Name: megakaryocyte culture in 3d methylcellulose-based hydrogel to improve cell maturation and study the impact of stiffness and confinement
Uploaded: 2021-08-26T13:30:00
Description: Watch this Scientific Journal Video about Megakaryocyte Culture in 3D Methylcellulose-Based Hydrogel to Improve Cell Maturation and Study the Impact of Stiffness and Confinement at JoVE.com

The authors would like to thank Fabien Pertuy and Alicia Aguilar who initially developed this technique in the lab, as well as Dominique Collin (Institut Charles Sadron - Strasbourg) who characterized the viscoelastic properties of the methylcellulose hydrogel. This work was supported by ARMESA (Association de Recherche et D&#233;veloppement en M&#233;decine et Sant&#233; Publique) and by an ARN grant (ANR-18-CE14-0037 PlatForMechanics). Julie Boscher is a recipient from the Fondation pour la Recherche M&#233;dicale (FRM grant number FDT202012010422).

All experiments should be performed in compliance with institutional guidelines for the care and use of laboratory animals. All protocols displayed in the video were carried out in strict accordance with the European law and the recommendations of the Review Board of the Etablissement Fran&#231;ais du Sang (EFS). A first version of this protocol was originally published in 2018 in Methods in Molecular Biology 8.
NOTE: Figure 1 presents a sc...

<ol>
	<li>Doolin, M. T., Moriarty, R. A., Stroka, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanosensing+of+Mechanical+Confinement+by+Mesenchymal-Like+Cells.">Mechanosensing of Mechanical Confinement by Mesenchymal-Like Cells.</a> Frontiers in Physiology. 11, (2020).</li><li>Wang, C., 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=Matrix+Stiffness+Modulates+Patient-Derived+Glioblastoma+Cell+Fates+in+Three-Dimensional+Hydrogels.">Matrix Stiffness Modulates Patient-Derived Glioblastoma Cell Fates in Three-Dimensional Hydrogels.</a> Tissue Engineering Part A. , (2020).</li><li>Doyle, A. D., Yamada, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanosensing+via+cell-matrix+adhesions+in+3D+microenvironments.">Mechanosensing via cell-matrix adhesions in 3D microenvironments.</a> Experimental Cell Research. 343 (1), 60-66 (2016).</li><li>Engler, A. J., Sen, S., Sweeney, H. L., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Matrix+Elasticity+Directs+Stem+Cell+Lineage+Specification.">Matrix Elasticity Directs Stem Cell Lineage Specification.</a> Cell. 126 (4), 677-689 (2006).</li><li>Choi, J. S., Harley, B. A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+combined+influence+of+substrate+elasticity+and+ligand+density+on+the+viability+and+biophysical+properties+of+hematopoietic+stem+and+progenitor+cells.">The combined influence of substrate elasticity and ligand density on the viability and biophysical properties of hematopoietic stem and progenitor cells.</a> Biomaterials. 33 (18), 4460-4468 (2012).</li><li>Shin, J. -. W., 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=Contractile+forces+sustain+and+polarize+hematopoiesis+from+stem+and+progenitor+cells.">Contractile forces sustain and polarize hematopoiesis from stem and progenitor cells.</a> Cell stem cell. 14 (1), 81-93 (2014).</li><li>Boscher, J., Guinard, I., Eckly, A., Lanza, F., L&#233;on, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+platelet+formation+at+a+glance.">Blood platelet formation at a glance.</a> Journal of cell science. 133 (20), (2020).</li><li>Aguilar, A., Boscher, J., Pertuy, F., Gachet, C., L&#233;on, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+culture+in+a+methylcellulose-based+hydrogel+to+study+the+impact+of+stiffness+on+megakaryocyte+differentiation.">Three-dimensional culture in a methylcellulose-based hydrogel to study the impact of stiffness on megakaryocyte differentiation.</a> Methods in Molecular Biology. 1812, 139-153 (2018).</li><li>Aguilar, A., 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=Importance+of+environmental+stiffness+for+megakaryocyte+differentiation+and+proplatelet+formation.">Importance of environmental stiffness for megakaryocyte differentiation and proplatelet formation.</a> Blood. 128, 2022-2032 (2016).</li><li>Hitchcock, I. S., Kaushansky, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thrombopoietin+from+beginning+to+end.">Thrombopoietin from beginning to end.</a> British Journal of Haematology. 165 (2), 259-268 (2014).</li><li>Leiva, O., Leon, C., Kah Ng, S., Mangin, P., Gachet, C., Ravid, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+extracellular+matrix+stiffness+in+megakaryocyte+and+platelet+development+and+function.">The role of extracellular matrix stiffness in megakaryocyte and platelet development and function.</a> American Journal of Hematology. 93 (3), 430-441 (2018).</li><li>Jansen, L. E., Birch, N. P., Schiffman, J. D., Crosby, A. J., Peyton, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanics+of+intact+bone+marrow.">Mechanics of intact bone marrow.</a> Journal of the Mechanical Behavior of Biomedical Materials. 50, 299-307 (2015).</li><li>Eckly, A., 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=Abnormal+megakaryocyte+morphology+and+proplatelet+formation+in+mice+with+megakaryocyte-restricted+MYH9+inactivation.">Abnormal megakaryocyte morphology and proplatelet formation in mice with megakaryocyte-restricted MYH9 inactivation.</a> Blood. 113 (14), 3182-3189 (2009).</li><li>Eckly, A., 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=Proplatelet+formation+deficit+and+megakaryocyte+death+contribute+to+thrombocytopenia+in+Myh9+knockout+mice.">Proplatelet formation deficit and megakaryocyte death contribute to thrombocytopenia in Myh9 knockout mice.</a> Journal of Thrombosis and Haemostasis. 8 (10), 2243-2251 (2010).</li></ol>

