The purpose of this project is to determine changes in proteins and signaling pathways in injured tendons of C57BL/6j and MRL/MpJ mice. The MRL.MpJ mice have been reported to have a strong repair ability compared to that of C57BL/6j mice. Identifying signaling pathways in MRL/MpJ tendons that are distinct from C57BL/6j tendons will help us understand the molecular mechanisms underlying the better healing ability of MRL/MpJ mice. The samples include normal and injured Achilles tendons 4 weeks after tenotomy surgery obtained from male and female C57BL/6j and MRL/MpJ. The Achilles injury surgery was performed at 12 weeks of age. Normal tendons were obtained age, sex and strain-matched mice without surgery. The collected normal and inured tendons were subjected to proteomics.