Human type VI collagen: purification from human subcutaneous fat tissue and an immunohistochemical study of morphea...

Collagen was isolated from human placenta by pepsin digestion and salt precipitation. This collagen was similar in its electrophoretic mobility and immunological reactivity with monoclonal antibody to form B of type VI collagen in the literature (Trueb B, Schreier T, Bruckner P and Winterhalter K. 1987. Eur. J. Biochem. 166: 699-703). We prepared polyclonal rabbit antiserum against alpha 2 chain of type VI collagen and performed an immunohistochemical study using this polyclonal antibody. It reacted in fat tissue and around vessels and peripheral nerves in normal human skin. To confirm the presence of type VI collagen in fat tissue, we isolated collagen from human subcutaneous tissue. This collagen showed a similar pattern in polyacrylamide gel electrophoresis with that from human placenta and cross-reacted with monoclonal or polyclonal antibody against type VI collagen. By immunohistochemical staining, abundant type VI collagen was observed in the septum of subcutaneous fat tissue in morphea or systemic sclerosis. In the mild hyalinizing areas or after treatment with 6M urea or hyaluronidase in highly hyalinized areas, the staining of type VI collagen increased. These data suggest that the amount of type VI collagen in subcutaneous tissue is involved in the early phases of these fibrosing disorders and that type VI collagen accumulates even more in hyalinizing tissue in late phases of these diseases.