THE EFFECT OF RELAXIN TREATMENT ON SKELETAL MUSCLE INJURIES

Professor Martin P Schwellnus, University of Cape Town, South Africa

Background: In the repair of injured skeletal muscle neutralisation of the effect of transforming growth factor-b1 (a key fibrotic cytokine) by the hormone relaxin may prevent fibrosis, increase muscle regeneration, and thereby improve the recovery following muscle injury.

Research question/s: Does the administration of relaxin, a member of the family of insulin-like growth factors, reduce fibrosis and improve the healing of injured muscle?

Methodology:Materials:Two studies: study 1 (in vitro), myoblasts (C2C12 cells) and myofibroblasts (transforming growth factor-β1-transfected myoblasts); study 2 (in vivo), 24 female mice.

Experimental procedure: In vitro study: myoblasts and myofibroblasts were incubated with relaxin and cell growth and differentiation were determined (myogenic and fibrotic protein expression).

In vivo study: relaxin was injected intramuscularly at different time points (none = control, days 3, 7 and 14) after the induction of a laceration injury in the skeletal muscle of the mice.

Measures of outcome: Skeletal muscle healing (histological, immunohistochemical, and physiologic parameters).

Main finding/s::

• In vivo study: relaxin administrtion decreased myofibroblast proliferation, down-regulated expression of the fibrotic protein α-smooth muscle actin in a dose-dependent manner.

• In vitro study: relaxin administration enhanced muscle regeneration, reduced fibrosis, and improved injured muscle strength.

Conclusion/s: In an …