p75 ^NTR orchestrates chondrogenesis and mechanoadaptation to preserve temporomandibular joint development and homeostasis

The temporomandibular joint (TMJ) is essential for oral functions such as chewing, speaking, and swallowing. Temporomandibular disorders that impair these functions notably reduce patients’ quality of life, and few therapeutic strategies are available to ameliorate these conditions. Here, we identify the neurotrophin receptor (p75 ^NTR ) as a central regulator of mandibular condylar cartilage development, mechanoadaptation, and homeostasis. p75 ^NTR loss causes condylar and disc hypoplasia, reduced chondrocyte number, impaired load-induced anabolism, and accelerated degeneration. Conditional deletion experiments demonstrate chondrocyte-autonomous requirements for the brain-derived neurotrophic factor (BDNF)–p75 ^NTR axis, which activates phosphoinositide 3-kinase AKT serine/threonine kinase and p38 mitogen-activated protein kinase signaling to promote proliferation and chondrogenic differentiation while restraining apoptosis. Degenerative human condyles exhibit reduced p75 ^NTR expression levels. Together, these data establish p75 ^NTR as a molecular hub integrating neurotrophic and mechanical cues to preserve postnatal TMJ architecture and highlight the BDNF-p75 ^NTR axis as a potential therapeutic target.