Effectiveness of combined salmon calcitonin and aspirin therapy for osteoporosis in ovariectomized rats

The objective of the present study was to assess the effectiveness of combined salmon calcitonin (sCT) and aspirin [acetylsalicylic acid (ASA)] treatment in an ovariectomized (OVX) rat model of postmenopausal osteoporosis. Following 12 weeks of treatment, therapeutic efficacy was assessed by evaluating changes in the biochemical and biophysical properties of bone (n=8 rats per group). Serological markers of bone metabolism were measured by ELISA; bone mineral densities (BMD) by dual energy X-ray absorptiometry; bone biomechanics of the femur and lumbar vertebrae by three-point stress test; trabecular bone morphology of lumbar vertebrae by hematoxylin and eosin staining; messenger RNA expression levels of osteoprotegerin (OPG) and receptor activator of nuclear factor κB ligand (RANKL) in bone marrow cells by reverse transcription-quantitative polymerase chain reaction and OPG and RANKL protein expression levels in the proximal tibia were analyzed by immunohistochemistry. Compared with treatment by sCT or ASA alone, combined treatment (sCT+ASA) increased BMD, improved femur bone strength, normalized trabecular network architecture and morphology, and increased mRNA and protein expression of OPG, while reducing the expression of RANKL. Collectively, these results demonstrated that combined treatment (sCT+ASA) of osteoporotic symptoms in OVX rats was more effective than treatment with sCT or ASA alone. Furthermore, these two drugs appeared to alter the expression of two distinct factors in the OPG/RANKL/RANK system, suggesting that their effects may be synergistic. Since sCT and ASA are currently approved for use in humans, the results of the present study suggest that the safety and efficacy of sCT+ASA combined therapy for postmenopausal osteoporosis should be assessed in clinical trials.