Novel comb-shaped PEG modification enhances the osteoclastic inhibitory effect and bone delivery of osteoprotegerin after intravenous administration in ovariectomized rats.

PURPOSE: Recombinant osteoprotegerin (OPG) has been proven to be useful for treating various bone disorders such as osteoporosis. To improve its in vivo pharmacological effect, OPG was conjugated to novel comb-shaped co-polymers of polyethylene glycol (PEG) allylmethylether and maleamic acid (poly(PEG), 5 kDa). Biodistribution and bioactivity were evaluated. METHODS: OPG was conjugated via lysine to poly(PEG) and to linear PEG (0.5 kDa and 5 kDa). Poly(PEG)-OPG was compared with linear PEG0.5k-OPG and PEG5k-OPG in terms of in vitro and in vivo efficacy and bone distribution. RESULTS: The in vitro receptor binding study showed that poly(PEG)-OPG could be the most bioactive among the three PEG-OPG derivatives. Pharmacokinetic studies in ovariectomized (OVX) rats showed that serum half-life and AUC of poly(PEG)-OPG were comparable with those of linear PEG-OPG derivatives. For in vivo pharmacological effect, poly(PEG)-OPG showed the strongest inhibitory effect on bone resorption activity in OVX rats. Poly(PEG)-OPG demonstrated enhanced bone marrow distribution with higher selectivity than linear PEG5k-OPG. CONCLUSION: Poly(PEG) modification could provide longer residence time in serum and higher bone-marrow specific delivery of OPG, leading to a higher in vivo pharmacological effect.

Cinética de expressão de moléculas co-estimulatórias de osteoclastos no desenvolvimento da doença periodontal experimental e sua modulação por citocinas / Kinetics of osteoclast co-stimulatory molecules throughout experimental periodontitis and mice and its modulation by cytokines

O processo de diferenciação e ativação de osteoclastos, essencial para a manutenção da homeostasia do tecido ósseo e também envolvido na patogênese de diversas patologias caracterizadas pela atividade osteolítica, depende de um sistema central de controle que envolve a ligação das moléculas RANK/RANKL. Além do sistema RANK/RANKL, moléculas co-estimulatórias de osteoclastos, tais como os complexos DAP-12, TREM-2 e SIRP1, e FcR, OSCAR e PIR-A, também apresentam um papel importante na geração e ativação de osteoclastos. Entretanto, a possível contribuição de tais moléculas para a progressão da doença periodontal (DP) permanece desconhecida, assim como o possível impacto de citocinas na modulação de sua expressão no microambiente periodontal. Nosso objetivo foi investigar, por RealTimePCR, o padrão de expressão de moléculas co-estimulatórias de osteoclastos (DAP-12, TREM-2 e SIRP1, e FcR, OSCAR e PIR-A) na periodontite crônica em humanos, além de avaliar a cinética de expressão destas moléculas e a sua modulação por citocinas (TNF-, IFN-, IL-17 e IL-10) ao longo do curso da DP em camundongos em camundongos C57Bl/6 wild-type (WT) e geneticamente modificados (TNFp55KO, IFNKO, IL17KO, IL10KO. Nossos resultados demonstram que nas lesões periodontais crônicas a expressão de todas as moléculas co-estimulatórias de osteoclastos apresentaram-se significativamente aumentadas quando comparadas às amostras controle. Com relação à periodontite experimental, verificamos que todas as moléculas co-estimulatórias alvo apresentavam aumento em sua expressão após a indução de doença quando comparado aos controles. Nos camundongos para TNFp55KO, IFNKO e IL17KO, observamos uma redução na severidade da DP (reabsorção óssea e quantidade de células inflamatórias) e na expressão de moléculas co-estimulatórias, ao contrário do observado nos camundongos IL10KO. Entretanto, ao normalizarmos os níveis...

