Project description:Multi-tissue regenerative capacity is lost in adult mammals with the exception of the distal digit, which regenerates via largely-uncharacterized mechanisms. Here, we demonstrate that following adult mouse distal digit removal, nerve-associated Schwann cell precursors (N-SCPs) dedifferentiate and secrete growth factors that promote expansion of the blastema and digit regeneration. Specifically, when N-SCPs were dysregulated or ablated, mesenchymal precursor proliferation in the blastema was decreased, nail and bone regeneration were impaired, and regeneration could be rescued by transplantation of exogenous N-SCPs. We show that N-SCPs secreted factors that promoted self-renewal of mesenchymal precursors, and we used transcriptomic and proteomic analysis to define candidate factors. Two of these, oncostatin M (OSM) and PDGF-AA, were made by N-SCPs in the regenerating digit, and rescued the deficits in regeneration caused by loss of N-SCPs due to denervation. Since nerves innervate every peripheral tissue, these results have broad implications for mammalian tissue repair and regeneration.
Project description:Multi-tissue regenerative capacity is lost in adult mammals with the exception of the distal digit, which regenerates via largely-uncharacterized mechanisms. Here, we demonstrate that following adult mouse distal digit removal, nerve-associated Schwann cell precursors (N-SCPs) dedifferentiate and secrete growth factors that promote expansion of the blastema and digit regeneration. Specifically, when N-SCPs were dysregulated or ablated, mesenchymal precursor proliferation in the blastema was decreased, nail and bone regeneration were impaired, and regeneration could be rescued by transplantation of exogenous N-SCPs. We show that N-SCPs secreted factors that promoted self-renewal of mesenchymal precursors, and we used transcriptomic and proteomic analysis to define candidate factors. Two of these, oncostatin M (OSM) and PDGF-AA, were made by N-SCPs in the regenerating digit, and rescued the deficits in regeneration caused by loss of N-SCPs due to denervation. Since nerves innervate every peripheral tissue, these results have broad implications for mammalian tissue repair and regeneration.
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.
Project description:Innate regeneration following digit tip amputation is one of the few examples of epimorphic regeneration in mammals. Digit tip regeneration is mediated by the blastema, the same structure invoked during limb regeneration in some lower vertebrates. By genetic lineage analyses in mice, the digit tip blastema has been defined as a population of heterogeneous, lineage restructed progenitor cells. These previous studies, however, do not comprehensively evaluate blastema heterogeneity or address lineage restruction of closely related cell types. Here we report single cell RNA sequencing of over 38,000 cells from mouse digit tip blastemas and unamputated control digit tips and generate an atlas of the cell types participating in digit tip regeneration.
Project description:Innate regeneration following digit tip amputation is one of the few examples of epimorphic regeneration in mammals. Digit tip regeneration is mediated by the blastema, the same structure invoked during limb regeneration in some lower vertebrates. By genetic lineage analyses in mice, the digit tip blastema has been defined as a population of heterogeneous, lineage restructed progenitor cells. These previous studies, however, do not comprehensively evaluate blastema heterogeneity or address lineage restruction of closely related cell types. Here we report one additional single cell RNA sequencing sample (28 days post-amputation) to add to our already published 38,000 cells from mouse digit tip blastemas and unamputated control digit tips used to generate an atlas of the cell types participating in digit tip regeneration.
Project description:Here, we investigate the origin and nature of blastema cells that regenerate the adult murine digit tip. We show that Pdgfra-expressing mesenchymal cells in uninjured digits establish the regenerative blastema and are essential for regeneration. Single cell profiling shows that the mesenchymal blastema cells are distinct from both uninjured digit and embryonic limb/digit Pdgfra-positive cells. This unique blastema state is environmentally determined; dermal fibroblasts transplanted into the regenerative, but not non-regenerative, digit express blastema markers and contribute to bone regeneration. Moreover, lineage tracing with single cell profiling indicates that endogenous osteoblasts/osteocytes acquire a blastema mesenchymal transcriptional state and contribute to both dermis and bone regeneration. Thus, mammalian digit tip regeneration occurs via a distinct adult mechanism where the regenerative environment promotes acquisition of a unique blastema state that allows cells from tissues like bone to contribute to regeneration of other mesenchymal tissues such as the dermis.
Project description:Mammalian digit-tip can regenerate upon amputation1-3, like amphibians. It is unknown why this capacity is limited to the area associated with the nail3-5. Here, we show that nail stem cells (NSCs) reside in the Wnt-suppressed proximal nail matrix and that the mechanisms governing NSC differentiation are directly coupled with their ability of orchestrating digit regeneration. Early nail progenitors located distal to the NCS region undergo Wnt-dependent differentiation into nail. Upon amputation, this Wnt activation is required for nail regeneration and also for attracting nerves that promote mesenchymal blastema growth, leading to regeneration of the entire digit. Amputations proximal to the Wnt-active nail progenitors result in failure to regenerate nail/digit. Nevertheless, β-catenin stabilization in the NSC region induced their regeneration. These results establish a link between NCS differentiation and digit regeneration, suggesting a utility of the NSCs in developing novel treatments for amputees. Nail matrix cells were harvested from proximal and distal matrix region by microdissection and processed to RNA extraction and hybridization on Affymetrix microarrays. We analyzed two proximal and two distal matrix cells.
Project description:Mammalian digit-tip can regenerate upon amputation1-3, like amphibians. It is unknown why this capacity is limited to the area associated with the nail3-5. Here, we show that nail stem cells (NSCs) reside in the Wnt-suppressed proximal nail matrix and that the mechanisms governing NSC differentiation are directly coupled with their ability of orchestrating digit regeneration. Early nail progenitors located distal to the NCS region undergo Wnt-dependent differentiation into nail. Upon amputation, this Wnt activation is required for nail regeneration and also for attracting nerves that promote mesenchymal blastema growth, leading to regeneration of the entire digit. Amputations proximal to the Wnt-active nail progenitors result in failure to regenerate nail/digit. Nevertheless, β-catenin stabilization in the NSC region induced their regeneration. These results establish a link between NCS differentiation and digit regeneration, suggesting a utility of the NSCs in developing novel treatments for amputees.