Identification of optimal harvest sites of ileal stem cells for treatment of bile acid malabsorption in a dog model

Intestinal stem cell organoid transplantation generates neomucosa in dogs

BACKGROUND AND AIMS

Intestinal stem cell organoid transplantation generates functional intestinal neomucosa and has been used therapeutically to improve nutrient absorption and cure bile acid malabsorption in rats. We hypothesized that intestinal organoids can be harvested and transplanted to generate intestinal neomucosa in a large animal model.

MATERIALS AND METHODS

In group 1, 2-month old beagles (n = 6) underwent autotransplantation of intestinal organoids prepared from a segment of their own ileum. In group 2, intestinal organoids were harvested from fetuses and allotransplanted into 10-month old mother animals (n = 4). Tissues were harvested after 4 weeks and analyzed by hematoxylin and eosin histology and fluorescent microscopy.

RESULTS

Large numbers of viable organoids were harvested in both groups. In group 1, no neomucosal growth was identified in any of the engraftment sites after autotransplantation of juvenile organoids. In group 2, neomucosal growth with large areas of crypts and villi was identified in 11 of 12 polyglycolic acid scaffolds after allotransplantation of fetal organoids. The neomucosa resembled normal canine mucosa in structure and composition.

CONCLUSIONS

Intestinal stem cell organoid transplantation can be used to generate neomucosa in dogs. This is the first report of successful generation of intestinal neomucosa using intestinal stem cell organoid transplantation in a large animal model.

Orthotopic transplantation of intestinal mucosal organoids in rodents

BACKGROUND

Orthotopic transplantation of intestinal mucosal organoids that contain putative mucosal stem cells serves as an important step toward implementing intestinal gene therapy and treatment for malabsorption syndromes in animals and humans. We hypothesized that intestinal mucosal organoids can be transplanted along the axis of the small bowel giving rise to a neomucosa expressing proteins of its donor origin.

METHODS

Epithelial organoids were harvested from neonatal mice or rat small intestine with the use of a combination of enzymatic digestion with dispase and collagenase, and gravity sedimentation. In adult syngeneic recipients, a 7-cm segment of midjejunum was isolated, leaving its vascular pedicle intact. The remaining proximal and distal segments were anastomosed to restore intestinal continuity. The isolated segments were randomly subjected to surgical or chemical mucosectomy with a chelator solution for 30, 45, or 60 minutes and then compared. Histologic examination was used to confirm the presence of enterocytes, goblet cells, enteroendocrine cells, and Paneth cells in the neomucosal segments. To confirm the presence of ileal bile acid transporter (IBAT) gene message and function, we measured sodium-dependent bile acid uptake and IBAT-messenger RNA. Immunohistochemical examination using anti-IBAT antibodies was performed to demonstrate the expression of IBAT in the neomucosal segments. Experiments were repeated in a murine model transgenic for the green fluorescent protein to verify donor origin of the engrafted mucosa expressing IBAT.

RESULTS

The area of peak IBAT function was found to be located in the terminal ileum. Organoid units harvested from this region were capable of generating a small-bowel neoileal mucosa after being seeded into the jejunum. This mucosa was histologically confirmed to differentiate into all 4 intestinal lineages and to express IBAT signal, confirming its donor-derived origin. Optimal engraftment of mucosa expressing the IBAT protein was found in isolated jejunal segments debrided for 45 minutes. Sodium-dependent bile acid uptake was 5-fold higher in the neoileum, compared with the jejunum. IBAT-mRNA levels in the neoileum were 18-100-fold higher than those in the jejunum. Areas of green fluorescent protein-positive mucosa stained positively with anti-IBAT antibody in adjacent sections, suggesting that the regenerated mucosa is from transplanted ileal stem cells.

CONCLUSIONS

Orthotopic transplantation of epithelial organoids containing ileal stem cells was used to generate a neoileal mucosa that expressed all 4 intestinal lineages along with a new zone of active bile acid uptake and IBAT expression in a recipient jejunal segment.

Treatment of bile acid malabsorption using ileal stem cell transplantation

BACKGROUND

We hypothesized that ileal stem cell clusters transplanted into a segment of jejunum can be used to treat bile acid malabsorption.

STUDY DESIGN

In adult Lewis rats, a 15-cm segment of jejunum was isolated with its blood circulation left intact and partially stripped of enterocytes using luminal high-velocity perfusions with 3mmol/L ethylenediamine tetra-acetic acid solutions. Continuity was restored by anastomosing the proximal and distal gut. Ileal stem cell clusters were harvested from neonatal Lewis rats and transplanted into the stripped segments to generate a "neoileum." After 4weeks, recipients underwent resection of the native ileum, and the isolated neoileum was anastomosed in its place. After an additional 4weeks, a 48-hour stool collection was performed. The engrafted segment was harvested for taurocholate uptake studies, ileal bile acid transporter (IBAT) protein by immunohistomorphometry, and IBAT mRNA quantitation by reverse transcription polymerease chain reaction. Data were analyzed by ANOVA/t-test. Rats undergoing ileectomy, jejunectomy, or sham operations served as controls.

RESULTS

Total bile acid loss in the stool was markedly lower in rats with a neoileum compared with rats with an ileectomy (p < 0.001). Total taurocholate uptake was notably increased in the neoileum compared with the jejunum (p < 0.001). IBAT protein signal intensity was considerably higher in the neoileum compared with jejunum (p < 0.001). IBAT mRNA amounts in the neoileal group were comparable with those in normal rat ileum and were considerably higher (p = 0.003) than in the jejunum.

CONCLUSIONS

Ileal stem cell clusters were used to establish a new zone of bile acid uptake and IBAT expression in a jejunal segment. This neoileum eliminated loss of bile acids in the stool after ileectomy. This is the first time that transplantation of intestinal stem cell clusters has been shown to correct a clinical malabsorption syndrome.