Correlation of histopathology and sulfated proteoglycans in human osteoarthritic hip cartilage

Abstract

The histopathologic characteristics, in vitro proteoglycan and glycosaminoglycan biosynthesis, and proteoglycan content of osteoarthritic (OA) cartilage tissue types from human femoral heads obtained at the time of total joint replacement were compared. Articular cartilage from fibrillated or discolored cartilage surfaces demonstrated overlapping histopathologic patterns, while cartilage from osteophytic areas was distinct. ³⁵SO₄ from each of these three tissue types was found in two peaks of radioactivity on a Sepharose CL-2B column. The average partition coefficient (K_av) of the first peak (peak I) was 0.07, while that of the second (peak II) was 0.63. Proteoglycan monomer predominated in discolored, fibrillated, and osteophytic OA cartilage in peak I. The hydrodynamic size on Sepharose CL-2B of the synthetic proteoglycan monomer was the same for discolored, fibrillated, and osteophytic samples (K_av, 0.25–0.28). Discolored and fibrillated tissues showed a similar percentage of proteoglycan monomer in peak II, whereas osteophyte was reduced in proteoglycan monomer content in peak II. In addition, the endogenous proteoglycans extracted from each cartilage area were generally of a smaller hydrodynamic size than the newly synthesized peak I or proteoglycan monomer. Glycosaminoglycans were predominantly chondroitin 6-sulfate. These results indicated that OA discolored and fibrillated cartilage tissue types from defined topographical areas of human femoral heads possessed neither unique histopathologic nor synthetic or endogenous proteoglycan characteristics. Osteophytic cartilage appeared more histopathologically distinct than either discolored or fibrillated OA cartilage, but synthesized proteoglycan monomer with similar hydrodynamic size to the other cartilage tissue types.