Studies on the Formation of Collagen

Abstract

The essential role of ascorbic acid in collagen formation has been shown b y numerous histological and biochemical studies (2-7). The mode of action, however, is still in doubt.The question as to whether a deficiency of ascorbic add prevents synthesis of collagen molecules or interferes with subsequent polymerization to fibrils was raised by Wolbach (2), who favored the latter possibility. Biochemical studies of the carrageenan granuloma by van Robertson and Schwartz (7) and of healing skin wounds in scorbutic guinea pigs by Gould and Woessner (6) led these investigators to postulate that ascorbie add was required for the hydroxylation of proline to hydroxyproline in the polypeptlde chain of a precursor of collagen. The hypothetical proline-rich, hydroxyproline-poor precursor, they suggested, is synthesized normally in the scorbutic state but not hydroxylated, and this defect accounts for the relatively large amounts of proline with little hydroxyproline found in scorbutic granulation tissues. As yet, there has not been a reported success in isolating this precursor.Biochemical studies of collagen formation in granulation tissue (open wounds, granulomas, and implanted plastic sponges) are complicated by the variety of physiologic responses involved in healing. A method for the study of collagen formation in the intact scorbutic animal was provided by the discovery of neutral salt-extractible collagen in intact dermis (8,9). This fraction (in tissues which are not undergoing degradation) is newly synthesized and appears to be converted to insoluble fibrils (10-12).Studies of the solubility of extracted collagen in vitro have indicated a possible mechanism for this process (13).

Wound Healing and Collagen Formation

“…Gross also observed this and noted, in addition, that pair-feeding indicates that the weight loss in the latter stages of scurvy is not due to inanition R. Ross AND E. P. BENDITT Wound Healing and Collagen Formation. IV alone (35). As in the previous experiments in scurvy (8,9), the animals gained weight on the seorbutigenic diet for the first 12 days.…”

“…Ascorbic acid deficiency presents a classical pathologic alteration of the connective tissues with a concomitant depression in the formation of a specific protein, collagen (5,6,17,18,20,21,23,24,35,54). The present observations further characterize the fine structure alterations in fibroblasts, during scurvy, and the reconstitution of the normal ultrastructure of the fibroblast following administration of vitamin C. The reappearance of the non-scorbutic configuration of FIGURE 3 This electron micrograph contains parts of two fibroblasts from a wound 4 hours after ascorbic acid administration.…”

“…However, the amino acid composition of protein extracted by methods presumed to extract collagen was not consistent with such a collagen precursor (27). Gross failed to observe in neutral salt extracts of scorbutic skin any proline-rich material (35). Later attempts by Gould et al (18,19) were also unsuccessful in recovering a protein rich in proline and glycine.…”

“…Earlier experiments (8,9,35,54) demonstrated that regular examination of weight, prior to the period of extreme weight loss from inanition, is a reliable indication of food intake in these animals. In addition, previous pair-feeding experiments (unpublished data) demonstrated that the weights of pair-fed animals are similar to those of the scorbutic animals during the experimental period.…”

Wound Healing and Collagen Formation

“…10) may be due to the fact that collagen is forming at a very slow rate, as postulated by Gould (41). Another possible explanation for the presence of very few fibrils is the one presented by Gross (42) in studying the neutral salt-soluble extracts of skin collagen. He could find no collagen in the extract of the skin from scorbutic guinea pigs.…”