Short Bowel Syndrome is an expensive, morbid condition with an increasing incidence. Fundamental congenital and perinatal conditions such as gastroschisis, malrotation, atresia, and necrotizing enterocolitis (NEC) may lead to short bowel syndrome (SBS). NEC is the most common gastrointestinal emergency in neonates and primarily occurs in premature infants As rates of prematurity are increasing, so are the numbers of children with SBS and NEC. In addition, prevalence is increased for other diagnoses such as gastroschisis, which has nearly doubled. Medical and surgical treatment options carry high dollar and human costs and morbidities including multiple infections and hospitalizations for vascular access, liver failure in conjunction with parenteral nutrition-associated cholestasis, and death. Small bowel transplant has a reported 5 year graft survival of 48%, but is attended by rejection, the morbidity of major surgery, and a lifelong need for anti-rejection medication. A report on 989 grafts in 923 patients by the Intestine Transplant Registry reveals improving outcomes, but one year graft/ patient survival rates are 65%/77%. Tissue engineered small intestine (TESI) offers a potential alternative durable autologous therapy that avoids the problems of donor graft supply for intestinal transplant and long term immunosuppression. TESI exactly recapitulates native intestine histology. All four epithelial lineages are seen in conjunction with a lamina propria, nerve elements, and muscularis mucosa. OU, when reduced to single cells or the single cell fraction obtained in the purification of OU do not form TESI. This multicellular OU transplantation strategy is distinctive in producing full-thickness TESI that recapitulates all the layers of native intestine, and in the Lewis rat, intact function. In order to meet regulatory requirements and to guarantee the best chance of success by optimizing all conditions, we must define the necessary and sufficient progenitor cell population that will be transplanted. In addition, defining the mechanisms by which TESI forms and therefore can be impelled will underpin the best chance of success in human trials. This grant proposal seeks to identify and surpass the barriers to using TESI as a human therapy for SBS.
Short Bowel Syndrome is an expensive, morbid condition with an increasing incidence. Fundamental congenital and perinatal conditions such as gastroschisis, malrotation, atresia, and necrotizing enterocolitis (NEC) may lead to short bowel syndrome (SBS). NEC is the most common gastrointestinal emergency in newborn babies in California and primarily occurs in premature infants As rates of prematurity are increasing, so are the numbers of children with SBS and NEC. In addition, more babies in California are getting SBS associated with other diagnoses such as gastroschisis, which has recently nearly doubled. Medical and surgical treatment options carry high dollar and human costs and children suffer from problems such as infections and hospitalizations for vascular access, liver failure, and death. The only therapy currently is small bowel transplant, but a recent study showed that the transplant only has a 65% chance of surviving in the first year, and the child has only a 77% chance of surviving that same year. We need to give these children a better future measured in decades. Tissue engineered small intestine (TESI) offers a potential therapy. This would come from the patient's own cells, and therefore would avoid the problems of finding a donor for small bowel transplant, and also would not require life-long medicine for immunosuppression as children must take who have had a transplant. In this proposal, we seek to identify and surpass the barriers to using TESI as a human therapy for SBS. This would benefit the children of California as well as the field of Regenerative medicine as these advances might also help with further somatic stem cell-based therapies to treat a wide range of problems for both children and adults.
The application is focused on short bowel syndrome, a childhood disease associated with significant morbidity and mortality. Currently small bowel transplants are the standard of care, but donors are in short supply, and the surgery and post-operative course are associated with poor long-term survival. The applicant proposes study of a novel alternative to transplantation of donor grafts, the use of a tissue engineered small intestine (TESI), created ultimately by autologous cells cultured to generate small intestine organoid units on biodegradable polymer scaffolds. The applicant plans to optimize and characterize growth of TESI using mouse cells, and to trace the lineage origins of the operant stem cell population in transgenic mouse models. TESI will also be tested functionally for responses to growth factors, and electrophysiologically. Then using human cells (obtained from surgical explants) the applicant will generate TESI and implant them into immunocompromised mice to determine function after engraftment. In the long-term the applicant plans primate studies based on the mouse work, but is not requesting funding for the large animal model work.
An important strength of the application was the straightforward design of the proposed studies. The stem cell populations will be characterized in sufficient detail to standardize the translational protocols. Reviewers were impressed by the quality of the preliminary data, in particular the normal microscopic appearance and architecture of the TESI generated so far, and the development of a surgical approach to the mouse. Reviewers were concerned that the developmental biology approaches were not detailed sufficiently, and because the markers chosen were not necessarily specific for the progenitor cells of interest and bioluminescence approaches not robust, this part of the research plan may run into trouble. In response to these concerns, the reviewers suggested more focus on the translational issues in surgical models. The reviewers all felt that the applicant had the ideal clinical-scientist background to bring into stem cell biology and regenerative medicine.
A weakness of the proposal was the lack of detail on how the applicant planned to scale up the experiments from mouse to primate, and the reviewers thought this part of the proposal poorly developed. In particular a discussion of how the information obtained in mouse studies will be applied in primates would have been welcomed. The reviewers were left wondering about how the applicant envisioned the surgical technique and immunosuppressive approaches for the primate studies. In the end, the potential for the rodent work to yield important information over-rode concerns about the primate studies, which are premature, and if set aside until the appropriate time, still leave a research plan that can stand on its own to yield significant insights into intestinal biology and therapy.
The applicant is a pediatric surgeon who trained at top medical school and residency programs, and has been an Assistant Professor of Surgery for 2 years. Letters of support from a previous mentor cited the applicant’s gift for independent thought and high intellectual capacity, and the applicant has won numerous awards. The applicant does not yet have independent publications. The applicant proposes to supplement clinical expertise with formal coursework and training in developmental biology, and has outlined an elaborate and ambitious career development plan. The strong institutional support is reflected in the several letters of reference, and speaks to the enthusiastic commitment to the applicant by the institution. Further, the institution and clinical department are protecting 75% of the applicant’s time for research in a unit where the applicant is surrounded by other investigators interested in gut regeneration. One mentor is a noted expert in the field and, with the other diverse mentors, will bring tremendous power to the application.
Overall the potential impact of this project could be tremendous, and could result in a source of intestinal replacement therapy that does not require immunosuppression. The work has implications for other intestinal diseases as well.