Although recombinant human bone morphogenetic proteins (BMPs) are used locally for treating bone defects in humans, their systemic effect on bone augmentation has not been explored. We have previously demonstrated that demineralized bone (DB) from ovariectomized (OVX) rats cannot induce bone formation when implanted ectopically at the subcutaneous site. Here we showed in vitro that 17␤-estradiol (E 2 ) specifically induced expression of Bmp6 mRNA in MC3T3-E1 preosteoblastic cells and that bone extracts from OVX rats lack BMPs. Next we demonstrated that 125 I-BMP-6 administered systemically accumulated in the skeleton and also restored the osteoinductive capacity of ectopically implanted DB from OVX rats. BMP-6 applied systemically to aged OVX rats significantly increased bone volume and mechanical characteristics of both the trabecular and cortical bone, the osteoblast surface, serum osteocalcin and osteoprotegerin levels, and decreased the osteoclast surface, serum C-telopeptide, and interleukin-6. E 2 was significantly less effective, and was not synergistic with BMP-6. Animals that discontinued BMP-6 therapy maintained bone mineral density gains for another 12 weeks. BMP-6 increased in vivo the bone expression of Acvr-1, Bmpr1b, Smad5, alkaline phosphatase, and collagen type I and decreased expression of Bmp3 and BMP antagonists, chordin and cerberus. These results show, for the first time, that systemically administered BMP-6 restores the bone inductive capacity, microarchitecture, and quality of the skeleton in osteoporotic rats.Bone loss during aging and after menopause in women is known to result from an imbalance between bone formation and resorption leading to altered bone microarchitecture and excess bone fragility. Inferior bone strength and increased bone fracture rate of bone in patients with osteoporosis might be associated with decreased osteoinductive and thus self-regenerative bone capacity eventually due to the lower content of growth and differentiation factors including bone morphogenetic proteins in the bone extracellular matrix (1-4).Demineralized bone matrix (DBM) 2 induces de novo bone formation when implanted into the rat muscle (5). On the contrary, DBM from OVX animals implanted into both normal and OVX rats induces only fibrous tissues suggesting that its decreased bone inducing activity is due to abnormal composition of bone from OVX rats and not to the 17␤-estradiol (E 2 )-deficient microenvironment (1). Lack of specific signals needed for ectopic bone induction may, at least in part, explain diminished bone potency to heal fractures in osteoporotic patients (6,7). It has been demonstrated that fetal osteoblastic cell lines treated by E 2 specifically express Bmp6 mRNA, whereas gene transcripts of other members of the BMP family are unaffected (8). A functional relationship between E 2 and BMP-6 was further suggested by E 2 binding to the Bmp6 gene promotor (9) and by increased BMP-6 immunostaining in bone marrow of mice treated with E 2 (10).Although numerous studies have unequivoc...

We tested the efficacy of three selective agonists of prostaglandin E(2) (PGE(2)) receptor, EP2 (CP-536,745-01), EP2/4 (CP-043,305-02), and EP4 (CP-044,519-02), in two models of acute and chronic kidney failure. In the nephrotoxic mercury chloride (HgCl(2)) rat model of acute kidney failure systemically administered EP4 agonist reduced the serum creatinine values and increased the survival rate. Although the EP2 or the EP2/4 agonist did not change the serum creatinine values, the EP2 receptor agonist increased the survival rate. Histological evaluation of kidneys from EP4-treated rats indicated less proximal tubular necrosis and less apoptotic cells. In a rat model of chronic renal failure, the three receptor agonists decreased the serum creatinine and increased the glomerular filtration rate at 9 weeks following therapy. Kidneys treated with the EP4 agonist had less glomerular sclerosis, better preservation of proximal and distal tubules and blood vessels, increased convoluted epithelium proliferation and less apoptotic cells. Nephrectomy had no influence on the expression of the EP4 receptor, whereas EP2 receptor expression was reduced by 50% and then corrected following treatment with EP2 and EP2/4 receptor agonists. These findings suggest that PGE(2) has an important role in acute kidney failure via the EP4 receptor, whereas in chronic kidney failure both EP2 and EP4 receptors are equally important in preserving the progression of chronic kidney failure. Thus, agonism of EP2 and EP4 receptors may provide a basis for treating acute and chronic kidney failure.

