Targeted Modulation of MMP-1 by Female Hormones in Mouse Fibrochondrocytes

Objectives: TMDs have a high preponderance in women of reproductive age suggesting a potential role of female hormones. Our previous study on rabbit TMJ fibrocartilaginous cells showed that relaxin induces collagenase-1(MMP-1), a response that is enhanced by β-estradiol. The use of transgenic mice will allow us to further understand the mechanisms by which hormones may mediate TMDs. In this preliminary study, we characterized whether mice fibrocartilaginous cells show similar responses to relaxin, β-estradiol and progesterone as observed in rabbit cells. Additionally, we examined if the responses of TMJ fibrochondrocytes to these hormones are similar to those shown by cells from the knee meniscus(MEN). Methods: TMJ, MEN, and the positive control pubic symphyseal(PS) fibrocartilage cells were cultured in α-MEM (10%FBS) until confluent. After trypsinization, 10⁵/cm² fibrochondrocytes were plated and maintained in serum-free medium for 6hrs followed by treatment with relaxin (0-100πg/ml) with or without β-estradiol (0.1πg/ml) or progesterone (10πg/ml). Conditioned medium and total RNA was retrieved after 48 hours, and subjected to substrate zymography, FITC-collagen degradation assay, and qRT-PCR. Results: Relaxin caused a significantly greater dose-dependent increase of MMP-1 mRNA in TMJ than in MEN cells. Similarly, substrate zymography demonstrated a more conspicuous dose-dependent increase in 53/58-kDa gelatinolytic enzyme (MMP-1) in TMJ versus MEN cells. These findings were consistent with those for collagenase activity. The PS demonstrated the greatest MMP-1 induction by relaxin. Finally, β-estradiol potentiated the MMP-1 induction by relaxin while progesterone attenuated this response in all cell types. Conclusion: The findings show that relaxin produces the targeted induction of MMP-1 in cells from mice TMJ disc and PS, but only minimally in MEN cells. This suggests that transgenic mice may serve as appropriate models to delineate the basis by which female hormones contribute to TMJ degeneration. (NIDCR DE007057 to KU, and DE11993 and DE00458 to SK)