Risedronate for prevention and treatment of osteoporosis in postmenopausal women

Chitosan-based biomaterials for the treatment of bone disorders

Bone is an alive and dynamic organ that is well-differentiated and originated from mesenchymal tissues. Bone undergoes continuous remodeling during the lifetime of an individual. Although knowledge regarding bones and their disorders has been constantly growing, much attention has been devoted to effective treatments that can be used, both from materials and medical performance points of view. Polymers derived from natural sources, for example polysaccharides, are generally biocompatible and are therefore considered excellent candidates for various biomedical applications. This review outlines the development of chitosan-based biomaterials for the treatment of bone disorders including bone fracture, osteoporosis, osteoarthritis, arthritis rheumatoid, and osteosarcoma. Different examples of chitosan-based formulations in the form of gels, micro/nanoparticles, and films are discussed herein. The work also reviews recent patents and important developments related to the use of chitosan in the treatment of bone disorders. Although most of the cited research was accomplished before reaching the clinical application level, this manuscript summarizes the latest achievements within chitosan-based biomaterials used for the treatment of bone disorders and provides perspectives for future scientific activities.

Application of Implantable Polylactic-Co-Glycolic Acid Microcapsule in Repairing Alveolar Bone Defects

Alveolar bone defects (ABDs) were a perennial problem, especially in the aged. Bisphosphonates, especially etidronate sodium (ET), were frequently used in clinical treatment of ABD. However, the oral administration of ET had poor absorption (<1%). Therefore, optimization of a suitable dosage form substituted with ET to locally repair the ABD was a straightforward approach. Polylactide-co-glycolide (PLGA) is a biodegradable material and had been used in locally implanted medical devices. Therefore, an ET-PLGA microcapsule may help local delivery and prolong the activity of healing ABD. In this paper, a preparation method of ET-PLGA microcapsule was optimized by the single-factor investigation and response surface method. Subsequently, the rat ABD model was used to evaluate the enhancement effect of these microcapsules. Finally, the optimum parameters were determined as follows: 40% dichloromethane, 160 mg/mL PLGA, 10% internal aqua/oil phase, 4% PVA, and emulsifying for 10 min. These microcapsules were spherical in shape and fairly monodisperse in a particle size of 27,51 μm (PDI = 0.3), encapsulation rate 96.6%, and drug loading 4.58%. Compared with the ET groups, the total healing volume of ABD in ET-PLGA groups was significantly increased (P < 0.05). ET-PLGA microcapsules significantly enhanced the effect of ET on ABD. This study provided important technical support for the treatment of ABD with bisphosphonates by local administration. This paper has an exploratory significance for the development of water-soluble bioactive components with low bioavailability for ABD.

Development of an animal fracture model for evaluation of cement augmentation femoroplasty: an in vitro biomechanical study

Osteoporotic hip fracture is the most severe kind of fracture with high morbidity and mortality. Patients' ambulation and quality of life are significantly affected by the fracture because only 50% regain their prefracture functional status, even if they undergo surgeries. There are many issues associated with the current preventive methods e.g., cost, side effects, patient compliance, and time for onset of action. Femoroplasty, the injection of bone cement into the proximal femur to augment femoral strength and to prevent fracture, has been an option with great potential. However, until now femoroplasty has remained at the stage of biomechanical testing. No in vivo study has evaluated its safety and effectiveness; there is not even an animal model for such investigations. The objective of this study was to develop a proximal femur fracture goat model that consistently fractures at the proximal femur when subject to vertical load, simulating osteoporotic hip fractures in human. Six pairs of fresh frozen mature Chinese goats' femora were obtained and randomly assigned into two groups. For the experimental group, a cylindrical bone defect was created at the proximal femur, while the control was left untreated. In addition, a configuration to mimic the mechanical axis of the goat femur was developed. When subjected to load along the mechanical axis, all the specimens from the bone defect group experienced femoral neck fractures, while fractures occurred at the femoral neck or other sites of the proximal femur in the control group. The biomechanical property (failure load) of the bone defect specimens was significantly lower than that of the control specimens (p<0.05). Osteoporotic hip fractures of humans were simulated by a goat fracture model, which may serve as a reference for future femoroplasty studies in vivo. The newly developed configuration simulating a femoral mechanical axis for biomechanical tests was practicable during the study.

Low-dose risedronate sodium protects bone cells after abrupt oestrogen withdrawal

OBJECTIVE

To investigate the effects of low-dose risedronate sodium on the in vitro cellular profile of osteoblasts, adipocytes, osteocytes and osteoclasts in a rat model of abrupt oestrogen deficiency.

