Restoration to a quiescent and contractile phenotype from a proliferative phenotype of myofibroblast-like human aortic smooth muscle cells by culture on type IV collagen gels.

Aortic smooth muscle cells (A-SMC) undergo phenotypic transition to a synthetic and proliferative state and become fibroblast-like cells upon serial passage with culture on plastic dishes, especially in the presence of serum. Such fibroblast-like cells (M-SMC) derived from A-SMC may correspond to the cells identified pathologically as myofibroblasts. We examined the effects of type IV collagen gels used as a culture substrate on the morphology and proliferation of M-SMC. The M-SMC underwent extreme elongation in shape when cultured on rigid type IV collagen gels, and eventually formed cell-to-cell junctions with the elongated processes. In contrast, M-SMC showed a spindle-like cell shape on dishes coated with a type IV collagen solution or type I collagen solution, or on type I collagen gels or fragile type IV collagen gels. Cell proliferation was totally repressed by culture on rigid type IV collagen gels for over 10 days, while the highest proliferative activity was seen for cells grown on dishes coated with type IV collagen solution. The expression of smooth muscle myosin heavy chains, specific markers for contractile A-SMC, was acquired by M-SMC cultured on rigid type IV collagen gels for 3 days, while M-SMC cultured on type IV collagen-coated dishes continued to show no expression. These results suggest that the quiescent and contractile phenotype of A-SMC might be restored in M-SMC by culture on rigid type IV collagen gels, even after they have become myofibroblastic.