Expression of estrogen receptor α (ERα) in the rat temporomandibular joint

Abstract

Numerous epidemiological studies have pointed out a higher frequency of temporomandibular disorder (TMD) in women than in men, which indicates the involvement of a sex hormone, such as estrogen, in the pathogenesis of TMD. Although estrogen is known to play pivotal roles in osteoarthrosis or rheumatoid arthritis in systemic joints, there have been few reports about the role of estrogen in the temporomandibular joint (TMJ). The effect of estrogen is generally mediated by the estrogen receptors (ERs) ER␣ (the predominant type) and ER␤. In this study we examined the expression of ER␣ protein and mRNA in the TMJ of adult male rats by immunocytochemistry and in situ hybridization histochemistry. Intense ER␣ immunoreactivity was localized in the synovial lining cells, stromal cells in the articular disc, and chondrocytes in the TMJ. These ER␣-immunopositive synovial lining cells are characteristic of cytoplasmic processes identified with confocal and immunoelectron microscopy, which indicates that they are synovial type B cells. In situ hybridization histochemistry confirmed intense signals for ER␣ in the synovial lining cells and the sublining fibroblasts at mRNA levels. The nuclei of chondrocytes showed an intense immunoreaction for ER␣ in the maturative and hypertrophic layers of the articular cartilage. In addition to the nuclear localization of ER␣, a weak immunoreaction appeared in the cytoplasm of some ER␣-positive cells. These findings support the hypothesis that TMJ tissue-at least in the male rat-has the potential to be an estrogen target tissue. Anat Rec Part A 274A: 934 -941, 2003.

Differential Effects of Estradiol on Encoding Properties of TMJ Units in Laminae I and V at the Spinomedullary Junction in Female Rats

“…Previously, JM-evoked c-fos production in superficial laminae was shown to depend on RGD binding integrins in OvX females, independent of the dose of E2 replacement, whereas males were not affected (Bereiter et al 2006). ER-positive cells found in most TMJ tissues (Yamada et al 2003) may contribute to the structural effects of estrogens (Abubaker et al 1996;Yasuoka et al 2000). Also, a small but significant percentage (18%) of TMJ units in superficial laminae of males received no convergent cutaneous input ("deep-only" cells), whereas no such cells were found in OvX females.…”

Excess genistein suppresses the synthesis of extracellular matrix in female rat mandibular condylar cartilage

“…In the literature, estrogen has been shown to play an important role in the development of TMJ and temporomandibular diseases [17][18][19] . These findings have been supported by the existence of estrogen receptors (ERs) in mandibular condylar cartilage [20,21] . As an estrogen-targeted tissue [20,21] , cartilage is usually a solid connective tissue that covers subchondral bone tissue and plays an important role in the development of OA.…”

“…These findings have been supported by the existence of estrogen receptors (ERs) in mandibular condylar cartilage [20,21] . As an estrogen-targeted tissue [20,21] , cartilage is usually a solid connective tissue that covers subchondral bone tissue and plays an important role in the development of OA. To the best of our knowledge, however, few studies of the effect of genistein on cartilage have been reported, especially in vivo studies.…”

Pathogenesis of degenerative temporomandibular joint arthritides

“…54,55 Estrogen receptors have been identified in TMJs of rat, baboon, and human female. [56][57][58] Estrogen receptors have also been detected in rat and human TMJs in both sexes using standard immunohistochemical approaches. 56,58 However, functional estrogen receptors were not found in TMJs obtained from male baboons, as assessed by in vivo binding of 3 H-17b estradiol.…”