Regenerative medicine: postnatal approaches.

Paper 2 of the paediatric regenerative medicine Series focuses on recent advances in postnatal approaches. New gene, cell, and niche-based technologies and their combinations allow structural and functional reconstitution and simulation of complex postnatal cell, tissue, and organ hierarchies. Organoid and tissue engineering advances provide human disease models and novel treatments for both rare paediatric diseases and common diseases affecting all ages, such as COVID-19. Preclinical studies for gastrointestinal disorders are directed towards oesophageal replacement, short bowel syndrome, enteric neuropathy, biliary atresia, and chronic end-stage liver failure. For respiratory diseases, beside the first human tracheal replacement, more complex tissue engineering represents a promising solution to generate transplantable lungs. Genitourinary tissue replacement and expansion usually involve application of biocompatible scaffolds seeded with patient-derived cells. Gene and cell therapy approaches seem appropriate for rare paediatric diseases of the musculoskeletal system such as spinal muscular dystrophy, whereas congenital diseases of complex organs, such as the heart, continue to challenge new frontiers of regenerative medicine.

Diffuse Anaplastic Wilms Tumor in a Child With LAMA2 -related Muscular Dystrophy.

Laminin alpha-2-related muscular dystrophy ( LAMA2 -MD), caused by mutations in the LAMA2 gene, is inherited in an autosomal recessive manner. There is no known association of LAMA2 -MD with cancer predisposition. We present a 4-year-old female with LAMA2 -MD and Children's Oncology Group stage III diffuse anaplastic Wilms tumor (DAWT). Given our patient's comorbidities, it was essential to tailor her adjuvant chemotherapy by omitting vincristine and doxorubicin to avoid the potential worsening of her neuromuscular dysfunction and cardiomyopathy. This report illustrates the sporadic occurrence of 2 rare events in our patient and highlights the successful risk-adapted management of DAWT based on the pathophysiology of LAMA2 -MD.

NH2-terminal deletion of specific phosphorylation sites on PHOX2B disrupts the formation of enteric neurons in vivo.

Mutations in the paired-like homeobox 2 b (PHOX2B) gene are associated with congenital central hypoventilation syndrome (CCHS), which is a rare condition in which both autonomic dysregulation with hypoventilation and an enteric neuropathy may occur. The majority of patients with CCHS have a polyalanine repeat mutation (PARM) in PHOX2B, but a minority of patients have nonpolyalanine repeat mutations (NPARMs), some of which have been localized to exon 1. A PHOX2B-Y14X nonsense mutation previously generated in a human pluripotent stem cell (hPSC) line results in an NH2-terminus truncated product missing the first 17 or 20 amino acids, possibly due to translational reinitiation at an alternate ATG start site. This NH2-terminal truncation in the PHOX2B protein results in the loss of two key phosphorylation residues. Though the deletion does not affect the potential for PHOX2BY14X/Y14X mutant hPSC to differentiate into enteric neural crest cells (ENCCs) in culture, it impedes in vivo development of neurons in an in vivo model of human aganglionic small intestine.NEW & NOTEWORTHY A mutation that affects only 17-20 NH2-terminal amino acids in the paired-like homeobox 2 b (PHOX2B) gene hinders the subsequent in vivo establishment of intestinal neuronal cells, but not the in vitro differentiation of these cells.

Sprouty2 limits intestinal tuft and goblet cell numbers through GSK3ß-mediated restriction of epithelial IL-33.

