In vitro organogenesis of gut-like structures from mouse embryonic stem cells

An Engineered Living Intestinal Muscle Patch Produces Macroscopic Contractions that can Mix and Break Down Artificial Intestinal Contents

The intestinal muscle layers execute various gut wall movements to achieve controlled propulsion and mixing of intestinal content. Engineering intestinal muscle layers with complex contractile function is critical for developing bioartificial intestinal tissue to treat patients with short bowel syndrome. Here, the first demonstration of a living intestinal muscle patch capable of generating three distinct motility patterns and displaying multiple digesta manipulations is reported. Assessment of contractility, cellular morphology, and transcriptome profile reveals that successful generation of the contracting muscle patch relies on both biological factors in a serum-free medium and environmental cues from an elastic electrospun gelatin scaffold. By comparing gene-expression patterns among samples, it is shown that biological factors from the medium strongly affect ion-transport activities, while the scaffold unexpectedly regulates cell-cell communication. Analysis of ligandreceptor interactome identifies scaffold-driven changes in intercellular communication, and 78% of the upregulated ligand-receptor interactions are involved in the development and function of enteric neurons. The discoveries highlight the importance of combining biomolecular and biomaterial approaches for tissue engineering. The living intestinal muscle patch represents a pivotal advancement for building functional replacement intestinal tissue. It offers a more physiological model for studying GI motility and for preclinical drug discovery.

Feasibility of intraperitoneal placental-derived mesenchymal stem cell injection in stomachs of diabetic mice

BACKGROUND AND AIM

Diabetic gastropathy is associated with loss of interstitial cells of Cajal and autonomic neuropathy. Effective management for diabetic gastropathy is still unavailable. This study was aimed to confirm the pathogenetic changes in diabetic gastropathy and to examine the effect of treatment with placental-derived mesenchymal stem cells (PDMSCs) in stomachs of animal models.

METHODS

Fourteen non-obese diabetic/ShiLtJ mice of 8 weeks were bled until week 30. Diabetes mellitus developed in 10 out of 14 mice, which all survived with insulin. The mice were grouped into three groups: nondiabetic group (n = 4), diabetic sham group (n = 5), and diabetic PDMSC group (n = 5) all of which were treated with intraperitoneal PDMSCs injection at week 30. All mice were killed at week 34, and the stomachs were examined by immunohistochemical stain with c-kit and neuronal nitric oxide synthase antibodies.

RESULTS

The number of c-kit positive cells in stomach decreased significantly in the diabetic sham group compared with that in the nondiabetic group (21.2 ± 6.7 vs 88.0 ± 29.3, P = 0.006) but increased with PDMSC treatment (21.2 ± 6.7 vs 64.0 ± 15.1, P = 0.02). The positive rate of neuronal nitric oxide synthase in neural plexus was also significantly lower in the diabetic sham group than in the nondiabetic group (22.3% ± 18.5% vs 48.0% ± 22.7%, P = 0.003) but increased with PDMSC treatment (22.3% ± 18.5% vs 43.3% ± 20.5%, P = 0.03).

CONCLUSIONS

Interstitial cells of Cajal and neural plexus decreased in stomachs of mice with diabetes mellitus but were significantly repaired with intraperitoneal injection of PDMSC.

Bioengineered intestinal muscularis complexes with long-term spontaneous and periodic contractions

Although critical for studies of gut motility and intestinal regeneration, the in vitro culture of intestinal muscularis with peristaltic function remains a significant challenge. Periodic contractions of intestinal muscularis result from the coordinated activity of smooth muscle cells (SMC), the enteric nervous system (ENS), and interstitial cells of Cajal (ICC). Reproducing this activity requires the preservation of all these cells in one system. Here we report the first serum-free culture methodology that consistently maintains spontaneous and periodic contractions of murine and human intestinal muscularis cells for months. In this system, SMC expressed the mature marker myosin heavy chain, and multipolar/dipolar ICC, uniaxonal/multipolar neurons and glial cells were present. Furthermore, drugs affecting neural signals, ICC or SMC altered the contractions. Combining this method with scaffolds, contracting cell sheets were formed with organized architecture. With the addition of intestinal epithelial cells, this platform enabled up to 11 types of cells from mucosa, muscularis and serosa to coexist and epithelial cells were stretched by the contracting muscularis cells. The method constitutes a powerful tool for mechanistic studies of gut motility disorders and the functional regeneration of the engineered intestine.

