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| |  AAOS: Estrogen May Play Role in Trapeziometacarpal Joint Arthritis By Coriene E. Hannapel Special to DG News DALLAS, TX -- February 18, 2002 -- Estrogen may play a role in the pathogenesis of trapeziometacarpal joint (TMJ) arthritis through complex biological effects of two receptor subtypes that may act independently or in unison, according to a poster presentation at the 69th Annual Meeting of the American Academy of Orthopedic Surgeons. Primary osteoarthritis (OA) of the human thumb, predominantly afflicts postmenopausal women by a ratio of nearly 15 to 1, despite a greater propensity for intra-articular injury in men. The etiology is not known, reported researchers at the Department of Orthopedics and Rehabilitation, Musculoskeletal Research Laboratory at The Milton S. Hershey Medical Center of the Pennsylvania State University College of Medicine, Hershey, PA, but a gender specific hormonal mechanism has been suggested. The study sought to define the presence of the classic estrogen receptor, ER-a, as well as the ER-b receptor within the human TMJ by using immunolocalization techniques. Researchers reported that Caucasian TMJ specimens were surgically harvested en bloc from symptomatic patients undergoing basal joint arthroplasty. Patients included 5 postmenopausal women and one man. The harvested specimens were excised, preserved in formalin, decalcified, embedded in paraffin, sectioned, and stained utilizing H & E as well as immunocytochemical methods for ER-a and ER-b utilizing antibody preparations. Light microscopy was used to analyze the intra-articular distribution of ER-a versus ER-b. Results indicated that ER-b localized to surface chondrocytes of trapezial and metacarpal arthritic cartilage, whereas ER-a was detected in superficial as well as in deeper cartilage layers, but neither receptor subtype was detected throughout the full thickness of diseased cartilage or on normal cartilage. ER-a and ER-b localized in a similar pattern to fibroblasts within the beak ligament insertion into the trapezium, but ER-a appeared to show stronger staining at the fibrocartilage transition zone insertion into the metacarpal, the researchers reported. No significant gender specific differences in the staining patterns were noted. Study results demonstrated differential staining of ER-a and ER-b within the human TMJ. The researchers indicated that it is thought that by differential expression and hormone binding affinities, ER-a acts independently as well as jointly with ER-b to regulate a variety of biological functions.
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