Desmosome formation in normal human epidermal cell culture.

Keratinocytes were dissociated from normal human adult epidermis with clostridial collagenase, dithio-erythritol and trypsin, and cultured. Immediately after this, no connection was seen between contiguous cells. Ruptured desmosomes, with masses of tonofilaments and distinct attachment plaques were still left on the cell surface. As culture proceeded, however, they became internalized into cytoplasm. As soon as culture was started and the cells established contact with each other, forming conglomerates, they began to form desmosomes. The cell membranes of a limited area which were in contact with neighbouring cells became thicker and formed attachment plaques. In the intercellular space of the desmosomal portion, fine filaments developed and a midline formed. The progress of desmosome formation was classified into six types.