Name: extra cellular matrix-based and extra cellular matrix-free generation of murine testicular organoids
Uploaded: 2020-10-07T14:00:00
Description: Watch this Scientific Journal Video about Extra Cellular Matrix-Based and Extra Cellular Matrix-Free Generation of Murine Testicular Organoids at JoVE.com

This work was funded by the National Institutes of Health, National Institute of Child Health and Human Development (NICHD) F31 HD089693, the National Institute for Environmental Health Sciences / National Center for Advancing Translational Sciences (NIEHS/NCATS) UH3TR001207 and 4UH3ES029073-03, and the Thomas J. Watkin&#8217;s Memorial Professorship.
The authors would like to thank Eric W. Roth for their assistance with transmission electron microscopy. This work made use of the BioCryo facility of Northwestern University&#8217;s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); and the State of Illinois, through the IIN. It also made use of the CryoCluster equipment, which has received support from the MRI program (NSF DMR-1229693). Graphics in Figure 1 were designed using BioRender.com.

All mouse experiments were approved by the Institutional Animal Care and Use Committee (IACUC) of Northwestern University, and all procedures were performed under IACUC-approved protocols.
1. Preparation of enzymatic tissue-dissociation solutions
<ol>
	<li>Use two different enzymatic solutions (Solution 1 and Solution 2), both made using a basal culture medium solution (BM).</li>
	<li>To prepare BM, add serum and penicillin-streptomycin to minimum essential medium to final concentrations of ...

With the completion of this organoid generation protocol, the user will have four different culture techniques available to them for assembling testicular constructs and organoids in either ECM or ECM-free environments. Importantly, all four methods allow the researcher to non-invasively observe organoid self-assembly over time through time-lapse imaging or video recording, and to noninvasively collect conditioned media for analysis of secreted hormones and cytokines, without disturbing tissues during culture. In all met...

Testicular organoids are a pioneering technique for studying testicular development, spermatogenesis, and physiology in vitro1,2,3,4. Several methods have been explored for organoid generation; these include a variety of extracellular matrix (ECM) and ECM-free culture systems, in both two-dimensional (2D) and three-dimensional (3D) orientations. Different generation methods can promote distinct cellular assembly strategies; this results in a high level of morphological and functional variability between published organoid models. The purpose of this article is to discuss the current state of in vitro testicular models, and to serve as a template for future investigators, when designing testicular organoid experiments. Within the present study, four different culture system archetypes are defined and characterized in experimental process and biological outcome. These include: 2D ECM-Free, 2D ECM, 3D ECM-Free, and 3D ECM culture methods. The strategies presented herein are intended to be simple, accessible, and highly reproducible between different laboratories and research groups.
Historically for the testis, the designation &#8220;in vitro&#8221;, has been used for several different culture methods of testicular tissues and cells. These include organotypic tissue/organ culture methods (i.e., explant culture)5, isolated seminiferous tubule culture6, testicular cell culture7, and methods of de novo tissue morphogenesis (i.e., biological constructs and organoids)1. The first investigations into in vitro spermatogenesis were performed approximately 100 years ago, with the culture of rabbit testis explants in 19208, and later in 1937 with mouse explants9. Within these initial experiments spermatogonia were observed to largely degenerate across the first week of culture, though some meiotically differentiating cells were identified. Reminiscent of these historical reports, testis explant culture was revived and optimized in 2011 to become a feasible technique for studying the testis10. Since 2011, explant culture has produced fertility competent sperm in multiple reports11,12,13. Yet, due to explant culture&#8217;s reliance upon pre-existing native testis tubules, these recent advances are more accurately described as examples of &#8220;ex vivo&#8221; testicular function and spermatogenesis, tissue function that was maintained or resumed upon removal from an organism&#8217;s body. Despite its prevalence in the literature, long-term germ cell maintenance and differentiation within testicular explants is challenging to replicate14,15,16,17,18, especially over timeframes long enough to fully observe in vitro spermatogenesis (~35 days in mice19 and 74 in humans20). It is intriguing to appreciate that many of the same challenges experienced 100 years ago, are still experienced within ex vivo spermatogenesis today.
Different than ex vivo approaches, testicular organoids are de novo assembled microtissues generated entirely in vitro from cellular sources (i.e., primary testicular cells). Testicular organoids provide a creative strategy to circumvent the field&#8217;s historical reliance upon pre-existing native tissue, and to recapitulate testicular biology completely in vitro. There are multiple requirements shared by most organoid tissue models; these include (1) in vivo-mimetic tissue morphology or architecture, (2) multiple major cell types of the represented tissue, (3) self-assembly or self-organization in their generation, and (4) the ability to simulate some level of the represented tissue&#8217;s function and physiology21,22,23,24. For the testis, this can be captured in four major hallmarks: (1) the inclusion of major testicular cell types, germ, Sertoli, Leydig, peritubular, and other interstitial cells, (2) cell-directed tissue assembly, (3) appropriately-compartmentalized cell types into separate tubular compartments (germ and Sertoli) and interstitial regions (all other cell types), and (4) some degree of tissue function (e.g., reproductive hormone secretion or tissue responses, and germ cell maintenance and differentiation). Considering the historic challenges in maintaining germ cell differentiation ex vivo and in vitro, the recapitulation of in vivo-mimetic testicular architectures (i.e., structures resembling seminiferous tubules) with additional markers suggesting simulation of testicular physiology (e.g., endocrine function), are priority milestones towards generating organoids which might one day sustain in vitro spermatogenesis.
The majority of published testicular organoid methods take advantage of commercially available ECM (e.g., collagen or proprietary ECM formulations)25,26,27 or custom-sourced ECMs (i.e., decellularized testis ECM-derived hydrogels)28,29,30. Exogenous ECM promotes de novo tissue formation through providing an assembly-supportive scaffold for tissue generation. ECM methods have afforded an impressive level of tissue formation, including some germ cell presence and tissue-mimetic morphology25,28. However, the ECMs they utilize are not always universally available (i.e., decellularized ECM-derived hydrogels), and some methods require sophisticated gel and cell seeding orientations (e.g., 3-layer gradients of ECM and 3D printing)25,31,32. Scaffold-free methods (e.g., hanging drop and nonadherent culture plates)33,34,35 have also generated robust and highly reproducible organoids without the need of ECM gels or scaffolds. However, the tissue morphology of these scaffold-free organoids is often dissimilar to in vivo testes, and most of these reports incorporate a biochemical ECM additive to promote tissue formation33,34,36, or alternatively, rely upon centrifugation for forced cell aggregation and compaction34, making them less ideal for studying cell-directed migration and self-organization.
The four organoid generation methods presented in this manuscript include both ECM-dependent and independent strategies, each using simple cell seeding that enables the observation of cell-driven organoid self-assembly. All four techniques can be performed from the same cell suspensions or can make use of custom and cell-type enriched populations. A strength of these methods is the ability to observe organoids self-assemble in real-time, and to directly compare how testicular structures self-assemble between different culture microenvironments. The phenotypic differences between these four culture methods should be considered for their impact on the research question or subject of the investigator. Each method produces biological constructs or organoids within 24 h or less. In conclusion, the methods presented here provide a toolkit of organoid assembly techniques for studying testicular organoid assembly, tissue development, and testicular physiology in vitro.

