Simvastatin and atorvastatin enhance gene expression of collagen type 1 and osteocalcin in primary human osteoblasts and MG-63 cultures

Effects of Simvastatin on Gene Expression and Alkaline Phosphatase Activity in the MG-63 Cell Line Treated With Hyperglycemia for Bone Regeneration

Background Dental implants have become a widespread treatment option for replacing missing teeth. Adequate bone is required for the placement of dental implants, in the absence of which, augmentation by bone regeneration is done. Antiresorptive drugs are used as treatment procedures for bone regeneration. One such antiresorptive drug is simvastatin (SV), a 3-hydroxy-3-methylglutaryl coenzyme used to manage hyperlipidemia. It reduces serum cholesterol levels and has an advantageous effect on new bone formation. Various studies establish that SV stimulates bone morphogenetic protein (BMP)-2 expression and leads to bone formation. SV prevents the production of isoprenoids and mevalonate, which are essential for osteoclastogenesis and contribute to the bone-sparing effect.  Aim The aim of the study was to investigate the osteoregenerative activity of SV in the osteoblast-like cell models, MG-63 cell line, with hyperglycemic conditions. Methodology MG-63 cultures were established under high glucose concentrations during the experiments and cultured with SV concentrations of 1 µM and 3 µM. The quantification of the expression of the genes, namely, BMP-2 and osteocalcin (OCN) was done by real-time quantitative polymerase chain reaction (RTqPCR). The measurement of alkaline phosphatase activity in the SV-treated cells was also determined. Results According to the results of the study, SV had osteoprotective properties resulting from the inhibition of osteoclast stimulation and osteoinductive properties, facilitated by BMP-2 and OCN. In addition, SV at concentrations of 1 µM and 3 µM increased the gene expression of BMP-2 and OCN in the MG-63 cell line. Conclusion The results of this study demonstrated that SV had a significant and direct effect on osteogenesis in osteoblasts in vitro.

Upregulation of human GD3 synthase (hST8Sia I) gene expression during serum starvation-induced osteoblastic differentiation of MG-63 cells

In this study, we have firstly elucidated that serum starvation augmented the levels of human GD3 synthase (hST8Sia I) gene and ganglioside GD3 expression as well as bone morphogenic protein-2 and osteocalcin expression during MG-63 cell differentiation using RT-PCR, qPCR, Western blot and immunofluorescence microscopy. To evaluate upregulation of hST8Sia I gene during MG-63 cell differentiation by serum starvation, promoter area of the hST8Sia I gene was functionally analyzed. Promoter analysis using luciferase reporter assay system harboring various constructs of the hST8Sia I gene proved that the cis-acting region at -1146/-646, which includes binding sites of the known transcription factors AP-1, CREB, c-Ets-1 and NF-κB, displays the highest level of promoter activity in response to serum starvation in MG-63 cells. The -731/-722 region, which contains the NF-κB binding site, was proved to be essential for expression of the hST8Sia I gene by serum starvation in MG-63 cells by site-directed mutagenesis, NF-κB inhibition, and chromatin immunoprecipitation (ChIP) assay. Knockdown of hST8Sia I using shRNA suggested that expressions of hST8Sia I and GD3 have no apparent effect on differentiation of MG-63 cells. Moreover, the transcriptional activation of hST8Sia I gene by serum starvation was strongly hindered by SB203580, a p38MAPK inhibitor in MG-63 cells. From these results, it has been suggested that transcription activity of hST8Sia I gene by serum starvation in human osteosarcoma MG-63 cells is regulated by p38MAPK/NF-κB signaling pathway.

