Developing a human pluripotent stem cell-based strategy for treating Hirschsprung disease

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Hirschsprung disease is a life-threatening intestinal disorder caused by an absence of intrinsic nerve cells (aganglionosis) in the most distal gastrointestinal tract. It occurs in approximately 1 in 5000 live births, making it one of the most common congenital diseases affecting the gut. Given that intrinsic gut nerve cells (enteric neurons) mediate the contractions necessary for normal gut function, their absence in Hirschsprung patients causes severe constipation or intestinal obstruction. The only treatment available is surgical removal of the affected part of the bowel combined with a 'pull through' procedure, which entails connecting the healthy part of the gut to the anus. However, the surgery necessitates retention of part of the abnormal gut including the anal sphincter, which is likely to account in part for the long-term, often life-long, gastrointestinal problems and poor quality of life suffered by the majority of patients with Hirschsprung disease. Surgery, readmissions and outpatients hospital appointments required for management of this condition present a significant burden for the healthcare system. Recent advances in the understanding of development of the gut's intrinsic (or enteric) nervous system and pathogenesis of the disease, as well as considerable progress in regenerative medicine, have highlighted potential for alternative treatments, such as cell replacement therapy.During normal embryonic development, the enteric nervous system is derived from a transient population of cells termed neural crest cells that migrate from the neural tube to innervate the gastrointestinal tract. In Hirschsprung disease these cells fail to colonize the distal gut leaving a variable segment of aganglionosis. Experiments in animal models have demonstrated that transplantation of enteric nervous system progenitor/stem cells (derivatives of the original neural crest cells and harvested from mouse gut explants or mouse embryonic stem cells) have the ability to differentiate into enteric neurons and colonize when transplanted into aganglionic gut explants. Similar neuronal progenitor cells obtained from human postnatal gut explants have been shown to effectively colonize and differentiate within aganglionic gut explants of Hirschsprung patients. However, the harvesting of such human nerve progenitor cells from gut is difficult and becomes more so with increasing post-natal age. Therefore, although such preclinical testing has demonstrated that cell therapy should be a viable option for curing Hirschsprung disease, the availability of human enteric neurons from post-natal gut remains a bottleneck for development of cell-based therapies.An attractive alternative source is offered by pluripotent stem cells, where there is significant potential of generating appropriate cells for therapy both in terms of numbers and tailoring cell properties for the task. We have recently developed efficient protocols to generate human neural crest cells and enteric nervous system progenitors from human pluripotent stem cells. In this project, we will test the ability of these progenitors to correct for the lack of enteric neurons in animal and patient-derived models of Hirschsprung disease following transplantation. We will also optimise the current methods of generating and purifying human enteric nervous system progenitors from pluripotent stem cellsand will develop a new improved animal model of Hirschsprung disease. In this way, we will establish the pre-clinical basis for a regenerative medicine approach for treating Hirschsprung disease by transplantation of cells derived from human pluripotent stem cells to re-innervate the affected part of the gut. In the first instance our goal will be to improve the outcome of current treatments by innervation of the short section remaining after routine surgery.