This research was supported by CIRM (DISC2COVID19-12022).

Airway Model for Studying Lung Barrier Integrity, Disease, and Drug Discovery

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The authors have nothing to disclose.

The development and implementation of a model of the blood-air barrier in the large airways for studying viral infections and other toxins require meticulous attention to detail to ensure the successful differentiation and function of the various cell types involved. This discussion will address key factors for successful differentiation, potential challenges, alternative applications, and implications for studying human diseases. 
To ensure a successful differentiation, attention to the type ...

The blood-air barrier in the large airways includes the trachea, bronchi, and bronchioles. It plays a crucial role in maintaining respiratory health and is made up of the airway epithelium, basement membrane, blood vessels and endothelial cells, and immune cells. The primary epithelial cells in the airway encompass basal cells, club cells, ciliated cells, and goblet cells. Basal cells, acting as the stem cells of the airway epithelium, are multipotent progenitors with high proliferative and self-renewal capabilities, giving rise to mature airway epithelial cells1. Club cells are non-ciliated, secretory cells that contribute to the maintenance of the airway lining by secreting protective proteins and surfactants2. Goblet cells, located in the lumen and in the submucosal glands, secrete mucins to trap debris and safeguard the airway3. Ciliated cells are integral to the mucociliary escalator mechanism, preventing the accumulation of harmful microorganisms4. The basement membrane is made up of an extracellular matrix, which provides structural support5. The trachea and the rest of the airway are surrounded by a rich network of blood vessels, which are lined with endothelial cells that play a vital role in supporting tracheal function by supplying nutrients and oxygen, removing waste, regulating inflammation, and contributing to tissue repair and angiogenesis6. Finally, airway macrophages are tissue-specific immune cells, essential for protecting the respiratory system from infections, clearing inhaled particles, and maintaining a balanced immune response7.
The coordinated actions of epithelial, mesenchymal, endothelial cells, and macrophage cells are critical for an effective immune response to pathogens in the airway8. Epithelial cells form the first line of defense against viral infections by acting as a physical barrier, with tight junctions restricting the passage of harmful substances. The coordinated action of ciliated cells and goblet cells helps to trap and remove inhaled particles, pathogens, and debris4. Additionally, airway epithelial cells produce cytokines and chemokines to recruit immune cells9. Endothelial cells maintain vascular integrity, preventing the spread of viral particles through the bloodstream, upregulate adhesion molecules (VCAM-1) to facilitate immune cell adhesion and produce pro-inflammatory cytokines to recruit immune cells from the bloodstream to the site of infection10. Airway macrophages engulf and digest viral particles, infected cells, and debris, present viral antigens to T cells, and produce cytokines to activate and recruit other immune cells, along with type I interferons to inhibit viral replication11. The coordinated actions of epithelial, mesenchymal, endothelial, and macrophage cells create a robust and dynamic defense system that protects the airway from viral infections and maintains respiratory health.
