The Expression of Extracellular Matrix During Adult Skeletal Muscle Regeneration: How the Basement Membrane, Interstitium and Myogenic Cells Collaborate

To determine whether differences in the expression of extracellular matrix (ECM) components correlate with the progression of skeletal muscle regeneration in vivo, the location and intensity of expression of basement membrane components (laminin al, ct2, a5 chains and collagen IV), matrix proteins upregnlated during inflammation (fibronectin and tcnascin-C), and cell adhesion molecules (VCAM-I and a4pl integrin} were examined by immuno fin orescent tissue staining in two models of'muscle regeneration in mice. Crush injury results in major disruption of the basement membranes of myoftbres and an early inflammatory response, whereas in whole muscle grafts the tissue architecture is largely preserved and there is a delayed inflammatory response. The patterns of ECM expression were similar in both models and corresponded closely with key cellular events. The only difference was the loss of basement membrane component nnmunoreactivity in necrotic myofibres in the centre of the crash injured muscles compared with sustained immunoreactivity in whole muscle grafts. There were no differences in the relative expression of ECM components between crushed muscles from SJL/J and BALB/c mice, which have a different efficiency of muscle regeneration following crush injury in vivo.