Molecular targets of statins and their potential side effects: Not all the glitter is gold

Statins are a class of drugs widely used worldwide to manage hypercholesterolemia and the prevention of secondary heart attacks. Currently, available statins vary in terms of their pharmacokinetic and pharmacodynamic profiles. Although the primary target of statins is the inhibition of HMG-CoA reductase (HMGR), the rate-limiting enzyme in cholesterol biosynthesis, statins exhibit many pleiotropic effects downstream of the mevalonate pathway. These pleiotropic effects include the ability to reduce myocardial fibrosis, pathologic cardiac disease states, hypertension, promote bone differentiation, anti-inflammatory, and antitumor effects through multiple mechanisms. Although these pleiotropic effects of statins may be a cause for enthusiasm, there are many adverse effects that, for the most part, are unappreciated and need to be highlighted. These adverse effects include myopathy, new-onset type 2 diabetes, renal and hepatic dysfunction. Although these adverse effects may be relatively uncommon, considering the number of people worldwide who use statins daily, the actual number of people affected becomes quite large. Also, co-administration of statins with several other medications, herbal agents, and foods, which interact through common enzymatic pathways, can have untoward clinical consequences. In this review, we address these concerns.

Nanofibrillated cellulose/glucosamine 3D aerogel implants loaded with rosuvastatin and bioactive ceramic for dental socket preservation

Recycling of agro-wastes presents a great economic and ecologic value. In this study, TEMPO-oxidized nanofibrillated cellulose (TONFC) originating from sugarcane bagasse pulp was exploited in regenerative medicine. TONFC in combination with glucosamine HCl (G) were used to prepare a 3D aerogel implant loaded with rosuvastatin as an integrative approach for extraction-socket healing. Comparing the prepared devices, aerogel composed of TONFC: G (4:1 wt ratio) had the best mechanical properties and integrity. Strontium borate-based bioactive ceramic particles were prepared and characterized for crystal structure, shape, porosity, and zeta potential. The particles had a crystalline diffraction pattern relative to Sr₃B₂O₆, and they were rod in shape with nanopores with a zeta potential value of -16 mV. The prepared bioactive ceramic (BC) was then added in different concentrations (3 or 6% w/w) to the selected aerogel implant. The BC had a concentration-dependent effect on the aerogel properties as it ameliorated its mechanical performance (compressive strength = 90 and 150 kPa for 3 and 6%, respectively) and retarded drug release (mean release time = 2.34 and 3.4 h for 3 and 6%, respectively) (p < 0.05). The microphotograph of the selected aerogel implant loaded with BC showed a rough surface with an interconnective porous structure. During cell biology testing, the selected implant loaded with the lower BC concentration had the highest ability to increase MG-63 cells proliferation. In conclusion, TONFC is a promising material to formulate rosuvastatin-loaded aerogel implant with the aid of glucosamine and bioactive ceramic for dental socket preservation.

The Effects of Fluvastatin on Indian Hedgehog Pathway in Endochondral Ossification

Statins have demonstrated to be effective for treating chondrodysplasia and its effects were believed to be associated with the fibroblast growth factor receptor 3 (FGFR3). Statins promoted the degradation of FGFR3 in studies using disease-specific induced pluripotent stem cells and model mice, however, recent studies using normal chondrocytes reported that statins did not degrade FGFR3. In order to further investigate the effects of statins in endochondral ossification, this study examined the influence of statins on Indian hedgehog (Ihh), another important component of endochondral ossification, and its related pathways. The chondrocyte cell line ATDC5 was used to investigate changes in cell proliferation, mRNA, and protein expression levels. In addition, an organ culture of a mouse metatarsal bone was performed followed by hematoxylin-eosin staining and fluorescent immunostaining. Results indicated that expression level of Ihh increased with the addition of statins, which activated the Ihh pathway and altered the localization of Ihh. Changes in cholesterol modification may have affected Ihh diffusibility; however, further experiments are necessary. A reactive increase in parathyroid hormone-related protein (PTHrP) was observed in addition to changes in the Wnt pathway through secreted-related protein 2/3 and low-density lipoprotein 5/6. This led to the promotion of cell proliferation, increase of the hypertrophic chondrocyte layer, inhibition of apoptosis, and decrease in mineralization. This study demonstrated that statins had an influence on Ihh, and that the hyperfunction of Ihh may prevent premature cell death caused by FGFR3-related chondrodysplasia through an indirect increase in the expression of PTHrP.

