Project description:The intestine is a barrier tissue whose epithelium has high intrinsic turnover rate; intestinal stem cells, in response to signals from the niche, self-renew and produce progeny that differentiate to fulfill the continuous demand for new epithelial cells that are continuously shed into the lumen. The intestine is innervated by a dense network of peripheral nerves that controls nutrient absorption, intestinal motility, and visceral pain sensation. However, the roles of neurons in regulating epithelial cell homeostasis or regeneration remain as yet undiscovered. Here we investigate the effects of gut-innervating sympathetic neurons on epithelial cell repair following irradiation (IR)-induced gut injury. We observed that sympathetic innervation density in the gut increases post IR, while chemical sympathetic denervation impairs gut regeneration. Combining single cell RNA-sequencing and in vivo experiments, we discovered that sympathetic neurons regulate gut regeneration through modulation of IL22 production in type 3 innate lymphoid cells (ILC3) downstream of 2-adrenergic receptor signaling. These results define a novel neuroimmune axis important for intestinal regeneration.
Project description:Piloerection (goosebump) requires concerted actions of the hair follicle, the arrector pili muscle (APM), and the sympathetic nerve, providing a model to study interactions across epithelium, mesenchyme, and nerves. Here, we show that APMs and sympathetic nerves form a dual component niche to modulate hair follicle stem cell (HFSC) activity. Sympathetic nerves form synapse-like structures with HFSCs and regulate HFSCs through norepinephrine, whereas APMs maintain sympathetic innervation to HFSCs. Without norepinephrine signaling, HFSCs enter a deep quiescence state by down-regulating cell cycle machinery and mitochondria metabolism, while up-regulating quiescence regulators Lhx2, Foxp1, and Fgf18. During development, HFSC progeny secrets Sonic Hedgehog (SHH) to direct the formation of this APM-sympathetic nerve niche, which in turn controls hair follicle regeneration in adults. Our results reveal a reciprocal interdependence between a regenerative tissue and its niche at different stages, and illustrate that nerves can modulate stem cell quiescence through synapses and neurotransmitters.
Project description:The sympathetic nervous system controls a wide spectrum of bodily functions including operation of vessels, cardiac rhythm, and the “flight or fight response”. Sympathetic neurons, which are neural crest-derived, develop in coordination with presynaptic motor nerves extending from the central nervous system (CNS). By using nerve-selective genetic ablations, we revealed that sympathetic ganglia development depends on CNS-derived motor innervation. In the absence of preganglionic motor nerves, trunk sympathetic chain ganglia were fragmented and smaller in size, while cervical ganglia were severely misshapen. Sympathetic neurons were misplaced along sensory fibers and projected towards abnormal paths, in some cases invading the sensory dorsal root ganglia. The misplaced progenitors of sympathoblasts corresponded to the nerve-associated, neural crest-derived Schwann cell precursors (SCPs). Notably, we found that SCPs activate the autonomic marker PHOX2B while migrating along motor nerves towards the region of the dorsal aorta in wildtype embryos, suggesting that SCP differentiate into sympathetic neurons while still nerve-associated in motor-ablated embryos. Ligand-receptor prediction from single cell transcriptomic data coupled with functional studies identified Semaphorin 3A/3F as candidate motor nerve-derived signals influencing neural crest migration along axons. Thus, motor nerves control the placement of sympathoblasts and their subsequent axonal navigation during critical periods of sympathetic chain development.
Project description:Empirical and anecdotal evidence have associated stress with accelerated hair greying (formation of unpigmented hairs), but the scientific evidence linking the two is scant. Here, we report that acute stress leads to hair greying through fast depletion of melanocyte stem cells (MeSCs). Combining adrenalectomy, denervation, chemogenetics, cell ablation, and MeSC-specific adrenergic receptor knockout, we found that stress-induced MeSC loss is independent of immune attack or adrenal stress hormones. Rather, hair greying results from activation of the sympathetic nerves that innervate the MeSC niche. Upon stress, sympathetic nerve activation leads to burst release of the neurotransmitter norepinephrine, which drives quiescent MeSCs into rapid proliferation, followed by differentiation, migration, and permanent depletion from the niche. Transient suppression of MeSC proliferation prevents stress-induced hair greying. Our studies demonstrate that acute stress-induced neuronal activity can drive rapid and permanent loss of somatic stem cells, and illustrate an example in which somatic stem cell maintenance is directly influenced by the overall physiological state of the organism.
Project description:Peripheral innervation plays an important role in regulating tissue repair and regeneration. Here, we provide evidence that injured peripheral nerves provide a reservoir of mesenchymal precursor cells that can directly contribute to murine digit tip regeneration and skin repair. In particular, using single-cell RNA sequencing and lineage tracing we identify transcriptionally-distinct mesenchymal cell populations within the control and injured adult nerve, including neural crest-derived cells in the endoneurium with characteristics of mesenchymal precursor cells. Culture and transplantation studies show that these nerve-derived mesenchymal cells have the potential to differentiate into non-nerve lineages. Moreover, following digit tip amputation, the neural crest-derived nerve mesenchymal cells contribute to the regenerative blastema and ultimately to the regenerated bone. Similarly, neural crest derived nerve mesenchymal cells contribute to the dermis during skin wound healing. These findings support a model where peripheral nerves directly contribute mesenchymal precursor cells to promote repair and regeneration of injured mammalian tissues.