Dynamic regulation of intestinal cell differentiation is crucial for both homeostasis and the response to injury or inflammation. Sprouty2, an intracellular signaling regulator, controls pathways including PI3K and MAPKs that are implicated in differentiation and are dysregulated in inflammatory bowel disease. Here, we ask whether Sprouty2 controls secretory cell differentiation and the response to colitis. We report that colonic epithelial Sprouty2 deletion leads to expanded tuft and goblet cell populations. Sprouty2 loss induces PI3K/Akt signaling, leading to GSK3ß inhibition and epithelial interleukin (IL)-33 expression. In vivo, this results in increased stromal IL-13+ cells. IL-13 in turn induces tuft and goblet cell expansion in vitro and in vivo. Sprouty2 is downregulated by acute inflammation; this appears to be a protective response, as VillinCre;Sprouty2F/F mice are resistant to DSS colitis. In contrast, Sprouty2 is elevated in chronic colitis and in colons of inflammatory bowel disease patients, suggesting that this protective epithelial-stromal signaling mechanism is lost in disease.

R-Spondin1 enhances wnt signaling and decreases weight loss in short bowel syndrome zebrafish.

BACKGROUND: R-spondins, including R-spondin 1 (RSPO1), are a family of Wnt ligands that help to activate the canonical Wnt/ß-catenin pathway, which is critical for intestinal epithelial cell proliferation and maintenance of intestinal stem cells. This proliferation underpins the epithelial expansion, or intestinal adaptation (IA), that occurs following massive bowel resection and short bowel syndrome (SBS). The purpose of this study was to identify if recombinant human RSPO1 (rhRSPO1) could be serially administered to SBS zebrafish to enhance cellular proliferation and IA. METHODS: Adult male zebrafish were assigned to four groups: sham + PBS, SBS + PBS, sham + rhRSPO1, and SBS + rhRSPO1. Sham fish had a laparotomy alone. SBS fish had a laparotomy with distal intestinal ligation and creation of a proximal stoma. Fish were weighed at initial surgery and then weekly. rhRSPO1 was administered post-operatively following either a one- or two-week dosing schedule with either 3 or 5 intraperitoneal injections, respectively. Fish were harvested at 7 or 14 days with intestinal segments collected for analysis. RESULTS: Repeated intraperitoneal injection of rhRSPO1 was feasible and well tolerated. At 7 days, intestinal epithelial proliferation was increased by rhRSPO1. At 14 days, SBS + rhRSPO1 fish lost significantly less weight than SBS + PBS fish. Measurements of intestinal surface area were not increased by rhRSPO1 administration but immunofluorescent staining for ß-catenin and gene expression for cyclin D1 was increased. CONCLUSIONS: Intraperitoneal injection of rhRSPO1 decreased weight loss in SBS zebrafish with increased ß-catenin + cells and cyclin D1 expression at 14 days, indicating improved weight maintenance might result from increased activation of the canonical Wnt pathway.

A Purpose in Liquidity: Perfusing 3D Open Scaffolds Improves "Mini-gut" Morphogenesis and Longevity.

Channeling morphogenic signaling gradients intrinsic to intestinal epithelial stem cells, Nikolaev et al. (2020) optimized a three-dimensional microchip perfusion system that augments growth, maturation, and longevity of tubular intestinal enteroids. Reported in Nature, this system may ultimately pave the way to study human intestinal development and pathophysiology, perhaps for therapeutic discovery.

Broad-spectrum antibiotics alter the microbiome, increase intestinal fxr, and decrease hepatic steatosis in zebrafish short bowel syndrome.