Nobiletin promotes osteogenic differentiation of human osteoblastic cell line (MG-63) through activating the BMP-2/RUNX-2 signaling pathway

Nobiletin (NOB) is polymethoxy flavonoids, which plentifully there in Citrus depressa and they demonstrate numerous pharmacological effects. NOB has an anti-proliferative effect, attenuates ovalbumin-treated eosinophilic airway inflammation and Type II collagen treated arthritis. NOB noticeably inhibits bone resorption and renovates bone loss in mice model, but role of NOB in bone metabolism is unclear. Human bone is a important organ that sustains its homeostasis among bone resorpting osteoclasts and bone developing osteoblasts. The balances of among these two kind of cell outcomes are implicated in bone remodeling. The current study designed to explore possessions of NOB on differentiation and proliferation of MG-63 cells and contribution of morphogenetic protein signaling. Cell proliferation was analyzed by MTT, mineralization analysis by alizarin red staining and morphogenetic signaling protein by RT-PCR. No stimulus outcome of NOB on cell proliferation was found at days of 1, 3 and 7. Accumulation of calcium was augmented after that treatment of NOB. The mRNA expression of BMP-2, COL-I, ALP, OCN, RUNX2 and COL1A1 augmented markedly with NOB supplement. Hence, NOB can stimulate osteogenic differentiation of MG-63, almost certainly by promoting RUNX2 and BMP-2 signaling and this result might provide to its action on stimulation of osteoblast development, differentiation and augments of bone mass.

The role of statins in the differentiation and function of bone cells

BACKGROUND

Statins are 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors blocking cholesterol biosynthesis in hepatic cells, thereby causing an increase in low-density lipoprotein (LDL) receptors resulting in enhanced uptake and clearance of atherogenic LDL-cholesterol (LDL-C) from the blood. Accordingly, statins decrease the risk of developing atherosclerosis and its acute complications, such as acute myocardial infarction and ischaemic stroke. Besides the LDL-C-lowering impact, statins also have other so-called pleiotropic effects. Among them, the ability to modulate differentiation and function of bone cells and exert direct effects on osteosynthesis factors. Specifically, earlier studies have shown that statins cause in vitro and in vivo osteogenic differentiation.

DESIGN

The most relevant papers on the bone-related 'pleiotropic' effects of statins were selected following literature search in databases and were reveiwed.

RESULTS

Statins increase the expression of many mediators involved in bone metabolism including bone morphogenetic protein-2 (BMP-2), glucocorticoids, transforming growth factor-beta (TGF-β), alkaline phosphatase (ALP), type I collagen and collagenase-1. As a result, they enhance bone formation and improve bone mineral density by modulating osteoblast and osteoclast differentiation.

CONCLUSION

This review summarizes the literature exploring bone-related 'pleiotropic' effects of statins and suggests an anabolic role in the bone tissue for this drug class. Accordingly, current knowledge encourages further clinical trials to assess the therapeutic potential of statins in the treatment of bone disorders, such as arthritis and osteoporosis.

Osteoporosis Entwined with Cardiovascular Disease: The Implication of Osteoprotegerin and the Example of Statins

Beyond being epiphenomenon of shared epidemiological factors, the integration of Osteoporosis (OP) with Cardiovascular Disease (CVD) - termed "calcification paradox" - reflects a continuum of aberrant cardiometabolic status. The present review provides background knowledge on "calcification paradox", focusing on the endocrine aspect of vasculature orchestrated by the osteoblastic molecular fingerprint of vascular cells, acquired via imbalance among established modulators of mineralization. Osteoprotegerin (OPG), the well-established osteoprotective cytokine, has recently been shown to exert a vessel-modifying role. Prompted by this notion, the present review interrogates OPG as the potential missing link between OP and CVD. However, so far, the confirmation of this hypothesis is hindered by the equivocal role of OPG in CVD, being both proatherosclerotic and antiatherosclerotic. Further research is needed to illuminate whether OPG could be a biomarker of the "calcification paradox". Moreover, the present review brings into prominence the dual role of statins - cardioprotective and osteoprotective - as a potential illustration of the integration of CVD with OP. Considering that the statins-induced modulation of OPG is central to the statins-driven osteoprotective signalling, statins could be suggested as an illustration of the role of OPG in the bone/vessels crosstalk, if further studies consolidate the contribution of OPG to the cardioprotective role of statins. Another outstanding issue that merits further evaluation is the inconsistency of the osteoprotective role of statins. Further understanding of the varying bone-modifying role of statins, likely attributed to the unique profile of different classes of statins defined by distinct physicochemical characteristics, may yield tangible benefits for treating simultaneously OP and CVD.

