Figure 3.

β-estradiol (E), relaxin (R), and progesterone (P) treatment have differential effects on the loss of collagen in fibrocartilages. Temporomandibular joint (TMJ) discs, pubic symphysis, knee meniscus, and articular cartilage were retrieved from control and hormone-treated rabbits, and the total collagen content was determined by the Sircol assay and normalized to the total dry weight for each sample. Histograms of the mean (± standard deviation) collagen concentration in sham-operated controls (SC), ovariectomized normal controls (NC), and rabbits treated with E, R, E + R (ER), P, P + R (PR), and E + P + R (EPR) groups were plotted. Ovariectomy resulted in a significant reduction of collagen content in TMJ disc (a) and increase collage in the pubic symphysis (b) but had no effect on collagen in knee articular cartilage (c) and meniscus (d). Administration of E, R, and ER maintained the reduction of collagen content in TMJ disc produced by ovariectomy and caused a significant reduction in collagen in pubic symphysis relative to NC and in knee articular cartilage relative to SC and NC. In contrast, progesterone antagonized the effects of E, R, and ER on collagen content in TMJ disc, pubic symphysis, and the knee articular cartilage. Collagen content in knee meniscus was not affected by treatment with any of these hormones. Data were collected from a minimum of six rabbits in each group. (* < 0.05; ** < 0.01; *** < 0.001; **** < 0.0001; a, versus SC; b, versus NC; c, versus P; d, versus PR; e, versus EPR; NS, not significant.)