Effects of eldecalcitol and ibandronate on secondary osteoporosis and muscle wasting in rats with adjuvant-induced arthritis

OBJECTIVES: Rheumatoid arthritis (RA) is characterized by chronic inflammation of the synovium, progressive erosion of the articular cartilage, and joint destruction. RA also causes secondary osteoporosis and muscle wasting. We investigated the effects of ibandronate (IBN), a bisphosphonate; eldecalcitol (ELD), an active vitamin D3 derivative; and combination treatment with both agents on secondary osteoporosis and muscle wasting using adjuvant-induced arthritis rats. METHODS: Arthritis was induced in 8-week-old male Lewis rats. Rats were randomized into 4 treatment groups and an untreated normal control group: IBN (subcutaneously, once every 2 weeks, 10 µg/kg), ELD (orally, once daily, 30 ng/kg/day), IBN + ELD, vehicle, and control. Paw thickness measurements were performed for evaluation of arthritis. The femur was scanned using dual-energy X-ray absorptiometry. Cross-sectional areas of left tibialis and anterior muscle fibers and the expression of MuRF1, atrogin-1, MyoD, and myogenin in the gastrocnemius muscle were measured to evaluate muscle wasting. RESULTS: IBN and/or ELD increased bone mineral density (BMD) in the femur. In addition, there was an additive effect of combination treatment compared with single treatments for BMD. However, IBN and/or ELD did not inhibit muscle wasting in adjuvant-induced arthritis rats. CONCLUSIONS: Combination treatment with IBN and ELD may be effective for secondary osteoporosis associated with RA. Other treatments are necessary for muscle wasting associated with RA. Studies in humans are needed to confirm these findings.

Effects of combined therapy of alendronate and low-intensity pulsed ultrasound on metaphyseal bone repair after osteotomy in the proximal tibia of glucocorticoid-induced osteopenia rats

OBJECTIVES: Glucocorticoid (GC) treatment inhibits activation of runt-related transcription factor 2 (Runx2), which is essential for osteoblast differentiation from stem cells. As a result, GC treatment results in bone loss, GC-induced osteoporosis (GIO), elevated fracture risk, and delayed bone healing. Bisphosphonates such as alendronate (ALN) are recommended for treating or preventing GIO, and lowintensity pulsed ultrasound (LIPUS) facilitates fracture healing and maturation of regenerated bone. Combined therapy with ALN and LIPUS may stimulate cancellous bone healing in GIO rats. Here, we examined the effect of ALN and LIPUS on cancellous bone osteotomy repair in the proximal tibia of GIO rats. METHODS: Prednisolone (10 mg/kg body weight/day) was administered for 4 weeks to induce GIO in 6-month-old female Sprague-Dawley rats. Tibial osteotomy was then performed and daily subcutaneous injection of ALN (1-µg/kg body weight) was subsequently administered alone or in combination with LIPUS (20 min/day) for 2 or 4 weeks. RESULTS: ALN significantly increased bone mineral density (BMD) at 2 and 4 weeks, and ALN + LIPUS significantly increased BMD at 4 weeks. Bone union rates were significantly increased after 2 and 4 weeks ALN and ALN + LIPUS treatment. Lastly, ALN and ALN + LIPUS significantly increased the proportion of Runx2 positive cells at 4 weeks. CONCLUSIONS: ALN monotherapy and combined ALN and LUPUS treatment augmented BMD and stimulated cancellous bone repair with increased Runx2 expression at the osteotomy site in GIO rats. However, the combined treatment had no additional effect on cancellous bone healing compared to ALN monotherapy.