In rats, giving the peptide GHRP-2 after a rotator cuff tear lowered harmful inflammation and helped the tendon reattach to bone better, making the repair stronger and improving how the animals walked.

To explore the potential of growth hormone-releasing peptide 2 (GHRP-2) for tendon-bone healing in a rat rotator cuff tear (RCT) model. The impact of GHRP-2 on M1 macrophage polarization in vitro was determined using real-time polymerase chain reaction, Western blot, and immunofluorescence staining. GHRP-2 was then applied in a rat RCT model, and the healing of the tendon-bone interface was systemically evaluated by histologic staining, radiologic assessments, gait analysis, and biomechanical tests. M1 macrophage polarization at the tendon-bone interface was assessed by immunofluorescence staining. GHRP-2 was found to reduce the expression of Cd86, Nos2, and tnfa (all P < .01), suggesting inhibited M1 macrophage polarization in vitro. The in vivo experiments showed that the proportion of M1 macrophages was reduced both 2 and 4 weeks after surgery (P < .01), and the number of M1 was reduced 4 weeks after surgery (P < .01) at the tendon-bone interface. The in vivo experiments also showed that histologic scores and bone mineral density were increased by GHRP-2 at 8 weeks postsurgery (P < .01), suggesting improved healing of the tendon-bone interface. Furthermore, the GHRP-2 group showed a better biomechanical property at both 4 and 8 weeks postsurgery, including maximal failure load, stiffness, and tension (all P < .01), and better gait parameters at 8 weeks postsurgery, including mean area of the left front foot and mean intensity of the right front foot (all P < .05). GHRP-2 may be associated with decreased M1 macrophage production and increased histologic and biomechanical tendon-bone healing properties in a rat RCT model. The present study might be a transitional study to show the efficacy of GHRP-2 in enhancing bone-tendon healing and reduce retear rate after rotator cuff repair.