In the previous decade, mechanobiology has raised more and more interest in many areas of biology. It is now commonly acknowledged that the mechanical environment surrounding the cells does play a role in their behavior, emphasizing the importance to study how megakaryocytes sense and respond to extracellular mechanical cues. It is challenging to accurately measure the stiffness of the bone marrow tissue in situ11, especially if we consider the hematopoietic red marrow as it is located in...

Cells in the body experience a complex 3D microenvironment and are subjected to the interplay between chemical and mechanophysical cues including stiffness from the tissue and confinement due to neighboring cells and surrounding matrix 1,2,3. The importance of stiffness and confinement for cell behavior has only been recognized in the last decades. In 2006, the seminal work from Engler et al. 4 highlighted the importance of the mechanical environment for cell differentiation. The authors demonstrated that variation in cell substrate stiffness resulted in the orientation of stem cells towards various differentiation lineages. Since then, the impact of mechanical cues on cell fate and behavior has become increasingly recognized and studied. Despite it being one of the softest tissues of the organism, the bone marrow has a 3D structural organization that is confined inside the bone. Marrow stiffness, although technically difficult to measure precisely, is estimated to lie between 15 and 300 Pa 5, 6. Within the stroma, cells are tightly confined to one another. In addition, most of them are migrating toward the sinusoid vessels to enter the blood circulation. These conditions create additional mechanical constraints on adjacent cells, which have to adapt to these forces. Mechanical cues represent an important parameter whose consequences on megakaryocyte differentiation and proplatelet formation have just recently been explored. Although megakaryocytes can differentiate in vitro in traditional liquid culture, they do not reach the degree of maturation observed in vivo, in part due to the absence of the mechanical cues from the 3D environment 7. Growing progenitors embedded in hydrogel brings 3D mechanical cues that are lacking in liquid milieu.
Hydrogels have been widely used for several decades in the hematological field, notably to grow cells in colony forming assays to quantify hematopoietic progenitors. However, such hydrogels have seldom been used to explore the biological impact of the 3D mechanical environment on maturation and differentiation of hematopoietic cells. Over the past few years our laboratory has developed a 3D culture model using a methylcellulose-based hydrogel 8. This nonreactive physical gel is a useful tool to mimic the physical constraints of the native megakaryocyte environment. It is derived from cellulose by replacement of hydroxyl residues (-OH) by methoxide groups (-OCH3). Both the degree of methyl substitution and the methylcellulose concentration determine the hydrogel stiffness once it has jellified. During the development stage of this technique, it was demonstrated that a Young&#39;s modulus in the range of 30 to 60 Pa is the optimal gel stiffness for megakaryocyte growth 9.
The following protocol describes a method to grow mouse megakaryocytic progenitors in a 3D methylcellulose hydrogel. It has been previously shown that compared with standard liquid culture, this hydrogel culture increases the degree of megakaryocyte polyploidization, improves the maturation and intracellular organization, and increases the capacity of megakaryocytes to extend proplatelets once resuspended in a liquid medium 9. This manuscript describes in detail the protocol for the isolation of mouse bone marrow Lin&#8722; cells and their embedding in a methylcellulose hydrogel for 3D culture as well as the quantification of their capacity to produce proplatelets and the recovery of the cells for further analyses.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>18-gauge needles</td>
