PROTEOGLYCAN DEPLETION AND SIZE-REDUCTION IN LESIONS OF EARLY GRADE CHONDROMALACIA OF THE PATELLA

Objective-To determine the content and molecular size of proteoglycans (PGs) in patellar chondromalacia (CRI) and control cartilages as a fi rst step in investigating the role of matrix alterations in the pathog enesis of this disease. Methods-Chondromalacia tissue from 10 patients was removed with a surgical knife. Using identical techniques, appare ntly healthy cartilage of the same site was obtained from 10 age match ed cadavers (mean age 31 years in both groups). Additional pathologica l cartilage was collected from 67 patients with grades II-IV CM (class ified according to Outer-bridge) using a motorised shaver under arthro scopic control. The shaved cartilage chips were collected with a dense net from the irrigation fluid of the shaver. The content of tissue PG s was determined by Safranin O precipitation or uronic acid content, a nd the molecular size by mobility on agarose gel electrophoresis. Resu lts-The mean PG content of the CM tissue sampled with a knife was dram atically reduced, being only 15% of that in controls. The cartilage ch ips collected from shaving operations of grades II, III, and IV CM sho wed a decreasing PG content: 9%, 5%, and 1% of controls, respectively. Electrophoretic analysis of PGs extracted with guanidium chloride fro m the shaved tissue samples suggested a significantly reduced size of aggrecans in the mild (grade II) lesions. Conclusion-These data show t hat there is already a dramatic and progressive depletion of PGs in CM grade II lesions. This explains the softening of cartilage, a typical finding in the arthroscopic examination of CM. The PG size reduction observed in grade II implicates proteolytic attack as a factor in the pathogenesis of CM.