Retinoic Acid Accelerates the Specification of Enteric Neural Progenitors from In-Vitro-Derived Neural Crest

Abstract

Summary The enteric nervous system (ENS) is derived primarily from the vagal neural crest, a migratory multipotent cell population emerging from the dorsal neural tube between somites 1 and 7. Defects in the development and function of the ENS cause a range of enteric neuropathies, including Hirschsprung disease. Little is known about the signals that specify early ENS progenitors, limiting progress in the generation of enteric neurons from human pluripotent stem cells (hPSCs) to provide tools for disease modeling and regenerative medicine for enteric neuropathies. We describe the efficient and accelerated generation of ENS progenitors from hPSCs, revealing that retinoic acid is critical for the acquisition of vagal axial identity and early ENS progenitor specification. These ENS progenitors generate enteric neurons in vitro and, following in vivo transplantation, achieved long-term colonization of the ENS in adult mice. Thus, hPSC-derived ENS progenitors may provide the basis for cell therapy for defects in the ENS.

Zebrafish: A Model Organism for Studying Enteric Nervous System Development and Disease

“…The general idea for transplantation in patients, which is currently the major focus of many groups worldwide, is to obtain enteric neuronal progenitor cells and, after in vitro expansion, transplant them back to the aganglionic distal colon of the patient. As mentioned in the previous section, retinoic acid increases enteric neuron numbers in vivo and is currently also used in vitro to enhance specification of enteric neural progenitors (Frith et al, 2020 ). During a chemical screening in cultured human ENCCs, pepstatin A was discovered to be capable of improving colonization of transplanted NCCs in vitro and in vivo (Fattahi et al, 2016 ).…”

Dynamic integration of enteric neural stem cells in ex vivo organotypic colon cultures

“…21 Similar to ENSC, pluripotent-derived ENS progenitors have been shown to engraft and migrate through the colonic muscularis to reside within endogenous ganglia structures, across a four week period, following in vivo transplantation. 22 Taken together, these findings suggest that the migration of donor ENSC-derived cells into the gut neuromusculature, and the "homing" of donor neurons to the myenteric plexus region, are likely central processes in the establishment of donor-derived functional responses within the host neuromusculature. However, to date, a more definitive timeframe and mechanistic understanding of donor cell integration remains elusive.…”

“…Recent studies have highlighted the potential of autologous, and pluripotent-derived ENS progenitorbased therapy, as a means of replacing neurons after in vivo transplantation to mouse colon. [14][15][16][17][19][20][21][22][23] However, the precise mechanisms by which donor-derived cells integrate within recipient tissue remain unclear. Therefore, studies to uncover the timeframe, and mechanisms, underlying donor cell integration are fundamental to progressing towards clinical application of stem cell therapy for gut disorders.…”

Cell-autonomous retinoic acid receptor signaling has stage-specific effects on mouse enteric nervous system

“…Retinoic acid regulates activity of the RAR/RXR transcription factor family to alter gene expression and influence many aspects of development (34). Prior studies using constitutive knockout mice, RAR antagonist, stem cells or vitamin A depletion in mice and rats show critical roles for RA in the developing ENS (21,(23)(24)(25)(26)(27)(28)(29)(31)(32)(33). For example, loss of the RA biosynthetic enzyme retinaldehyde dehydrogenase 2 (RALDH2) causes extensive bowel aganglionosis in Raldh2-/-mice (28), while Raldh1-/-and Raldh3-/-mice have milder ENS defects (25).…”

“…Maturation of the ENS continues during fetal development and remodeling continues after birth (18)(19)(20). Retinoic acid (RA), the active metabolite of vitamin A, is an important morphogen with an integral role in ENCDC migration, proliferation, and differentiation (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). RA functions mainly as a transcriptional regulator that binds to and activates retinoic acid receptor (RAR)/retinoid x receptor (RXR) heterodimers (34).…”