The Potential for Gut Organoid Derived Interstitial Cells of Cajal in Replacement Therapy

Effective digestion requires propagation of food along the entire length of the gastrointestinal tract. This process involves coordinated waves of peristalsis produced by enteric neural cell types, including different categories of interstitial cells of Cajal (ICC). Impaired food transport along the gastrointestinal tract, either too fast or too slow, causes a range of gut motility disorders that affect millions of people worldwide. Notably, loss of ICC has been shown to affect gut motility. Patients that suffer from gut motility disorders regularly experience diarrhoea and/or constipation, insomnia, anxiety, attention lapses, irritability, dizziness, and headaches that greatly affect both physical and mental health. Limited treatment options are available for these patients, due to the scarcity of human gut tissue for research and transplantation. Recent advances in stem cell technology suggest that large amounts of rudimentary, yet functional, human gut tissue can be generated in vitro for research applications. Intriguingly, these stem cell-derived gut organoids appear to contain functional ICC, although their frequency and functional properties are yet to be fully characterised. By reviewing methods of gut organoid generation, together with what is known of the molecular and functional characteristics of ICC, this article highlights short- and long-term goals that need to be overcome in order to develop ICC-based therapies for gut motility disorders.

Intestinal organoids as tissue surrogates for toxicological and pharmacological studies

Recently developed cell culture protocols have allowed for the derivation of multi-cellular structures dubbed intestinal "organoids" from embryonic stem cells (ESCs), induced pluripotent stem cells (IPSCs), and adult intestinal stem cells (ISCs). These structures resemble in vivo intestinal crypts, both in structure and developmental processes, and can be grown quickly and in relatively large quantities. Although much research has focused on developing intestinal organoids for tissue repair, more immediate applications include high-throughput screening for agents that target intestinal epithelium. Here we describe current methods for deriving mouse and human intestinal organoids and discuss some applications aimed at developing novel therapies or preventive agents for diseases of the lower GI tract such as inflammatory bowel diseases and colorectal cancer.

Generating intestinal tissue from stem cells: potential for research and therapy

Intestinal resection and malformations in adult and pediatric patients result in devastating consequences. Unfortunately, allogeneic transplantation of intestinal tissue into patients has not been met with the same measure of success as the transplantation of other organs. Attempts to engineer intestinal tissue in vitro include disaggregation of adult rat intestine into subunits called organoids, harvesting native adult stem cells from mouse intestine and spontaneous generation of intestinal tissue from embryoid bodies. Recently, by utilizing principles gained from the study of developmental biology, human pluripotent stem cells have been demonstrated to be capable of directed differentiation into intestinal tissue in vitro. Pluripotent stem cells offer a unique and promising means to generate intestinal tissue for the purposes of modeling intestinal disease, understanding embryonic development and providing a source of material for therapeutic transplantation.

Musashi1 and hairy and enhancer of split 1 high expression cells derived from embryonic stem cells enhance the repair of small-intestinal injury in the mouse

BACKGROUND

Embryonic stem cells have great plasticity. In this study, we repaired impaired small intestine by transplanting putative intestinal epithelial stem cells (Musashi1 and hairy and enhancer of split 1 high expression cells) derived from embryonic stem cells.

METHODS

The differentiation of definitive endoderm in embryoid bodies, derived from male ES-E14TG2a cells by the hanging-drop method, was monitored to define a time point for maximal induction of putative intestinal epithelial stem cells by epidermal growth factor. Furthermore, to evaluate the regenerative potential of intestinal epithelium, these putative stem cells were engrafted into NOD/SCID mice and female mice with enteritis. Donor cells were located by SRY DNA in situ hybridization.

