Bone Loss In Animal Model Research Articles

Effects of pharmacological inhibition of cathepsin K on fracture repair in mice

Cathepsin K inhibitors (CatK-I) have been developed and established to restore bone mass in both animal models of bone loss and postmenopausal osteoporotic patients. We investigated the effects of a CatK-I L-006235 on bone repair and compared to alendronate (ALN) for its known effects on fracture healing in preclinical models. Femoral fractures were performed on wild type mice that were given vehicle (CON), CatK-I or ALN from day 0 post-fracture until euthanasia. Radiologic and micro-CT analyses demonstrated that CatK-I enhanced mineralization within the calluses at day 21 post-fracture, but to a lesser degree than ALN. Histological analyses showed residual unmineralized and mineralized cartilage in the calluses of CatK-I and ALN treated groups at day 21 post-fracture compared to that in CON. CatK-I enhanced the number of tartrate-resistant acid phosphatase positive (TRAP+) osteoclasts in the fracture calluses compared to ALN and CON treated groups. However, relative levels of serum C-terminal telopeptides of type I collagen (CTX) normalized to the number of TRAP+ osteoclasts within the calluses were significantly decreased in both CatK-I and ALN groups compared to CON. Additionally, the percentages of osteoblast surface over mineralized calluses and levels of the bone formation marker serum N-terminal propeptide of type I procollagen (P1NP) were comparable between CatK-I versus CON groups, while these bone formation parameters were decreased by ALN. Taken together, these results indicate that unlike ALN, CatK-I inhibits osteoclastic activity without changing bone formation, and the inhibition of CatK delayed but did not abrogate callus remodeling during bone repair.

Osteoporosis Treatment with New Osteogenic Factors, Osteoporosis

Bone homeostasis is maintained through a delicate balance between osteoblastic bone formation and osteoclastic bone resorption. Bone loss may be due to decreased osteoblastic bone formation and increased osteoclastic bone resorption. Osteoporosis is induced with its accompanying decrease in bone mass. Nutrition and functional food factors may play a role in the prevention of bone loss. This is worthy of notice in the treatment of osteoporsis. It has been shown that functional food factors including zinc, genistein and vitamin K2 (menaquinone-7) have potential osteogenic effects in vitro and in vivo. These factors have been shown to have stimulatory effects on osteoblastic bone formation and suppressive effects on osteoclastic bone resorption. Moreover, the osteogenic effects of genistein, menaquinone-7, and vitamin D3 have been found to be synergistically enhanced with combination of zinc, which plays an essential role in protein synthesis at translational process and gene expression related to zinc finger transcription factors. Intake with their combination has been shown to have potential effects in the treatment of bone loss in animal models of osteoporosis and human subjects. Supplemental intake with these compositions may have potential effects on osteoporosis treatment.

Role of carotenoid β-cryptoxanthin in bone homeostasis.

Bone homeostasis is maintained through a balance between osteoblastic bone formation and osteoclastic bone resorption. Aging induces bone loss due to decreased osteoblastic bone formation and increased osteoclastic bone resorption. Osteoporosis with its accompanying decrease in bone mass is widely recognized as a major public health problem. Nutritional factors may play a role in the prevention of bone loss with aging. Among various carotenoids (carotene and xanthophylls including beta (β)-cryptoxanthin, lutein, lycopene, β-carotene, astaxanthin, and rutin), β-cryptoxanthin, which is abundant in Satsuma mandarin orange (Citrus unshiu MARC.), has been found to have a stimulatory effect on bone calcification in vitro. β-cryptoxanthin has stimulatory effects on osteoblastic bone formation and inhibitory effects on osteoclastic bone resorption in vitro, thereby increasing bone mass. β-cryptoxanthin has an effect on the gene expression of various proteins that are related osteoblastic bone formation and osteoclastic bone resororption in vitro. The intake of β-cryptoxanthin may have a preventive effect on bone loss in animal models for osteoporosis and in healthy human or postmenopausal women. Epidemiological studies suggest a potential role of β-cryptoxanthin as a sustainable nutritional approach to improving bone health of human subjects. β-Cryptoxanthin may be an osteogenic factor in preventing osteoporosis in human subjects.

