Morphogenesis and origin of fibrous long-spacing collagen fibers in collagenase-treated mouse skin tissues.

Morphogenesis and origin of fibrous long-spacing collagen (FLS) fibers in newborn mouse skin tissues treated with collagenase were examined using ultrastructural observation, morphometry, histochemical methods, and immunoelectron microscopy. The enzyme caused both the partial destruction of basal laminae and the formation of abundant FLS fibers in the dermal matrix. The fibers were usually distributed in the vicinity of basal laminae in the capillaries or basal layer cells. The fibers were characterized by the cross-striated dark bands with about 91 nm periodicity and longitudinally aligned filaments with a diameter of about 6.5 nm. The dark bands of FLS fibers were often continuous with the basal laminae. Histochemical results showed that the dark bands contained the similar mucopolysaccharides which were involved in the basal laminae. Immunoelectron microscopic results showed that laminin was present in the dark bands as well as in the basal laminae, and that type VI collagen was located in the filaments of FLS fibers. These results suggest that the dark bands are formed by products similar to basal laminae and that the products were precipitated on type VI collagen-contained filaments with periodic intervals of about 91 nm. Morphometric examination revealed that there was no differences in ultrastructure between FLS fibers of a collagenase-treated mouse and those of a human neural tumor.