<table>
	<tbody>
		<tr>
			<td>0.22 um Media Sterile Filters</td>
			<td>Millipore Sigma</td>
			<td>scgpu05re</td>
			<td>For sterile filtering media</td>
		</tr>
		<tr>
			<td>3&#946;HSD primary antibody</td>
			<td>Cosmo Bio Co</td>
			<td>K0607</td>
			<td>Leydig cell marker, 1:500 dilution</td>
		</tr>
		<tr>
			<td>AlexaFluor 568 &#945;-Mouse</td>
			<td>Thermo Fisher Scientific</td>
			<td>A-21202</td>
			<td>Fluorescence-tagged secondary antibody</td>
		</tr>
		<tr>
			<td>AlexaFluor 568 &#945;-Rabbit</td>
			<td>Thermo Fisher Scientific</td>
			<td>A10042</td>
			<td>Fluorescence-tagged secondary antibody</td>
		</tr>
		<tr>
			<td>Alpha Minimum Essential Medium</td>
			<td>Thermo Fisher Scientific</td>
			<td>11-095-080</td>
			<td>Base of culture media</td>
		</tr>
		<tr>
			<td>Collagenase I</td>
			<td>Worthington Bio</td>
			<td>LS004197</td>
			<td>For dissociation solution 1</td>
		</tr>
		<tr>
			<td>Corning Matrigel Membrane Matrix, LDEV-free</td>
			<td>Corning</td>
			<td>354234</td>
			<td>Extracellular matrix used for casting 2D and 3D ECM culture gels</td>
		</tr>
		<tr>
			<td>Countess Cell counter</td>
			<td>Thermo Fisher Scientific</td>
			<td>C10227</td>
			<td>Autmated cell counter (hemacytometer machine)</td>
		</tr>
		<tr>
			<td>Countess Cell Counting Chamber Slides</td>
			<td>Thermo Fisher Scientific</td>
			<td>C10228</td>
			<td>Hemacytometer slide for use with Countess automated counter</td>
		</tr>
		<tr>
			<td>DDX4 primary antibody</td>
			<td>Abcam</td>
			<td>138540</td>
			<td>Spermatogonia marker, 1:500 dilution</td>
		</tr>
		<tr>
			<td>Deoxyribonuclease I (2,280 u/mgDW)</td>
			<td>Worthington Bio</td>
			<td>LS002140</td>
			<td>For dissociation solution 1</td>
		</tr>
		<tr>
			<td>DPBS 1X, + CaCl + MgCl</td>
			<td>Thermo Fisher Scientific</td>
			<td>14040182</td>
			<td>For reconstituting Hyaluronidase</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Phosphate Buffered Saline +Ca/+Mg</td>
			<td>Thermo Fisher Scientific</td>
			<td>14040117</td>
			<td>PBS</td>
		</tr>
		<tr>
			<td>Embryo Grade H2O</td>
			<td>MIllipore Sigma</td>
			<td>W1503</td>
			<td>For reconstituting Collagenase I and Dnase I</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Thermo Fisher Scientific</td>
			<td>16000044</td>
			<td>For quencing enzyme dissocation solutions</td>
		</tr>
		<tr>
			<td>Follicle stimulating hormone</td>
			<td>Abcam</td>
			<td>ab51888</td>
			<td>For long-term organoid culture</td>
		</tr>
		<tr>
			<td>Human chorionic gonadotropin</td>
			<td>Millipore Sigma</td>
			<td>C1063</td>
			<td>For long-term organoid culture</td>
		</tr>
		<tr>
			<td>Hyaluronidase, from bovine testes</td>
			<td>Millipore Sigma</td>
			<td>H4272</td>
			<td>For dissociation solution 2</td>
		</tr>
		<tr>
			<td>Inhibin B Enzyme-linked Immunosorbent Assay</td>
			<td>Ansh Labs</td>
			<td>AL-107</td>
			<td>Inhibin B ELISA Kit</td>
		</tr>
		<tr>
			<td>KnockOut Serum Replacement</td>
			<td>Thermo Fisher Scientific</td>
			<td>10828-028</td>
			<td>Serum source for Basal media</td>
		</tr>
		<tr>
			<td>MicroTissues 3D Petri Dish micro-mold spheroids (24-35, 5x7 array)</td>
			<td>Millipore Sigma</td>
			<td>Z764051</td>
			<td>For 3D ECM-Free organoid fabrication</td>
		</tr>
		<tr>
			<td>Nunc, Lab Tek II Chamber Slide System, 4-well</td>
			<td>Thermo Fisher Scientific</td>
			<td>12-565-7</td>
			<td>For 2D ECM-free, and 2D, 3D ECM culture</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Thermo Fisher Scientific</td>
			<td>15-140-122</td>
			<td>Antibiotic for media</td>
		</tr>
		<tr>
			<td>Richard-Allan Scientific; Histogel, Specimen processing gel</td>
			<td>Thermo Fisher Scientific</td>
			<td>HG-4000-012</td>
			<td>For aiding paraffin embedding</td>
		</tr>
		<tr>
			<td>SOX9 primary antibody</td>
			<td>Millipore Sigma</td>
			<td>AB5535</td>
			<td>Sertoli Marker, 1:500 dilution</td>
		</tr>
		<tr>
			<td>Tedklad Global Mouse Chow (Breeder)</td>
			<td>Teklad Global</td>
			<td>2920</td>
			<td>Mouse food without phytoestrogens</td>
		</tr>
		<tr>
			<td>Tedklad Global Mouse Chow (Maintenance)</td>
			<td>Teklad Global</td>
			<td>2916</td>
			<td>Mouse food without phytoestrogens</td>
		</tr>
		<tr>
			<td>Testosterone Enzyme-linked Immunosorbent Assay</td>
			<td>Calbiotech</td>
			<td>TE373S</td>
			<td>Testosterone ELISA Kit</td>
		</tr>
		<tr>
			<td>Trypan Blue Solution, 0.4%</td>
			<td>Thermo Fisher Scientific</td>
			<td>15250061</td>
			<td>For cell counting</td>
		</tr>
		<tr>
			<td>&#945;SMA primary antibody</td>
			<td>Millipore Sigma</td>
			<td>A2547</td>
			<td>Peritubular marker, 1:500 dilution</td>
		</tr>
		<tr>
			<td>&#946;Catenin primary antibody</td>
			<td>BD Biosciences</td>
			<td>610154</td>
			<td>Sertoli Cytoplasm marker, 1:100 dilution</td>
		</tr>
	</tbody>
</table>

