EXPRESSION OF HEPATOCYTE GROWTH-FACTOR IN GROWING AND REGENERATING RAT SKELETAL-MUSCLE

The expression of hepatocyte growth factor (HGF) was studied in rat sk eletal muscle during postnatal growth and during regeneration after is chemic injury. By Northern blot analysis two RNA transcripts with esti mated sizes of 6.0 and 3.1 kb, respectively, could be detected in imma ture skeletal muscle at 2, 4, and 10 days after birth, whereas no sign al could be detected in adult skeletal muscle. In regenerating muscle, HGF mRNA was reexpressed, and a distinct signal was evident during th e first days after the injury. One week after the injury only a weak s ignal was obtained. By in situ hybridization staining, HGF mRNA could be demonstrated in the immature muscle tissue of newborn rats but not in adult skeletal muscle. In regenerating muscle, the staining for HGF mRNA could be demonstrated in the regenerating muscle cells during th e early phase of the regeneration. One week after the injury, only fai nt staining for HGF mRNA persisted in the regenerated fibers. It is co ncluded that HGF expression is developmentally regulated in skeletal m uscle and that HGF is reexpressed in a transient manner during postisc hemic muscle regeneration.