# Collagenase treatment does not impair fiber contractile function in muscle biopsies from children with cerebral palsy

## TL;DR

Collagenase treatment does not harm muscle fiber function in children with cerebral palsy, suggesting it could be a viable treatment for reducing muscle stiffness.

## Contribution

The study is the first to show that collagenase does not impair active contractile properties in CP muscle fibers.

## Key findings

- Maximal active stress and calcium sensitivity did not significantly differ after collagenase treatment.
- Myosin and actin content remained unchanged following collagenase incubation.
- Collagenase may be a feasible treatment for reducing muscle fibrosis in children with CP.

## Abstract

Cerebral palsy (CP) often presents with increased passive stiffness of the skeletal muscles, primarily due to increased collagen in the extracellular matrix. Collagenase from Clostridium histolyticum (CCH), an enzyme that degrades collagen, is used clinically to treat fibrotic conditions such as Dupuytren's contracture and Peyronie's disease. Although prior work demonstrated reduced passive stiffness in muscle bundles from children with CP following CCH incubation, its effects on active contractile properties remain unknown. Thus, this study was aimed at investigating the maximal active force, calcium sensitivity, and myofibrillar protein content (myosin and actin) after CCH incubation. Nine muscle biopsies from children with CP were used for skinned fiber mechanical testing at an average sarcomere length of 2.4 μm, and for myosin and actin analysis using 12% SDS‐PAGE. Maximal active stress (control 59.8 ± 24.2 kPa; CCH 63.2 ± 24.5 kPa; p = 0.51) and pCa₅₀ (control 6.04 ± 0.10; CCH 5.99 ± 0.18; p = 0.43) did not significantly differ. Similarly, the normalized myosin (control 1.000 ± 0.167, CCH 1.004 ± 0.178; p = 0.93) and actin (control 1.000 ± 0.336, CCH 1.107 ± 0.330; p = 0.231) content did not differ between conditions. These results suggest that collagenase does not impair the contractile function in muscle fibers from children with CP and thus might be a feasible treatment to reduce stiffness due to muscle fibrosis. Research into whole‐muscle force transmission following collagenase treatment is needed to evaluate its clinical viability.