Mechanism of Huoxue Huayu Decoction Promoting Tibial Fracture Healing in Rats via Notch1/PPARγ/CD36 Signaling Pathway

Tibial fractures are a common type of traumatic injury, typically treated through surgical reduction and fixation; however, the healing outcomes are often suboptimal.This work aimed to investigate the mechanism of Huoxue Huayu Decoction (HXHYD, a traditional Chinese herbal formula composed of Bupleuri Radix, Paeoniae Radix Alba, and Leonuri Herba known for promoting blood circulation and resolving stasis) promoting tibial fracture healing in rats via Notch1/PPAR/CD36 pathway.Forty-eight male Sprague-Dawley rats of clean grade were randomly allocated into a control group (sham surgery, 10 mL/kg/d saline gavage, n=12), a model group (fracture model, 10 mL/kg/d saline gavage, n=12), a positive group (fracture model, 0.27 g/kg/d Xianling Gubao capsule gavage (standardized extract equivalent to human dose of 3 g/d, calculated by body surface area, n=12), and a HXHYD group (fracture model, 13.45 mL/kg/d HXHYD gavage, n=12).Rats in each group were administered gavage once daily for 28 consecutive days.Xray imaging outcomes and Lane-Sandhu scores were employed to assess tibial fracture healing.Enzyme-linked immunosorbent assay (ELISA) measured serum inflammatory cytokine levels and bone formation markers.Tibial tissue from rats was collected to measure biomechanical parameters.Western blot analysis quantified bone-regulatory factors' expression.Relative to control group, model group showed a reduced Lane-Sandhu score, elevated serum TNF-, IL-1, IL-6, and bone formation markers ALP, BGP, and IGF-1, and a decrease in tibial maximum load, elastic load, and maximum deflection.Additionally, tibial BMP-2, RUNX2, VEGF, Notch1, and CD36 protein levels were increased, while tibial PPAR protein expression was decreased (P<0.05).HXHYD group showed the most prominent improvements, including a 45% increase in Lane-Sandhu score, 30% reduction in TNF- levels, and 50% elevation in BMP-2 expression versus model group (P<0.05).HXHYD also enhanced maximum tibial load (25.32.1 N vs. 18.51.8N in model group) and suppressed PPAR expression by 40%, while upregulating Notch1 and CD36 (P<0.05).Relative to positive group, HXHYD group showed more pronounced improvements in all indicators (P<0.05).HXHYD promotes tibial fracture healing by alleviating inflammation, enhancing osteogenesis, and modulating Notch1/PPAR/CD36 pathway.Hence, HXHYD can serve as a complementary therapy to surgery, optimizing the bone repair microenvironment and accelerating functional recovery.