medium into each well, and incubate at 37 degrees Celsius for one day. After osteoclasts have formed, collect 50 microliters of medium from each well of the 96-well plate.In this step, aspirate the medium, and wash the sample gently three times with 1X PBS. Next, fix the cells in each well of the 96-well plate with 100 microliters of fix solution for 30 seconds at room temperature. After fixation, aspirate the fix solution, and wash the cells gently three times with deionized water prewarmed to 37 degrees Celsius.Then, aspirate the deionized water, and add 100 microliters of TRAP stain into each well of the 96-well plate. Place the plate in an incubator at 37 degrees Celsius for 30 minutes, and shield from light. After staining, aspirate the TRAP stain, and gently wash three times with deionized water.Subsequently, image the osteoclasts in an inverted microscope at 40X magnification. Then, transfer 30 microliters of the medium collected before to a new 96-well plate. Next, add 90 microliters of substrate mixture into each well of the 96-well plate.Place the plate in an incubator at 37 degrees Celsius for one hour, and shield from light. After an hour, stop the reaction by adding 30 microliters of three molar sodium hydroxide into each well of the 96-well plate. Then, measure the absorbance at the wavelength of 405 nanometers by the EnVision Multilabel Plate Reader.Here is the representative view of the osteoclasts observed in bright field on day six. The red line outlined the border of the osteoclasts. And shown here is a typically giant, multinucleated, TRAP-positive osteoclast.The black arrow indicated two nuclei of the multinucleated osteoclast. This figure shows TRAP staining of BMMs on day six. High-magnification images of the squares in wild-type and Ctsk-Cre Raptor knockout groups are shown, respectively.These were less giant, TRAP-positive osteoclasts formed in the Ctsk-Cre Raptor knockout BMMs in comparison to the wild-type group. This figure shows the TRAP activity of cultured wild-type and Ctsk-Cre Raptor knockout BMMs. Once mastered, this technique can be done within one week if it's performed properly.While attempting this procedure, it's important to remember to maintain the viability of the bone marrow macrophages, as the optimal seeding density of viable bone marrow macrophages is critical. It is recommended to keep the bone on ice no more than one hour and resuspend the cells gently. This procedure can be combined with other methods, such as the osteoclast resorption assay with bone slices, to study the normal and the pathological physiology of osteoclast.With this method, we found mTORC1 play an important role in osteoclast formation, which may act as a potential pharmacologic target for the treatment of bone metabolic disorders, such as osteoporosis, in the future.

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Developmental Biology

An Optogenetic Approach for Assessing Formation of Neuronal Connections in a Co-culture System

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are reprogrammed from human fibroblasts using episomal vectors. Colonies of iPSCs can be observed 30 days after initiation of fibroblast reprogramming. Pluripotent colonies are manually picked and grown in neural induction medium to permit differentiation into neural progenitor cells (NPCs). iPSCs rapidly convert into neuroepithelial cells within 1 week and retain the capability to self-renew when maintained at a high culture density. Primary mouse NPCs are differentiated into astrocytes by exposure to a serum-containing medium for 7 days and form a monolayer upon which embryonic day 18 (E18) rat cortical neurons (transfected with channelrhodopsin-2 (ChR2)) are added. Human NPCs tagged with the fluorescent protein, tandem dimer Tomato (tdTomato), are then seeded onto the astrocyte/cortical neuron culture the following day and allowed to differentiate for 28 to 35 days. We demonstrate that this system forms synaptic connections between iPSC-derived neurons and cortical neurons, evident from an increase in the frequency of synaptic currents upon photostimulation of the cortical neurons. This co-culture system provides a novel platform for evaluating the ability of iPSC-derived neurons to create synaptic connections with other neuronal populations.

A protocol to generate a co-culture system consisting of neurons derived from induced pluripotent stem cells (iPSCs), primary cortical neurons and astrocytes is described. This co-culture system allows detection of the formation of synaptic contacts and circuits between new, iPSC-derived neurons and pre-existing cortical neurons expressing channelrhodopsin-2.

