INTEGRATIVE REPAIR OF ARTICULAR-CARTILAGE IN-VITRO - ADHESIVE STRENGTH OF THE INTERFACE REGION

The objective of this study was to quantify the strength of the repair tissue that forms at the interface between pairs of cartilage explant s maintained in apposition in an in vitro culture system. Articular ca rtilage explants were harvested from calves and from adult bovine anim als, dissected into uniform blocks, and incubated in pairs within a ch amber that maintained a 4 x 5 mm area of tissue overlap. Following 1-3 weeks of incubation, integrative repair was assessed by testing sampl es in a tensile single-lap configuration to estimate adhesive strength . After incubation in medium containing 20% fetal bovine serum, the ad hesive strength between pairs of calf cartilage blocks and pairs of ad ult bovine cartilage blocks increased at a rate of 7.0 and 10.5 kPa/we ek, respectively. This repair process appeared to be dependent on viab le cells, since lyophilization of adult bovine cartilage before incuba tion completely inhibited the development of an interface with a measu rable adhesive strength. The repair process was dependent on serum com ponents in the medium. Incubation of sample pairs for 3 weeks in mediu m supplemented with 20% fetal bovine serum resulted in a relatively hi gh proteoglycan content as well as a relatively high adhesive strength (34 kPa), whereas incubation in basal medium with or without 0.1% bov ine serum albumin resulted in a 54-70% lower proteoglycan content and a 65-88% lower adhesive strength. Samples incubated for 3 weeks with s erum also had a 20% higher DNA content than samples maintained in basa l medium. Histological analysis indicated some cell division at the fr ee surfaces of the explant and also occasional cells within the interf ace region between explants.