extra cellular matrix-based and extra cellular matrix-free generation of murine testicular organoids

Testicular organoids provide a tool for studying testicular development, spermatogenesis, and endocrinology in vitro. Several methods have been developed in order to create testicular organoids. Many of these methods rely upon extracellular matrix (ECM) to promote de novo tissue assembly, however, there are differences between methods in terms of biomimetic morphology and function of tissues. Moreover, there are few direct comparisons of published methods. Here, a direct comparison is made by studying differences in organoid generation protocols, with provided outcomes. Four archetypal generation methods: (1) 2D ECM-free, (2) 2D ECM, (3) 3D ECM-free, and (4) 3D ECM culture are described. Three primary benchmarks were used to assess the testicular organoid generation. These are cellular self-assembly, inclusion of major cell types (Sertoli, Leydig, germ, and peritubular cells), and appropriately compartmentalized tissue architecture. Of the four environments tested, 2D ECM and 3D ECM-free cultures generated organoids with internal morphologies most similar to native testes, including the de novo compartmentalization of tubular versus interstitial cell types, the development of tubule-like-structures, and an established long-term endocrine function. All methods studied utilized unsorted, primary murine testicular cell suspensions and used commonly accessible culture resources. These testicular organoid generation techniques provide a highly accessible and reproducible toolkit for research initiatives into testicular organogenesis and physiology in vitro.

Organoid generation was considered unsuccessful if testicular cells did not self-assemble within 72 h of culture, however, all methods presented here assemble within 24 h when using juvenile (5 dpp) murine cells. Failure of biological construct generation presented as a continuation of freely suspended cells (0 h column in Figure 1) even after extended culture (72 h). In the absence of tissue self-assembly, any apparent cell clusters easily dispersed into individual cells upon even gentle ma...

Watch this Scientific Journal Video about Extra Cellular Matrix-Based and Extra Cellular Matrix-Free Generation of Murine Testicular Organoids at JoVE.com

Extra Cellular Matrix-Based and Extra Cellular Matrix-Free Generation of Murine Testicular Organoids

Here, four methods for generating testicular organoids from primary neonatal murine testicular cells are described i.e., extracellular matrix (ECM) and ECM-free 2D and 3D culture environments. These techniques have multiple research applications and are especially useful for studying testicular development and physiology in vitro.

Testicular organoids provide a tool for studying testicular development, spermatogenesis, and endocrinology in vitro. Several methods have been developed ...

These protocols enable the user to produce a large number of structurally mimetic and endocrine functional testicular organoids in both ECM and DCM-free environments in 2D or 3D culture conditions. These techniques are highly reproducible, easily applied to standard biological laboratory settings, and only utilize common tools and materials. Testicular organoids are a novel tool for simulating spermatogenesis and reproductive endocrinology in vitro, and might one day enable the study of in vitro gametogenesis.Begin by placing the euthanized mouse supine on a dissection mat and sterilizing the abdomen with 70%ethanol. Tent the skin of the lower abdomen with forceps and open it with scissors. Locate the testes in the lower left and right inguinal regions of the abdomen and cut their connections to the vas deferens and any anchoring connective tissue.Then lift the entire testes from the animal. Place it in a Petri dish of pre-equilibrated BM.Under a dissection microscope, make a small incision in the tunica albuginea on one end of each testis with either small micro dissection scissors or by gently tearing with two fine forceps. While holding the testis from the opposite end of the incision, gently squeeze it with fine forceps and push in a sweeping motion towards the hole in the tunica, which will release the testicular tissue as one cohesive piece.Cut the tissue into smaller pieces. Place the pieces into one milliliter of prewarm dissociation solution one and incubate them at 37 degrees Celsius for 10 minutes. After the incubation, gently triturate the testes pieces 50 times with a P1000 pipette.Ensure that the tubules separate from one another and from the interstitial tissue. If clumps remain, incubate for an additional five minutes and triturate again. Add 33 microliters of hyaluronidase stock solution per one milliliter of the dissociation mixture.Then triturate 50 times