The osteoclast differentiation and activation are essential to bone tissue homeostasis and in the development of bone pathologies, which RANK/RANKL signaling molecules are the major osteoclastogenic factor. However, osteoclast co-stimulatory molecules, such as DAP-12, TREM-2, SIRP1, FcR, OSCAR and PIR-A, also present an important role in the osteoclastogenesis. However, the exact role and regulation of these molecules in human and mice periodontal diseases (PD) development have not completely known. Our aim was to investigate the pattern of osteoclast co-stimulatory expression (DAP-12, TREM-2, SIRP1, FcR, OSCAR and PIR-A) in human chronic periodontitis (CP), apart from analyze the kinetic of these molecules and their regulation by cytokines (TNF-, IFN-, IL-17 and IL-10) in the development of experimental periodontal disease in mice C57Bl/6 and knockout. Our results demonstrated that all osteoclast co-stimulatory molecules presented highly expressed in CP patients when compared with control. Similar results are presented about experimental PD, where all co-stimulatory molecules was presented highly expressed in infected mice when compared with control mice. We observed in TNFp55KO, IFNKO and IL17KO mice a decrease in PD scores and co-stimulatory molecules expression, the opposite of IL10KO mice. However, when we standardized the co-stimulatory molecules levels by the number of inflammatory cells, we found that TNF- and IL-17 are associated with increased expression of co-stimulatory molecules, while IFN- and IL-10 appear to negatively regulate the expression of such molecules. In conclusion, we demonstrated that osteoclast co-stimulatory molecules shown increased in human and experimental PD, and cytokines appear to modulate their expression by direct and indirect mechanisms, such as inflammatory cells migration to the PD infected tissue.

Cinética de expressão de moléculas co-estimulatórias de osteoclastos no desenvolvimento da doença periodontal experimental e sua modulação por citocinas / Kinetics of osteoclast co-stimulatory molecules throughout experimental periodontitis and mice and its modulation by cytokines

O processo de diferenciação e ativação de osteoclastos, essencial para a manutenção da homeostasia do tecido ósseo e também envolvido na patogênese de diversas patologias caracterizadas pela atividade osteolítica, depende de um sistema central de controle que envolve a ligação das moléculas RANK/RANKL. Além do sistema RANK/RANKL, moléculas co-estimulatórias de osteoclastos, tais como os complexos DAP-12, TREM-2 e SIRP1, e FcR, OSCAR e PIR-A, também apresentam um papel importante na geração e ativação de osteoclastos. Entretanto, a possível contribuição de tais moléculas para a progressão da doença periodontal (DP) permanece desconhecida, assim como o possível impacto de citocinas na modulação de sua expressão no microambiente periodontal. Nosso objetivo foi investigar, por RealTimePCR, o padrão de expressão de moléculas co-estimulatórias de osteoclastos (DAP-12, TREM-2 e SIRP1, e FcR, OSCAR e PIR-A) na periodontite crônica em humanos, além de avaliar a cinética de expressão destas moléculas e a sua modulação por citocinas (TNF-, IFN-, IL-17 e IL-10) ao longo do curso da DP em camundongos em camundongos C57Bl/6 wild-type (WT) e geneticamente modificados (TNFp55KO, IFNKO, IL17KO, IL10KO. Nossos resultados demonstram que nas lesões periodontais crônicas a expressão de todas as moléculas co-estimulatórias de osteoclastos apresentaram-se significativamente aumentadas quando comparadas às amostras controle. Com relação à periodontite experimental, verificamos que todas as moléculas co-estimulatórias alvo apresentavam aumento em sua expressão após a indução de doença quando comparado aos controles. Nos camundongos para TNFp55KO, IFNKO e IL17KO, observamos uma redução na severidade da DP (reabsorção óssea e quantidade de células inflamatórias) e na expressão de moléculas co-estimulatórias, ao contrário do observado nos camundongos IL10KO. Entretanto, ao normalizarmos os níveis...

The osteoclast differentiation and activation are essential to bone tissue homeostasis and in the development of bone pathologies, which RANK/RANKL signaling molecules are the major osteoclastogenic factor. However, osteoclast co-stimulatory molecules, such as DAP-12, TREM-2, SIRP1, FcR, OSCAR and PIR-A, also present an important role in the osteoclastogenesis. However, the exact role and regulation of these molecules in human and mice periodontal diseases (PD) development have not completely known. Our aim was to investigate the pattern of osteoclast co-stimulatory expression (DAP-12, TREM-2, SIRP1, FcR, OSCAR and PIR-A) in human chronic periodontitis (CP), apart from analyze the kinetic of these molecules and their regulation by cytokines (TNF-, IFN-, IL-17 and IL-10) in the development of experimental periodontal disease in mice C57Bl/6 and knockout. Our results demonstrated that all osteoclast co-stimulatory molecules presented highly expressed in CP patients when compared with control. Similar results are presented about experimental PD, where all co-stimulatory molecules was presented highly expressed in infected mice when compared with control mice. We observed in TNFp55KO, IFNKO and IL17KO mice a decrease in PD scores and co-stimulatory molecules expression, the opposite of IL10KO mice. However, when we standardized the co-stimulatory molecules levels by the number of inflammatory cells, we found that TNF- and IL-17 are associated with increased expression of co-stimulatory molecules, while IFN- and IL-10 appear to negatively regulate the expression of such molecules. In conclusion, we demonstrated that osteoclast co-stimulatory molecules shown increased in human and experimental PD, and cytokines appear to modulate their expression by direct and indirect mechanisms, such as inflammatory cells migration to the PD infected tissue.

