The p75 neurotrophin receptor controls the skeletal stem cell niche through sensory innervation

Low bone mass is frequently observed in Alzheimer's disease (AD), yet the underlying mechanisms remain poorly understood. In this study, we demonstrate that sensory nerves constitute a critical component of the skeletal stem cell (SSC) niche. Deletion of the neurotrophin receptor p75NTR in neurons or sensory-specific cells, but not in osteogenic or sympathetic cells, resulted in reduced sensory innervation, disrupted SSC homeostasis, and significant bone loss. Although a cell-intrinsic role of p75NTR in SSCs cannot be ruled out, further experiments involving sensory denervation or transplantation into hosts with sensory-neuron-specific p75NTR deficiency confirmed impaired SSC osteogenesis. Mechanistically, p75NTR controls the expression of neuronal osteopontin (SPP1), which in turn promotes SSC self-renewal and osteogenic differentiation. Notably, this p75NTR-SPP1 signaling axis was found to be disrupted in AD mouse models, offering a direct mechanistic explanation for AD-associated osteopenia and highlighting the therapeutic potential of targeting neural control of SSCs.