Understanding the dynamic interactions among various cell types in the human lung is crucial for comprehending the lung&#39;s response to viral infections, inflammatory diseases, and drug delivery. In vitro co-cultures allow for the study of cell-cell signaling between the epithelium, endothelial cells, and innate immune cells12. We developed the first authentic multi-cell type lung model derived from patient-specific hiPSCs13. This incorporates both epithelial and mesenchymal cell populations, formed in a 3D orientation. Subsequently, the lung progenitor cells can be differentiated into an &#34;airway organoid&#34;14, cultured onto sterile cell culture inserts, and exposed to an air-liquid interface (ALI), replicating the conditions of the human airway15,16,17. iPSC-derived endothelial cells are cultured on the basolateral side of the membrane, mimicking their orientation in the human airway, situated below the epithelial/mesenchymal layer in the basement membrane. Finally, iPSC-derived macrophages are added to the apical side of the membrane, interacting with epithelial cells and awaiting activation signals (Figure 1A). This model accurately reproduces the biology and function of the airway. We posit that hiPSC-derived, patient-specific, authentic multi-cell type iAirway cultures are best suited to elucidate the intrinsic, acute response of the airway barrier and pathogens, including viral infections. For instance, this model can be used to (1) study viral entry and replication, (2) investigate the initial immune response by epithelial and tissue-specific immune cells, (3) examine barrier integrity and function, (4) test the efficacy of therapeutic agents, and (5) study cellular and molecular mechanisms of pathogenesis in a patient-specific model.
This article describes a detailed protocol for preparing multi-cellular lung co-cultures to study cellular responses to viral infections.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>12 well plates</td>
			<td>Corning</td>
			<td>3512</td>
			<td></td>
		</tr>
		<tr>
			<td>12-well inserts, 0.4 &#181;m, translucent&#160;</td>
			<td>VWR</td>
			<td>10769-208</td>
			<td></td>
		</tr>
		<tr>
			<td>2-mercaptoethanol&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>M3148</td>
			<td></td>
		</tr>
		<tr>
			<td>Accutase</td>
			<td>Innovative Cell Tech</td>
			<td>AT104</td>
			<td></td>
		</tr>
		<tr>
			<td>Activin A</td>
			<td>R&#38;D Systems</td>
			<td>338-AC</td>
			<td></td>
		</tr>
		<tr>
			<td>All-trans retinoic acid (RA)&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>R2625</td>
			<td></td>
		</tr>
		<tr>
			<td>ascorbic acid</td>
			<td>Sigma</td>
			<td>A4544</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 without retinoic acid&#160;</td>
			<td>ThermoFisher</td>
			<td>12587010</td>
			<td></td>
		</tr>
		<tr>
			<td>BMP4&#160;</td>
			<td>R&#38;D Systems</td>
			<td>314-BP/CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA) Fraction V, 7.5% solution&#160;</td>
			<td>Gibco</td>
			<td>15260-037</td>
			<td></td>
		</tr>
		<tr>
			<td>Br-cAMP</td>
			<td>Sigma-Aldrich</td>
			<td>B5386</td>
			<td></td>
		</tr>
		<tr>
			<td>CD 14 (FITC)</td>
			<td>BioLegend</td>
			<td>982502</td>
			<td></td>
		</tr>
		<tr>
			<td>CD 31 PECAM-1(APC)</td>
			<td>R&#38;D System</td>
			<td>FAB3567A</td>
			<td></td>
		</tr>
		<tr>
			<td>CD 45 (PE)</td>
			<td>BD Biosciences</td>
			<td>560975</td>
			<td></td>
		</tr>
		<tr>
			<td>CD 68 (PE)</td>
			<td>BioLegend</td>
			<td>33808</td>
			<td></td>
		</tr>
		<tr>
			<td>CHIR99021&#160;</td>
			<td>Abcam</td>
			<td>ab120890</td>
			<td></td>
		</tr>
		<tr>
			<td>CPM</td>
			<td>Fujifilm</td>
			<td>014-27501</td>
			<td></td>
		</tr>
		<tr>
			<td>Dexamethasone&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>D4902</td>
			<td></td>
		</tr>
		<tr>
			<td>Dispase&#160;</td>
			<td>StemCellTech</td>
