Macrodactyly is a disabling congenital disease characterized by overgrowth of soft tissues and bones, which leads to finger enlargement and joint deformity. The mechanism of bone overgrowth in macrodactyly was rarely understood. In our study bone manifestations of three macrodactyly patients were analyzed by micro-CT. PIK3CA mutation was detected by next-generation sequencing (NGS) of a tumor gene-panel. The PI3K/AKT/mTOR pathway activation and target genes were analyzed. The osteogenic potential of macrodactyly-derived bone marrow mesenchymal stem cells (MAC-BMSCs) was compared with polydactyly-derived bone marrow mesenchymal stem cells (PD-BMSCs). PIK3CA inhibitors were tested for proliferation and osteogenesis potential of MAC-BMSCs. Activating PIK3CA mutations and activation of PI3K/AKT/mTOR pathway were detected in all MAC-BMSCs. MAC-BMSCs had enhanced osteogenesis potential compared with PD-BMSCs. PIK3CA knockdown by shRNA or BYL719 treatment significantly reduced osteogenic differentiation capacity of MAC-BMSCs. RNA-Seq and qRT-PCR revealed the upregulation of distal-less homeobox 5 (DLX5) in MAC-BMSCs compared with PD-BMSCs. The osteogenic potential of MAC-BMSCs was inhibited by DLX5 knockdown, indicating that DLX5 is a downstream target of PIK3CA activation-mediated osteogenesis. This study revealed that osteogenic differentiation in MAC-BMSCs is enhanced by PIK3CA activation mutation through PI3K/AKT/mTOR signaling pathway and can be reversed by PIK3CA knockdown or drug inhibition.

巨指是一种致残的先天性疾病，其特征是软组织和骨骼过度生长，导致手指肿大和关节畸形。宏观上骨骼过度生长的机制鲜为人知。在我们的研究中，通过micro-CT分析了三名巨乳患者的骨表现。通过肿瘤基因面板的下一代测序（NGS）检测到PIK3CA突变。分析了PI3K / AKT / mTOR途径的激活和靶基因。比较了大指衍生骨髓间充质干细胞（MAC-BMSCs）和多指衍生骨髓间充质干细胞（PD-BMSCs）的成骨潜能。测试了PIK3CA抑制剂对MAC-BMSCs增殖和成骨的潜力。激活PIK3CA在所有MAC-BMSC中均检测到PI3K / AKT / mTOR途径的突变和激活。与PD-BMSC相比，MAC-BMSC具有增强的成骨潜能。shRNA或BYL719处理对PIK3CA的抑制作用显着降低了MAC-BMSC的成骨分化能力。RNA-Seq和qRT-PCR显示，与PD-BMSC相比，MAC-BMSC中的远侧同源盒5（DLX5）上调。DLX5抑制了MAC-BMSCs的成骨潜能，表明DLX5是PIK3CA激活介导的成骨作用的下游靶标。这项研究表明PIK3CA增强了MAC-BMSCs的成骨分化通过PI3K / AKT / mTOR信号通路引起的激活突变，可以被PIK3CA抑制或药物抑制逆转。