			<td>Sigma-Aldrich</td>
			<td>1001735825</td>
			<td></td>
		</tr>
		<tr>
			<td>21-gauge needles</td>
			<td>BD Microlance</td>
			<td>301155</td>
			<td></td>
		</tr>
		<tr>
			<td>23-gauge needles</td>
			<td>Terumo</td>
			<td>AN*2332R1</td>
			<td></td>
		</tr>
		<tr>
			<td>25-gauge neeldes</td>
			<td>BD Microlance</td>
			<td>300400</td>
			<td></td>
		</tr>
		<tr>
			<td>4-well culture dishes</td>
			<td>Thermo Scientific</td>
			<td>144444</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL syringes</td>
			<td>Terumo</td>
			<td>SS+05S1</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytoclips</td>
			<td>Microm Microtech</td>
			<td>F/CLIPSH</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytofunnels equiped with filter cards</td>
			<td>Microm Microtech</td>
			<td>F/JC304</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytospin centrifuge</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td>Cytospin 4</td>
		</tr>
		<tr>
			<td>Dakopen</td>
			<td>Dako</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM 1x</td>
			<td>Gibco, Life Technologies</td>
			<td>41 966-029</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS</td>
			<td>Life Technologies</td>
			<td>14190-094</td>
			<td>Sterile Dulbecco&#8217;s phosphate-buffered saline</td>
		</tr>
		<tr>
			<td>EasySep magnets</td>
			<td>Stem Cell Technologies</td>
			<td>18000</td>
			<td></td>
		</tr>
		<tr>
			<td>EasySep Mouse Hematopoietic Progenitor Cell isolation Kit</td>
			<td>Stem Cell Technologies</td>
			<td>19856A</td>
			<td>biotinylated antibodies (CD5,CD11b, CD19, CD45R/B220, Ly6G/C(Gr-1), TER119,7&#8211;4) and streptavidin-coated magnetic beads</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Invitrogen</td>
			<td>15575-020</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Healthcare Life Science</td>
			<td>SH30071.01</td>
			<td></td>
		</tr>
		<tr>
			<td>Luer lock 1 mL syringes</td>
			<td>Sigma-Aldrich</td>
			<td>Z551546-100EA</td>
			<td>or 309628 syringes from BD MEDICAL</td>
		</tr>
		<tr>
			<td>Luer lock syringes connectors</td>
			<td>Fisher Scientific</td>
			<td>11891120</td>
			<td></td>
		</tr>
		<tr>
			<td>MC 3%</td>
			<td>R&#38;D systems</td>
			<td>HSC001</td>
			<td></td>
		</tr>
		<tr>
			<td>Polylysin coated slides</td>
			<td>Thermo Scientific</td>
			<td>J2800AMNZ</td>
			<td></td>
		</tr>
		<tr>
			<td>PSG 100x</td>
			<td>Gibco, Life Technologies</td>
			<td>1037-016</td>
			<td>10,000 units/mL penicillin, 10,000 &#956;g/mL streptomycin and 29.2 mg/mL glutamine</td>
		</tr>
		<tr>
			<td>Rat serum</td>
			<td>Stem Cell Technologies</td>
			<td>13551</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant hirudin</td>
			<td>Transg&#232;ne</td>
			<td>rHV2-Lys47</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant human trombopoietin (rhTPO)</td>
			<td>Stem Cell Technologies</td>
			<td>2822</td>
			<td>10,000 units/mL</td>
		</tr>
		<tr>
			<td>Round bottomed 10 mL plastique tubes</td>
			<td>Falcon</td>
			<td>352054</td>
			<td></td>
		</tr>
		<tr>
			<td>Round bottomed 5 mL polystyrene tubes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

megakaryocyte culture in 3d methylcellulose-based hydrogel to improve cell maturation and study the impact of stiffness and confinement