			<td>7913</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/F12&#160;</td>
			<td>Gibco</td>
			<td>10565042</td>
			<td></td>
		</tr>
		<tr>
			<td>Dorsomorphin</td>
			<td>R&#38;D Systems</td>
			<td>3093</td>
			<td></td>
		</tr>
		<tr>
			<td>E-CAD/CD 324 (APC)</td>
			<td>BioLegend</td>
			<td>324107</td>
			<td></td>
		</tr>
		<tr>
			<td>EGF</td>
			<td>R&#38;D Systems</td>
			<td>236-EG</td>
			<td></td>
		</tr>
		<tr>
			<td>EGM2 Medium</td>
			<td>Lonza</td>
			<td>CC-3162</td>
			<td></td>
		</tr>
		<tr>
			<td>EPCAM/CD 326 (APC)</td>
			<td>BioLegend</td>
			<td>324212</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS&#160;</td>
			<td>Gibco</td>
			<td>10082139</td>
			<td></td>
		</tr>
		<tr>
			<td>FGF10</td>
			<td>R&#38;D Systems</td>
			<td>345-FG/CF</td>
			<td></td>
		</tr>
		<tr>
			<td>FGF7</td>
			<td>R&#38;D Systems</td>
			<td>251-KG/CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibronectin</td>
			<td>Fisher</td>
			<td>356008</td>
			<td></td>
		</tr>
		<tr>
			<td>Forskolin</td>
			<td>Abcam</td>
			<td>ab120058</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutamax&#160;</td>
			<td>Life Technologies</td>
			<td>35050061</td>
			<td></td>
		</tr>
		<tr>
			<td>Ham&#8217;s F12&#160;</td>
			<td>Invitrogen</td>
			<td>11765-054</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Gibco</td>
			<td>15630-080</td>
			<td></td>
		</tr>
		<tr>
			<td>IBMX (3-Isobtyl-1-methylxanthine)</td>
			<td>Sigma-Aldrich</td>
			<td>I5879</td>
			<td></td>
		</tr>
		<tr>
			<td>IL-3</td>
			<td>Peprotech</td>
			<td>200-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Iscove&#8217;s Modified Dulbecco&#8217;s Medium (IMDM) + Glutamax&#160;</td>
			<td>Invitrogen</td>
			<td>31980030</td>
			<td></td>
		</tr>
		<tr>
			<td>Knockout Serum Replacement (KSR)</td>
			<td>Life Technologies</td>
			<td>10828028</td>
			<td></td>
		</tr>
		<tr>
			<td>Matrigel</td>
			<td>Corning</td>
			<td>354230</td>
			<td></td>
		</tr>
		<tr>
			<td>M-CSF</td>
			<td>Peprotech&#160;</td>
			<td>300-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Monothioglycerol&#160;</td>
			<td>Sigma</td>
			<td>M6145</td>
			<td></td>
		</tr>
		<tr>
			<td>mTeSR plus Kit (10/case)</td>
			<td>Stem Cell Tech</td>
			<td>5825</td>
			<td></td>
		</tr>
		<tr>
			<td>N2&#160;</td>
			<td>ThermoFisher</td>
			<td>17502048</td>
			<td></td>
		</tr>
		<tr>
			<td>NEAA</td>
			<td>Life Technologies</td>
			<td>11140050</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Gibco</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr>
			<td>Pen/strep</td>
			<td>Lonza</td>
			<td>17-602F</td>
			<td></td>
		</tr>
		<tr>
			<td>ReleSR</td>
			<td>Stem Cell Tech</td>
			<td>5872</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI1640 + Glutamax&#160;</td>
			<td>Life Technologies</td>
			<td>12633012</td>
			<td></td>
		</tr>
		<tr>
			<td>SB431542&#160;</td>
			<td>R&#38;D Systems</td>
			<td>1614</td>
			<td></td>
		</tr>
		<tr>
			<td>SCF</td>
			<td>PeproTech</td>
			<td>300-07</td>
			<td></td>
		</tr>
		<tr>
			<td>SMA</td>
			<td>Invitrogen</td>
			<td>50-9760-80</td>
			<td></td>
		</tr>
		<tr>
			<td>STEMdiff APEL 2 Medium</td>
			<td>STEMCELL Technologies</td>
			<td>5275</td>
			<td></td>
		</tr>
		<tr>
			<td>TrypLE Express</td>
			<td>Gibco</td>
			<td>12605-028</td>
			<td></td>
		</tr>
		<tr>
			<td>VEGF165</td>
			<td>Preprotech</td>
			<td>100-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Vimentin</td>
			<td>Cell Signaling</td>
			<td>5741S</td>
			<td></td>
		</tr>
		<tr>
			<td>Y-27632 (Rock Inhibitor)&#160;</td>
			<td>R&#38;D Systems</td>
			<td>1254/1</td>
			<td></td>
		</tr>
		<tr>
			<td>ZO-1</td>
			<td>Invitrogen</td>
			<td>339100</td>
			<td></td>
		</tr>
	</tbody>
</table>