Here we describe a protocol to generate a co-culture consisting of 2 different neuronal populations. Induced pluripotent stem cells (iPSCs) are ...

Using Confocal Analysis of Xenopus laevis to Investigate Modulators of Wnt and Shh Morphogen Gradients

This protocol describes a method to visualise ligands distributed across a field of cells. The ease of expressing exogenous proteins, together with the large size of their cells in early embryos, make Xenopus laevis a useful model for visualising GFP-tagged ligands. Synthetic mRNAs are efficiently translated after injection into early stage Xenopus embryos, and injections can be targeted to a single cell. When combined with a lineage tracer such as membrane tethered RFP, the injected cell (and its descendants) that are producing the overexpressed protein can easily be followed. This protocol describes a method for the production of fluorescently tagged Wnt and Shh ligands from injected mRNA. The methods involve the micro dissection of ectodermal explants (animal caps) and the analysis of ligand diffusion in multiple samples. By using confocal imaging, information about ligand secretion and diffusion over a field of cells can be obtained. Statistical analyses of confocal images provide quantitative data on the shape of ligand gradients. These methods may be useful to researchers who want to test the effects of factors that may regulate the shape of morphogen gradients.

Using Confocal Analysis of Xenopus laevis to Investigate Modulators of Wnt and Shh Morphogen Gradients

The manuscript here provides a simple set of methods for analysing the secretion and diffusion of fluorescently tagged ligands in Xenopus. This provides a context for testing the ability of other proteins to modify ligand distribution and allowing experiments that may give insight into mechanisms regulating morphogen gradients.

This protocol describes a method to visualise ligands distributed across a field of cells. The ease of expressing exogenous proteins, together with the ...

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka and zebrafish larvae are widely used to analyze the behavior of bone cells during bone formation, degeneration, and repair. Their optical clarity allows the visualization of fluorescently labeled bone cells and fluorescent dyes bound to the mineralized skeletal matrix. Our lab has generated transgenic medaka fish that express the osteoclast-inducing factor Receptor Activator of Nuclear-factor &#954;B Ligand (RANKL) under the control of a heat&#160;shock-inducible promoter. Ectopic expression of RANKL results in the excess formation of activated osteoclasts, which can be visualized in reporter lines with nlGFP expression under the control of the cathepsin K (ctsk) promoter. RANKL induction and ectopic osteoclast formation leads to severe osteoporosis-like phenotypes. Compound transgenic medaka lines that express ctsk:nlGFP in osteoclasts, as well as mCherry under the control of the osterix (osx) promoter in premature osteoblasts, can be used to study the interaction of both cell types. This facilitates the in vivo observation of cellular behavior under conditions of bone degeneration and repair. Here, we describe the use of this system to test a drug commonly used in human osteoporosis therapy and describe a protocol for live imaging. The medaka model complements studies in cell culture and mice, and offers a novel system for the in vivo analysis of drug action in the skeletal system.

Drug Treatment and In Vivo Imaging of Osteoblast-Osteoclast Interactions in a Medaka Fish Osteoporosis Model

Small laboratory fish have become popular models for bone research on the mechanisms underlying human bone disorders and for the screening of bone-modulating drugs. In this report, we describe a protocol to assess the effect of alendronate on bone cells in medaka larvae with osteoporotic lesions.

Bone-forming osteoblasts interact with bone-resorbing osteoclasts to coordinate the turnover of bone matrix and to control skeletal homeostasis. Medaka ...

Temporal Ordering of Dynamic Expression Data from Detailed Spatial Expression Maps