Simvastatin-loaded graphene oxide embedded in polycaprolactone-polyurethane nanofibers for bone tissue engineering applications

Here, the role of simvastatin-loaded graphene oxide embedded in polyurethane-polycaprolactone nanofibers for bone tissue engineering has been investigated. The scaffolds were physicochemically and mechanically characterized, and obtained polymeric composites were used as MG-63 cell culture scaffolds. The addition of graphene oxide-simvastatin to nanofibers generates a homogeneous and uniform microstructure as well as a reduction in fiber diameter. Results of water-scaffolds interaction indicated higher hydrophilicity and absorption capacity as a function of graphene oxide addition. Scaffolds’ mechanical properties and physical stability improved after the addition of graphene oxide. Inducing bioactivity after the addition of simvastatin-loaded graphene oxide terminated its capability for hard tissue engineering application, evidenced by microscopy images and phase characterization. Nanofibrous scaffolds could act as a sustained drug carrier. Using the optimal concentration of graphene oxide-simvastatin is necessary to avoid toxic effects on tissue. Results show that the scaffolds are biocompatible to the MG-63 cell and support alkaline phosphatase activity, illustrating their potential use in bone tissue engineering. Briefly, graphene-simvastatin-incorporated in polymeric nanofibers was developed to increase bioactive components’ synergistic effect to induce more bioactivity and improve physical and mechanical properties as well as in vitro interactions for better results in bone repair.

Cu-Catalyzed C-H Alkenylation of Benzoic Acid and Acrylic Acid Derivatives with Vinyl Boronates

An efficient Cu-catalyzed C-H alkenylation with acyclic and cyclic vinyl boronates was realized for the first time under mild conditions. The scope of the vinyl borons and the compatibility with functional groups including heterocycles are superior than Pd-catalyzed C-H coupling with vinyl borons, providing a reliable access to multisubstituted alkenes and dienes. Subsequent hydrogenation of the product from the internal vinyl borons will lead to installation of secondary alkyls.

20(S)-hydroxycholesterol and simvastatin synergistically enhance osteogenic differentiation of marrow stromal cells and bone regeneration by initiation of Raf/MEK/ERK signaling

Previous studies have demonstrated the significant roles of simvastatin (SVA) and oxysterols in the osteogenesis process. In this study, we evaluate the effect of a combination of SVA and 20(S)-hydroxycholesterol (20(S)OHC) on the cell viability and osteogenic differentiation of bone marrow stromal cells (BMSCs). After treatment with a control vehicle, SVA (0.025, 0.10, 0.25 or 1.0 μM), 20(S)OHC (5 μM), or a combination of both (0.25 μM SVA + 5 μM 20(S)OHC), the proliferation, apoptosis, ALP activity, mineralization, osteogenesis-related gene expression and Raf/MEK/ERK signaling activity in BMSCs were measured. Our results showed that high concentrations of SVA (0.25 and 1.0 μM) enhanced osteogenesis-related genes expression while attenuating cell viability. The addition of 5 μM 20(S)OHC induced significantly higher proliferative activity, which neutralized the inhibitory effect of SVA on the viability of BMSCs. Moreover, compared to supplementation with only one of the additives, combined supplementation with both SVA and 20(S)OHC induced significantly enhanced ALP activity, calcium sedimentation, osteogenesis-related genes (ALP, OCN and BMP-2) expression and Raf/MEK/ERK signaling activity in BMSCs; these enhancements were attenuated by treatment with the inhibitor U0126, indicating a significant role of Raf/MEK/ERK signaling in mediating the synergistically enhanced osteogenic differentiation of BMSCs by combined SVA and 20(S)OHC treatment. Additionally, histological examination confirmed a synergistic effect of SVA and 20(S)OHC on enhancing bone regeneration in a rabbit calvarial defect model. This newly developed SVA/20(S)OHC formulation may be used as an osteoinductive drug to enhance bone healing.