PEGylation of osteoprotegerin/osteoclastogenesis inhibitory factor (OPG/OCIF) results in decreased uptake into rats and human liver.

OBJECTIVES: Our aim was to investigate the effect of PEGylation on the uptake of osteoprotegerin/osteoclastogenesis inhibitory factor (OPG/OCIF) into rat liver, kidney and spleen, and human liver. METHODS: Copolymer of polyethyleneglycol allylmethylether and maleamic acid sodium salt with OCIF (poly(PEG)-OCIF) (0.5 mg/kg) was administered to rats and the concentrations of poly(PEG)-OCIF in the liver, kidney and spleen at 15 min after administration were measured by ELISA. For human liver uptake, the liver perfusion of OCIF and (3)H-labelled poly(PEG)-OCIF was conducted using fresh human liver block. KEY FINDINGS: The tissue uptake of poly(PEG)-OCIF in rats was significantly lower compared with that of OCIF. In fresh human liver perfusion, (3)H-poly(PEG)-OCIF was rarely taken up into the liver. On the other hand, more than 50% of the perfused OCIF was taken up. CONCLUSIONS: PEGylation of OCIF using poly(PEG) dramatically suppressed the uptake of OCIF into human liver as well as into rat liver and could be a promising approach for improving the pharmacokinetic and pharmacological effects of OCIF in the clinical setting.

Improved bone delivery of osteoprotegerin by bisphosphonate conjugation in a rat model of osteoarthritis.

This study investigated the delivery of a model therapeutic protein, namely, osteoprotegerin (OPG), to bone sites in an animal model of osteoarthritis. The OPG was chemically conjugated to a "bone seeking" thiol-bisphosphonate (thiolBP) via a disulfide linkage. The BP conjugates of OPG were shown to display a higher hydroxyapatite affinity in vitro as compared to unmodified OPG. After intravenous injection, the bone uptake of OPG-thiolBP conjugate was increased 2-fold over that of control OPG under conditions of normal bone turnover. Furthermore, the retention of the OPG-thiolBP conjugate was significantly higher after 72 h. When administered to osteoarthritic rats undergoing active bone remodeling, the delivery of OPG-thiolBP conjugate to bone was increased more than 4-fold over that of control OPG after 24 h. These results suggest a significant advantage of BP conjugation as a drug delivery strategy for therapeutic cytokines in osteopenic bone diseases.

Pharmacokinetics and disposition of recombinant human osteoprotegerin (rhOPG) after intravenous administration in female fischer rats.

1. Osteoprotegerin (OPG) is a secreted member of the tumour necrosis factor receptor (TNFR) family that leads to the suppression of the differentiation, activation and survival of osteoclasts. The objective was to investigate the in vivo pharmacokinetics and tissue distribution of full-length recombinant human OPG (rhOPG) as well as its clearance mechanism using (125)I-labelled protein ((125)I-rhOPG) after intravenous administration to female Fischer rats. 2. (125)I-rhOPG was rapidly and predominantly distributed to the liver after dosing (3 mg kg(-1)). Immunohistochemical analysis indicated that rhOPG was located in the sinusoids of the liver. 3. The hepatic uptake of (125)I-rhOPG (0.01 mg kg(-1)) was partly regulated under a saturable process. Pre-dosing of some sulfated glycans (20 mg kg(-1)), especially dextran sulfate, heparin and fucoidan, markedly inhibited the hepatic uptake of (125)I-rhOPG. The clearance of (125)I-rhOPG was markedly reduced by the conjugation of dextran sulfate. 4. The results suggested that the hepatic clearance of (125)I-rhOPG was mainly mediated by the interaction with glycosaminoglycans.

Population PK-PD model for Fc-osteoprotegerin in healthy postmenopausal women.

