Effect of parecoxib and dexamethasone on the temporomandibular joint of orchiectomized rats: Morphological and immunological analysis.

Objective: To evaluate the effects of parecoxib (a selective COX-2 inhibitor) and dexamethasone (a corticosteroid) on the temporomandibular joint (TMJ) of orchiectomized rats, a model of testosterone deficiency, through histological and immunological analyses.

Methods: Thirty-six rats were divided into six groups (n = 6). Sham groups received saline, parecoxib (0.3 mg/kg), or dexamethasone (0.1 mg/kg). ORX groups received the same treatments. TMJs were processed for histological staining (toluidine blue and picrosirius red) and analyzed by histomorphometry, measuring total cartilage thickness and its layers (fibrous, proliferative, mature, hypertrophic). Cytokines (IL-1α, IL-1β, IL-6, TNF-α) were quantified by ELISA. Data were analyzed using ANOVA-Welch and Kruskal-Wallis tests.

Results: ORX increased IL-1α, IL-1β, and TNF-α levels. IL-6 was reduced by dexamethasone. Dexamethasone also decreased cartilage thickness and accelerated its differentiation into subchondral bone. In contrast, parecoxib preserved cartilage thickness, especially in the fibrous and proliferative layers, and increased proteoglycan content. Both drugs reduced inflammatory markers, but with distinct structural effects.

Conclusions: Testosterone deficiency enhanced TMJ inflammation and impaired cartilage structure. While both dexamethasone and parecoxib modulated these effects, their actions differed: dexamethasone promoted cartilage-to-bone differentiation, potentially unfavorable long term, whereas parecoxib preserved cartilage integrity. These findings underscore hormonal influence and support selective anti-inflammatory strategies for TMJ preservation under androgen deficiency.