Reply to Scott, Sale, Greeves, and Fraser

to the editor: We thank Scott et al.([1][1]) for their interest in our recent study ([2][2]) that examined the acute response of bone turnover markers to a single bout of resistance training (RT) or plyometrics (PLY). We appreciate the acknowledgement of the strengths of our study design: we

Type 17 T-helper cells might be a promising therapeutic target for osteoporosis

Osteoporosis, a disease characterized by low bone mass and deterioration of bone tissue, is a pressing public health problem. Recent studies have suggested a possible role of T-helper (Th) cells in the pathogenesis of bone loss which occurs in systemic inflammatory diseases. However, there are contradictions in the published literature regarding the functional role of Th1/Th2 cells in the regulation of the differentiation of osteoclasts. These paradoxes have now been clarified by the recent discovery of Th17 cells, a novel subset of Th cells that selectively secrete several proinflammatory cytokines, mainly IL-17. It has been confirmed that Th17 cells have stimulatory effects on osteoclastogenesis and accelerate bone loss in animal models with inflammatory disorders. Targeting Th17 cells or IL-17 may inhibit the bone resorption with RA. Thus, we are led to suppose that Th17 cells might be promising therapeutic targets in osteoporosis.

Genistein aglycone effect on bone loss is not enhanced by supplemental calcium and vitamin D3: A dose ranging experimental study

Genistein aglycone (GEN) has a favorable effect on bone loss. We investigated the effects of GEN alone or in combination with supplemental calcium and vitamin D(3) in an animal model of bone loss to evaluate if there was additional benefit. Ovariectomized (OVX) and SHAM-OVX rats were used. OVX were divided into 12 groups and randomized to receive: GEN at 27, 54, 200, 500 or 1000 mg (human equivalent dose (HED)/day/ip injection alone or with calcium carbonate (Ca) (360 mg/kg/day/gavages) and vitamin D(3) (D(3)) (50 IU/kg/day/gavages) or Ca/D(3) without GEN or untreated for 6 weeks. SHAM-OVX were randomized into 7 groups and treated with: Ca and D(3) alone or in combination with GEN (same doses as OVX), or left untreated. Bone mineral density (BMD), bone-alkaline phosphatase (b-ALP), collagen C-telopeptides (CTX), osteoprotegerin (OPG) and soluble receptor activator of NFκB ligand (sRANKL) were assessed. Femurs were excised and tested for breaking strength and histology. Uterine weight was analyzed to assess GEN's estrogenic effects on the SHAM-OVX. The most effective dose of GEN, independent of Ca/D(3) supplementation, was 54 mg/day. Higher doses yielded no further improvement in bone biomarkers, histology or strength. Only 1000 mg/day HED of genistein produced statistically significant changes in uterine weight of the SHAM-OVX. This study suggests that 54 mg/day of GEN is the threshold dose for efficacy. In addition, supplemental calcium and vitamin D(3), beyond normal dietary intake do not enhance the effects of genistein on improving measures of bone loss. This observation has implications regarding the use of calcium and vitamin D(3) supplementation.

Evaluation of Pharmaceuticals With a Novel 50-Hour Animal Model of Bone Loss

Osteoporosis remains a major public health problem through its associated fragility fractures. Several animal models for the study of osteoporotic bone loss, such as ovariectomy (OVX) and denervation, require surgical skills and several weeks to establish. Osteoclast differentiation and activation is mediated by RANKL. Here we report the establishment of a novel and rapid bone loss model by the administration of soluble RANKL (sRANKL) to mice. Mice were injected intraperitoneally with sRANKL and used to evaluate existing anti-osteoporosis drugs. sRANKL decreased BMD within 50 h in a dose-dependent manner. The marked decrease in femoral trabecular BMD shown by pQCT and the 3D images obtained by microCT were indistinguishable from those observed in the OVX model. Histomorphometry showed that osteoclastic activity was significantly increased in the sRANKL-injected mice. In addition, serum biochemical markers of bone turnover such as Ca, C-telopeptide of type 1 collagen (CTX), and TRACP5b were also significantly increased in the sRANKL-injected mice in a dose-dependent manner. Bisphosphonates (BPs), selective estrogen receptor modulators (SERMs), and PTH are commonly used for the treatment of osteoporosis. We successfully evaluated the effects of anti-bone-resorbing agents such as BPs, a SERM, and anti-RANKL-neutralizing antibody on bone resorption in a couple of weeks. We also evaluated the effects of PTH on bone formation in 2 wk. A combination of sRANKL injections and OVX made it possible to evaluate a SERM. The sRANKL model is the simplest, fastest, and easiest of all osteoporosis models and could be useful in the evaluation of drug candidates for osteoporosis.