Osteoporosis is a metabolic bone disease resulting from increased bone resorption and characterized by low bone mass that leads to increased bone fragility and risk of fracture, particularly of the hip, spine and wrist. Bone resorption is dependent on receptor activator of NF-kappa B ligand (RANKL), which binds to RANK receptor on preosteoclasts to initiate osteoclastogenesis and maintains osteoclast function and survival. To neutralize the effects of RANKL, the body naturally produces the protein osteoprotegerin (OPG), which acts as a decoy receptor for RANKL and contributes to bone homeostasis. We describe the piecewise development of a three-compartment pharmacokinetic model with both linear and Michaelis-Menten eliminations, and an indirect pharmacodynamic response model to describe the pharmacokinetics and pharmacodynamics, respectively, of the fusion protein, Fc-osteoprotegerin (Fc-OPG), in healthy postmenopausal women. Subsequently, model verification was performed and used to address study design questions via simulation. The model was developed using data from eight cohorts (n = 13 subjects/cohort; Fc-OPG:placebo = 10:3) classified by dose level (0.1, 0.3, 1.0, or 3.0 mg/kg) and route of administration (intravenous [IV] or subcutaneous [SC]). Fc-OPG serum concentrations and urinary N-telopeptide/creatinine ratios (NTX) following both IV and SC administration were available. The model provided an adequate fit to the observed data and physiologically plausible parameter estimates. Model robustness was tested via a posterior predictive check with the model performing well in most cases. Subsequent clinical trial simulations demonstrated that a single 3.0-mg/kg SC dose of Fc-OPG would be expected to produce, at 14 days post-dose, a median NTX percentage change from baseline of -45% (with a 95% prediction interval ranging from -34% to -60%). Lastly, model ruggedness was evaluated using local and global sensitivity analysis methods. In conclusion, the model selection and simulation strategies we applied were rigorous, useful, and easily generalizable.

Iontophoresis significantly increases the trans-dentinal delivery of osteoprotegerin, alendronate, and calcitonin.

The purpose of this study was to evaluate the delivery of alendronate, calcitonin, and osteoprotegerin (OPG) through human dentin by both diffusion and iontophoresis for the potential treatment of invasive cervical resorption. Radiolabeled alendronate, calcitonin, and OPG were added to the top of a split chamber device that contained 1-mm thick dentin disks devoid of a smear layer. Transdentinal movement of medicaments by either random diffusion or application of an iontophoretic current was measured by analysis of gamma emission of effluent fractions. In addition, calcitonin delivery was evaluated at differing magnitudes of current (0-4 mA) by using the aforementioned chamber. Diffusion of all 3 medicaments was minimal. In contrast, the application of a 3-mA iontophoretic gradient significantly increased delivery for all 3 compounds at 10-, 20-, and 30-minute intervals. In addition, a linear increase in permeability was seen for calcitonin as milliamperes were increased from 0 to 4 (r = 0.947), with more than a 100-fold increase in delivery observed with iontophoresis. Delivery of the tested medicaments by using iontophoresis might prove to be a useful technique for treatment of invasive cervical resorption.

Heparin induces mobilization of osteoprotegerin into the circulation.

Heparin treatment may induce osteoporosis by an unknown mechanism. Osteoprotegerin (OPG), a glycoprotein with a heparin-binding site, is a decoy receptor for RANKL which is responsible for osteoclast development. The objective was to investigate the effect of unfractionated heparin (UFH) and lowmolecular-weight heparin (LMWH; dalteparin) on plasma levels of OPG. Twenty-two male students were allocated to the following treatment regimens; A) one bolus of 5,000 IU UFH iv followed by infusion of 450 IU/kg/24 h for 72 hours (n = 7), B) sc administration of LMWH (200 IU/kg) once daily for 72 hours (n = 8), C) sc administration of 100 IU/kg LMWH once (n = 8), D) sc administration of 250 IU/kg UFH once (n = 7), E) control infusion of saline for 12 hours (n = 7). UFH boluses of 5,000 IU were given 4 and 24 hours after cessation of regimens A and B. Bolus injection of UFH iv caused a prompt increase in plasma OPG from 0.68 ng/ml (SD = 0.09) to 1.13 ng/ml (SD = 0.30) (p = 0.003) which declined during the continuous UFH infusion and reached baseline values after 8 hours (regime A). Similar increases in plasma OPG was obtained by repeated UFH boluses after cessation of treatment. Subcutaneous administration of LMWH (200 IU/kg) caused a modest, but significant (p = 0.002) increase in plasma OPG similar to the mobilization by 250 IU/kg UFH sc, but the LMWH treatment caused a three-fold higher anti-Xa activity (p < 0.001). We conclude that UFH causes a more pronounced vascular mobilization of OPG than LMWH, indicating that UFH has a higher affinity for OPG than LMWH.