Short bowel syndrome (SBS) is associated with changes in the intestinal microbiome and marked local and systemic inflammation. There is also a late complication of SBS, intestinal failure associated liver disease (IFALD) in which hepatic steatosis progresses to cirrhosis. Most patients with SBS arrive at massive intestinal resection after a contaminating intraabdominal catastrophe and have a history of exposure to broad-spectrum antibiotics. We therefore investigated whether the administration of broad-spectrum antibiotics in conjunction with SBS in zebrafish (ZF) would replicate these systemic effects observed in humans to identify potentially druggable targets to aid in the management of SBS and resulting IFALD. In zebrafish with SBS, broad-spectrum antibiotics altered the microbiome, decreased inflammation, and reduced the development of hepatic steatosis. After two weeks of broad-spectrum antibiotics, these fish exhibited decreased alpha diversity, with less variation in microbial community composition between SBS and sham fish. Additionally, administration of broad-spectrum antibiotics was associated with decreased expression of intestinal toll-like receptor 4 (tlr4), increased expression of the intestinal gene encoding the Farnesoid X receptor (fxr), decreased expression of downstream hepatic cyp7a1, and decreased development of hepatic steatosis. SBS in zebrafish reproducibly results in increased epithelial surface area as occurs in human patients who demonstrate intestinal adaptation, but antibiotic administration in zebrafish with SBS reduced these gains with increased cell death in the intervillus pocket that contains stem/progenitor cells. These alternate states in SBS zebrafish might direct the development of future human therapies.NEW & NOTEWORTHY In a zebrafish model that replicates a common clinical scenario, systemic effects of the administration of broad-spectrum antibiotics in a zebrafish model of SBS identified two alternate states that led to the establishment of fat accumulation in the liver or its absence. Broad-spectrum antibiotics given to zebrafish with SBS over 2 wk altered the intestinal microbiome, decreased intestinal and hepatic inflammation, and decreased hepatic steatosis.

Grading TESI: Crypt and villus formation in tissue-engineered small intestine alters with stem/progenitor cell source.

The small intestine has a remarkable ability to enhance its absorptive and digestive surface area through the formation of villi, a process known as villification. We sought to learn whether developing mouse and human tissue-engineered small intestine (TESI) followed known developmental biology routes to villification, such as Sonic hedgehog (SHH)/Indian hedgehog (IHH) and bone morphogenetic protein 4 (BMP4)/forkhead box F1 (FOXF1) signaling to identify targets to enhance the development of TESI. After generating TESI from prenatal and postnatal stem cell sources, we evaluated the effect of cell source derivation on villification with a grading scheme to approximate developmental stage. χ2 analysis compared the prevalence of TESI grade from each stem cell source. RNAscope probes detected genes known to direct villification and the development of the crypt-villus axis in mouse and human development. These were compared in TESI derived from various pluripotent and progenitor cell donor cell types as well as native human fetal and postnatal tissues. Prenatal and pluripotent cell sources form mature villus and crypt-like structures more frequently than postnatal donor sources, and there are alternate routes to villus formation. Human TESI recapitulates epithelial to mesenchymal crosstalk of several genes identified in development, with fetal and pluripotent donor-derived TESI arriving at villus formation following described developmental patterns. However, postnatal TESI is much less likely to form complete villus-crypt patterns and demonstrates alternate SHH/IHH and BMP4/FOXF1 signaling patterns. Grading TESI and other cellular constructs may assist discoveries to support future human therapies.NEW & NOTEWORTHY The small intestine can enhance its absorptive and digestive surface area through a process known as villification. Tissue-engineered small intestine achieves mature villification at varying levels of success between differing sources. We have developed a consistent grading schema of morphology and characterized it across multiple developmental pathways, allowing objective comparison between differing constructs and sources.

Thermal Injection Measurement (TIM) Adds Accuracy to Injections and Can Assess Cold Chain Management.

BACKGROUND: Inaccurate assessment of injected drug delivery may increase cost and morbidity or reduce efficacy. Yet currently most injections are evaluated solely by the formation of a visible wheal that might not truly estimate the actual area of effect. We hypothesized that thermal injection measurement (TIM) might verify appropriate temperature at the time of injection, as required for some temperature-sensitive vaccines and provide more accurate information about the area of delivery. METHODS: 0.1 mL of either iced (n = 11) or room temperature (n = 17) methylene blue solution was injected subcutaneously in mice under anesthesia and photos taken with an iPhone 7 built-in camera and Thermal Seek Camera phone plug-in. After 5 min, true values were determined at necropsy. RESULTS: TIM was closer in value to the measured area at necropsy than the area of the visualized skin wheal at both ice temperature and room temperature. The difference between the true value and thermal area assessment of iced solution averaged 0.15 cm2 as compared with the difference between the true value and wheal size, which averaged 0.27 cm2 (P = 0.04). At room temperature, this was maintained for thermal and visible wheal differences, 0.23 cm2 and 0.65 cm2, respectively (P = 0.0006). CONCLUSIONS: TIM can assess temperature at the time of injection and is more accurate than visual inspection. TIM could be applied to colorless injections and areas that are hard to visualize such as scar. As a portable phone plug-in, it might be a useful adjunct to aid the evaluation of injected drug delivery including in resource-limited settings.