The 3D environment leading to both confinement and mechanical constraints is increasingly recognized as an important determinant of cell behavior. 3D culture has thus been developed to better approach the in vivo situation. Megakaryocytes differentiate from hematopoietic stem and progenitor cells (HSPCs) in the bone marrow (BM). The BM is one of the softest tissues of the body, confined inside the bone. The bone being poorly extensible at the cell scale, megakaryocytes are concomitantly subjected to a weak stiffness and high confinement. This protocol presents a method for the recovery of mouse lineage negative (Lin-) HSPCs by immuno-magnetic sorting and their differentiation into mature megakaryocytes in a 3D medium composed of methylcellulose. Methylcellulose is non-reactive towards megakaryocytes and its stiffness may be adjusted to that of normal bone marrow or increased to mimic a pathological fibrotic marrow. The process to recover the megakaryocytes for further cell analyses is also detailed in the protocol. Although proplatelet extension is prevented within the 3D milieu, it is described below how to resuspend the megakaryocytes in liquid medium and to quantify their capacity to extend proplatelets. Megakaryocytes grown in 3D hydrogel have a higher capacity to form proplatelets compared to those grown in a liquid milieu. This 3D culture allows i) to differentiate progenitors towards megakaryocytes reaching a higher maturation state, ii) to recapitulate phenotypes that may be observed in vivo but go unnoticed in classical liquid cultures, and iii) to study transduction pathways induced by the mechanical cues provided by a 3D environment.

Data obtained using this protocol were originally published in Blood in 20169.
According to the protocol, the cells were seeded in either liquid or methylcellulose hydrogel medium. Cells in liquid medium have all sedimented at the bottom of the well, in contact with the stiff plastic surface and sometime with other cells. In contrast, cells embedded in methylcellulose hydrogel are distributed homogeneously in the gel and are isolated from neighboring cells (<strong clas...

Watch this Scientific Journal Video about Megakaryocyte Culture in 3D Methylcellulose-Based Hydrogel to Improve Cell Maturation and Study the Impact of Stiffness and Confinement at JoVE.com

Megakaryocyte Culture in 3D Methylcellulose-Based Hydrogel to Improve Cell Maturation and Study the Impact of Stiffness and Confinement

It is now acknowledged that the three-dimensional environment of cells can play an important role in their behavior, maturation and/or differentiation. This protocol describes a three-dimensional cell culture model designed to study the impact of physical containment and mechanical constraints on megakaryocytes.

The 3D environment leading to both confinement and mechanical constraints is increasingly recognized as an important determinant of cell behavior. 3D ...