ipsc-derived epithelial, mesenchymal, endothelial, and immune cell co-culture to model airway barrier integrity in lung health and disease

Human lung tissue is composed of an interconnected network of epithelium, mesenchyme, endothelium, and immune cells from the upper airway of the nasopharynx to the smallest alveolar sac. Interactions between these cells are crucial in lung development and disease, acting as a barrier against harmful chemicals and pathogens. Current in vitro co-culture models utilize immortalized cell lines with different biological backgrounds, which may not accurately represent the cellular milieu or interactions of the lung. We differentiated human iPSCs into 3D lung organoids (containing both epithelium and mesenchyme), endothelial cells, and macrophages. These were co-cultured in an air-liquid interface (ALI) format to form an epithelial/mesenchymal apical barrier invested with macrophages and a basolateral endothelial barrier (iAirway). iPSC-derived iAirways showed a reduction in barrier integrity in response to infection with respiratory viruses and cigarette toxins. This multi-lineage lung co-culture system provides a platform for studying cellular interactions, signaling pathways, and molecular mechanisms underlying lung development, homeostasis, and disease progression. iAirways closely mimic human physiology and cellular interactions, can be generated from patient-derived iPSC&#39;s, and can be customized to include different cell types of the airway. Overall, iPSC-derived iAirway models offer a versatile and powerful tool for studying barrier integrity to better understand genetic drivers for disease, pathogen response, immune regulation, and drug discovery or repurposing in vitro, with the potential to advance our understanding and treatment of airway diseases.

There are multiple stages at which the differentiation of iPSC-derived airway organoids, endothelial cells, immune cells, and co-cultures can be assessed as successfully completed. Differentiations can be performed in different iPSC lines, and this protocol has been tested in at least five different lines. The protocol does need to be adapted to every new iPSC line, specifically by modifying and optimizing the seeding density.
The successful yield of iPSC-derived airway organoids can be assess...

Author Spotlight: Modeling Human Airway Remodeling and Viral Responses Using Isogenic Epithelial, Endothelial, and Immune Cells

This article describes the generation of a complex, multi-cellular airway barrier model composed of induced pluripotent stem cell (iPSC)-derived lung epithelium, mesenchyme, endothelial cells, and macrophages in an air-liquid interface culture.

iPSC-Derived Epithelial, Mesenchymal, Endothelial, and Immune Cell Co-Culture to Model Airway Barrier Integrity in Lung Health and Disease

Human lung tissue is composed of an interconnected network of epithelium, mesenchyme, endothelium, and immune cells from the upper airway of the ...

ipsc-derived-epithelial-mesenchymal-endothelial-immune-cell-co

Research

JoVE Journal

Developmental Biology

617 Views.  Sanford Consortium for Regenerative Medicine. This article describes the generation of a complex, multi-cellular airway barrier model composed of induced pluripotent stem cell (iPSC)-derived lung epithelium, mesenchyme, endothelial cells, and macrophages in an air-liquid interface culture. 

Video: Author Spotlight: Modeling Human Airway Remodeling and Viral Responses Using Isogenic Epithelial, Endothelial, and Immune Cells

Culture and Co-Culture of Mouse Ovaries and Ovarian Follicles

The mammalian ovary is composed of ovarian follicles, each follicle consisting of a single oocyte surrounded by somatic granulosa cells, enclosed together within a basement membrane. A finite pool of follicles is laid down during embryonic development, when oocytes in meiotic arrest form a close association with flattened granulosa cells, forming primordial follicles. By or shortly after birth, mammalian ovaries contain their lifetime&#8217;s supply of primordial follicles, from which point onwards there is a steady release of follicles into the growing follicular pool.
The ovary is particularly amenable to development in vitro, with follicles growing in a highly physiological manner in culture. This work describes the culture of whole neonatal ovaries containing primordial follicles, and the culture of individual ovarian follicles, a method which can support the development of follicles from an immature through to the preovulatory stage, after which their oocytes are able to undergo fertilization in vitro. The work outlined here uses culture systems to determine how the ovary is affected by exposure to external compounds. We also describe a co-culture system, which allows investigation of the interactions that occur between growing follicles and the non-growing pool of primordial follicles.

