Targeting muscle fibrosis using non-specific collagenase injections destabilizes the basal lamina and induces matrix remodeling

Background: Muscle fibrosis is a hallmark of neuromuscular diseases such as Duchenne Muscular Dystrophy (DMD), where excessive extracellular matrix (ECM) accumulation impairs muscle function and regeneration. While anti-fibrotic therapies are urgently needed, the reversibility of fibrosis in DMD remains a challenge. Collagenase Clostridium histolyticum (CCH), an FDA-approved enzyme, has shown promise in digesting ECM components in non-muscle tissue. This study evaluated the therapeutic potential and safety of intramuscular injections of non-specific CCH in D2.mdx mice, a model of DMD, and wildtype controls. Methods: Unilateral injections of CCH were administered to the tibialis anterior and gastrocnemius muscles. Muscle function was assessed via in vivo plantarflexion strength and ex vivo mechanical testing. Histological and biochemical analyses quantified changes in total and cross-linked collagen content, ECM architecture, and markers of muscle regeneration and damage. Results: The data demonstrated that crude CCH effectively digested muscle ECM, acutely reducing collagen. However, this did not translate into therapeutic benefit. Instead, CCH injections induced muscle weakness, intramuscular bleeding, and basal lamina thickening within 7 days. Passive muscle stiffness tended to decrease after 1 day, but by day 7 had increased relative to saline injected limbs. Muscle strength declined initially, but did recover by day 7. Notably, CCH degraded collagen IV networks in the basal lamina, leading to ECM remodeling and increased susceptibility to bleeding, but did not exacerbate damage from eccentric contractions. Conclusions: These findings highlight the impact of non-specific collagenase therapy in skeletal muscle, particularly the unintended targeting of non-fibrillar collagens such as collagen IV, which are critical for muscle fiber stability and force transmission. The study concludes that future anti-fibrotic strategies should employ collagenases specific to fibrillar collagens and incorporate physical therapy protocols to preserve muscle function while reducing fibrosis. Overall, non-specific CCH injections destabilize the basal lamina and induce matrix remodeling dramatically, however, they compromise muscle integrity and function. Targeted collagenases may offer a safer and more effective approach for treating muscle fibrosis in neuromuscular diseases. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.