Volumetric Muscle Loss Repair in Rats

Adult Sprague Dawley rats (n = 20) weighing ~ 350 g, were subjected to an established VML injury model^{67 (link)}. VML defects were created in the middle third of the Tibialis anterior (TA) muscle in the left leg by excising about 20% of the TA weight using an 8 mm biopsy punch. VML defect plugs were minced using a scalpel blade into 1 mm³ fragments and used to repair the VML injuries. Fascia and skin were closed using interrupted stiches with 5–0 Vicryl sutures (J463G, Ethicon). The contralateral limb was not injured and served as an uninjured control. Buprenorphine (0.1 mL at 0.3 mg/mL) (LIST 7571, Buprenex) was administered to all rats subcutaneously for postoperative analgesia and access to Rimadyl (MD150-2, Bio-Serv) was provided at up to 1 mg per day for seven days post-injury + repair (DPI). Food and water were provided ad libitum. All animal procedures were approved by the Institutional Animal Care and Use Committee of the University of Arkansas. All experiments were performed in accordance with all guidelines and ARRIVE guidelines. Animals were randomly assigned to one of two treatment groups (n = 10/treatment group): either rat recombinant IL-10 (400-19, PeproTech) in sterile phosphate buffered solution (PBS) (2000 ng/ml) or PBS injection (IM at site of repair) beginning 7 days after the initial surgery and continuing until day 14 (100 µL every other day = 4 injections total) (Fig. 1a,b). Animals (n = 5/treatment/time point) from each treatment group were allowed either 14 or 56 days of recovery.