Injectable calcium phosphate foams for the delivery of Pitavastatin as osteogenic and angiogenic agent

Apatitic bone cements have been used as a clinical bone substitutes and drug delivery vehicles for therapeutic agents in orthopedic applications. This has led to their combination with different drugs with known ability to foster bone formation. Recent studies have evaluated Simvastatin for its role in enhanced bone regeneration, but its lipophilicity hampers incorporation and release to and from the bone graft. In this study, injectable calcium phosphate foams (i-CPF) based on α-tricalcium phosphate were loaded for the first time with Pitavastatin. The stability of the drug in different conditions relevant to this study, the effect of the drug on the i-CPFs properties, the release profile, and the in vitro biological performance with regard to mineralization and vascularization were investigated. Pitavastatin did not cause any changes in neither the micro nor the macro structure of the i-CPFs, which retained their biomimetic features. PITA-loaded i-CPFs showed a dose-dependent drug release, with early stage release kinetics clearly affected by the evolving microstructure due to the setting of cement. in vitro studies showed dose-dependent enhancement of mineralization and vascularization. Our findings contribute towards the design of controlled release with low drug dosing bone grafts: i-CPFs loaded with PITA as osteogenic and angiogenic agent.

New potentials for 3-hydroxy-3-methyl-glutaryl-coenzymeA reductase inhibitors: Possible applications in retarding diabetic complications

The prevalence of diabetes mellitus is increasing all over the world and it is apparent that treatment of diabetic complications has the same importance as primary diabetes treatment and glycemic control. Diabetic complications occur as a result of prolonged hyperglycemia and its consequences, such as advanced glycation end products and reactive oxygen species. Impairment of lipid profile is also contributed to worsening diabetic complications. Therefore, it seems that the application of lipid-lowering agents may have positive effects on reversing diabetic complications besides glycemic control. Statins, a group of lipid-lowering compounds, have been shown to exert antioxidant, immunomodulatory, anti-inflammatory, and antiproliferative properties beyond their lipid-lowering effects. Furthermore, they have been reported to improve diabetic complications with different pathways. In this review, we will discuss the clinical importance, molecular biology of the most important microvascular/macrovascular diabetic complications, possible application of statins and their mechanism of action in retarding these complications.

Biodegradable Simvastatin-Containing Polymeric Prodrugs with Improved Drug Release

Simvastatin was previously converted to a polymeric prodrug with higher drug loading, but the hydrophobic nature of the poly(simvastatin) component of the block copolymer led to slow release of the drug in vitro. In this study, we hypothesized that degradation could be accelerated by chemically modifying the polymer backbone by introducing glycolide and lactide comonomers. Copolymers were formed by ring-opening polymerization using 5 kDa monomethyl ether poly(ethylene glycol) as the microinitiator in presence of triazabicyclodecene catalyst. In addition to simvastatin, modified reaction mixtures contained lactide or glycolide. Incorporation of the less hydrophobic glycolide comonomer led to in vitro degradation of up to two times greater mass loss, release of up to ~7 times more simvastatin, and a 2-3 times increase in compressive modulus compared to the lactide-containing and parent polymers.