RESULTS

The results revealed that definitive endodermal markers were highly expressed in 5-day embryoid bodies. These embryoid body cells were induced into putative intestinal epithelial stem cells on the 5th day of epidermal growth factor administration. Grafts from these cells consisted of adenoid structures and nonspecific structural cells with strong expression of small-intestinal epithelial cell markers. In situ hybridization revealed that the donor cells could specifically locate in damaged intestinal epithelium, contribute to epithelial structures, and enhance regeneration.

CONCLUSIONS

In conclusion, the Musashi1 and hairy and enhancer of split 1 high expression cells, derived from mouse embryonic stem cells, locate predominantly in impaired small-intestinal epithelium after transplantation and contribute to epithelial regeneration.

Intestinal lineage commitment of embryonic stem cells

Generating lineage-committed intestinal stem cells from embryonic stem cells (ESCs) could provide a tractable experimental system for understanding intestinal differentiation pathways and may ultimately provide cells for regenerating damaged intestinal tissue. We tested a two-step differentiation procedure in which ESCs were first cultured with activin A to favor formation of definitive endoderm, and then treated with fibroblast-conditioned medium with or without Wnt3A. The definitive endoderm expressed a number of genes associated with gut-tube development through mouse embryonic day 8.5 (Sox17, Foxa2, and Gata4 expressed and Id2 silent). The intestinal stem cell marker Lgr5 gene was also activated in the endodermal cells, whereas the Msi1, Ephb2, and Dcamkl1 intestinal stem cell markers were not. Exposure of the endoderm to fibroblast-conditioned medium with Wnt3A resulted in the activation of Id2, the remaining intestinal stem cell markers and the later gut markers Cdx2, Fabp2, and Muc2. Interestingly, genes associated with distal gut-associated mesoderm (Foxf2, Hlx, and Hoxd8) were also simulated by Wnt3A. The two-step differentiation protocol generated gut bodies with crypt-like structures that included regions of Lgr5-expressing proliferating cells and regions of cell differentiation. These gut bodies also had a smooth muscle component and some underwent peristaltic movement. The ability of the definitive endoderm to differentiate into intestinal epithelium was supported by the vivo engraftment of these cells into mouse colonic mucosa. These findings demonstrate that definitive endoderm derived from ESCs can carry out intestinal cell differentiation pathways and may provide cells to restore damaged intestinal tissue.

Potential of cell therapy to treat pediatric motility disorders

Gut motility disorders represent a significant challenge in clinical management with current palliative approaches failing to overcome disease and treatment-related morbidity. The recent progress with stem cells to restore missing or defective elements of the gut neuromusculature offers new hope for potential cure. Focusing on enteric neuropathies such as Hirschsprung's disease, the review discusses the progress that has been made in the sourcing of putative stem cells and the studies into their biology and therapeutic potential. It also explores the practical challenges that must be overcome before stem cell-based therapies can be applied in the clinical arena. Although many obstacles remain, the speed of advancement of the enteric stem cell field suggests that such therapies are on the horizon.

Transplantation of mesenchymal stem cells to prevent radiation-induced intestinal injury in mice