with a P1000 pipette and incubate the sample at 37 degrees Celsius for five minutes. After the incubation, triturate it 50 times with a P200 pipette. After ensuring that no visible tubules or clumps of cells are present, quench the dissociation enzymes by adding FBS to 10%of the total volume of the sample and triturate it several times with a P200 pipette.Wet the center of a 40 micrometer cell strainer with media and aspirate it away, then add the sample to the pre-wetted strainer and filter it to produce a single-cell suspension. Centrifuge the suspension at 100 times g for seven minutes. Discard the supernatant and resuspend the cells in fresh BM.Count the viable cells on a hemocytometer using trypan blue exclusion, then re-centrifuge and resuspend them in fresh BM.For 2D ECM-free culture, plate single-cell suspensions directly onto four-well chamber slides and place the slides into a 35 degree Celsius incubator.For 2D ECM-culture, dispense 100 microliters of cold one-to-one diluted extracellular matrix medium into a four-well chamber slide, ensuring that the gel covers the dish bottom. Place the slide in the incubator for a minimum of 30 minutes to allow the ECM to polymerize into a gel, then add the cell suspension on top. For a 3D ECM-free culture, place agarose 3D Petri dishes into a 24-well culture dish and cover them with one milliliter of BM.Let the dishes equilibrate in BM for at least 30 minutes in a 35 degree Celsius incubator, then discard the BM and repeat the equilibration once more with one milliliter of fresh BM.Remove all BM from the well and dispense 200 microliters of fresh BM around but not inside the center recess of the 3D Petri dish, then collect any remaining BM from inside the center cell seeding recess of the micro well insert.Dispense the single-cell suspension into the center recess and gently triturate up and down. Place the dish into a humidified 35 degree Celsius incubator for culture. On the next day, slowly and carefully remove existing media from around the agarose 3D Petri dish and replace with one milliliter of fresh BM.The organoids should have compacted overnight, allowing them to rest at the bottom.For 3D ECM culture, prepare a single-cell suspension by combining equal parts of the cell suspension in BM with cold pre-thawed ECM. Triturate several times to ensure it is well mixed. Then immediately dispense the mixture into a four-well chamber slide, ensuring that it covers the entire bottom of the plate.Incubate the chamber slides at 35 degrees Celsius and allow its contents to polymerize for at least 30 minutes. After the polymerization, add 500 microliters of BM on top of the culture. Culture all organoid model types at 35 degrees Celsius.For all culture types, exchange half of their media with fresh BM every two days. This protocol was used to achieve organoid generation within 24 hours using juvenile murine testicular cells. Successfully generated tissues were initially observed as 3D cell clusters.In ECM environments, the cell clusters possessed clear margins between the cluster and their surrounding environment. Cell clusters were also observed to migrate across the ECM and fuse together. The 3D ECM culture required significantly more time to assemble de novo structures than all other culture methods.And the 3D ECM-free culture produced the largest clusters with a single large and compact cluster within each well of the 3D agarose Petri dish. To assess whether the organoid models resemble the native tissue, the biological constructs were probed for cell-specific markers and visualized with immunofluorescence. The 2D ECM and 3D ECM-free methods produced organoids with an inner morphology highly mimetic of testicular compartmentalization.A long-term analysis was performed on the 3D ECM-free assembled organoids. The organoids were cultured for 14 days and then probed for cell and structure-specific markers. Tubule-like structures were observed.The 3D ECM-free organoids were also studied for endocrine function in a 12-week culture with gonadotropin stimulation. Testosterone and inhibin B were both quantified from organoid-conditioned medium. After 12 weeks, gonadotropins were removed for 48 hours, causing testosterone and inhibin B concentrations to decrease.When the gonadotropins were returned, both hormone concentrations significantly increased, demonstrating proper endocrine responsiveness. Organoid assembly takes advantage of the autonomous behavior of viable immature testicular cells. Creative experiments can be easily devised through using customized cell sorted or hybrid cell mixtures.Following cell seeding, live video imaging or time-lapse imaging can be used to quantify organoid self-assembly. Across culture, organoids and condition medium can be collected for histological and amino assay analyses.