Bone marrow stromal cells from low-turnover osteoporotic mouse model are less sensitive to the osteogenic effects of fluvastatin

This study aimed to investigate the effects of fluvastatin on the differentiation of bone marrow stromal cells (BMSCs) into osteoblasts in senescence-accelerated mouse prone 6 (SAMP6) compared with that in the normal senescence-accelerated-resistant mouse (SAMR1) model. SAMP strains arose spontaneously from the AKR/J background and display shortened life span and an array of signs of accelerated aging, compared with control SAMR strains. The dose effects of fluvastatin were also evaluated. BMSCs were cultured with/without fluvastatin (0 μM, 0.1 μM, 0.5 μM, and 1.0 μM). WST-1-based colorimetry was performed to evaluate cell proliferation. To evaluate cell differentiation, gene expression levels of bmp2 and runx2 were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR), and protein expression levels were determined using enzyme-linked immunosorbent assay (BMP2) and immunofluorescence staining (BMP2 and Runx2). Alkaline phosphatase (ALP) activity assay and histochemical detection were determined; the effect of noggin, a BMP-specific antagonist, was examined using ALP histochemical detection. To assess for mature osteogenic marker, gene expression levels of bglap2 were determined by qRT-PCR and mineralization was determined by alizarin red staining. RhoA activity was also examined by Western blotting. In SAMP6, BMP2, Runx2 and Bglap2 mRNA and protein expressions were significantly increased by fluvastatin, and ALP activity was increased by BMP2 action. RhoA activity was also inhibited by fluvastatin. The concentration of fluvastatin sufficient to increase BMP2 and Runx2 expression and ALP activity was 0.5 μM in SAMP6 and 0.1 μM in SAMR1. In conclusion, the present study revealed that fluvastatin promoted BMSC differentiation into osteoblasts by RhoA-BMP2 pathway in SAMP6. BMSCs of SAMP6 are less sensitive to the osteogenic effects of fluvastatin than SAMR1.

Current advances for bone regeneration based on tissue engineering strategies

Bone tissue engineering (BTE) is a rapidly developing strategy for repairing critical-sized bone defects to address the unmet need for bone augmentation and skeletal repair. Effective therapies for bone regeneration primarily require the coordinated combination of innovative scaffolds, seed cells, and biological factors. However, current techniques in bone tissue engineering have not yet reached valid translation into clinical applications because of several limitations, such as weaker osteogenic differentiation, inadequate vascularization of scaffolds, and inefficient growth factor delivery. Therefore, further standardized protocols and innovative measures are required to overcome these shortcomings and facilitate the clinical application of these techniques to enhance bone regeneration. Given the deficiency of comprehensive studies in the development in BTE, our review systematically introduces the new types of biomimetic and bifunctional scaffolds. We describe the cell sources, biology of seed cells, growth factors, vascular development, and the interactions of relevant molecules. Furthermore, we discuss the challenges and perspectives that may propel the direction of future clinical delivery in bone regeneration.

In Vitro Comparative Study of Oxygen Plasma Treated Poly(Lactic⁻Co⁻Glycolic) (PLGA) Membranes and Supported Nanostructured Oxides for Guided Bone Regeneration Processes

(1) Background: The use of physical barriers to prevent the invasion of gingival and connective tissue cells into bone cavities during the healing process is called guided bone regeneration. The objective of this in-vitro study was to compare the growth of human osteoblasts on Poly(Lactic⁻co⁻Glycolic) (PLGA) membranes modified with oxygen plasma and Hydroxyapatite (HA), silicon dioxide (SiO₂), and titanium dioxide (TiO₂) composite nanoparticles, respectively. (2) Methods: All the membranes received a common treatment with oxygen plasma and were subsequently treated with HA nanostructured coatings (n = 10), SiO₂ (n = 10) and TiO₂ (n = 10), respectively and a PLGA control membrane (n = 10). The assays were performed using the human osteoblast line MG-63 acquired from the Center for Scientific Instrumentation (CIC) from the University of Granada. The cell adhesion and the viability of the osteoblasts were analyzed by means of light-field microphotographs of each condition with the inverted microscope Axio Observer A1 (Carl Zeiss). For the determination of the mitochondrial energy balance, the MitoProbe™ JC-1 Assay Kit was employed. For the determination of cell growth and the morphology of adherent osteoblasts, two techniques were employed: staining with phalloidin-TRITC and staining with DAPI. (3) Results: The modified membranes that show osteoblasts with a morphology more similar to the control osteoblasts follow the order: PLGA/PO₂/HA > PLGA/PO₂/SiO₂ > PLGA/PO₂/TiO₂ > PLGA (p < 0.05). When analysing the cell viability, a higher percentage of viable cells bound to the membranes was observed as follows: PLGA/PO₂/SiO₂ > PLGA/PO₂/HA > PLGA/PO₂/TiO₂ > PLGA (p < 0.05), with a better energy balance of the cells adhered to the membranes PLGA/PO₂/HA and PLGA/PO₂/SiO₂. (4) Conclusion: The membrane in which osteoblasts show characteristics more similar to the control osteoblasts is the PLGA/PO₂/HA, followed by the PLGA/PO₂/SiO₂.

