# Effect of Allogenic Mesenchymal Stem Cell Injection on Functional Repair Outcomes Following Skeletal Muscle Laceration Injury

## TL;DR

Injecting allogenic mesenchymal stem cells improves muscle recovery after laceration injuries in rats, showing better force recovery and less fibrosis.

## Contribution

Demonstrates short-term functional benefits of allogenic MSCs in skeletal muscle laceration repair in a rat model.

## Key findings

- MSC-treated muscle showed significantly higher force recovery compared to saline-treated and untreated groups by day 14.
- MSC-treated muscle exhibited lower fibrosis and better histological outcomes than saline-treated muscle.
- Force recovery in MSC-treated muscle was comparable to intact muscle at both time points.

## Abstract

Background: Skeletal muscle laceration injuries remain a clinical challenge owing to limited and often delayed functional recovery. Surgical repair often fails to fully restore injured muscle, causing fibrosis and functional impairments. Mesenchymal stem cells (MSCs) represent a potential therapy due to their regenerative and immunomodulatory properties. However, their short-term regenerative effects in laceration injuries remain under-explored. Objective: We aim to evaluate the short-term effects of allogenic bone marrow-derived MSCs on skeletal muscle regeneration following laceration injury in rats. Methods: Sprague Dawley rats underwent laceration injury to the right gastrocnemius muscle and received local injection of either saline (n = 6) or allogeneic bone marrow-derived MSCs (2 × 106 cells; n = 6) two weeks after injury. Muscle functional recovery was evaluated by measuring tetanic contraction force of the injured relative to the contralateral uninjured leg and compared among MSC-treated, saline-treated, untreated injured (n = 6), and intact control groups (n = 6) on days 7 and 14 post-treatment. Histological assessment of the treated muscle groups using Hematoxylin and Eosin and Masson’s Trichrome staining was conducted on day 7 post-treatment. Results: On day 7 post-treatment, MSC-treated muscle showed higher normalised force (96.8 ± 15.0%) than saline-treated (76.7 ± 4.6%) (p = 0.0393), but not untreated, muscle (83.1 ± 14.7%) (p = 0.2259). By day 14, the MSC-treated group exhibited significantly greater recovery of muscle force (110.8 ± 6.46%) than both the saline-treated (78.4 ± 6.47%) (p < 0.0001) and untreated groups (88.1 ± 3.41%) (p = 0.0001). Force recovery in the MSC-treated muscle was comparable to that in intact muscle (102.6 ± 10.4%) at both time points (p = 0.230). Supplementary histological analysis showed mild inflammatory cell infiltration, well-formed myoblasts, and a lower fibrosis index in MSC-treated muscle (29.30 ± 0.29%) compared with saline-treated muscle (31.77 ± 0.43%) (p < 0.0001) on day 7 post-treatment. Conclusions: Allogeneic bone marrow-derived MSC therapy is associated with enhanced repair of lacerated skeletal muscle over a short recovery period; however, larger studies with broader assessments are needed to confirm its potential clinical applicability.