We have recently shown that human recombinant BMP-6 (rhBMP-6), given systematically, can restore bone in animal models of osteoporosis. To further elucidate the underlying mechanisms of new bone formation following systemic application of BMPs, we conducted gene expression profiling experiments using bone samples of oophrectomised mice treated with BMP-6. Gene set enrichment analysis revealed enrichment of insulin-like growth factor-I and epidermal growth factor related pathways in animals treated with BMP-6. Significant upregulation of IGF-I and EGF expression in bones of BMP-6 treated mice was confirmed by quantitative PCR. To develop an in vitro model for evaluation of the effects of BMP-6 on cells of human origin, we cultured primary human osteoblasts. Treatment with rhBMP-6 accelerated cell differentiation as indicated by the formation of mineralised nodules by day 18 of culture versus 28-30 days in vehicle treated cultures. In addition, alkaline phosphatase gene expression and activity were dramatically increased upon BMP-6 treatment. Expression of IGF-I and EGF was upregulated in human osteoblast cells treated with BMP-6. These results collectively indicate that BMP-6 exerts its osteoinductive effect, at least in part, through IGF-I and EGF pathways, which can be observed both in a murine model of osteopenia and in human osteoblasts.Résumé Nous avons récemment pu mettre en évidence que la BMP-6 (rhBMP-6), administrée de façon systématique, pouvait améliorer la restauration du capital osseux de modèles animaux avec ostéoporose. Nous avons conduit une expérimentation utilisant des souris ovarieactomisées traitées par BMP-6. L'analyse a montré qu'il y avait un apport d'insulin like growth factor et d'épidermal growth factor chez les animaux traités par BMP-6. Pour développer un modèle in vitro nous avons étudié l'effet de la BMP-6 sur les cellules de type ostéoplasties d'origine humaine. Le traitement par BMP-6 accélère la différenciation cellulaire au 18ème jour alors que normalement cette différence est notée aux alentours du 28ème et 30ème jour. De plus, l'expression du gène de la phosphatase alkaline et l'activité sont augmentées par le traitement par la BMP-6, de même en ce qui concerne l'IGF-1 et l'EGF. Ces résultats nous permettent de penser que le BMP-6 a un effet ostéo conducteur notamment pour les pathologies intéressant IGF-1 et EGF. Nous avons observé ces effets dans un modèle animal avec ostéoplastie et sur les ostéoblastes humains.

Bone morphogenetic protein-7 promotes differentiation and mineralization of cementoblasts via inducing PCPE1 and BMP1 responsible for processing of type I collagen.

Ovaricetomized (OVX) animals represent an optimal model to investigate bone loss in osteoporosis. To further elucidate the underlying mechanisms of decreased bone formation and increased bone resorption following OVX, we conducted gene expression profiling experiments using bone samples of ovariectomized C57BL/6J mice. Following OVX, genes involved in immune response, cell cycle regulation, growth, apoptosis and bone resorption were upregulated, while genes that are important for regular cell processes, mitosis, metabolism of carbohydrates, extracellular matrix structure, angiogenesis, skeletal development and morphogenesis were downregulated. Among bone specific genes we observed upregulation of interleukin 7 (IL-7), IL-7 receptor and matrix metallopeptidase 8, while genes such as transforming growth factor-beta 3, procollagen type I and procollagen type VI exhibited marked decrease in expression. We also observed downregulation of two genes, parathyroid hormone receptor 1 and WD repeat domain 5, that are involved in skeletal development but were not previously reported to be altered in osteoporosis. We further performed gene set enrichment analysis (GSEA) in order to calculate enrichment of pathways specifically altered in murine bones following ovariectomy. In conclusion, OVX greatly influences expression of various genes involved in diverse biological processes confirming the notion that numerous pathways play an important role in pathophysiology of osteoporosis.