Abaloparatide increases bone mass by increasing bone formation regardless of alendronate pretreatment in mice

The effects of bisphosphonate pretreatment on the bone anabolic effects of abaloparatide (ABL) in mice were investigated. Mice were administered alendronate (ALN) at different doses for 21 days, followed by 28 days of ABL. ABL increased femoral bone mineral density at all ALN doses, with effects equal to or greater than those observed in mice without ALN. Histological analysis demonstrated that ABL increased ALPase- and PHOSPHO1-positive osteoblasts, irrespective of ALN pretreatment. However, the increase in TRAP-positive osteoclasts by ABL was attenuated at higher ALN doses. These findings suggest that ABL promotes bone formation in mice, independently of ALN pretreatment.