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Research

JoVE Journal

Developmental Biology

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

Mouse genetics offers a powerful tool determining the role of specific genes during development. Analyzing the resulting phenotypes by immunohistochemical and molecular methods provides information of potential target genes and signaling pathways. To further elucidate specific regulatory mechanisms requires a system allowing the manipulation of only a small number of cells of a specific tissue by either overexpression, ablation or re-introduction of specific genes and follow their fate during development. To achieve this ex utero electroporation of hippocampal structures, especially the dentate gyrus, followed by organotypic slice culture provides such a tool. Using this system to generate mosaic deletions allows determining whether the gene of interest regulates cell-autonomously developmental processes like progenitor cell proliferation or neuronal differentiation. Furthermore it facilitates the rescue of phenotypes by re-introducing the deleted gene or its target genes. In contrast to in utero electroporation the ex utero approach improves the rate of successfully targeting deeper layers of the brain like the dentate gyrus. Overall ex utero electroporation and organotypic slice culture provide a potent tool to study regulatory mechanisms in a semi-native environment mirroring endogenous conditions.

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

Here we present a protocol providing a tool to examine regulatory mechanisms of specific genes during hippocampal development. Employing ex utero electroporation and organotypic slice culture allows the up- and down-regulation of the expression of genes of interest in single cells and follow their fate during development.

Mouse genetics offers a powerful tool determining the role of specific genes during development. Analyzing the resulting phenotypes by immunohistochemical ...

Generation of Genetically Modified Organotypic Skin Cultures Using Devitalized Human Dermis

Organotypic cultures allow the reconstitution of a 3D environment critical for cell-cell contact and cell-matrix interactions which mimics the function and physiology of their in vivo tissue counterparts. This is exemplified by organotypic skin cultures which faithfully recapitulates the epidermal differentiation and stratification program. Primary human epidermal keratinocytes are genetically manipulable through retroviruses where genes can be easily overexpressed or knocked down. These genetically modified keratinocytes can then be used to regenerate human epidermis in organotypic skin cultures providing a powerful model to study genetic pathways impacting epidermal growth, differentiation, and disease progression. The protocols presented here describe methods to prepare devitalized human dermis as well as to genetically manipulate primary human keratinocytes in order to generate organotypic skin cultures. Regenerated human skin can be used in downstream applications such as gene expression profiling, immunostaining, and chromatin immunoprecipitations followed by high throughput sequencing. Thus, generation of these genetically modified organotypic skin cultures will allow the determination of genes that are critical for maintaining skin homeostasis.

