Adult human skin maintained in organ culture: I. The ultrastructure of the acellular compartment of connective tissue.

Collagenolytic enzymes are produced by cultured skin explants. During cultivation the acellular compartment of the dermal connective tissues is digested away. The ultrastructure of the connective tissue resorption has been studied in human skin maintained in organ culture for 2--10 weeks. The connective tissue changes are: (1) Collagen fibrils with normal axial periodicity but decreasing diameters. On cross sections these fibrils have irregular outlines, while the longitudinal sections show fibrils separated into thin bundles of filaments 40--80 A thick with preserved normal axial periodicity. (2) Cross-banded filamentous aggregations (CBFA) consisting of fine parallel filaments 25 A thick and without axial periodicity. The CBFA has 350 A thick bands at 525 A intervals. At the end of the cultivation, the CBFA are replaced by solitary filaments 25 A thick. (3) The elastic fibres show no marked changes of the amorphous matrix, while the fibrils disappear. The loss of collagen and elastic fibrils during cultivation of the skin gives direct evidence of connective tissue degradation. The described changes are discussed in relation to previous ultrastructural studies on connective tissue resorption of various tissues.