Remnant Intestinal Length Defines Intestinal Adaptation and Hepatic Steatosis: Two Zebrafish Models.

BACKGROUND: Short bowel syndrome (SBS) is a condition that results from inadequate intestinal absorptive capacity, usually after the loss of functional intestine. We have previously developed a severe model of SBS in zebrafish that demonstrated increased intestinal adaptation (IA) and epithelial proliferation in SBS zebrafish. However, many children with SBS do not have this extreme intestinal loss. Therefore, in this study, we developed a variation of this model to evaluate the effects of increasing intestinal length on IA and the complications of SBS. MATERIALS AND METHODS: After Institutional Animal Care and Use Committee approval, adult male zebrafish were assigned to three groups: sham (n = 30), S1-SBS (n = 30), and S3-SBS (n = 30). Sham surgery included ventral laparotomy alone. S1-SBS surgery consisted of laparotomy with creation of a proximal stoma at S1 (jejunostomy equivalent) and ligation at S4. S3-SBS surgery had stoma creation at S3 (ileostomy equivalent) and the same ligation. Fish were harvested at 14 d. Markers of IA were measured from proximal intestinal segments, and the liver was analyzed for development of hepatic steatosis. RESULTS: At 14 d, S3-SBS fish lost less weight than S1-SBS and had increased markers of IA compared with sham fish, which were decreased compared with S1-SBS fish. S3-SBS fish had decreased proximal intestinal inflammation compared with S1-SBS fish. S1-SBS fish developed extensive hepatic steatosis. Although S3-SBS fish have increased hepatic steatosis compared with sham fish, it is decreased compared with S1-SBS. CONCLUSIONS: Longer remnant intestine decreases the extent of IA, inflammation, and hepatic steatosis in a zebrafish model of SBS.

R-Spondin 1 (RSPO1) Increases Mouse Intestinal Organoid Unit Size and Survival in vitro and Improves Tissue-Engineered Small Intestine Formation in vivo.

Introduction: Cell therapy and tissue engineering has recently emerged as a new option for short bowel syndrome (SBS) treatment, generating tissue engineered small intestine (TESI) from organoid units (OU) and biodegradable scaffolds. The recombinant human R-Spondin 1 (rhRSPO1) protein may be a key player in this process due to its mitogenic activity in intestinal stem cells. Objective: Aiming at optimizing the TESI formation process and advancing this technology closer to the clinic, we evaluated the effects of rhRSPO1 protein on OU culture and TESI formation. Methods: Intestinal OU were isolated from C57BL/6 mice and cultured in Matrigel in the presence or absence of recombinant human rhRSPO1. Throughout the culture, OU growth and survival rates were evaluated, and cells were harvested on day 3. OU were seeded onto biodegradable scaffolds, in the presence or absence of 5 µg of rhRSPO1 and implanted into the omentum of NOD/SCID mice in order to generate TESI. The explants were harvested after 30 days, weighed, fixed in formalin and embedded in paraffin for histological analysis and immunofluorescence for different cell markers. Results: After 3 days, rhRSPO1-treated OU attained a larger size, when compared to the control group, becoming 5.7 times larger on day 6. Increased survival was observed from the second day in culture, with a 2-fold increase in OU survival between days 3 and 6. A 4.8-fold increase of non-phosphorylated ß-catenin and increased relative expression of Lgr5 mRNA in the rhRSPO1-treated group confirms activation of the canonical Wnt pathway and suggests maintenance of the OU stem cell niche and associated stemness. After 30 days of in vivo maturation, rhRSPO1-treated TESI presented a larger mass than constructs treated with saline, developing a more mature intestinal epithelium with well-formed villi and crypts. In addition, the efficiency of OU-loaded rhRSPO1-treated scaffolds significantly increased, forming TESI in 100% of the samples (N = 8), of which 40% presented maximum degree of development, as compared to 66.6% in the control group (N = 9). Conclusion: rhRSPO1 treatment improves the culture of mouse intestinal OU, increasing its size and survival in vitro, and TESI formation in vivo, increasing its mass, degree of development and engraftment.

