Wang W, Hayami T, Kapila S
University of Michigan, Ann Arbor, MI 48109-1078, USA.
Osteoarthritis Cartilage. 2009 May;17(5):646-54. doi: 10.1016/j.joca.2008.09.015. Epub 2008 Oct 17.
Despite the female predilection for joint diseases, and the known effects of female hormones in regulating chondrocyte function, the various female hormone receptor subtypes in joints are not well characterized, and comparisons in receptor profiles between joints and genders are lacking. This investigation characterized and compared the relative levels of estrogen receptors (ER)-alpha and -beta, relaxin receptors LGR7 and LGR8, and progesterone receptor (PR) in the temporomandibular joint (TMJ) disc, knee meniscus (KM) and pubic symphysis fibrocartilages.
Fibrocartilaginous cells from 12-week-old mice were maintained in serum-containing alpha-modified Eagle's medium (MEM) until confluence. Total RNA and cell lysates were assayed by RT-PCR, qRT-PCR, immunocytochemistry and Western blots, and joint sections subjected to immunohistochemistry.
All hormone receptors assayed were present in the three joints, but showed substantial differences in expression levels between joints. TMJ cells had higher ER-alpha (>2.8-fold), ER-beta (>2.2-fold), LGR7 (>3-fold) and PR (>1.8-fold), and lower LGR8 (0.5-fold) gene expression levels than KM cells. The ratio of ER-alpha:ER-beta and LGR7:LGR8 was 1.8- and 7.5-fold higher, respectively, in TMJ than in KM cells. The profile of hormone receptors in the TMJ disc was similar to those in the pubic symphysis. Immunochemistry confirmed the differential expression patterns of these receptors in the three tissues. The TMJ cells demonstrated sexual dimorphism in the levels of both ER isoforms, but not of LGR7, LGR8 or PR.
The findings suggest that these fibrocartilages are putative target tissues for actions of female hormones. The differential expression profiles of the hormone receptors in the three joint fibrocartilages and the sexual dimorphism in ERs in TMJ disc cells are likely to result in varied downstream effects in response to hormones within these fibrocartilaginous tissues.
尽管关节疾病女性患病率更高，且已知女性激素对软骨细胞功能有调节作用，但关节中各种女性激素受体亚型尚未得到充分表征，且缺乏关节与性别之间受体谱的比较。本研究对颞下颌关节（TMJ）盘、膝关节半月板（KM）和耻骨联合纤维软骨中雌激素受体（ER）-α和-β、松弛素受体LGR7和LGR8以及孕激素受体（PR）的相对水平进行了表征和比较。
将12周龄小鼠的纤维软骨细胞置于含血清的α-改良伊格尔培养基（MEM）中培养至汇合。通过逆转录聚合酶链反应（RT-PCR）、定量逆转录聚合酶链反应（qRT-PCR）、免疫细胞化学和蛋白质免疫印迹法检测总RNA和细胞裂解物，并对关节切片进行免疫组织化学检测。
所检测的所有激素受体均存在于这三个关节中，但在不同关节之间的表达水平存在显著差异。与KM细胞相比，TMJ细胞的ER-α（>2.8倍）、ER-β（>2.2倍）、LGR7（>3倍）和PR（>1.8倍）基因表达水平更高，而LGR8基因表达水平更低（0.5倍）。TMJ中ER-α:ER-β和LGR7:LGR8的比例分别比KM细胞高1.8倍和7.5倍。TMJ盘中激素受体谱与耻骨联合中的相似。免疫化学证实了这些受体在这三种组织中的差异表达模式。TMJ细胞在两种ER亚型水平上表现出性别差异，但在LGR7、LGR8或PR水平上未表现出性别差异。
这些发现表明，这些纤维软骨是女性激素作用的假定靶组织。三种关节纤维软骨中激素受体的差异表达谱以及TMJ盘细胞中ER的性别差异可能导致这些纤维软骨组织内对激素产生不同的下游效应。