METHODS

Oestrogen deficiency was induced by ovariectomy in 24 female rats. The rats were treated with low-dose (0.24 μg/kg) or high-dose (2.4 μg/kg) risedronate sodium for 4 days presurgery, continuing every 3 days until 15 days postsurgery. Osteogenic and adipogenic differentiation were determined in cultured bone marrow cells by alkaline phosphatase and Oil Red O staining, respectively, and by osteogenic and adipogenic gene expression. Osteoclast formation was measured in bone marrow cells stimulated with macrophage colony-stimulating factor and receptor activator of nuclear factor κB ligand, and stained with tartrate-resistant acid phosphatase. Osteocyte apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling assay and B-cell lymphoma-2 (Bcl-2) immunohistochemistry.

RESULTS

Low-dose risedronate sodium enhanced osteoblast differentiation, suppressed adipocyte differentiation and osteoclast formation, and reduced osteocyte apoptosis through regulation of Bcl-2 and Bcl-2-associated X protein.

CONCLUSIONS

Low-dose risedronate sodium may have clinical benefit in protecting against bone loss after abrupt oestrogen deficiency.

The effect of weight training on bone mineral density and bone turnover in postmenopausal breast cancer survivors with bone loss: a 24-month randomized controlled trial

SUMMARY

This study examined whether 24 months of weight training exercises enhanced the effectiveness of risedronate, calcium, and vitamin D in maintaining or improving bone mineral density (BMD) in 223 postmenopausal breast cancer survivors. Subjects who were > or =50% adherent to exercise had no improvement in BMD but were less likely to lose BMD.

INTRODUCTION

This study examined whether (1) postmenopausal breast cancer survivors (BCS) with bone loss taking 24 months of risedronate, calcium, and vitamin D had increased bone mineral density (BMD) at the total hip, femoral neck, L1-L4 spine, total radius and 33% radius, and decreased bone turnover; (2) subjects who also participated in strength/weight training (ST) exercises had greater increases in BMD and greater decreases in bone turnover; and (3) subjects who also exercised were more likely to preserve (at least maintain) BMD.

METHODS

Postmenopausal BCS (223) were randomly assigned to exercise plus medication or medication only groups. Both groups received 24 months of 1,200 mg of calcium and 400 IU of vitamin D daily and 35 mg of risedronate weekly, and the exercise group additionally had ST exercises twice weekly.

RESULTS

After 24 months, women who took medications without exercising had significant improvements in BMD at the total hip (+1.81%) and spine (+2.85%) and significant decreases in Alkphase B (-8.7%) and serum NTx (-16.7%). Women who also exercised had additional increases in BMD at the femoral neck (+0.29%), total hip (+0.34%), spine (+0.23%), total radius (+0.30%), and additional decreases in Alkphase B (-2.4%) and Serum NTx (-6.5%). Additional changes in BMD and bone turnover with exercise were not significant. Subjects who were > or =50% adherent to exercise were less likely to lose BMD at the total hip (chi-square [1] = 4.66, p = 0.03) and femoral neck (chi-square [1] = 4.63, p = 0.03).

CONCLUSION

Strength/weight training exercises may prevent loss of BMD in postmenopausal BCS at risk for bone loss.

A biomechanical evaluation of femoroplasty under simulated fall conditions

OBJECTIVES

To test the hypotheses that, compared with controls: 1) femoroplasty (the injection of bone cement into the proximal femur in an attempt to prevent fragility fracture) increases the yield and ultimate loads, yield and ultimate energies, and stiffness of the proximal osteoporotic femur in a simulated fall model; and 2) the manner in which the cement distributes in the proximal femur affects the extent to which those mechanical properties are altered.

METHODS

In 10 pairs of osteoporotic human cadaveric femora, we injected one femur of each pair with 40 to 50 mL of polymethylmethacrylate bone cement; the noninjected femur served as the control. The filling percentage was calculated in four anatomic regions of the femur: head, neck, trochanter, and subtrochanter. All specimens were biomechanically tested in a configuration that simulated a fall on the greater trochanter. Student t test, linear regression, and multinomial logistic regression statistical analyses were conducted where appropriate with significant difference defined as P < 0.05.

RESULTS

Femoroplasty significantly increased yield load (22.0%), ultimate load (37.3%), yield energy (79.6%), and ultimate energy (154%) relative to matched controls but did not significantly change stiffness (-10.9%). There was a strong (r = 0.7) correlation between yield load and filling percentage in the femoral neck.

CONCLUSIONS

This study showed that 1) femoroplasty significantly increased fracture load and energy to fracture when osteoporotic femora were loaded in simulated fall conditions, and 2) cement filling in the femoral neck may have an important role in the extent to which femoroplasty affects mechanical strength of the proximal femur.