This protocol allows for in vitro evaluation of the impact of confinement and medium stiffness to which native megakaryocytes are exposed to in the bone marrow on their behavior and maturation. The main advantage of this technique is a simplified model which eliminates cell-cell and cell matrix interactions and focuses on the mechanical aspects. Good laboratory practice and sterile working conditions are to be strictly observed.Indeed, even a slight contamination of the hydrogel can have a dramatic impact on megakaryocyte differentiation. To obtain a single well of hydrogel cell culture, begin by thawing two one milliliter aliquots of 3%methylcellulose at room temperature, then coat a one milliliter Luer lock syringe with the methylcellulose by first drawing one milliliter and then expelling all of it. Next, using the same syringe and needle, draw 333 microliters of methylcellulose from a fresh aliquot.After carefully removing the needle, use sterilized forceps to screw a Luer lock connector onto the end of the syringe, then attach a second non-coated one milliliter Luer lock syringe to the connector. Equally distribute the methylcellulose between the two syringes and set them aside. Next, resuspend the previously isolated mouse lineage negative hematopoietic stem and progenitor cells in the concentrated culture medium at a density of one times 10 to the six cells per 167 microliters.Disconnect one of the syringes from the connector and pipette 167 microliters of the cell suspension directly into the connector while simultaneously drawing the syringe plunger slowly to make room for the cell suspension. After adding all of the cell suspension into the connector, draw the plunger further to withdraw the suspension from the connector and carefully reconnect the second syringe, taking care not to lose any suspension in the screw thread. To homogenize the methylcellulose medium with the cell suspension, slowly move the plungers back and forth between the two syringes 10 times, then draw the total volume into one syringe and disconnect the two syringes, leaving the connector on the empty one.Empty the contents of the syringe into one well of a four-well plate and incubate the plate at 37 degrees under 5%carbon dioxide. To analyze proplatelets, on day three of culture, carefully transfer all cells from one well into a 15 milliliter tube containing 10 milliliters of DMEM with 1%PSG. Resuspend the cells by gently pipetting to completely dilute the methylcellulose, then centrifuge the tube for five minutes at 300 times G at room temperature.After discarding the supernatant, resuspend the cell pellet in one milliliter of complete culture medium and re-seed the cells at 500 microliters per well of a four-well plate. Incubate the plate at 37 degrees Celsius under 5%carbon dioxide. On the following day, using a Brightfield microscope with a 20X objective, randomly acquire 10 images per well, making sure not to have too many cells in the field of view and capturing at least five megakaryocytes per field.Using ImageJ, count the total number of megakaryocytes and those extending proplatelets in each image to calculate the proportion of megakaryocytes extending proplatelets. To fix the cells for future analyses, add the fixative solution on top of the methylcellulose without disrupting the gel. After waiting for an appropriate time depending on the fixative used, use a P1000 pipette to gently pipette the fixative and gel until the methylcellulose has been homogeneously diluted.And using the same pipette tip, transfer all the contents of the well into a 15 milliliter tube containing 10 milliliters of DPBS and homogenize by mixing. Centrifuge the mixture. Discard the supernatant and resuspend the megakaryocyte pellet in a medium appropriate for the desired analysis.By day three of culture, megakaryocytes in the liquid medium have sedimented at the bottom of the well and are in contact with the stiff plastic surface, as well as other cells. In contrast, cells embedded in the methylcellulose hydrogel are homogeneously distributed and isolated from neighboring cells. An analysis of the mean diameter of megakaryocytes under different culture conditions shows that 2%methylcellulose slightly increases the mean megakaryocyte diameter compared to the liquid culture.However, increasing the methylcellulose concentration by 0.5%impairs megakaryocyte differentiation as indicated by a smaller mean diameter. In representative transmission electron microscopy images, the intracytoplasmic membranes in megakaryocytes differentiated in vivo within the bone marrow appear to be closely opposed with delineated cytoplasmic territories. In liquid culture, the membranes mostly have a small round oval appearance or elongated vesicles without delimitation of cytoplasmic territories.In contrast, the 2%methylcellulose culture has closely opposed membranes with delimiting cytoplasmic territories resembling the in situ structure. By day four of culture, megakaryocytes previously cultured in hydrogel show increased proplatelet formation compared to those cultured in liquid medium. The mean proportion of megakaryocyte extending proplatelets is usually around 15 to 20%with a liquid pre-culture compared to 35 to 40%with a methylcellulose hydrogel pre-culture.When attempting this procedure, it is important to pipette the appropriate volumes very precisely as a minor change in the final methylcellulose concentration can significantly modify the media stiffness. Following cell maturation in the hydrogel, megakaryocytes can be recovered for ploidy and cell marker analysis by flow cytometry or fixed for electron microscopy or immunostaining of protein of interest.

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Testing Visual Sensitivity to the Speed and Direction of Motion in Lizards

Testing visual sensitivity in any species provides basic information regarding behaviour, evolution, and ecology. However, testing specific features of the visual system provide more empirical evidence for functional applications. Investigation into the sensory system provides information about the sensory capacity, learning and memory ability, and establishes known baseline behaviour in which to gauge deviations (Burghardt, 1977). However, unlike mammalian or avian systems, testing for learning and memory in a reptile species is difficult. Furthermore, using an operant paradigm as a psychophysical measure of sensory ability is likewise as difficult. Historically, reptilian species have responded poorly to conditioning trials because of issues related to motivation, physiology, metabolism, and basic biological characteristics. Here, I demonstrate an operant paradigm used a novel model lizard species, the Jacky dragon (Amphibolurus muricatus) and describe how to test peripheral sensitivity to salient speed and motion characteristics. This method uses an innovative approach to assessing learning and sensory capacity in lizards. I employ the use of random-dot kinematograms (RDKs) to measure sensitivity to speed, and manipulate the level of signal strength by changing the proportion of dots moving in a coherent direction. RDKs do not represent a biologically meaningful stimulus, engages the visual system, and is a classic psychophysical tool used to measure sensitivity in humans and other animals. Here, RDKs are displayed to lizards using three video playback systems. Lizards are to select the direction (left or right) in which they perceive dots to be moving. Selection of the appropriate direction is reinforced by biologically important prey stimuli, simulated by computer-animated invertebrates.

Testing visual sensitivity in lizards using an operant conditioning paradigm that employs video playback of random-dot kinematograms and computer-generated invertebrates.

Testing visual sensitivity in any species provides basic information regarding behaviour, evolution, and ecology. However, testing specific features of ...