This protocol describes the primary culture/co-culture of mouse ovarian tissue, using ovaries from neonatal mice and individual ovarian follicles from prepubertal mice. The culture techniques support development in a highly physiological manner, allowing investigation of the effect of extrinsic agents on the ovary, and of interactions between ovarian follicles.

The mammalian ovary is composed of ovarian follicles, each follicle consisting of a single oocyte surrounded by somatic granulosa cells, enclosed together ...

3D Organotypic Co-culture Model Supporting Medullary Thymic Epithelial Cell Proliferation, Differentiation and Promiscuous Gene Expression

Intra-thymic T cell development requires an intricate three-dimensional meshwork composed of various stromal cells, i.e., non-T cells. Thymocytes traverse this scaffold in a highly coordinated temporal and spatial order while sequentially passing obligatory check points, i.e., T cell lineage commitment, followed by T cell receptor repertoire generation and selection prior to their export into the periphery. The two major resident cell types forming this scaffold are cortical (cTECs) and medullary thymic epithelial cells (mTECs). A key feature of mTECs is the so-called promiscuous expression of numerous tissue-restricted antigens. These tissue-restricted antigens are presented to immature thymocytes directly or indirectly by mTECs or thymic dendritic cells, respectively resulting in self-tolerance.
Suitable in vitro models emulating the developmental pathways and functions of cTECs and mTECs are currently lacking. This lack of adequate experimental models has for instance hampered the analysis of promiscuous gene expression, which is still poorly understood at the cellular and molecular level. We adapted a 3D organotypic co-culture model to culture ex vivo isolated mTECs. This model was originally devised to cultivate keratinocytes in such a way as to generate a skin equivalent in vitro. The 3D model preserved key functional features of mTEC biology: (i) proliferation and terminal differentiation of CD80lo, Aire-negative into CD80hi, Aire-positive mTECs, (ii) responsiveness to RANKL, and (iii) sustained expression of FoxN1, Aire and tissue-restricted genes in CD80hi mTECs.

Studying medullary thymic epithelial cells in vitro has been largely unsuccessful, as current 2D culture systems do not mimic the in vivo scenario. The 3D culture system described herein - a modified skin organotypic culture model - has proven superior in recapitulating mTEC proliferation, differentiation and maintenance of promiscuous gene expression.

Intra-thymic T cell development requires an intricate three-dimensional meshwork composed of various stromal cells, i.e., non-T cells. Thymocytes traverse ...

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema and diminished visual acuity. However, human CECs are prone to compromised proliferative potential. Furthermore, stimulation of cell growth is often complicated by gradual endothelial-mesenchymal transition (EnMT). Therefore, understanding the mechanism of EnMT is necessary for facilitating the regeneration of CECs with competent function. In this study, we prepared a primary culture of bovine CECs by peeling the CECs with Descemet's membrane from the corneal button and demonstrated that bovine CECs exhibited the EnMT process, including phenotypic change, nuclear translocation of &#946;-catenin, and EMT regulators snail and slug, in the in vitro culture. Furthermore, we used a rat corneal endothelium cryoinjury model to demonstrate the EnMT process in vivo. Collectively, the in vitro primary culture of bovine CECs and in vivo rat corneal endothelium cryoinjury models offers useful platforms for investigating the mechanism of EnMT.

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

A primary culture of bovine corneal endothelial cells was used to investigate the mechanism of corneal endothelial-mesenchymal transition. Furthermore, a rat corneal endothelium cryoinjury model was used to demonstrate corneal endothelial-mesenchymal transition in vivo.

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema ...

