Characterization of costal cartilage collagen in funnel chest

Parallel measurements of pyridinoline content, the ratio of soluble:insoluble collagen, and the percentage of endogenous collagenolysis were made in samples of costal cartilage from forty-five children with funnel chest (FC) and from twenty-two control children. From an analysis of the influence of different factors, such as FC type (isolated or syndromic), a diagnosed syndrome, extent of FC depression (second or third), and age, two biochemical variants of FC-variants a and b, which were not related to the presence or absence of a known concurrent syndrome, were distinguished. These variants differed from each other in all the parameters under study. Variant a occurred about five times less frequently than b, and was characterized by a pyridinoline content of about 50% of that of b, an elevated soluble:insoluble collagen ratio, and an increased percentage of endogenous collagenolysis compared to controls. For variant b, the pyridinoline content fell within normal limits, but the soluble:insoluble collagen ratio, and the percentage of endogenous collagenolysis were below normal. The data suggest that the formation of variant a may be related to defect(s) in collagen crosslinking, whereas the formation of variant b may result from other unknown factor(s) involved in the formation and maturation of costal cartilage.