During somitogenesis, pairs of epithelial somites form in a progressive manner, budding off from the anterior end of the pre-somitic mesoderm (PSM) with a strict species-specific periodicity. The periodicity of the process is regulated by a molecular oscillator, known as the "segmentation clock," acting in the PSM cells. This clock drives the oscillatory patterns of gene expression across the PSM in a posterior-anterior direction. These so-called clock genes are key components of three signaling pathways: Wnt, Notch, and fibroblast growth factor (FGF). In addition, Notch signaling is essential for synchronizing intracellular oscillations in neighboring cells. We recently gained insight into how this may be mechanistically regulated. Upon ligand activation, the Notch receptor is cleaved, releasing the intracellular domain (NICD), which moves to the nucleus and regulates gene expression. NICD is highly labile, and its phosphorylation-dependent turnover acts to restrict Notch signaling. The profile of NICD production (and degradation) in the PSM is known to be oscillatory and to resemble that of a clock gene. We recently reported that both the Notch receptor and the Delta ligand, which mediate intercellular coupling, themselves exhibit dynamic expression at both the mRNA and protein levels. In this article, we describe the sensitive detection methods and detailed image analysis tools that we used, in combination with the computational modeling that we designed, to extract and overlay expression data from distinct points in the expression cycle. This allowed us to construct a spatio-temporal picture of the dynamic expression profile for the receptor, the ligand, and the Notch target clock genes throughout an oscillation cycle. Here, we describe the protocols used to generate and culture the PSM explants, as well as the procedure to stain for the mRNA or protein. We also explain how the confocal images were subsequently analyzed and temporally ordered computationally to generate ordered sequences of clock expression snapshots, hereafter defined as "kymographs," for the visualization of the spatiotemporal expression of Delta-like1 (Dll1) and Notch1 throughout the PSM.

The segmentation clock drives oscillatory gene expression across the pre-somitic mesoderm (PSM). Dynamic Notch activity is key to this process. We use imaging and computational analyses to extract temporal dynamics from spatial expression data to demonstrate that Delta ligand and Notch receptor expression oscillate in the vertebrate PSM.

During somitogenesis, pairs of epithelial somites form in a progressive manner, budding off from the anterior end of the pre-somitic mesoderm (PSM) with a ...

Stimulation of Notch Signaling in Mouse Osteoclast Precursors

Notch signaling is a key component of multiple physiological and pathological processes. The nature of Notch signaling, however, makes in vitro investigation of its varying and sometimes contradictory roles a challenge. As a component of direct cell-cell communication with both receptors and ligands bound to the plasma membrane, Notch signaling cannot be activated in vitro by simple addition of ligands to culture media, as is possible with many other signaling pathways. Instead, Notch ligands must be presented to cells in an immobilized state. 
Variations in methods of Notch signaling activation can lead to different outcomes in cultured cells. In osteoclast precursors, in particular, differences in methods of Notch stimulation and osteoclast precursor culture and differentiation have led to disagreement over whether Notch signaling is a positive or negative regulator of osteoclast differentiation. While closer comparisons of osteoclast differentiation under different Notch stimulation conditions in vitro and genetic models have largely resolved the controversy regarding Notch signaling and osteoclasts, standardized methods of continuous and temporary stimulation of Notch signaling in cultured cells could prevent such discrepancies in the future.
This protocol describes two methods for stimulating Notch signaling specifically in cultured mouse osteoclast precursors, though these methods should be applicable to any adherent cell type with minor adjustments. The first method produces continuous stimulation of Notch signaling and involves immobilizing Notch ligand to a tissue culture surface prior to the seeding of cells. The second, which uses Notch ligand bound to agarose beads allows for temporary stimulation of Notch signaling in cells that are already adhered to a culture surface. This protocol also includes methods for detecting Notch activation in osteoclast precursors as well as representative transcriptional markers of Notch signaling activation.

Notch signaling is a form of cellular communication that relies upon direct contact between cells. To properly induce Notch signaling in vitro, Notch ligands must be presented to cells in an immobilized state. This protocol describes methods for in vitro stimulation of Notch signaling in mouse osteoclast precursors.

Notch signaling is a key component of multiple physiological and pathological processes. The nature of Notch signaling, however, makes in vitro ...