The effective treatments of radiation-induced intestinal injury are currently unavailable. Developing new treatments for radiation-induced intestinal injury is thus important. The present study investigated whether transplantation of mesenchymal stem cells (MSCs) is able to prevent radiation-induced intestinal injury. Intestines of female nude mice (ICR nu/nu) were irradiated at a single dose of 30 Gy. Transplantation of male MSCs (C57BL/6) was then immediately performed into the walls of irradiated intestine by direct injection for the irradiation + MSCs group. Mice were weighed daily and survival was recorded for 13 days after irradiation. From 13 to 27 days after irradiation, intestines of mice were obtained in order to assay histological changes by staining with hematoxylin-eosin and Masson trichrome. Mean body weight of the irradiation + MSC group was significantly higher than that of the irradiation-only group from 8 days after irradiation. In addition, survival rates were significantly higher in the irradiation + MSC group than for the irradiation-only group from 5 days after irradiation. Histological observation revealed that intestines of irradiation + MSC-transplanted mice were thick in the submucosal and muscle layers, and had almost fully recovered from radiation-induced intestinal injury at day 27. Specifically, ulcerated areas in the intestines of the irradiation + MSC-transplanted mice were smaller by 13 days after irradiation and were fewer in numbers at 27 days when compared with the irradiation-only group. Our results suggest that transplanted MSCs may play an important role in preventing radiation-induced injury and may offer a novel method to treat radiation-induced intestinal injury.

Evaluation of in vitro cytotoxicity and paracellular permeability of intact monolayers with mouse embryonic stem cells

Mouse embryonic stem (mES) cells were induced to form intact monolayers in cell culture inserts, using combinations of extracellular matrix (ECM) components and growth factors (GFs). Progressive formation of intact monolayers was monitored using transepithelial electrical resistance (TEER) and passage of paracellular permeability (PP) markers. The mES cells were initially inoculated on inactivated mouse embryonic fibroblasts (MEFs) plus leukemia inhibitory factor (LIF). At 75% confluence, cells were passaged in the absence of MEF and LIF to stimulate formation of rounded multicellular aggregates (MA). After 4 days, cultures containing MA were transferred to culture inserts coated with ECM components only, and grown in the presence of selected individual GFs. An additional 10-14 days revealed confluent monolayers with TEER values of 500-700 ohms cm2 (Omega cm2). Monolayers grown on inserts coated with ECM components, such as fibronectin or collagen-IV, in the presence of epidermal growth factor or keratinocyte growth factor in the medium, yielded the highest TEER measurements when compared to cultures grown without GFs or ECM. Acute cytotoxicity (AC) studies with confluent monolayers of mES cells in 96-well plates indicated that there is a high correlation (R2=0.91) between cell viability and TEER for 24-h exposure time. Also, decrease in TEER is inversely proportional with increase in PP of markers. In comparison to standardized Registry of Cytotoxicity (RC) data and TEER measurements, MTT IC50 values for mES cells are lower. Thus, at equivalent concentrations for the same chemicals, cell viability decreases before the integrity of the monolayer is compromised. This system represents a novel approach for the manipulation of mES cells toward specific intact monolayers, as an in vitro model for biological monolayer formation, and most importantly, for applications to cytotoxicity testing.

In vitro development of gut-like tissue demonstrating rhythmic contractions from embryonic mouse intestinal cells

The rhythmic motility of the intestine is regulated by the interstitial cells of Cajal (ICC) and the enteric nervous system. Rhythmic motility is considered to occur after the differentiation of mesenchymal progenitor cells into ICC during the late embryonic period. In this study, we successfully reconstructed a gut-like tissue demonstrating rhythmic contractions by culturing dispersed cells enzymatically isolated from the mouse intestine during the mid-embryonic period. These intestinal cells were reconstituted into a collagen gel at high density, made to proliferate considerably, and grew into a gut-like tissue after 1 week of culturing. The reconstituted tissue showed rhythmic contractions and stained positive for the specific marker proteins of neurones and ICC, PGP9.5 and c-Kit. The tissue also demonstrated network formation by developing nerve cells and ICC. Moreover, in the presence of nifedipine, c-Kit-immunopositive cells showed spontaneous Ca(2+) oscillation, which is considered to be coupled to the electrical activity that corresponds to slow waves. Therefore, this culture system may be of use in elucidating the developmental mechanisms of gastrointestinal motility.

