DEVELOPMENTAL EXPRESSION OF EXTRACELLULAR-MATRIX COMPONENTS IN INTRAMUSCULAR CONNECTIVE-TISSUE OF BOVINE SEMITENDINOSUS MUSCLE

We have investigated the expression patterns of extracellular matrix c omponents in intramuscular connective tissue during the development of bovine semitendinosus muscle by means of indirect immunofluorescence techniques. Types I, III, V, and VI collagen and fibronectin were loca ted in the endomysium and the perimysium. Type IV collagen, laminin, a nd heparan sulfate proteoglycans (PGs) were exclusively located in the endomysium, and dermatan sulfate PGs existed only in the perimysium. The localization of these components in the intramuscular connective t issue of semitendinosus muscle remained unchanged throughout prenatal and postnatal growth of cattle, suggesting that they are essential for forming and maintaining structures of the endomysium and perimysium i n bovine semitendinosus muscle. On the other hand, decorin was undetec table in the endomysium of neonates, although other matrix components were already expressed. It was expressed slightly in the endomysium of 2-month-old calves, and clearly detectable in the endomysium of cattl e more than 6 months old. Chondroitin sulfate PGs were barely detectab le in the perimysium of fetuses and neonatal calves, and progressively appeared during postnatal development of the muscle. It seems likely that these PGs are closely related to the postnatal development of the endomysium and perimysium.