Treatment with tacrolimus enhances alveolar bone formation and decreases osteoclast number in the maxillae: a histomorphometric and ultrastructural study in rats.

Recent studies have suggested that tacrolimus monotherapy is a beneficial therapeutic alternative for the normalization of cyclosporin-induced bone loss in animal models and humans. The mechanism accounting for this action is unclear at present. In the present study, we attempted to determine the effect of tacrolimus monotherapy on alveolar bone using histological, histomorphometric and transmission electron microscopy (TEM). Groups of rats (n=10 each) were treated with either tacrolimus (1mg/kg/day, s.c.) or drug vehicle for 60 days. Fragments containing maxillary molars were processed for light microscopy to investigate the alveolar bone volume, trabecular separation, number of osteoclasts and osteoblasts, and transmission electron microscopy to investigate their ultrastructural basic phenotype. Treatment with tacrolimus monotherapy during 60 days may induce increases in alveolar bone volume (BV/TV,%; P<0.05) and a non-significant decrease in trabecular separation (Tb.Sp,mm; P>0.05), represented by a decrease in osteoclast number (N.Oc/BS; P<0.05) and maintenance of osteoblast number (N.Ob/BS; P>0.05). Osteoblasts were often observed as a continuous layer of active cells on the bone surface. Osteoclasts appeared to be detached from the resorbed bone surface, which was often filled by active osteoblasts and collagen-rich matrix. Moreover, osteoclasts in the treated group were frequently observed as inactive cells (without ruffled border, clear zone and detached from the bone surface). Within the limits of the present study, we conclude that tacrolimus leads to an increase in alveolar bone formation, which probably exerts action on osteoclasts. Tacrolimus could, therefore, play a crucial role in the control of both early osteoclast differentiations from precursors, as well as in functional activation.

Inhibition of Protein Kinase c-Src as a Therapeutic Approach for Cancer and Bone Metastases

c-Src is a proto-oncogene involved in the genesis of and invasion by many cancers. This non-receptor tyrosine kinase also plays a crucial role in bone homeostasis, since inhibition or deletion of c-Src impairs the function of osteoclasts, the bone resorbing cells. It is thus conceivable that c-Src could be a suitable target for the pharmacological treatment of cancers, skeletal metastases and diseases of bone loss, such as osteoporosis. The pyrrolo-pyrimidines CGP77675 and CGP76030 proved to be effective in preventing bone loss in animal models, while the effect of AZD0530, a dually active inhibitor of c-Src and Bcr-ABL, on bone resorption, has been tested in a Phase I clinical trials with promising results. As far as the metastatic bone disease is concerned, c-Src inhibitors could potentially have inhibitory effects both on osteoclasts and on tumour cells, and could disrupt the vicious circle established between these cell types in the bone microenvironment. In accord with this idea, CGP76030 is able to reduce the incidence of osteolytic lesions and of visceral metastases, and to suppress morbidity and lethality in a bone metastasis mouse model without obvious adverse effects. The purine-based c-Src inhibitor AP23451 and the dual c-Src/Abl inhibitors AP22408 and AP23236 proved efficacious in reducing bone metastases in preclinical studies. These results open a new avenue for the development of innovative therapies for the treatment of bone metastatic disease.

Tumor αvβ3 Integrin Is a Therapeutic Target for Breast Cancer Bone Metastases

In breast cancer bone metastasis, tumor cells stimulate osteoclast-mediated bone resorption, and bone-derived growth factors released from resorbed bone stimulate tumor growth. The alphavbeta3 integrin is an adhesion receptor expressed by breast cancer cells and osteoclasts. It is implicated in tumor cell invasion and osteoclast-mediated bone resorption. Here, we hypothesized that the therapeutic targeting of tumor alphavbeta3 integrin would prevent bone metastasis formation. We first showed that, compared with mock-transfected cells, the i.v. inoculation of alphavbeta3-overexpressing MDA-MB-231 breast cancer cells in animals increased bone metastasis incidence and promoted both skeletal tumor burden and bone destruction. The direct inoculation of alphavbeta3-overexpressing transfectants into the tibial bone marrow cavity did not however enhance skeletal tumor burden and bone destruction, suggesting that alphavbeta3 controls earlier events during bone metastasis formation. We next examined whether a nonpeptide antagonist of alphavbeta3 (PSK1404) exhibits meaningful antitumor effects in experimental breast and ovarian cancer bone metastasis. A continuous PSK1404 treatment, which inhibited osteoclast-mediated bone resorption in an animal model of bone loss, substantially reduced bone destruction and decreased skeletal tumor burden. Importantly, a short-term PSK1404 treatment that did not inhibit osteoclast activity also decreased skeletal tumor burden and bone destruction. This dosing regimen caused a profound and specific inhibition of bone marrow colonization by green fluorescent protein, alphavbeta3-expressing tumor cells in vivo and blocked tumor cell invasion in vitro. Overall, our data show that tumor alphavbeta3 integrin stands as a therapeutic target for the prevention of skeletal metastases.

