PI3K/AKT is one of the key pathways that regulate cell behaviors including apoptosis, proliferation, and differentiation. Although previous studies have demonstrated that this pathway is a crucial regulator of osteoblasts, the role of PI3K/AKT in fracture healing remains unclear. It is well known that the Wnt/β-catenin pathway plays an essential role in bone regeneration. However, whether there exists crosstalk between Wnt/β-catenin and PI3K/AKT in regulating osteoblasts and bone repair has not been reported. To address these issues, we establish a stabilized fracture model in mice and show that PI3K inhibitor LY294002 substantially inhibits the bone healing process, suggesting that PI3K/AKT promotes fracture repair. More importantly, we report that PI3K/AKT increases phosphorylation of GSK-3β at Ser9 and phosphorylation of β-catenin at Ser552 in fracture callus and murine osteoblastic MC3T3-E1 cells, both of which lead to β-catenin stabilization, nuclear translocation, as well as β-catenin-mediated TCF-dependent transcription, suggesting that β-catenin is activated downstream of PI3K/AKT. Furthermore, we show that ICG001, the inhibitor of β-catenin transcriptional activity, attenuates PI3K/AKT-induced osteoblast proliferation, differentiation, and mineralization, indicating that the PI3K/AKT/β-catenin axis is functional in regulating osteoblasts. Notably, the PI3K/AKT pathway is also activated by Wnt3a and is involved in Wnt3a-induced osteoblast proliferation and differentiation. Hence, our results reveal the existence of a Wnt/PI3K/AKT/β-catenin signaling nexus in osteoblasts, highlighting complex crosstalk between PI3K/AKT and Wnt/β-catenin pathways that are critically implicated in fracture healing.

PI3K / AKT是调节细胞行为（包括凋亡，增殖和分化）的关键途径之一。尽管以前的研究表明该途径是成骨细胞的关键调节剂，但PI3K / AKT在骨折愈合中的作用仍不清楚。众所周知，Wnt /β-catenin途径在骨骼再生中起着至关重要的作用。然而，尚未报道在调节成骨细胞和骨修复中Wnt /β-catenin和PI3K / AKT之间是否存在串扰。为了解决这些问题，我们在小鼠中建立了稳定的骨折模型，并显示PI3K抑制剂LY294002实质上抑制了骨愈合过程，表明PI3K / AKT促进了骨折修复。更重要的是，我们报道，PI3K / AKT增加了骨折call和鼠成骨细胞MC3T3-E1细胞中Ser9处GSK-3β的磷酸化和Ser552中β-catenin的磷酸化，两者均导致β-catenin稳定，核易位以及β -catenin介导的TCF依赖性转录，表明β-catenin在PI3K / AKT的下游被激活。此外，我们表明，ICG001，β-连环蛋白转录活性的抑制剂，减弱了PI3K / AKT诱导的成骨细胞的增殖，分化和矿化，表明PI3K / AKT /β-catenin轴在调节成骨细胞中发挥功能。值得注意的是，PI3K / AKT途径也被Wnt3a激活，并参与Wnt3a诱导的成骨细胞增殖和分化。因此，