Bmpr1a Regulates Bone Regeneration Via Pi3k-Akt Signaling

The role of BMPR1A-mediated BMP signaling in bone regeneration remains incompletely understood. Here, we investigated its stage-specific effects using osteolineage-specific Bmpr1a conditional knockout (Bmpr1a-cKO) and overexpression (Bmpr1a-CA) mouse models. Temporal inhibition of Bmpr1a during early bone repair significantly accelerated femoral defect healing, characterized by enhanced bone formation, improved trabecular connectivity, and expedited marrow cavity restoration. Histological and cellular analyses revealed that Bmpr1a ablation robustly increased osteoprogenitor proliferation while unexpectedly elevating osteoclast activity. In vitro studies demonstrated that Bmpr1a knockdown preferentially activated canonical BMP-SMAD1/5/9 signaling over non-canonical pathways. RNA sequencing of Bmpr1a-cKO callus tissues identified widespread transcriptomic alterations, with KEGG pathway analysis highlighting PI3K-AKT as the most significantly enriched pathway. Functional validation confirmed that Bmpr1a inactivation upregulated GNG4, a GPCR subunit that activated PI3K-AKT signaling to drive osteoprogenitor proliferation. Critically, silencing Gng4 reversed the hyperproliferative phenotype induced by Bmpr1a deficiency. This study establishes the BMPR1A-GNG4-PI3K-AKT axis as a central regulator of osteoprogenitor expansion during bone regeneration. By delineating receptor-specific mechanisms, our findings provide a rationale for targeting BMPR1A to achieve localized and controlled bone repair, addressing the systemic limitations of conventional BMP ligand therapies.