Laminin 2 (merosin), but not laminin 1 (EHS-laminin), may be a major laminin isoform present in normal and fibrotic rat liver

Abstract

Recently several laminin isoforms were newly identified and found to distribute in a tissue and cell type-specific manner. We have studied the expression of several laminin isoforms, including α1(A), α2(M), β1(B1), β2(S), and γ1(B2) subunits, in normal and CCl 4-induced fibrotic rat liver by RT-PCR and performed immunohistochemical study with newly developed monoclonal antibody to merosin (laminin-2). RT-PCR study for laminin subunits revealed that α2(M) subunit mRNA transcript was dominant chain present in normal rat liver tissue, but α1(A) subunit mRNA was not. Laminin β1(B1) and γ1(B2) subunit mRNA were detected strongly and β2(S) subunit mRNA was detected weakly. During the CCl 4-induced rat hepatic fibrosis, α2, β1, β2, and γ1 subunit mRNA showed increased expression, but α1 transcript could not be detected during fibrotic process even in the condition where α1 subunit mRNA was detectable in rat placental tissue. Immunohistochemical studies with a novel monoclonal antibody to merosin also revealed that deposition of merosin increased during CCl 4-induced rat fibrotic liver. These data strongly suggest that laminin isoform containing α2 subunit (merosin) may be a major laminin present in normal and fibrotic rat liver.