The goal of this paper is to provide a comprehensive and detailed protocol on how to generate genetically modified human organotypic skin from epidermal keratinocytes and devitalized human dermis.

Organotypic cultures allow the reconstitution of a 3D environment critical for cell-cell contact and cell-matrix interactions which mimics the function ...

Isolation of Murine Embryonic Hemogenic Endothelial Cells

The specification of hemogenic endothelial cells from embryonic vascular endothelium occurs during brief developmental periods within distinct tissues, and is necessary for the emergence of definitive HSPC from the murine extra embryonic yolk sac, placenta, umbilical vessels, and the embryonic aorta-gonad-mesonephros (AGM) region. The transient nature and small size of this cell population renders its reproducible isolation for careful quantification and experimental applications technically difficult. We have established a fluorescence-activated cell sorting (FACS)-based protocol for simultaneous isolation of hemogenic endothelial cells and HSPC during their peak generation times in the yolk sac and AGM. We demonstrate methods for dissection of yolk sac and AGM tissues from mouse embryos, and we present optimized tissue digestion and antibody conjugation conditions for maximal cell survival prior to identification and retrieval via FACS. Representative FACS analysis plots are shown that identify the hemogenic endothelial cell and HSPC phenotypes, and describe a methylcellulose-based assay for evaluating their blood forming potential on a clonal level.

Hematopoietic stem and progenitor cells (HSPC) derive from specialized (hemogenic) endothelial cells during development, yet little is known about the process by which some endothelial cells specify to become blood forming. We demonstrate a flow-cytometry based method allowing simultaneous isolation of hemogenic endothelial cells and HSPC from murine embryonic tissues.

The specification of hemogenic endothelial cells from embryonic vascular endothelium occurs during brief developmental periods within distinct tissues, ...

Evaluation of Injury-induced Senescence and In Vivo Reprogramming in the Skeletal Muscle

Cellular senescence is a stress response that is characterized by a stable cellular growth arrest, which is important for many physiological and pathological processes, such as cancer and ageing. Recently, senescence has also been implicated in tissue repair and regeneration. Therefore, it has become increasingly critical to identify senescent cells in vivo. Senescence-associated &#946;-galactosidase (SA-&#946;-Gal) assay is the most widely used assay to detect senescent cells both in culture and in vivo. This assay is based on the increased lysosomal contents in the senescent cells, which allows the histochemical detection of lysosomal &#946;-galactosidase activity at suboptimum pH (6 or 5.5). In comparison with other assays, such as flow cytometry, this allows the identification of senescent cells in their resident environment, which offers valuable information such as the location relating to the tissue architecture, the morphology, and the possibility of coupling with other markers via immunohistochemistry&#160;(IHC). The major limitation of the SA-&#946;-Gal assay is the requirement of fresh or frozen samples.
Here, we present a detailed protocol to understand how cellular senescence promotes cellular plasticity and tissue regeneration in vivo. We use SA-&#946;-Gal to detect senescent cells in the skeletal muscle upon injury, which is a well-established system to study tissue regeneration. Moreover, we use&#160;IHC to detect Nanog, a marker of pluripotent stem cells, in a transgenic mouse model. This protocol enables us to examine and quantify cellular senescence in the context of induced cellular plasticity and in vivo reprogramming.

Evaluation of Injury-induced Senescence and In Vivo Reprogramming in the Skeletal Muscle

Here we present a detailed protocol to detect both senescent and pluripotent stem cells in the skeletal muscle upon injury while inducing in vivo reprogramming. This method is suitable for evaluating the role of cellular senescence during tissue regeneration and reprogramming in vivo.

Cellular senescence is a stress response that is characterized by a stable cellular growth arrest, which is important for many physiological and ...

In Vivo Tracking of Human Adipose-derived Mesenchymal Stem Cells in a Rat Knee Osteoarthritis Model with Fluorescent Lipophilic Membrane Dye

In order to support the clinical application of human adipose-derived mesenchymal stem cell (haMSC) therapy for knee osteoarthritis (KOA), we examined the efficacy of cell persistence and biodistribution of haMSCs in animal models. We demonstrated a method to label the cell membrane of haMSCs with lipophilic fluorescent dye. Subsequently, intra-articular injection of the labeled cells in rats with surgically induced KOA was monitored dynamically by an in vivo imaging system. We employed the lipophilic carbocyanines DiD (DilC18 (5)), a far-red fluorescent Dil (dialkylcarbocyanines) analog, which utilized a red laser to avoid excitation of the natural green autofluorescence from surrounding tissues. Furthermore, the red-shifted emission spectra of DiD allowed deep-tissue imaging in live animals and the labeling procedure caused no cytotoxic effects or functional damage to haMSCs. This approach has been shown to be an efficient tracking method for haMSCs in a rat KOA model. The application of this method could also be used to determine the optimal administration route and dosage of MSCs from other sources in pre-clinical studies.