Generation of iPSC-derived Human Brain Organoids to Model Early Neurodevelopmental Disorders

The restricted availability of suitable in vitro models that can reliably represent complex human brain development is a significant bottleneck that limits the translation of basic brain research into clinical application. While induced pluripotent stem cells (iPSCs) have replaced the ethically questionable human embryonic stem cells, iPSC-based neuronal differentiation studies remain descriptive at the cellular level but fail to adequately provide the details that could be derived from a complex, 3D human brain tissue. 
This gap is now filled through the application of iPSC-derived, 3D brain organoids, "Brains in a dish," that model many features of complex human brain development. Here, a method for generating iPSC-derived, 3D brain organoids is described. The organoids can help with modeling autosomal recessive primary microcephaly (MCPH), a rare human neurodevelopmental disorder. A widely accepted explanation for the brain malformation in MCPH is a depletion of the neural stem cell pool during the early stages of human brain development, a developmental defect that is difficult to recreate or prove in vitro. 
To study MCPH, we generated iPSCs from patient-derived fibroblasts carrying a mutation in the centrosomal protein CPAP. By analyzing the ventricular zone of microcephaly 3D brain organoids, we showed the premature differentiation of neural progenitors. These 3D brain organoids are a powerful in vitro system that will be instrumental in modeling congenital brain disorders induced by neurotoxic chemicals, neurotrophic viral infections, or inherited genetic mutations.

Modeling human brain development has been hindered due to the unprecedented complexity of neural epithelial tissue. Here, a method for the robust generation of brain organoids to delineate early events of human brain development and to model microcephaly in vitro is described.

The restricted availability of suitable in vitro models that can reliably represent complex human brain development is a significant bottleneck that ...

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 ...

Real-time Measurement of Epithelial Barrier Permeability in Human Intestinal Organoids

Advances in 3D culture of intestinal tissues obtained through biopsy or generated from pluripotent stem cells via directed differentiation, have resulted in sophisticated in vitro models of the intestinal mucosa. Leveraging these emerging model systems will require adaptation of tools and techniques developed for 2D culture systems and animals. Here, we describe a technique for measuring epithelial barrier permeability in human intestinal organoids in real-time. This is accomplished by microinjection of fluorescently-labeled dextran and imaging on an inverted microscope fitted with epifluorescent filters. Real-time measurement of the barrier permeability in intestinal organoids facilitates the generation of high-resolution temporal data in human intestinal epithelial tissue, although this technique can also be applied to fixed timepoint imaging approaches. This protocol is readily adaptable for the measurement of epithelial barrier permeability following exposure to pharmacologic agents, bacterial products or toxins, or live microorganisms. With minor modifications, this protocol can also serve as a general primer on microinjection of intestinal organoids and users may choose to supplement this protocol with additional or alternative downstream applications following microinjection.

This protocol describes the measurement of epithelial barrier permeability in real-time following pharmacologic treatment in human intestinal organoids using fluorescent microscopy and live cell microscopy.

Advances in 3D culture of intestinal tissues obtained through biopsy or generated from pluripotent stem cells via directed differentiation, have resulted ...

Partial Lobular Hepatectomy: A Surgical Model for Morphologic Liver Regeneration

Morphological organ regeneration following acute tissue loss is common among lower vertebrates, but is rarely observed in mammalian postnatal life. Adult liver regeneration after 70% partial hepatectomy results in hepatocyte hypertrophy with some replication in remaining lobes with restoration of metabolic activity, but with permanent loss of the injured lobe&#39;s morphology and architecture. Here, we detail a new surgical method in the neonate that leaves a physiologic environment conducive to regeneration. This model involves amputation of the left lobe apex and a subsequent conservative management regimen, and lacks the necessity for ligation of major liver vessels or chemical injury, leaving a physiologic environment where regeneration may occur. We extend this protocol to amputations on juvenile (P7-14) mice, during which the injured liver transitions from organ regeneration to compensatory growth by hypertrophy. The presented, brief 30 min protocol provides a framework to study the mechanisms of regeneration, its age-associated decline in mammals, and the characterization of putative hepatic stem or progenitors.

Here, we present a new method for partial resection of the left hepatic lobe in neonatal (day 0) mice. This new protocol is suitable for studying acute liver injury and injury response in the neonatal setting.

Morphological organ regeneration following acute tissue loss is common among lower vertebrates, but is rarely observed in mammalian postnatal life. Adult ...