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global DNA methylation level of chondrocytes is considered to be a suitable biomarker for the loss of the chondrocyte phenotype. However, results based on different experimental methods can be inconsistent. Therefore, it is important to establish a precise, simple, and rapid method to quantify global DNA methylation levels during chondrocyte dedifferentiation.
Current genome-wide methylation analysis techniques largely rely on bisulfite genomic sequencing. Due to DNA degradation during bisulfite conversion, these methods typically require a large sample volume. Other methods used to quantify global DNA methylation levels include high-performance liquid chromatography (HPLC). However, HPLC requires complete digestion of genomic DNA. Additionally, the prohibitively high cost of HPLC instruments limits HPLC&#39;s wider application.
In this study, genomic DNA (gDNA) was extracted from human chondrocytes cultured with varying number of passages. The gDNA methylation level was detected using a methylation-specific dot blot assay. In this dot blot approach, a gDNA mixture containing the methylated DNA to be detected was spotted directly onto an N+ membrane as a dot inside a previously drawn circular template pattern. Compared with other gel electrophoresis-based blotting approaches and other complex blotting procedures, the dot blot method saves significant time. In addition, dot blots can detect overall DNA methylation level using a commercially available 5-mC antibody. We found that the DNA methylation level differed between the monolayer subcultures, and therefore could play a key role in chondrocyte dedifferentiation. The 5-mC dot blot is a reliable, simple, and rapid method to detect the general DNA methylation level to evaluate chondrocyte phenotype.

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro

We present a method to quantify DNA methylation based on the 5-methylcytosine (5-mC) dot blot. We determined the 5-mC levels during chondrocyte dedifferentiation. This simple technique could be used to quickly determine the chondrocyte phenotype in ACI treatment.

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global ...

Bioengineering of Humanized Bone Marrow Microenvironments in Mouse and Their Visualization by Live Imaging

Human hematopoietic stem cells (HSCs) reside in the bone marrow (BM) niche, an intricate, multifactorial network of components producing cytokines, growth factors, and extracellular matrix. The ability of HSCs to remain quiescent, self-renew or differentiate, and acquire mutations and become malignant depends upon the complex interactions they establish with different stromal components. To observe the crosstalk between human HSCs and the human BM niche in physiological and pathological conditions, we designed a protocol to ectopically model and image a humanized BM niche in immunodeficient mice. We show that the use of different cellular components allows for the formation of humanized structures and the opportunity to sustain long-term human hematopoietic engraftment. Using two-photon microscopy, we can live-image these structures in situ at the single-cell resolution, providing a powerful new tool for the functional characterization of the human BM microenvironment and its role in regulating normal and malignant hematopoiesis.

A method to create and live-image different humanized bone-marrow niches in mice is presented. Based on the supportive niche created by human mesenchymal cells, the addition of human endothelial cells induces the formation of human vessels, while the addition of rhBMP-2 induces the formation of human-mouse chimeric mature bone tissue.

Human hematopoietic stem cells (HSCs) reside in the bone marrow (BM) niche, an intricate, multifactorial network of components producing cytokines, growth ...

The Aortic Ring Co-culture Assay: A Convenient Tool to Assess the Angiogenic Potential of Mesenchymal Stromal Cells In Vitro

Angiogenesis is a complex, highly regulated process responsible for providing and maintaining adequate tissue perfusion. Insufficient vasculature maintenance and pathological malformations can result in severe ischemic diseases, while overly abundant vascular development is associated with cancer and inflammatory disorders. A promising form of pro-angiogenic therapy is the use of angiogenic cell sources, which can provide regulatory factors as well as physical support for newly developing vasculature.
Mesenchymal Stromal Cells (MSCs) are extensively investigated candidates for vascular regeneration due to their paracrine effects and their ability to detect and home to ischemic or inflamed tissues. In particular, first trimester human umbilical cord perivascular cells (FTM HUCPVCs) are a highly promising candidate due to their pericyte-like properties, high proliferative and multilineage potential, immune-privileged properties, and robust paracrine profile. To effectively evaluate potentially angiogenic regenerative cells, it is a requisite to test them in reliable and &#34;translatable&#34; pre-clinical assays. The aortic ring assay is an ex vivo angiogenesis model that allows for easy quantification of tubular endothelial structures, provides accessory supportive cells and extracellular matrix (ECM) from the host, excludes inflammatory components, and is fast and inexpensive to set up. This is advantageous when compared to in vivo models (e.g., corneal assay, Matrigel plug assay); the aortic ring assay can track the administered cells and observe intercellular interactions while avoiding xeno-immune rejection.
We present a protocol for a novel application of the aortic ring assay, which includes human MSCs in co-cultures with developing rat aortic endothelial networks. This assay allows for the analysis of the MSC contribution to tube formation and development through physical pericyte-like interactions and of their potency for actively migrating to sites of angiogenesis, and for evaluating their ability to perform and mediate ECM processing. This protocol provides further information on changes in MSC phenotype and gene expression following co-culture.