In Vivo Tracking of Human Adipose-derived Mesenchymal Stem Cells in a Rat Knee Osteoarthritis Model with Fluorescent Lipophilic Membrane Dye

This protocol describes an efficient way to monitor the cell persistence and biodistribution of human adipose-derived mesenchymal stem cells (haMSCs) by far-red fluorescence labeling in a rat knee osteoarthritis (KOA) model via intra-articular (IA) injection.

In order to support the clinical application of human adipose-derived mesenchymal stem cell (haMSC) therapy for knee osteoarthritis (KOA), we examined the ...

Visualization of Cellular Electrical Activity in Zebrafish Early Embryos and Tumors

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling processes of excitable neuronal and muscular cells and many other biological processes, such as embryonic developmental patterning. However, there is a need for in vivo electrical activity monitoring in vertebrate embryogenesis. The advances of genetically encoded fluorescent voltage indicators (GEVIs) have made it possible to provide a solution for this challenge. Here, we describe how to create a transgenic voltage indicator zebrafish using the established voltage indicator, ASAP1 (Accelerated Sensor of Action Potentials 1), as an example. The Tol2 kit and a ubiquitous zebrafish promoter, ubi, were chosen in this study. We also explain&#160;the processes of Gateway site-specific cloning, Tol2 transposon-based zebrafish transgenesis, and the imaging process for early-stage fish embryos and fish tumors using regular epifluorescent microscopes. Using this fish line, we found that there are cellular electric voltage changes during zebrafish embryogenesis, and fish larval movement. Furthermore, it was observed that in a few zebrafish malignant peripheral nerve sheath tumors, the tumor cells were generally polarized compared to the surrounding normal tissues.

Here, we show the process of creating a cellular electric voltage reporter zebrafish line to visualize embryonic development, movement, and fish tumor cells in vivo.

Bioelectricity, endogenous electrical signaling mediated by ion channels and pumps located on the cell membrane, plays important roles in signaling ...

Generation of Scaffold-free, Three-dimensional Insulin Expressing Pancreatoids from Mouse Pancreatic Progenitors In Vitro

The pancreas is a complex organ composed of many different cell types that work together to regulate blood glucose homeostasis and digestion. These cell types include enzyme-secreting acinar cells, an arborized ductal system responsible for the transportation of enzymes to the gut, and hormone-producing endocrine cells. 
Endocrine beta-cells are the sole cell type in the body that produce insulin to lower blood glucose levels. Diabetes, a disease characterized by a loss or the dysfunction of beta-cells, is reaching epidemic proportions. Thus, it is essential to establish protocols to investigate beta-cell development that can be used for screening purposes to derive the drug and cell-based therapeutics. While the experimental investigation of mouse development is essential, in vivo studies are laborious and time-consuming. Cultured cells provide a more convenient platform for screening; however, they are unable to maintain the cellular diversity, architectural organization, and cellular interactions found in vivo. Thus, it is essential to develop new tools to investigate pancreatic organogenesis and physiology.
Pancreatic epithelial cells develop in the close association with mesenchyme from the onset of organogenesis as cells organize and differentiate into the complex, physiologically competent adult organ. The pancreatic mesenchyme provides important signals for the endocrine development, many of which are not well understood yet, thus difficult to recapitulate during the in vitro culture. Here, we describe a protocol to culture three-dimensional, cellular complex mouse organoids that retain mesenchyme, termed pancreatoids. The e10.5 murine pancreatic bud is dissected, dissociated, and cultured in a scaffold-free environment. These floating cells self-assemble with mesenchyme enveloping the developing pancreatoid and a robust number of endocrine beta-cells developing along with the acinar and the duct cells. This system can be used to study the cell fate determination, structural organization, and morphogenesis, cell-cell interactions during organogenesis, or for the drug, small molecule, or genetic screening.

Generation of Scaffold-free, Three-dimensional Insulin Expressing Pancreatoids from Mouse Pancreatic Progenitors In Vitro

Here, we present a protocol to generate insulin expressing 3D murine pancreatoids from free-floating e10.5 dissociated pancreatic progenitors and the associated mesenchyme.

The pancreas is a complex organ composed of many different cell types that work together to regulate blood glucose homeostasis and digestion. These cell ...

