Regulation of Revival Stem Cells in the Intestinal Epithelium

The intestinal epithelium is an inherently regenerative tissue which undergoes continuous self-renewal driven by the highly proliferative Lgr5+ intestinal stem cell (ISC) population. Following damage, the Lgr5+ ISC population is depleted, and must be reconstituted to reinstate homeostatic function. Regeneration is achieved through the reprogramming of a subset of epithelial cells into fetal-like, multipotent, revival stem cells (revSCs). RevSCs are rare in the homeostatic gut, but are transiently upregulated during injury, successfully restoring the intestine following irradiation (IR), genetic ablation of Lgr5+ ISCs, chemically induced colitis, and infection. As revSCs are a novel cell type, the regulatory networks driving their cell state dynamics are under-characterized; however, we previously show that Yap signalling contributes. Here, I identify that transient activation of the p53 and TGFβ pathways also regulate revSC induction and facilitate successful intestinal regeneration. Through a combination of in vitro and in vivo studies, I demonstrate that the transient p53 signalling critically regulates the generation of revSCs. I further observed that TGFβ potently induced a functional revSC population in vitro, yet in vivo, loss of TGFβ delayed regeneration, but did not completely preclude revSC production, similar to the phenotype of Yap- and Yap/Taz-deficient models. My work thus indicates functional redundancy between Hippo and TGFβ signalling, such that concurrent pathway abrogation prevented the emergence of revSCs leading to subsequent complete intestinal collapse due to a failure of ISC reconstitution. Together, this work indicates that p53, Hippo and TGFβ pathways coalesce to regulate revSCs and achieve effective intestinal regeneration. Unraveling the mechanisms that govern damage-induced fetal reprogramming provides insight across the spectrum of intestinal health and disease. The processes of development, regeneration, inflammation, and oncogenesis are remarkably interconnected. Thus, understanding the higher order integration of signalling pathways is paramount to providing insight into cell fate determination and therapeutic strategies that seek to balance between physiological and wound-healing states to achieve effective repair. This not only has implications for intestinal disease, but across tissues, as research continues to identify conserved mechanisms regulating cell plasticity during tissue regeneration.