Decoding muscle-resident Schwann cell dynamics during neuromuscular junction remodeling [spinal crush]

This investigation leverages single-cell RNA sequencing (scRNA-Seq) to delineate the contributions of muscle-resident Schwann cells to neuromuscular junction (NMJ) remodeling in models of healthy, partially denervated, and completely denervated muscles. The study identifies several distinct Schwann cell subtypes, notably a novel terminal Schwann cell (tSC) subtype integral to the denervation-reinnervation cycle, distinguished by a transcriptomic signature indicative of cell migration and polarization. It also characterizes three myelin Schwann cell subtypes, which are notably enriched with genes associated with myelin production, in addition to mesenchymal differentiation and collagen synthesis. Importantly, SPP1 signaling emerges as a pivotal regulator of NMJ dynamics, promoting Schwann cell proliferation and muscle reinnervation across the studied nerve injury models. These findings advance our understanding of NMJ maintenance and regeneration and underscore the therapeutic potential of targeting specific molecular pathways to treat neuromuscular and neurodegenerative disorders. S100GFPtg and S100GFPtg Sod1-/- mice were bred at the University of Michigan, were fed normal chow ad libitum, and housed 12:12 hour light-dark cycle under the UofM veterinary staff supervision. All procedures were approved by the University Committee on the Use and Care of Animals at UM and were in accordance with the U.S. National Institute of Health (NIH). We used 2-month-old male mice from each genotype (n=4 per group). Additionally, we included an S100GFPtg mouse that underwent sciatic nerve crush injury and was harvested at 7 days post-injury (7dpi), referred to as S100GFPtg 7dpi. We simultaneously harvested and processed hind limb muscles (Tibialis Anterior and Gastrocnemius) from all groups. Using Fluorescence-Activated Cell Sorting, we separated GFP+ and GFP- single cells. The sorted cells then underwent 10X Genomics library preparation and sequencing.