AGE-DEPENDENT AND INJURY-DEPENDENT CONCENTRATIONS OF TRANSFORMING GROWTH-FACTOR-BETA-1 AND PROTEOGLYCAN FRAGMENTS IN RABBIT KNEE-JOINT FLUID

Objective: The purpose of the study was to characterize maturation-rel ated changes of TGF-beta 1 and proteoglycan fragment (PG concentration s in joint fluid of healthy rabbit knees, and to investigate changes a ssociated with osteochondral injury and spontaneous repair. Methods: I n 26 young (age range: 12-15 weeks). 26 adolescent (18-23 weeks), and 26 adult (33-44 weeks) New Zealand white rabbits, TGF-beta 1 and PG co ncentrations were analyzed in joint fluid samples which were taken bef ore, and at several time intervals (max. 1 year) after creation of a o steochondral defect in the knee medial femoral condyle. At death, the characteristics of the regenerated tissue in the defect and any signs of degeneration of adjacent cartilage were recorded and graded. Result s: In preoperative samples, TGF-beta 1 and PG concentrations decreased with maturation (P < 0.01), and were moderately correlated (r = 0.51, P < 0.001). Shortly after trauma, the concentrations of both substanc es were found increased, which was followed by a decrease up to 3 mont hs. and then again an increase up to 1 year. However er, meanwhile PCT concentrations had similar magnitude irrespective of age, TGF-beta 1 concentrations nel er leached similarly high levels in adulthood as in infancy or adolescence, The cartilage adjacent to the defect had more signs for degeneration in younger rabbits, and also osteophytes were more common in young than adult animals. Conclusion: The similar patte rn for TGF-beta 1 and PG concentrations during postnatal maturation ma y reflect the stimulatory effect of TGF-beta 1 on proteoglycan synthes is. The higher TGF-beta 1 concentrations in younger animals may be a r eason for their better healing capacity, but also for their higher sus ceptibility to osteoarthritic change compared to adult animals.