Estrogen receptor-beta is the predominant estrogen receptor subtype in normal human synovia.
OBJECTIVE
Joint pain increases after menopause with more than 50% of woman suffering from arthralgies. Since pain and inflammation of joints originate from synovial tissue, we aimed to discover whether estrogen receptors are present in the human synovia.


METHODS
This in vitro study was performed on samples of human synovial tissue, obtained from pre- (n = 8) and postmenopausal woman (n = 11) and men (n = 5) following surgery due to traumatic lesions. Fresh synovial tissue specimens were assessed for the localization as well as the presence of estrogen receptor-alpha (ER alpha) and estrogen receptor-beta (ER beta) by means of immunohistochemistry, as well as Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively.


RESULTS
ER beta protein and mRNA were found to be equally and highly expressed in synovial stroma and lining cells of all explants independent of sex or menopausal status. In contrast, weak ER alpha staining was localized in the synovial lining cells in only three of 24 explants. ER alpha protein was found to be weakly expressed in three of ten explants. ER alpha mRNA was found with highly variable amounts in seven of ten explants.


CONCLUSIONS
In view of our observation that ER beta but not ER alpha is expressed regularly in normal human synovia in high amounts, we propose that estrogen could play a significant role in synovial membrane function in women and men, operating preferably via the ER beta isoform.
Dietrich
Wolf
W
Department of Obstetrics and Gynecology, Division of Gynecologic Endocrinology and Reproductive Medicine, Medical University of Vienna, Vienna, Austria.
Haitel
Andrea
A
Holzer
Gerold
G
Huber
Johannes C
JC
Kolbus
Andrea
A
Tschugguel
Walter
W
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D047628:Estrogen Receptor alpha / Q000032:analysis; D047629:Estrogen Receptor beta / Q000032:analysis*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D017698:Postmenopause / Q000378:metabolism; D017697:Premenopause / Q000378:metabolism; D020033:Protein Isoforms / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013582:Synovial Fluid / Q000737:chemistry*
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D020033:Protein Isoforms; D012333:RNA, Messenger