Micro-CT imaging analysis for the effects of ibandronate and eldecalcitol on secondary osteoporosis and arthritis in adjuvant-induced arthritis rats

Association of bisphosphonate with bone loss and pain-related behaviour in an adjuvant-induced osteoporosis model

OBJECTIVES

Osteoporosis animal models are used extensively to determine the mechanisms of disease pathology and identify potential biological targets. The study aimed to establish a bone loss model, identify pain-related behaviour in neighbouring joints using an adjuvant-induced osteoporosis model, and examine the therapeutic effect of bisphosphonates.

METHODS

Complete Freund's adjuvant was injected subcutaneously into the back of the right foot of 8-week-old female ddY mice. Subsequently, pain, arthritis, and bone density in the right knee were monitored over time.

RESULTS

Pain evaluation using von Frey filaments showed a significantly exacerbated knee pain threshold compared to the control group (saline administration) at 7- and 14-day intervals after complete Freund's adjuvant administration, and bone density during the same period also significantly declined. The adjuvant-induced osteoporosis model was created similarly; alendronate 40 μg/kg was subcutaneously injected twice and vehicle once from 7 to 14 days after onset. In the alendronate administration group on the 14th day, significant improvements in bone density, arthritis, and pain threshold around the knee were observed compared to the untreated group.

CONCLUSIONS

Alendronate may contribute to pain improvement through the simultaneous effects of bone mass improvement and suppression of osteoporotic pain.

Combination treatment with ibandronate and eldecalcitol prevents osteoporotic bone loss and deterioration of bone quality characterized by nano-arrangement of the collagen/apatite in an ovariectomized aged rat model

Combination therapy with bisphosphonates and vitamin D₃ analogs has been frequently used for the treatment of osteoporosis. However, its effects on bone anisotropies, such as orientations of collagen and apatite at the nanometer-scale, which is a promising bone quality index, and its trabecular architecture at the micrometer scale, are not well understood despite its important mechanical properties and its role in fracture risk. In the present study, we analyzed the effects of ibandronate (IBN), eldecalcitol (ELD), and their combination on the collagen/apatite orientation and trabecular architectural anisotropy using an estrogen-deficiency-induced osteoporotic rat model. Estrogen deficiency caused by ovariectomy (OVX) excessively increased the degree of collagen/apatite orientation or trabecular architectural anisotropy along the craniocaudal axis in the lumbar vertebra compared to that of the sham-operated group. The craniocaudal axis corresponds to the direction of principal stress in the spine. The excessive material anisotropy in the craniocaudal axis contributed to the enhanced Young's modulus, which may compensate for the reduced mechanical resistance by bone loss to some extent. The solo administration of IBN and ELD prevented the reduction of bone fraction (BV/TV) determined by μ-CT, and combination therapy showed the highest efficacy in BV/TV gain. Furthermore, the solo administration and combination treatment significantly decreased the degree of collagen/apatite orientation to the sham level. Based on the results of bone mass and collagen/apatite orientation, combination treatment is an effective strategy. This is the first report to demonstrate the efficacy of IBN, ELD, and combination treatment with IBN and ELD relative to the bone micro-architectural anisotropy characterized by collagen/apatite orientation.

Analysis of bone in adenine-induced chronic kidney disease model rats

Objectives

The purpose of this study is to investigate the stage of chronic kidney disease (CKD) in adenine-induced CKD model rats by serum analyses, and to examine bone mineral density (BMD), bone strength, and microstructure of trabecular and cortical bone in these rats.

Methods

Eight-week-old, male Wistar rats (n = 42) were divided into 2 groups: those fed a 0.75% adenine diet for 4 weeks until 12 weeks of age to generate CKD model rats (CKD group); and sham rats. The CKD and sham groups were sacrificed at 12, 16, and 20 weeks of age (n = 7 in each group and at 12, 16, and 20 weeks), and various parameters were evaluated, including body weight, renal wet weight, muscle wet weight, renal histology, biochemical tests, BMD, biomechanical testing, and micro-computed tomography (CT). The parameters were compared between the 2 groups at the various time points.

Results

In the CKD model rats, at 20 weeks of age, serum creatinine, phosphorus, and intact-PTH levels were elevated, and serum calcium levels were normal, indicating that the CKD was stage IV and associated with secondary hyperparathyroidism. Decreased BMDs of the whole body and the femur were observed as bone changes, and micro-CT analysis showed deterioration of bone microstructure of the cortical bone that resulted in decreased bone strength in the cortical and trabecular bone.

Conclusions

These CKD model rats showed stage IV CKD and appear appropriate for evaluating the effects of several treatments for CKD-related osteoporosis and mineral bone disorder.