CYCLIC LOADING IS HARMFUL TO ARTICULAR-CARTILAGE FROM WHICH PROTEOGLYCANS HAVE BEEN PARTIALLY DEPLETED BY RETINOIC ACID

We studied whether cyclic loading is harmful to degraded cartilage. Se ts of four cartilage-bearing sesamoid bones were dissected from 5-year -old cows. One bone from each set was cultured for 17 h in control med ium to serve as an ex vivo control. The three others were cultured for 1 week in control medium to which 0, 10 or 300 ng/ml retinoic acid (R Ac), which depletes the cartilage matrix of proteoglycans, had been ad ded, Two were then cultured for another week in control medium. During the last week, one of the two was subjected to a cyclic load (1 MPa, 0.2 Hz). Following treatment with RAc, glycosaminoglycan content and s ynthesis were significantly decreased, as confirmed by safranin 0 stai ning and autoradiography. They were further diminished by loading duri ng the second week of culture. Increased amounts of 3-B-3(-) epitope w ere found in cartilage that had been treated with 300 ng/ml RAc and th en loaded. While loading cartilage matrix that was only slightly degra ded proved to be damaging, loading severely degraded cartilage matrix apparently induced osteoarthritic-like changes.