DISTRIBUTION OF MINOR COLLAGENS DURING SKIN DEVELOPMENT

The skin is a tissue containing a large number of collagen types. Seve ral collagens are restricted at the dermo-epidermal junction, contrari ly to others present throughout the dermis. However, the distribution of the dermal collagen varies during embryonic development. In this co ntribution, we have been interested in the collagen types associated w ith the major collagenous components of the dermis, which are the coll agen types I and III. Type V collagen, which is mixed with collagen ty pes I and III to form heterotypic fibrils, has been studied during mou se embryo development. Transcripts of the alpha 1(V) gene have been lo calized by in situ hybridization, on flattened cells of the stratum ge rminativum first, and then only on dermal cells. The expression of the gene decreases at birth, while the expression of the alpha 1(I) gene remains constant, with, however, a ring of high intensity around hair follicles. Other collagen types (VI, and the fibril-associated collage ns XII and XIV) have been studied during calf embryonic development by immunofluorescence and ultrastructural immunogold detection. Type VI collagen appears homogeneously distributed throughout the dermis. Type XII collagen is first widely distributed and becomes restricted in th e upper, papillary dermis after 6 months of gestation. Type XIV collag en, on the contrary, is first located as a delicate framework around h air follicles (at 19 weeks of gestation), and progressively invades th e whole dermis where it appears abundant just before birth. The differ ent functions of all these collagens are discussed in terms of dermis architecture, mechanical properties and physiology. (C) 1997 Wiley-Lis s, Inc.