COLLAGEN-SYNTHESIS AND TYPE-I, TYPE-III, TYPE-IV, AND TYPE-VI COLLAGENS IN AN ANIMAL-MODEL OF DISC DEGENERATION

Study Design. The present study sought to elucidate the changes that o ccur in collagen chemistry in the early phases of disc degeneration. O bjective. To monitor the healing process of the injured anulus fibrosu s and the secondary degenerative reactions in the nucleus pulposus. Su mmary of Background Data. Despite the importance of collagen chemistry under pathologic conditions in the intervertebral disc, knowledge of this aspect is very limited. Methods. Fourteen pigs were stabbed with a scalpel blade in the anterior part of the anulus fibrosus of a lumba r disc. The animals were killed 2 weeks to 5 months after injury. The activities of prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyl transferase, the total collagen content, and staining patterns for Typ es I, III, IV, and VI collagens were analyzed from different parts of the disc. Results. The most active phase of the heating process, asses sed from the activities of enzymes involved in collagen biosynthesis, took place during the first month postoperatively. The anular lesion w as found to cicatrize through formation of disorganized granulation ti ssue in which Type I, III, and, IV collagens were deposited. In the nu cleus pulposus, activities of prolyl 4-hydroxylase and galactosylhydro xylysyl glucosyltransferase and total collagen content increased, and the originally rounded cells became more elongated, resembling fibrobl asts. Conclusions. The results of this study suggest that the altered composition of collagens observed in the degenerate porcine nucleus pu lposus results from changes in cell phenotype: Notochondral cells were replaced by fibroblast-like cells. It is likely that trauma to the an ulus fibrosus can initiate a progressive degenerative process in the d isc tissue.