Gut-like structures from mouse embryonic stem cells as an in vitro model for gut organogenesis preserving developmental potential after transplantation

Recently, we reported the formation of gut-like structures from mouse ESCs in vitro. To determine whether ESCs provide an in vitro model of gastrointestinal (GI) tracts and their organogenesis, we investigated the morphological features, formation process, cellular development, and regional location within the GI tract by immunohistochemistry, electron microscopy, and reverse transcription-polymerase chain reaction. We also examined the developmental potential by transplantation into kidney capsules. The results demonstrated that Id2-expressing epithelium developed first, alpha-smooth muscle actin appeared around the periphery, and finally, the gut-like structures were formed into a three-layer organ with well-differentiated epithelium. A connective tissue layer and musculature with interstitial cells of Cajal developed, similar to organogenesis of the embryonic gut. Enteric neurons appeared underdeveloped, and blood vessels were absent. Many structures expressed intestinal markers Cdx2 and 5-hydroxytryptamine but not the stomach marker H(+)/K(+) ATPase. Transplants obtained blood vessels and extrinsic nerve growth from the host to prolong life, and even grafts of premature structures did not form teratoma. In conclusion, gut-like structures were provided with prototypical tissue components of the GI tract and are inherent in the intestine rather than the stomach. The formation process was basically same as in gut organogenesis. They maintain their developmental potential after transplantation. Therefore, gut-like structures provide a unique and useful in vitro system for development and stem cell studies of the GI tract, including transplantation experiments.

Crucial transcription factors in endoderm and embryonic gut development are expressed in gut-like structures from mouse ES cells

Mouse embryonic stem (ES) cells are pluripotent and retain the potential to form an organ similar to the gut showing spontaneous contractions in vitro. The morphological features of these structures and their formation, as assessed using the hanging drop method to produce embryoid bodies (EBs), seem to be similar to those in vivo. To determine whether the same molecular mechanisms are involved in the formation process, the expression pattern of transcription factors regulating endoderm and gut development in the mouse embryo was examined by in situ hybridization and compared with in vivo expression. Expression of gene products was also examined by immunohistochemistry, and expression colocalization was analyzed with double staining. The results showed that all factors examined, that is, Sox17, Id2, HNF3beta/Foxa2, and GATA4, were expressed in both EBs and gut-like structures. Moreover, their expression patterns were similar to those in the mouse embryo. EBs after the hanging drop period and before outgrowth already expressed all factors that were colocalized with each other in EB epithelial structures. These findings suggest that the origin of the gut-like structure is determined during the hanging drop period and that the gut-like structure is formed as the epithelial structure in EBs during the hanging drop period. They also indicate that the in vitro system using mouse ES cells mimics in vivo development and should prove useful in the study of molecular mechanisms for endoderm and gut development.

Enteric nervous system

PURPOSE OF THE REVIEW

The purpose of this review is to provide a synopsis of how the field of enteric neurobiology has advanced during the past 2 years.

RECENT FINDINGS

With more than 500 studies from which to choose, the authors have focused on several themes that illustrate recent progress. There has been an explosion of interest in the development of the enteric nervous system driven by the need to understand development abnormalities, particularly in Hirschsprung disease, and fueled by technical advances for investigating how neural crest-derived cells migrate, proliferate, and differentiate into enteric neurons and glia. The use of neural stem cells as a therapeutic strategy aimed at repopulating regions of bowel, where enteric neurones are reduced or absent, is on the horizon. Enteric reflexes involve interactions between sensory neurons, interneurons, and motor neurons. Recent findings suggest this distinction may be blurred, with neurons having multifunctional properties, perhaps because enteric neurons, unlike their central nervous system counterparts, are directly exposed to mechanical forces that they regulate. Another topic the authors have highlighted is pharmacology, with new tools for investigating ion channels, receptors, and transporters, leading to an expanding list of molecular mechanisms that regulate neuronal excitability. Long-term alterations in the expression of these molecules during disease or injury may underlie many gastrointestinal disorders that currently have unknown etiology. The authors finish with a look to the future and what may be the subject of this review next time.

SUMMARY

Basic science information gathered during the past 2 years provides insight into pathophysiologic processes and will pave the wave for improved understanding of both organic and 'functional' gastrointestinal disorders.