ObjectiveTo investigate the effect and mechanism of cordycepin in inhibiting fat infiltration after rotator cuff injuries in rats by regulating the Wnt/β-catenin signaling pathway， providing a theoretical basis for clinical treatment of rotator cuff injuries. MethodsFifty SPF-grade female SD rats were used in this study， with 10 randomly selected as the blank group. A rotator cuff injury repair model was established by supraspinatus tendon and suprascapular nerve compression. The successfully modeled rats were randomized into model and low-dose （20 mg·kg^-1）， medium-dose （40 mg·kg^-1）， and high-dose （80 mg·kg^-1） cordycepin groups. After 6 weeks of treatment， the gait analysis was performed to assess the limb function in rats. Oil red O staining and Masson staining were employed to observe pathological changes in the muscle tissue. Enzyme-linked immunosorbent assay （ELISA） was used to measure the levels of interleukin-1β （IL-1β）， interleukin-6 （IL-6）， and tumor necrosis factor-α （TNF-α） in the serum. Immunohistochemistry （IHC） was employed to detect the expression of peroxisome proliferator-activated receptor γ （PPARγ） and CCAAT/enhancer-binding protein α （C/EBPα）， which are markers of adipogenesis. Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） and Western blot were employed to determine the mRNA and protein levels， respectively， of Wnt3a， Wnt10b， and β-catenin. ResultsCompared with the blank group， the model group showed decreases in stride length and paw print area （P<0.01）， an increase in ratio of wet muscle mass reduction and a decrease in muscle fiber cross-sectional area （P<0.05）， and decreased ratios of fat infiltration area and collagen fiber area （P<0.01）. Additionally， the model group showed elevated levels of IL-1β， IL-6， and TNF-α （P<0.05）， up-regulated protein levels of PPARγ and C/EBPα （P<0.01）， and down-regulated mRNA and protein levels of Wnt3a， Wnt10b， and β-catenin （P<0.05， P<0.01）. Compared with the model group， the low-， medium-， and high-dose cordycepin groups showed increases in stride length and paw print area （P<0.01）， a decrease in ratio of wet muscle mass reduction and an increase in muscle fiber cross-sectional area （P<0.05）， and increases in ratios of fat infiltration area and collagen fiber area （P<0.05， P<0.01）. In addition， cordycepin lowered the serum levels of IL-1β， IL-6， and TNF-α （P<0.05， P<0.01）， down-regulated the protein levels of PPARγ and C/EBPα （P<0.01）， and up-regulated the mRNA and protein levels of Wnt3a， Wnt10b， and β-catenin （P<0.05， P<0.01）. ConclusionCordycepin can improve the limb function， alleviate rotator cuff muscle atrophy， fat infiltration， and fibrosis， and inhibit inflammation in rats by regulating the Wnt/β-catenin signaling pathway.