Induced pluripotent stem cell-derived enteric neural crest cells repopulate human aganglionic tissue-engineered intestine to form key components of the enteric nervous system.

Models for enteric neuropathies, in which intestinal nerves are absent or injured, are required to evaluate possible cell therapies. However, existing options, including transgenic mice, are variable and fragile. Here immunocompromised mice were implanted with human pluripotent stem cell-derived tissue-engineered small intestine 10 weeks prior to a second survival surgery in which enteric nervous system precursor cells, or saline controls, were injected into the human intestinal organoid-derived tissue-engineered small intestine and analyzed 4 weeks later. Human intestinal organoid-derived tissue-engineered small intestine implants injected with saline as controls illustrated formation of intestinal epithelium and mesenchyme without an enteric nervous system. Second surgical introduction of human pluripotent stem cell-generated enteric nervous system precursors into developing human intestinal organoid-derived tissue-engineered small intestine implants resulted in proliferative migratory neuronal and glial cells, including multiple neuronal subtypes, and demonstrated function in contractility assays.

Spleen Organoid Units Generate Functional Human and Mouse Tissue-Engineered Spleen in a Murine Model.

Introduction: Splenectomy is common after trauma or hematologic disease, and alters immune protection against pathogens, which may lead to fulminant infection with high mortality. Yet the spleen has demonstrable regenerative capacity and cells might be recovered and reimplanted at the time of injury or excision to avoid these risks. Methods: Tissue-engineered spleen (TESp) was generated from ActinGFP mice (mTESp) or human donor spleen (hTESp) through implantation of spleen organoid units (spleen OU), in NOD/SCID mice with concurrent splenectomy, on a biodegradable scaffold. Explants were evaluated and blood smears were obtained to investigate the presence of target cells or Howell-Jolly bodies, which are erythrocyte sequelae of asplenia. Results: TESp was generated from mouse (mTESp) and human (hTESp) donor cells with essential splenic components: red and white pulp with trabeculae. mTESp and hTESp demonstrated green fluorescent protein- or lamin-positive costaining with proliferating cell nuclear antigen, CD4, and CD11c, identifying proliferative donor cells and key immune components of the spleen of donor origin. Animals with hTESp and mTESP combined with splenectomy had significantly fewer Howell-Jolly bodies on blood smears than controls. Conclusion: TESp from mouse and human donor cells can be generated by 4 weeks and contains donor immune cells identified by CD4 and CD11c. TESp reduces postsplenectomy erythrocyte inclusions, indicating possible function. Impact Statement Overwhelming postsplenectomy infection is rare but highly mortal. Tissue-engineered spleen (TESp) was generated from murine (mTESp) and human (hTESp) donors and appeared histologically similar to native spleen. Both mTESp and hTESp demonstrated proliferative cells of donor spleen origin. Importantly, functional cells were demonstrated on imaging with a corresponding reduction in the number of erythrocyte inclusions in blood smears that are typically identified in patients with asplenia and indicate a lack of clearance by functional spleen tissue. Taken together, these findings indicate that this approach might be clinically relevant as a future human therapy.

