Effect of Estrogen and Food Hardness on Metabolism and Turnover of Condylar Cartilage

Aims: To clarify the effect of estrogen and food hardness on condylar cartilage and the cartilage-bone interface. Methods: A total of 56 rats were divided into four groups: (1) ovariectomized rats fed a normal (pressed pellet) food, (2) ovariectomized rats fed a soft (powder) food, (3) control rats fed a normal (pressed pellet) food, and (4) control rats fed a soft (powder) food. Some rats (n = 29) were sacrificed at the age of 67 days and others (n = 27) at the age of 87 days, and then 5-μm-thick sagittal paraffin sections were prepared from each temporomandibular joint (TMJ). Toluidine blue staining, in situ hybridization with type X collagen, terminal deoxynucleotidyl transferase and deoxyuridine triphosphate nick end labeling (TUNEL-assay), and tartrate-resistant acid phosphatase (TRAP) histochemistry were performed. Immunohistochemical analyses included cathepsin K, adiponectin, proliferating cell nuclear antigen (PCNA), and type X collagen staining. Analysis of variance and appropriate post-hoc tests were used in all analyses. Results: Ovariectomy and normal food consistency increased the thickness of condylar cartilage (P .001), PCNA expression (P .001) and type X collagen expression (P .001). Ovariectomy decreased the number (P .05) and size of osteoclasts (P .01). Soft food increased the number of cartilage cells stained positively against adiponectin (P .01). Conclusion: Decreased estrogen level and normal food hardness increase the thickness of condylar cartilage by various mechanisms. Keywords: adiponectin, estrogen, food hardness, loading, mandibular condylar cartilage, osteoclast, PCNA, proliferation, TRAP, type X collagen