Induction and Validation of Cellular Senescence in Primary Human Cells

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a hallmark of various pathophysiological conditions including tumor suppression, tissue remodeling and aging. The inducers of cellular senescence in vivo are still poorly characterized. However, a number of stimuli can be used to promote cellular senescence ex vivo. Among them, most common senescence-inducers are replicative exhaustion, ionizing and non-ionizing radiation, genotoxic drugs, oxidative stress, and demethylating and acetylating agents. Here, we will provide detailed instructions on how to use these stimuli to induce fibroblasts into senescence. This protocol can easily be adapted for different types of primary cells and cell lines, including cancer cells. We also describe different methods for the validation of senescence induction. In particular, we focus on measuring the activity of the lysosomal enzyme Senescence-Associated &#946;-galactosidase (SA-&#946;-gal), the rate of DNA synthesis using 5-ethynyl-2&#39;-deoxyuridine (EdU) incorporation assay, the levels of expression of the cell cycle inhibitors p16 and p21, and the expression and secretion of members of the Senescence-Associated Secretory Phenotype (SASP). Finally, we provide example results and discuss further applications of these protocols.

Here, we discuss a series of protocols for induction and validation of cellular senescence in cultured cells. We focus on different senescence-inducing stimuli and describe the quantification of common senescence-associated markers. We provide technical details using fibroblasts as a model, but the protocols can be adapted to various cellular models.

Cellular senescence is a state of permanent cell cycle arrest activated in response to different damaging stimuli. Activation of cellular senescence is a ...

Generation of Organoids from Mouse Extrahepatic Bile Ducts

Cholangiopathies, which affect extrahepatic bile ducts (EHBDs), include biliary atresia, primary sclerosing cholangitis, and cholangiocarcinoma. They have no effective therapeutic options. Tools to study EHBD are very limited. Our purpose was to develop an organ-specific, versatile, adult stem cell-derived, preclinical cholangiocyte model that can be easily generated from wild type and genetically engineered mice. Thus, we report on the novel technique of developing an EHBD organoid (EHBDO) culture system from adult mouse EHBDs. The model is cost-efficient, able to be readily analyzed, and has multiple downstream applications. Specifically, we describe the methodology of mouse EHBD isolation and single cell dissociation, organoid culture initiation, propagation, and long-term maintenance and storage. This manuscript also describes EHBDO processing for immunohistochemistry, fluorescent microscopy, and mRNA abundance quantitation by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). This protocol has significant advantages in addition to producing EHBD-specific organoids. The use of a conditioned medium from L-WRN cells significantly reduces the cost of this model. The use of mouse EHBDs provides almost unlimited tissue for culture generation, unlike human tissue. Generated mouse EHBDOs contain a pure population of epithelial cells with markers of endodermal progenitor and differentiated biliary cells. Cultured organoids maintain homogenous morphology through multiple passages and can be recovered after a long-term storage period in liquid nitrogen. The model allows for the study of biliary progenitor cell proliferation, can be manipulated pharmacologically, and may be generated from genetically engineered mice. Future studies are needed to optimize culture conditions in order to increase plating efficiency, evaluate functional cell maturity, and direct cell differentiation. Development of co-culture models and a more biologically neutral extracellular matrix are also desirable.

This protocol describes the production of a mouse extrahepatic bile duct 3-dimensional organoid system. These biliary organoids can be maintained in culture to study cholangiocyte biology. Biliary organoids express markers of both progenitor and biliary cells and are composed of polarized epithelial cells.

Cholangiopathies, which affect extrahepatic bile ducts (EHBDs), include biliary atresia, primary sclerosing cholangitis, and cholangiocarcinoma. They have ...

Generation of Multicellular Human Primary Endometrial Organoids

The human endometrium is one of the most hormonally responsive tissues in the body and is essential for the establishment of pregnancy. This tissue can also become diseased and cause morbidity and even death. Model systems to study human endometrial biology have been limited to in vitro culture systems of single cell types. In addition, the epithelial cells, one of the major cell types of the endometrium, do not propagate well or retain their physiological traits in culture, and thus our understanding of endometrial biology remains limited. We have generated, for the first time, endometrial organoids that consist of both epithelial and stromal cells of the human endometrium. These organoids do not require any exogenous scaffold materials and specifically organize so that epithelial cells encompass the spheroid-like structure and become polarized with stromal cells in the center that produce and secrete collagen. Estrogen, progesterone and androgen receptors are expressed in the epithelial and stromal cells and treatment with physiological levels of estrogen and testosterone promote the organization of the organoids. This new model system can be used to study normal endometrial biology and disease in ways that were not possible before.

A protocol to generate human primary endometrial organoids that consist of epithelial and stromal cells and retain characteristics of the native endometrial tissue is presented. This protocol describes methods from uterine tissue acquisition to the histologic processing of endometrial organoids.

The human endometrium is one of the most hormonally responsive tissues in the body and is essential for the establishment of pregnancy. This tissue can ...