Tissue-Engineering the Intestine: The Trials before the Trials.

Building complex tissues requires the development of innovative interdisciplinary engineering solutions. In this Forum, the INTENS Consortium discuss experimental considerations and challenges for generating a tissue-engineered intestine for the treatment of short bowel syndrome, taking into account cell source, scaffold choice, and design strategy for achieving proper assembly and function.

Wnt signaling inhibition by monensin results in a period of Hippo pathway activation during intestinal adaptation in zebrafish.

Intestinal adaptation (IA) is a critical response to increase epithelial surface area after intestinal loss. Short bowel syndrome (SBS) may follow massive intestinal resection in human patients, particularly without adequate IA. We previously validated a model in zebrafish (ZF) that recapitulates key SBS pathophysiological features. Previous RNA sequencing in this model identified upregulation of genes in the Wnt and Hippo pathways. We therefore sought to identify the timeline of increasing cell proliferation and considered the signaling that might underpin the epithelial remodeling of IA in SBS. SBS was created in a ZF model as previously reported and compared with sham fish with and without exposure to monensin, an ionophore known to inhibit canonical Wnt signaling. Rescue of the monensin effects was attempted with a glycogen synthase kinase 3 inhibitor that activates wnt signaling, CHIR-99021. A timeline was constructed to identify peak cellular proliferation, and the Wnt and Hippo pathways were evaluated. Peak stem cell proliferation and morphological changes of adaptation were identified at 7 days. Wnt inhibition diminished IA at 2 wk and resulted in activation of genes of the Wnt/ß-catenin and Yes-associated protein (YAP)/Hippo pathway. Increased cytoplasmic YAP was observed in monensin-treated SBS fish. Genes of the WASP-interacting protein (WIP) pathway were elevated during Wnt blockade. In conclusion, cellular proliferation and morphological changes accompany SBS even in attempted Wnt blockade. Wnt/ß-catenin, YAP/Hippo pathway, and WIP pathway genes increase during early Wnt blockade. Further understanding of the effects of Wnt and YAP pathway signaling in proliferating stem cells might enrich our knowledge of targets to assist IA. NEW & NOTEWORTHY Intestinal adaptation is a critical response to increase epithelial surface area after large intestinal losses. Inhibition of Wnt/ß-catenin signaling impairs intestinal adaptation in a zebrafish model of short bowel syndrome. There is a subsequent upregulation in genes of the Yes-associated protein/Hippo and WIP pathway. These may be targets for future human therapies, as patients are salvaged by the compensation of increased intestinal epithelial surface area through successful intestinal adaptation.

Differential epithelial growth in tissue-engineered larynx and trachea generated from postnatal and fetal progenitor cells.

Postnatal organ-specific stem and progenitor cells are an attractive potential donor cell for tissue-engineering because they can be harvested autologous from the recipient and have sufficient potential to regenerate the tissue of interest with less risk for ectopic growth or tumor formation compared to donor cells from embryonic or fetal sources. We describe the generation of tissue-engineered larynx and trachea (TELT) from human and mouse postnatal organoid units (OU) as well as from human fetal OU. Mouse TELT contained differentiated respiratory epithelium lining large lumens, cartilage and smooth muscle. In contrast, human postnatal TE trachea, formed small epithelial lumens with rare differentiation, in addition to smooth muscle and cartilage. Human fetal TELT contained the largest epithelial lumens with all differentiated cell types as well as smooth muscle and cartilage. Increased epithelial cytokeratin 14 was identified in both human fetal and postnatal TELT compared to native trachea, consistent with regenerative basal cells. Cilia in TELT epithelium also demonstrated function with beating movements. While both human postnatal and fetal progenitors have the potential to generate TELT, there is more epithelial growth and differentiation from fetal progenitors, highlighting fundamental differences in these cell populations.

Stem cells for babies and their surgeons: The future is now.

