Analysis of changes in mRNA levels of myoblast- and fibroblast-derived gene products in healing skeletal muscle using quantitative reverse transcription-polymerase chain reaction

Changes in expression of type III alpha1-collagen and myosin II heavy chain s were characterized in rabbit skeletal muscle following single stretch inj ury using quantitative reverse transcription-polymerase chain reaction. Col lagen III expression was highly elevated in the injured leg compared with t he control limb both at the myotendinous junction and in the distal muscle belly. While upregulation of collagen III expression at the myotendinous ju nction was maximal on day 1, collagen III expression in the distal muscle b elly was unchanged on day 1 but highly elevated by day 3. Over the initial 7-day period, there was on average a 94% increase in collagen III expressio n at the myotendinous junction and a 42% increase in the distal muscle bell y. On the other hand, there was little difference, in fact, slightly less e xpression of myosin II isoforms, in the injured leg compared with the contr ol side. Immunohistochemical analysis of injured muscle showed significant collagen III deposition at the myotendinous junction beginning at day 3 pos t-injury and still evident by day 14. Focal deposits of type I and III coll agen were first apparent in the distal muscle belly by day 3 and striking b y day 7. Taken together, the data suggest the formation of connective tissu e scar at the injury site and the absence of significant muscle regeneratio n following muscle stretch. Furthermore, microinjuries distant to the prima ry site of injury may result in more general muscle fibrosis and scarring. (C) 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. A ll rights reserved.