Endothelial Cell Co-culture Mediates Maturation of Human Embryonic Stem Cell to Pancreatic Insulin Producing Cells in a Directed Differentiation Approach

Embryonic stem cells (ESC) have two main characteristics: they can be indefinitely propagated in vitro in an undifferentiated state and they are pluripotent, thus having the potential to differentiate into multiple lineages. Such properties make ESCs extremely attractive for cell based therapy and regenerative treatment applications 1. However for its full potential to be realized the cells have to be differentiated into mature and functional phenotypes, which is a daunting task. A promising approach in inducing cellular differentiation is to closely mimic the path of organogenesis in the in vitro setting. Pancreatic development is known to occur in specific stages 2, starting with endoderm, which can develop into several organs, including liver and pancreas. Endoderm induction can be achieved by modulation of the nodal pathway through addition of Activin A 3 in combination with several growth factors 4-7. Definitive endoderm cells then undergo pancreatic commitment by inhibition of sonic hedgehog inhibition, which can be achieved in vitro by addition of cyclopamine 8. Pancreatic maturation is mediated by several parallel events including inhibition of notch signaling; aggregation of pancreatic progenitors into 3-dimentional clusters; induction of vascularization; to name a few. By far the most successful in vitro maturation of ESC derived pancreatic progenitor cells have been achieved through inhibition of notch signaling by DAPT supplementation 9. Although successful, this results in low yield of the mature phenotype with reduced functionality. A less studied area is the effect of endothelial cell signaling in pancreatic maturation, which is increasingly being appreciated as an important contributing factor in in-vivo pancreatic islet maturation 10,11.
The current study explores such effect of endothelial cell signaling in maturation of human ESC derived pancreatic progenitor cells into insulin producing islet-like cells. We report a multi-stage directed differentiation protocol where the human ESCs are first induced towards endoderm by Activin A along with inhibition of PI3K pathway. Pancreatic specification of endoderm cells is achieved by inhibition of sonic hedgehog signaling by Cyclopamine along with retinoid induction by addition of Retinoic Acid. The final stage of maturation is induced by endothelial cell signaling achieved by a co-culture configuration. While several endothelial cells have been tested in the co-culture, herein we present our data with rat heart microvascular endothelial Cells (RHMVEC), primarily for the ease of analysis.

The current study describes a directed differentiation approach in inducing pancreatic differentiation of human embryonic stem cells. Of great significance is the finding that endothelial cell co-culture mediates maturation of human embryonic stem cell derived pancreatic progenitors into insulin expressing cells.

Embryonic stem cells (ESC) have two main characteristics: they can be indefinitely propagated in vitro in an undifferentiated state and they are ...

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In laboratories, biological samples are often stored in cryovials or cryoboxes stacked in stainless steel racks within the Dewar tanks1. These storage racks are provided with a long shaft to prevent boxes from slipping out from the racks and into the bottom of Dewars during routine handling. All too often, however, boxes or vials with precious samples slip out and sink to the bottom of liquid nitrogen filled tank. In such cases, samples could be tediously retrieved after transferring the liquid nitrogen into a spare container or discarding it. The boxes and vials can then be relatively safely recovered from emptied Dewar. However, the cryogenic nature of liquid nitrogen and its expansion rate makes sunken sample retrieval hazardous. It is commonly recommended by Safety Offices that sample retrieval be never carried out by a single person. Another alternative is to use commercially available cool grabbers or tongs to pull out the vials3. However, limited visibility within the dark liquid filled Dewars poses a major limitation in their use.
In this article, we describe the construction of a Cryotolerant DIY retrieval device, which makes sample retrieval from Dewar containing cryogenic fluids both safe and easy.

Here we present a low cost, durable cryotolerant device for sample retrieval from Dewar tanks filled with liquid nitrogen. The ease of construction and modular design of the device makes the process of sample retrieval from cryogenic tanks safe and easy.

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term ...

Combined Immunofluorescence and DNA FISH on 3D-preserved Interphase Nuclei to Study Changes in 3D Nuclear Organization

Fluorescent in situ hybridization using DNA probes on 3-dimensionally preserved nuclei followed by 3D confocal microscopy (3D DNA FISH) represents the most direct way to visualize the location of gene loci, chromosomal sub-regions or entire territories in individual cells. This type of analysis provides insight into the global architecture of the nucleus as well as the behavior of specific genomic loci and regions within the nuclear space. Immunofluorescence, on the other hand, permits the detection of nuclear proteins (modified histones, histone variants and modifiers, transcription machinery and factors, nuclear sub-compartments, etc). The major challenge in combining immunofluorescence and 3D DNA FISH is, on the one hand to preserve the epitope detected by the antibody as well as the 3D architecture of the nucleus, and on the other hand, to allow the penetration of the DNA probe to detect gene loci or chromosome territories 1-5. Here we provide a protocol that combines visualization of chromatin modifications with genomic loci in 3D preserved nuclei.