Pediatric surgeons are ideal allies for the translation of basic science including stem cell therapies. In the spirit of Robert E. Gross, of applying creative solutions to pediatric problems with technical expertise, we describe the impending cellular therapies that may be derived from stem and progenitor cells. Understanding the types and capabilities of stem and progenitor cells is important for pediatric surgeons to join and facilitate progress for babies. We are developing an induced pluripotent stem cell therapy for enteric neuropathies such as Hirschsprung disease that might be helpful for children in the near future. Our goals, which we hope to share with other surgeons and scientists, include working to establish safe clinical trials and meeting regulatory standards in a thoughtful way that balances patients need and unknown risks.

Short-term and long-term human or mouse organoid units generate tissue-engineered small intestine without added signalling molecules.

NEW FINDINGS: What is the central question of this study? Tissue-engineered small intestine was previously generated in vivo by immediate implantation of organoid units derived from both mouse and human donor intestine. Although immediate transplantation of organoid units into patients shows promise as a potential future therapy, some critically ill patients might require delayed transplantation. What is the main finding and its importance? Unlike enteroids, which consist of isolated intestinal crypts, short- and long-term cultured organoid units are composed of epithelial and mesenchymal cells derived from mouse or human intestine. Organoid units do not require added signalling molecules and can generate tissue-engineered intestine in vivo. ABSTRACT: Mouse and human postnatal and fetal organoid units (OUs) maintained in either short-term culture (2 weeks) or long-term culture (from 4 weeks up to 3 months) without adding exogenous growth factors were implanted in immunocompromised mice to form tissue-engineered small intestine (TESI) in vivo. Intestinal epithelial stem and neuronal progenitor cells were maintained in long-term OU cultures from both humans and mice without exogenous growth factors, and these cultures were successfully used to form TESI. This was enhanced with OUs derived from human fetal tissues. Organoid unit culture is different from enteroid culture, which is limited to epithelial cell growth and requires supplementation with R-Spondin, noggin and epidermal growth factor. Organoid units contain multiple cell types, including epithelial, mesenchymal and enteric nervous system cells. Short- and long-term cultured OUs derived from mouse and human intestine develop into TESI in vivo, which contains key components of the small intestine similar to native intestine.

Marked stem/progenitor cell expansion occurs early after murine ileostomy: a new model.

BACKGROUND: Improving treatment for short bowel syndrome requires a better understanding of how intestinal adaptation is affected by factors like mechanoluminal stimulation. We hypothesized that in mice, luminal diversion via an ileostomy would drive adaptive changes similar to those seen in human intestine after diversion while offering the opportunity to study the immediate events after resection that precede intestinal adaptation. MATERIALS AND METHODS: With Institutional Animal Care and Use Committee approval, a distal ileostomy with a long distal Hartman's was created in 9- to 14-week-old C57/B6 mice (n = 8). Control mice only had a midline laparotomy without stoma formation (n = 5). A rim of tissue from the proximal stoma was resected as a historical control for the proximal segment. Postoperatively, mice received a high-protein liquid diet and water ad libitum. On day 3, tissue from both the proximal and distal limbs were collected for histologic and RNA analysis. Morphometric measures, immunofluorescent antigen detection, and RNA expression were compared with Student paired t-tests with a P value < 0.05 considered significant. RESULTS: At 3 d, survival for mice with an ileostomy was 87% and average weight loss was 12.5% of initial weight compared to 6.05% for control mice. Compared to the distal limb, the proximal limb in mice with an ileostomy demonstrated significantly taller villi with deeper and wider crypts. The proximal limb also had decreased expression of intestinal stem cell markers lgr5, bmi1, sox9, and ascl2. Fewer goblet and enteroendocrine cells per hemivillus were also noted in the proximal limb. In control mice, none of these measures were significant between proximal and distal ileum except for villus height. CONCLUSIONS: This new murine ileostomy model allows study of intestinal adaptation without intestinal anastomosis, which can be technically challenging and morbid.