Micro-architectural and nano-mechanical properties of trabecular bone with strontium treatment in osteoporotic goats

Abstract

Introduction: Strontium (Sr) is one of the most exciting concepts in the field of osteoporosis treatment by concomitantly inhibiting bone resorption and enhancing bone formation. Previously, we developed a Sr fortified calcium (Ca) compound. In this study, the micro-architecture and nano-mechanical property of lumbar vertebra were evaluated after administration of this Sr compound in osteoporotic goats.

Methods: 18 aged goats were ovariectomized to establish an osteoporosis model. One (1) year post-ovariectomy, animals were randomly assigned to four (4) different groups and treated as follows: control group (3 goats); normal Ca diet (Ca), normal Ca plus low Sr diet (Ca + LSr) and normal Ca plus high Sr diet (Ca + HSr) (5 goats per group) respectively. After treating daily for 16 weeks, trabecular micro-architectural parameters from μCT were quantified. The biomechanical properties of single trabeculae were determined by nanoindentation. Compressive test were performed on the whole lumbar spine body (L4) by means of a materials testing system (MTS).

Results and Discussion: Ca alone and Ca + HSr treatment increased trabecular bone volume (BV/TV) by 3.53% and 5.39%, respectively. BV/TV significantly increased 8.59% in Ca + 24Sr group primarily by increasing trabecular thickness (Tb.Th⁎). The increase in apparent BMD and BV/TV in Ca combined with Sr treatment seemed to result from increased bone formation rate. Elastic modulus (E) of single trabeculaes was not changed in Sr combined with Ca treatment despite a slight decrease in hardness (H). In the treatment with Sr administration, a considerably higher E/H ratio, without statistical significance, was observed. The result might provide evidences for fracture risks reduction as observed in postmenopausal women after treatment with Sr containing drug. The compression test indicated an increase by 22.19% (p = 0.099) and 4.26% (p = 0.702) in Ca + LSr and Ca + HSr treatment groups, respectively. In the Ca alone treatment group, the maximal load was comparable to the mean value noted in the control animals (p = 0.936). A very slight modification of bone stiffness was observed between these groups. The observed trend for increase in the bone strength under the effect of Sr treatment was not statistically significant but this may be due, in part, to the relatively small number of animals studied.

Conclusion: Combination of Sr and Ca treatment significantly increased BV/TV, primarily by increasing Tb.Th⁎. Ironically, Sr and Ca treatment did not significantly affect the mechanical property of either single trabecula or the whole lumbar vertebra body. Acknowledgement: Hong Kong ITF fund GHP/009/06 and RGC HKU7147/07E.