Comparison of the effect of vitamin K₂ and risedronate on trabecular bone in glucocorticoid-treated rats: A bone histomorphometry study

Purpose: To compare the effect of vitamin K₂ and risedronate on trabecular bone in glucocorticoid (GC)-treated rats. Materials and Methods: Forty-eight Sprague-Dawley female rats, 3 months of age, were randomized by the stratified weight method into 5 groups according to the following treatment schedule: age-matched control, GC administration, and GC administration with concomitant administration of vitamin K₂, risedronate, or vitamin K₂ + risedronate. GC (methylprednisolone sodium succinate, 5.0 mg/kg) and risedronate (10 μg/kg) were administered subcutaneously three and five times a week, respectively. Vitamin K₂ (menatetrenone, 30 mg/kg) was administered orally three times a week. At the end of the 8-week experiment, bone histomorphometric analysis was performed on trabecular bone of the tibial proximal metaphysis. Results: GC administration decreased trabecular bone mass compared with age-matched controls because of decreased bone formation (mineralizing surface, mineral apposition rate, and bone formation rate) and increased bone erosion. Vitamin K₂ attenuated GC-induced trabecular bone loss by preventing GC-induced decrease in bone formation (mineralizing surface) and subsequently reducing GC-induced increase in bone erosion. Risedronate prevented GC-induced trabecular bone loss by preventing GC-induced increase in bone erosion although it also suppressed bone formation (mineralizing surface, mineral apposition rate, and bone formation rate). Vitamin K₂ mildly attenuated suppression of bone formation (mineralizing surface) and bone erosion caused by risedronate without affecting trabecular bone mass when administered in combination. Conclusion: The present study showed differential effect of vitamin K₂ and risedronate on trabecular bone in GC-treated rats.