Altered expression of collagen phenotype in osteoarthrosis.

Immunofluorescence studies have shown the presence of collagen type III in addition to types I and II in osteoarthrotic cartilage. The presence of collagen type III was verified biochemically: collagen was isolated and purified from the pronase digest of osteoarthrotic cartilage. Mixtures of different collagen types were fractionated first by two different DEAE-cellulose runs and then the collagen polymers were isolated by molecular sieve chromatography. Afterwards the collagenous material was reduced, Alkylated, and rechromatographed on an agarose column. Three major peaks corresponding to gamma-, beta- and alpha-chains were observed. Amino acid analyses and the CNBr peptide pattern indicated the identity of the alpha peak as alpha 1 (III). Additional staining of control and disease cartilages for fibronectin revealed the presence of this protein in the diseased tissue.