Mesangial cell-matrix interactions: modulation of matrix expression in mesangial cells by extracellular matrices

Aberrant extracellular matrices (ECMs) observed in mesangial areas during the progression of glomerulonephropathy could be produced by mesangial cells (MCs), interacting with altered ECM components, under the influence of various mediators. We studied the interaction between MCs and ECMs, especially focusing on matrix expression of MCs in contact with ECMs. We analyzed mRNA expression and protein synthesis of ECM components by cultured rat MCs which were plated on different types of ECMs, basement membrane-type matrix (BMM), type IV collagen and type I collagen. The level of mRNA for ECM components (alpha 1 type I collagen, alpha 1 type IV collagen, fibronectin and laminin B2) increased in MCs on the two types of collagen compared with BMM. The relative increase of alpha 1 type I collagen mRNA expression in MCs on type I collagen was greater than that of alpha 1 type IV collagen expression. At the protein level, type I collagen production by MCs on coated type I collagen showed a 2.2-fold increase relative to that on BMM. MCs on type IV collagen produced it at an intermediate level. The phenomena were not associated with differences of proliferative activity, but were accompanied by minor morphological differences. These results indicate that ECMs can modulate the phenotype of MCs in terms of matrix expression and suggest that MC-matrix interaction may in part contribute to abnormal ECM accumulation in diseased glomeruli.