Here we describe a protocol for simultaneous detection of histone modifications by immunofluorescence and DNA sequences by DNA FISH followed by 3D microscopy and analyses (3D immuno-DNA FISH).

Fluorescent in situ hybridization using DNA probes  on 3-dimensionally preserved nuclei followed by 3D confocal microscopy (3D DNA  FISH) represents the ...

The Slice Culture Method for Following Development of Tooth Germs In Explant Culture

Explant culture allows manipulation of developing organs at specific time points&#160;and is therefore an important method for the developmental biologist. For many organs it is difficult to access developing tissue to allow monitoring during ex vivo culture. The slice culture method allows access to tissue so that morphogenetic movements can be followed and specific cell populations can be targeted for manipulation or lineage tracing.
In this paper we describe a method of slice culture that has been very successful for culture of tooth germs in a range of species. The method provides excellent access to the tooth germs, which develop at a similar rate to that observed in vivo, surrounded by the other jaw tissues. This allows tissue interactions between the tooth and surrounding tissue to be monitored. Although this paper concentrates on tooth germs, the same protocol can be applied to follow development of a number of other organs, such as salivary glands, Meckel&#39;s cartilage, nasal glands, tongue, and ear.

Here we detail a method to culture tooth germs in mandible slices using a tissue chopper. This method allows unique access to the tooth during development, providing excellent opportunity for manipulation and lineage tracing, not available using more traditional culture methods.

Explant culture allows manipulation of developing organs at specific time points&#160;and is therefore an important method for the developmental ...

An Ex vivo Culture System to Study Thyroid Development

The thyroid is a bilobated endocrine gland localized at the base of the neck, producing the thyroid hormones T3, T4, and calcitonin. T3 and T4 are produced by differentiated thyrocytes, organized in closed spheres called follicles, while calcitonin is synthesized by C-cells, interspersed in between the follicles and a dense network of blood capillaries. Although adult thyroid architecture and functions have been extensively described and studied, the formation of the &#8220;angio-follicular&#8221; units, the distribution of C-cells in the parenchyma and the paracrine communications between epithelial and endothelial cells is far from being understood.
This method describes the sequential steps of mouse embryonic thyroid anlagen dissection and its culture on semiporous filters or on microscopy plastic slides. Within a period of four days, this culture system faithfully recapitulates in vivo thyroid development. Indeed, (i) bilobation of the organ occurs (for e12.5 explants), (ii) thyrocytes precursors organize into follicles and polarize, (iii) thyrocytes and C-cells differentiate, and (iv) endothelial cells present in the microdissected tissue proliferate, migrate into the thyroid lobes, and closely associate with the epithelial cells, as they do in vivo.
Thyroid tissues can be obtained from wild type, knockout or fluorescent transgenic embryos. Moreover, explants culture can be manipulated by addition of inhibitors, blocking antibodies, growth factors, or even cells or conditioned medium. Ex vivo development can be analyzed in real-time, or at any time of the culture by immunostaining and RT-qPCR.
In conclusion, thyroid explant culture combined with downstream whole-mount or on sections imaging and gene expression profiling provides a powerful system for manipulating and studying morphogenetic and differentiation events of thyroid organogenesis.

An Ex vivo Culture System to Study Thyroid Development

This protocol describes dissection of mouse embryonic thyroid anlagen and the culture of explants on semiporous filters or on microscopy plastic slides. This system is ideal to study morphogenetic or differentiation events occurring during thyroid development of wild type or knockout embryos, and is amenable to gain- and loss-of-function experiments.

The thyroid is a bilobated endocrine gland localized at the base of the neck, producing the thyroid hormones T3, T4, and calcitonin. T3 and T4 are ...