The Aortic Ring Co-culture Assay: A Convenient Tool to Assess the Angiogenic Potential of Mesenchymal Stromal Cells In Vitro

Here, we present a novel application of the aortic ring assay where prelabelled mesenchymal cells are co-cultured with rat aorta-derived endothelial networks. This novel method allows visualization of Mesenchymal Stromal Cells (MSCs) homing and integration with endothelial networks, quantification of network properties, and evaluation of MSC immunophenotypes and gene expression.

Angiogenesis is a complex, highly regulated process responsible for providing and maintaining adequate tissue perfusion. Insufficient vasculature ...

Isolation, Culture, and Differentiation of Bone Marrow Stromal Cells and Osteoclast Progenitors from Mice

Bone marrow stromal cells (BMSCs) constitute a cell population routinely used as a representation of mesenchymal stem cells in vitro. They reside within the bone marrow cavity alongside hematopoietic stem cells (HSCs), which can give rise to red blood cells, immune progenitors, and osteoclasts. Thus, extractions of cell populations from the bone marrow results in a very heterogeneous mix of various cell populations, which can present challenges in experimental design and confound data interpretation. Several isolation and culture techniques have been developed in laboratories in order to obtain more or less homogeneous populations of BMSCs and HSCs invitro. Here, we present two methods for isolation of BMSCs and HSCs from mouse long bones: one method that yields a mixed population of BMSCs and HSCs and one method that attempts to separate the two cell populations based on adherence. Both methods provide cells suitable for osteogenic and adipogenic differentiation experiments as well as functional assays.

In this article, we present methods to isolate and differentiate bone marrow stromal cells and hematopoietic stem cells from mouse long bones. Two different protocols are presented yielding different cell populations suitable for expansion and differentiation into osteoblasts, adipocytes, and osteoclasts.

Bone marrow stromal cells (BMSCs) constitute a cell population routinely used as a representation of mesenchymal stem cells in vitro. They reside within ...

A Cell-based Assay to Investigate Non-muscle Myosin II Contractility via the Folded-gastrulation Signaling Pathway in Drosophila S2R+ Cells

We have developed a cell-based assay using Drosophila cells that recapitulates apical constriction initiated by folded gastrulation (Fog), a secreted epithelial morphogen. In this assay, Fog is used as an agonist to activate Rho through a signaling cascade that includes a G-protein-coupled receptor (Mist), a G&#945;12/13 protein (Concertina/Cta), and a PDZ-domain-containing guanine nucleotide exchange factor (RhoGEF2). Fog signaling results in the rapid and dramatic reorganization of the actin cytoskeleton to form a contractile purse string. Soluble Fog is collected from a stable cell line and applied ectopically to S2R+ cells, leading to morphological changes like apical constriction, a process observed during developmental processes such as gastrulation. This assay is amenable to high-throughput screening and, using RNAi, can facilitate the identification of additional genes involved in this pathway.

A Cell-based Assay to Investigate Non-muscle Myosin II Contractility via the Folded-gastrulation Signaling Pathway in Drosophila S2R+ Cells

Here we describe a contractility assay using Drosophila S2R+ cells. The application of an exogenous ligand, folded gastrulation (Fog), leads to the activation of the Fog signaling pathway and cellular contractility. This assay can be used to investigate the regulation of cellular contractility proteins in the Fog signaling pathway.

We have developed a cell-based assay using Drosophila cells that recapitulates apical constriction initiated by folded gastrulation (Fog), a secreted ...