The Ratio of Soluble to Insoluble Collagen in Normal Chick Dermis ∗ †

Abstract

Weiss and Matoltsy (1) reported a total absence of wound healing in chick embryos prior to the tenth day of incubation. The epithelial cells of the wound margin, instead of covering the wound surface as they do in older embryos, penetrate the underlying mesenchymal stroma. We thought that the explanation for this behavior of the epithelium should be sought in the embryonic mesenchyme.

The importance of the mesenchyme, e.g., the dermis, for the differentiation of the epidermis and its derivatives during embryogenesis has been well established (2-5). Differentiation and proliferation of epidermal cells in newts was found to be dependent on mesenchymal factors (6). McLoughlin (7) was able to alter specifically the differentiation of embryonic epidermis by combination with mesenchyme from various organs. Epidermal cells cultured without mesenchyme do not differentiate but degenerate, whereas frozen-thawed mesenchyme is able to support epidermal differentiation (8).

This property of frozen-thawed mesenchyme, however, is lost after its exposure to trypin (8). This tinding supports the assumption that large molecules are responsible for the inductive action of the mesenchyme. Wessells (9) succeeded in inducing and maintaining cornification of embryonic chick epidermis in the absence of mesenchyme by explanting it on top of a Millipore membrane and supplying it with a suitable concentration of embryo juice. Other subtrate failed to support epidermal differentiation. These findings are reqarded as evidence for the importance of the physical structure of the substrate for epidermal cornification.

Collagen is one of the most important structural elements of the dermis. Dodson obtained differentiation of epidermis grown on collaqen gells. Enquist and Adamson (10) stated that “a lack of healing means absence of collagen sqnlthesis.” In view of these data, a correlation between collagen polymerization in granulation tissue and epidermal wound coverage appears plausible. Our investigations, reported in this paper, were concerned with the question of the extent to which changes in collagen polymerization are correlated with changes in wound healing in chick embryos.