Sequential Application of Glass Coverslips to Assess the Compressive Stiffness of the Mouse Lens: Strain and Morphometric Analyses

The eye lens is a transparent organ that refracts and focuses light to form a clear image on the retina. In humans, ciliary muscles contract to deform the lens, leading to an increase in the lens&#39; optical power to focus on nearby objects, a process known as accommodation. Age-related changes in lens stiffness have been linked to presbyopia, a reduction in the lens&#39; ability to accommodate, and, by extension, the need for reading glasses. Even though mouse lenses do not accommodate or develop presbyopia, mouse models can provide an invaluable genetic tool for understanding lens pathologies, and the accelerated aging observed in mice enables the study of age-related changes in the lens. This protocol demonstrates a simple, precise, and cost-effective method for determining mouse lens stiffness, using glass coverslips to apply sequentially increasing compressive loads onto the lens. Representative data confirm that mouse lenses become stiffer with age, like human lenses. This method is highly reproducible and can potentially be scaled up to mechanically test lenses from larger animals.

Age-related increases in eye lens stiffness are linked to presbyopia. This protocol describes a simple, cost-effective method for measuring mouse lens stiffness. Mouse lenses, like human lenses, become stiffer with age. This method is precise and can be adapted for lenses from larger animals.

The eye lens is a transparent organ that refracts and focuses light to form a clear image on the retina. In humans, ciliary muscles contract to deform the ...

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

We present detailed protocols for isolation of aortas from mouse and measurement of their elastic modulus using atomic force microscopy.

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a ...

Isolation and 3D Collagen Sandwich Culture of Primary Mouse Hepatocytes to Study the Role of Cytoskeleton in Bile Canalicular Formation In Vitro

Hepatocytes are the central cells of the liver responsible for its metabolic function. As such, they form a uniquely polarized epithelium, in which two or more hepatocytes contribute apical membranes to form a bile canalicular network through which bile is secreted. Hepatocyte polarization is essential for correct canalicular formation and depends on interactions between the hepatocyte cytoskeleton, cell-cell contacts, and the extracellular matrix. In vitro studies of hepatocyte cytoskeleton involvement in canaliculi formation and its response to pathological situations are handicapped by the lack of cell culture, which would closely resemble the canaliculi network structure in vivo. Described here is a protocol for the isolation of mouse hepatocytes from the adult mouse liver using a modified collagenase perfusion technique. Also described is the production of culture in a 3D collagen sandwich setting, which is used for immunolabeling of cytoskeletal components to study bile canalicular formation and its response to treatments in vitro. It is shown that hepatocyte 3D collagen sandwich cultures respond to treatments with toxins (ethanol) or actin cytoskeleton altering drugs (e.g., blebbistatin) and serve as a valuable tool for in vitro studies of bile canaliculi formation and function.

Presented here is a protocol for the isolation of mouse hepatocytes from adult mouse livers using a modified collagenase perfusion technique. Also described is the long-term culture of hepatocytes in a 3D collagen sandwich setting as well as immunolabeling of the cytoskeletal components to study bile canalicular formation and its response to treatment.

Hepatocytes are the central cells of the liver responsible for its metabolic function. As such, they form a uniquely polarized epithelium, in which two or ...

An Adipocyte Cell Culture Model to Study the Impact of Protein and Micro-RNA Modulation on Adipocyte Function

Alteration of adipocyte function contributes to the pathogenesis of metabolic diseases including Type 2 diabetes and insulin resistance. This highlights the need to better understand the molecular mechanism involved in adipocyte dysfunction to develop new therapies against obesity-related diseases. Modulating the expression of proteins and micro-RNAs in adipocytes remains highly challenging. This paper describes a protocol to differentiate murine fibroblasts into mature adipocytes and to modulate the expression of proteins and micro-RNAs in mature adipocytes through reverse-transfection using small-interfering RNA (siRNA) and micro-RNA mimicking (miR mimic) oligonucleotides. This reverse-transfection protocol involves the incubation of the transfection reagent and the oligonucleotides to form a complex in the cell culture plate to which the mature adipocytes are added. The adipocytes are then allowed to reattach to the adherent plate surface in the presence of the oligonucleotides/transfection reagent complex. Functional analyses such as the study of insulin signaling, glucose uptake, lipogenesis, and lipolysis can be performed on the transfected 3T3-L1 mature adipocytes to study the impact of protein or micro-RNA manipulation on adipocyte function.

Presented here is a protocol to deliver oligonucleotides such as small-interfering RNA (siRNA), micro-RNA mimics (miRs), or anti-micro-RNA (anti-miR) into mature adipocytes to modulate protein and micro-RNA expression.

Alteration of adipocyte function contributes to the pathogenesis of metabolic diseases including Type 2 diabetes and insulin resistance. This highlights ...