Whole-mount Confocal Microscopy for Adult Ear Skin: A Model System to Study Neuro-vascular Branching Morphogenesis and Immune Cell Distribution

Here, we present a protocol of a whole-mount adult ear skin imaging technique to study comprehensive three-dimensional neuro-vascular branching morphogenesis and patterning, as well as immune cell distribution at a cellular level. The analysis of peripheral nerve and blood vessel anatomical structures in adult tissues provides some insights into the understanding of functional neuro-vascular wiring and neuro-vascular degeneration in pathological conditions such as wound healing. As a highly informative model system, we have focused our studies on adult ear skin, which is readily accessible for dissection. Our simple and reproducible protocol provides an accurate depiction of the cellular components in the entire skin, such as peripheral nerves (sensory axons, sympathetic axons, and Schwann cells), blood vessels (endothelial cells and vascular smooth muscle cells), and inflammatory cells. We believe this protocol will pave the way to investigate morphological abnormalities in peripheral nerves and blood vessels as well as the inflammation in the adult ear skin under different pathological conditions.

Here, we describe a high resolution whole-mount imaging method in the entire adult mouse ear skin, which enables us to visualize branching morphogenesis and patterning of peripheral nerves and blood vessels, as well as immune cell distribution.

Here, we present a protocol of a whole-mount adult ear skin imaging technique to study comprehensive three-dimensional neuro-vascular branching ...

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by Sertoli cell junctions at the blood-testis barrier (BTB), which is the tightest tissue barrier in the mammalian body and segregates the seminiferous epithelium into two compartments, a basal and an adluminal. The BTB creates a unique microenvironment for germ cells in meiosis I/II and for the development of postmeiotic spermatids into spermatozoa via spermiogenesis. Here, we describe a reliable assay to monitor BTB integrity of mouse testis in vivo. An intact BTB blocks the diffusion of FITC-conjugated inulin from the basal to the apical compartment of the seminiferous tubules. This technique is suitable for studying gene candidates, viruses, or environmental toxicants that may affect BTB function or integrity, with an easy procedure and a minimal requirement of surgical skills compared to alternative methods.

An In Vivo Method to Study Mouse Blood-Testis Barrier Integrity

Here, we present a protocol to assess the blood-testis barrier integrity by injecting inulin-FITC into testes. This is an efficient in vivo method to study blood-testis barrier integrity that can be compromised by genetic and environmental elements.

Spermatogenesis is the development of spermatogonia into mature spermatozoa in the seminiferous tubules of the testis. This process is supported by ...

An In Vitro 3D Model and Computational Pipeline to Quantify the Vasculogenic Potential of iPSC-Derived Endothelial Progenitors

Induced pluripotent stem cells (iPSCs) are a patient-specific, proliferative cell source that can differentiate into any somatic cell type. Bipotent endothelial progenitors (EPs), which can differentiate into the cell types necessary to assemble mature, functional vasculature, have been derived from both embryonic and induced pluripotent stem cells. However, these cells have not been rigorously evaluated in three-dimensional environments, and a quantitative measure of their vasculogenic potential remains elusive. Here, the generation and isolation of iPSC-EPs via fluorescent-activated cell sorting are first outlined, followed by a description of the encapsulation and culture of iPSC-EPs in collagen hydrogels. This extracellular matrix (ECM)-mimicking microenvironment encourages a robust vasculogenic response; vascular networks form after a week of culture. The creation of a computational pipeline that utilizes open-source software to quantify this vasculogenic response is delineated. This pipeline is specifically designed to preserve the 3D architecture of the capillary plexus to robustly identify the number of branches, branching points, and the total network length with minimal user input.

Endothelial progenitors derived from induced pluripotent stem cells (iPSC-EPs) have the potential to revolutionize cardiovascular disease treatments and to enable the creation of more faithful cardiovascular disease models. Herein, the encapsulation of iPSC-EPs in three-dimensional (3D) collagen microenvironments and a quantitative analysis of these cells&#8217; vasculogenic potential are described.

Induced pluripotent stem cells (iPSCs) are a patient-specific, proliferative cell source that can differentiate into any somatic cell type. Bipotent ...