Abstract
A total of 6 α chains [α1 (IV) to α6 (IV)] have been identified in type IV collagen. We examined the localization of these chains in the myocardium of patients with dilated (DCM) and hypertrophic (HCM) cardiomyopathy. The localization of α1 (IV)-α6 (IV) in biopsy specimens of 5 patients with DCM and 4 with HCM was examined using immunohistochemistry with monoclonal antibodies. Both α1 (IV) and α2 (IV) immunostaining formed thin homogeneous outlines around myocytes in control hearts. In the DCM specimens, α1 (IV) and α2 (IV) immunostaining formed thick and irregular patterns around myocytes. Staining for α1 (IV) and α2 (IV) was also obscrved in some enlarged intercellular spaces. In 3 DCM hearts, moderate staining for α1 (IV) and α2 (IV) was observed in small replacement fibrotic lesions. In large replacement fibrotic lesions, no α1 (IV) or α2 (IV) staining was observed. In the HCM specimcns, α1 (IV) and α2 (IV) staining formed thick homogeneous patterns around myocytes. In the enlargcd intercellular spaces, no α1 (IV) or α2 (IV) staining was observcd. No labeling for α3 (IV)-α6 (IV) was observed in any heart examined. In conclusion, the present results demonstrate that type IV collagen consisting of α1 and α2 chains appears in the fibrotic lesions of DCM, indicating its contribution to the development of fibrotic changes in the myocardium of DCM patients. In contrast, type IV collagen was restricted to the myocyte membrane in the HCM hearts. Fibrotic processes in the intercellular spaces may differ between DCM and HCM hearts.
