Regulation of progenitor cell proliferation and neuronal differentiation in enteric nervous system neurospheres.

Enteric nervous system (ENS) progenitor cells isolated from mouse and human bowel can be cultured in vitro as neurospheres which are aggregates of the proliferating progenitor cells, together with neurons and glial cells derived from them. To investigate the factors regulating progenitor cell proliferation and differentiation, we first characterised cell proliferation in mouse ENS neurospheres by pulse chase experiments using thymidine analogs. We demonstrate rapid and continuous cell proliferation near the neurosphere periphery, after which postmitotic cells move away from the periphery to become distributed throughout the neurosphere. While many proliferating cells expressed glial markers, expression of the neuronal markers ß-tubulin III (Tuj1) and nitric oxide synthase was detected in increasing numbers of post-mitotic cells after a delay of several days. Treatment of both mouse and human neurospheres with the γ-secretase inhibitor N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) reduced expression of the transcription factors Hes1 and Hes5, demonstrating inhibition of Notch signaling. DAPT treatment also inhibited progenitor cell proliferation and increased the numbers of differentiating neurons expressing Tuj1 and nitric oxide synthase. To confirm that the cellular effects of DAPT treatment were due to inhibition of Notch signaling, siRNA knockdown of RBPjκ, a key component of the canonical Notch signaling pathway, was demonstrated both to reduce proliferation and to increase neuronal differentiation in neurosphere cells. These observations indicate that Notch signaling promotes progenitor cell proliferation and inhibits neuronal differentiation in ENS neurospheres.

Hirschsprung's disease: current management and prospects for transplantation of enteric nervous system progenitor cells.

Hirschsprung's disease affects 1 in 5000 newborns and is caused by an absence of ganglion cells in a variable length of the distal gut. It commonly presents in the newborn period with life-threatening bowel obstruction requiring surgery. Despite apparently successful surgery the long-term outcomes are often unsatisfactory with some children facing a lifetime of continence issues or debilitating constipation. This article exams the reasons for this and describes advances that have occurred in the surgical management of the disease. In the last two decades rapid progress has been made in understanding the genetics and molecular pathology of Hirschsprung's disease. The potential for harnessing this knowledge to develop a stem cell based therapy for Hirschsprung's disease is discussed.