Lower femoral neck bone mineral density (BMD) in elderly women not on statins

The effect of topical administration of simvastatin on entochondrostosis and intramembranous ossification: An animal experiment

Background

Simvastatin, a drug for lowering serum cholesterol, has been shown to enhance bone regeneration, but few studies have qualitatively and quantitatively tested its effect when used topically in different animal models. This study aims to investigate topical administration of simvastatin as a bone regeneration inducer by testing its effect on bone formation in both long tubular bone and flat bone defect, and the mechanism involved.

Methods

Two animal models were used for testing the effect of simvastatin on entochondrostosis and intramembranous ossification respectively. Simvastatin of different dosages combined with poly lactic acid were implanted in extreme radial defects of 12 adult male New Zealand rabbits. Bone formation was monitored using x-ray and CT-scan and measured using x-ray scales, pixel values and spiral CT-scan for 16 weeks before being subject to histological and immunohistochemistry examination. The result was compared with that of autograft and blank control groups. Simvastatin with thrombin and fibrin sealant were implanted in calvarial defects of three Rhesus monkeys and monitored for 18 weeks. Bone formation was compared between the simvastatin and the blank control group using spiral CT-scan and histological examination.

Results

Both visual and quantitative measurements by x-ray and spiral CT-scan indicated significant bone formation in radial defects in all simvastatin groups and the autograft group whereas no bone formation was found in control groups. There was no significant difference in bone formation quantity between 100 ​mg simvastatin and autograft. Histological and immunohistochemistry examination indicated entochondrostosis in association with positive expression of BMP-2 and HIF-1 alpha. Spiral CT-scan and histological examination of calvarial defects of monkeys showed intramembranous ossification after simvastatin implantation. No change was found in the control group.

Conclusions

Topical administration of simvastatin induces entochondrostosis and intramembranous ossification by enhancing expression of BMP-2 and HIF-1 alpha. The effect of simvastatin on bone regeneration is comparable to autograft.

The translational potential of this article

Topical administration of simvastatin can repair bone defect in both long tubular bones and flat bones of rabbits and monkeys as effectively as autograft. Given that it is cheap, safe and already in clinical use, simvastatin might be considered as a bone regeneration inducer with great potential.

Regulation of calcific vascular and valvular disease by nuclear receptors

PURPOSE OF REVIEW

This review addresses recent developments in studies of lipid regulation of calcific disease of arteries and cardiac valves, including the role of nuclear receptors. The role of lipid-soluble signals and their receptors is timely given the recent evidence and concerns that lipid-lowering treatment may increase the rate of progression of coronary artery calcification, which has been long associated with increased cardiovascular risk. Understanding the mechanisms will be important for interpreting such clinical information.

RECENT FINDINGS

New findings support regulation of calcific vascular and valvular disease by nuclear receptors, including the vitamin D receptor, glucocorticoid receptor, nutrient-sensing nuclear receptors (liver X receptor, farnesoid X receptor, and peroxisome proliferator-activated receptors), and sex hormone (estrogen and androgen) receptors. There were two major unexpected findings: first, vitamin D supplementation, which was previously believed to prevent or reduce vascular calcification, showed no cardiovascular benefit in large randomized, controlled trials. Second, both epidemiological studies and coronary intravascular ultrasound studies suggest that treatment with HMG-CoA reductase inhibitors increases progression of coronary artery calcification, raising a question of whether there are mechanically stable and unstable forms of coronary calcification.

SUMMARY

For clinical practice and research, these new findings offer new fundamental mechanisms for vascular calcification and provide new cautionary insights for therapeutic avenues.