Nonsteroid Immune Modulators and Bone Disease

Glucocorticoids have been the main agents for preventing organ rejection,but unfortunately they possess serious side effects. Newer immunosuppressive agents have therefore been introduced to overcome these effects and have had a dramatic impact on reducing the incidence of organ rejection, enhancing donor organ acceptance, and hence patient survival posttransplantation. However, calcineurin inhibitors (CIs), such as cyclosporine and tacrolimus, also have serious effects causing rapid and severe bone loss in animal models and humans. The mechanism accounting for this action is unclear at present, but the role of T lymphocyte action via RANKL seems to be of essence in triggering bone loss. The mechanism is complex and in vitro studies often produce results that are opposite to those seen in vivo. In addition to acute, rapid, and severe bone loss (ARSBL), the clinical picture shows an extremely high incidence of fractures at all sites, and depends upon the organ transplanted, preexisting bone disease, interval before transplantation, and the dose and duration of multiple immunosuppressive drugs. Other immune-modifying drugs, such as azathioprine, mycophenolate mofetil, and sirolimus, which are used in conjunction with glucocorticoids and CIs have not been shown to promote bone loss experimentally or clinically. With the exception of glucocorticoids, all of the agents discussed here demand further investigation with regard to their effects on bone health in the clinical setting.

Tyrosine kinase src inhibitors: potential therapeutic applications.

More than 20 years after its discovery, tyrosine kinase Src is still the focus of intense research, in both academia and the pharmaceutical industry. A prototype for non-receptor tyrosine kinases and proto-oncogenes, Src also has a specific role in bone biology. Src's essential role in osteoclast-mediated bone resorption relies on its high expression in this cell type and on the presence of specific substrates, the identity of which is currently being unraveled. Recent identification of selective, potent and orally available Src family kinase inhibitors and their detailed characterization in cells and in animal models of bone loss has produced a new impetus and a novel tool in the field. Here we review the cellular and molecular mechanisms through which Src kinase inhibitors could find an application as therapeutics, particularly in the fields of bone and cancer-induced bone metastases.

Possible exposure organic solvents in table tennis

A phenomenological theory of bone remodeling was developed with improved spatial stability compared to some of the more standard formulations. The improved stability was created by changing the nature of the remodeling differential equation to have an exponential character. As a result, the theoretical predictions are consistent with the experimental observation that changes in bone density during disuse, after hip surgery, during growth and during aging are all consistent with an exponential dependence of density on time. The new theory and the standard theory were both used to model the time course of bone changes in two animal models of bone loss during disuse. The new theory was better able to model the results of the experiments than the standard theory.The basic continuum theory underlying the remodeling theory was presented in some detail. This presentation was used to motivate the development of the new theory, as the standard theories can predict non-smooth distributions of bone density rather than the expected smooth distributions. It was shown that these non-smooth distributions are a violation of the continuum assumption, one of the bases for the theory of finite element stress analysis. The new model's stability was investigated using example problems and shown to be improved compared to the standard model.

The adaptation of bone apparent density to applied load

A phenomenological theory of bone remodeling was developed with improved spatial stability compared to some of the more standard formulations. The improved stability was created by changing the nature of the remodeling differential equation to have an exponential character. As a result, the theoretical predictions are consistent with the experimental observation that changes in bone density during disuse, after hip surgery, during growth and during aging are all consistent with an exponential dependence of density on time. The new theory and the standard theory were both used to model the time course of bone changes in two animal models of bone loss during disuse. The new theory was better able to model the results of the experiments than the standard theory. The basic continuum theory underlying the remodeling theory was presented in some detail. This presentation was used to motivate the development of the new theory, as the standard theories can predict non-smooth distributions of bone density rather than the expected smooth distributions. It was shown that these non-smooth distributions are a violation of the continuum assumption, one of the bases for the theory of finite element stress analysis. The new model's stability was investigated using example problems and shown to be improved compared to the standard model.