Enhanced osteogenesis and angiogenesis by mesoporous hydroxyapatite microspheres-derived simvastatin sustained release system for superior bone regeneration

Biomaterials with both excellent osteogenic and angiogenic activities are desirable to repair massive bone defects. In this study, simvastatin with both osteogenic and angiogenic activities was incorporated into the mesoporous hydroxyapatite microspheres (MHMs) synthesized through a microwave-assisted hydrothermal method using fructose 1,6-bisphosphate trisodium salt (FBP) as an organic phosphorous source. The effects of the simvastatin-loaded MHMs (S-MHMs) on the osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) and angiogenesis in EA.hy926 cells were investigated. The results showed that the S-MHMs not only enhanced the expression of osteogenic markers in rBMSCs but also promoted the migration and tube formation of EA.hy926 cells. Furthermore, the S-MHMs were incorporated into collagen matrix to construct a novel S-MHMs/collagen composite scaffold. With the aid of MHMs, the water-insoluble simvastatin was homogenously incorporated into the hydrophilic collagen matrix and presented a sustained release profile. In vivo experiments showed that the S-MHMs/collagen scaffolds enhanced the bone regeneration and neovascularization simultaneously. These results demonstrated that the water-insoluble simvastatin could be incorporated into the MHMs and maintained its biological activities, more importantly, the S-MHMs/collagen scaffolds fabricated in this study are of immense potential in bone defect repair by enhancing osteogenesis and angiogenesis simultaneously.

Effects of Statins on Bone Mineral Density and Fracture Risk: A PRISMA-compliant Systematic Review and Meta-Analysis

Although observational studies have identified the protective effect of statins on bone health, the effects remain controversial in randomized controlled trials (RCTs). We conducted a meta-analysis of RCTs to evaluate the effects of statins on bone mineral density (BMD) and fracture risk among adults.We searched electronic databases of Medline, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) and conducted a bibliography review to identify articles published until May, 2015.Studies included in this meta-analysis should be randomized controlled trials conducted in adults, using statins in the intervention group. Information on changes in BMD or odds ratio, relative risk or hazard ratio (HR) for fracture risk with the corresponding 95% confidence interval (CI) was provided.Two investigators independently reviewed the title or abstract, further reviewed the full-texts and extracted information on study characteristics and study outcomes. Net change estimates of BMD and pooled HR of fracture risk comparing the intervention group with the control group were estimated across trials using random-effects models.Of the relevant 334 citations, 7 trials (including 27,900 randomized participants in total) meeting the eligibility criteria were included. Of the 7 trials, 5 were conducted to assess the association of statins use with BMD change and 2 with fracture risk. Compared with the control group, statins use was associated with significant increase in BMD of 0.03 g/cm (95% CI: 0.006, 0.053; I = 99.2%; P < 0.001), but null association with fracture risk, with the pooled HR of 1.00 (95% CI: 0.87, 1.15; I = 0; P = 0.396). Sensitivity analyses revealed that the associations were consistent and robust.The effect of statins use on bone health among subpopulation could not be identified due to limited number of trials.These findings provide evidence that statins could be used to increase BMD other than decreasing fracture risk in participant with dyslipidemia. In addition, further trials with the primary outcome of bone health-related measurements in subpopulation are warranted to ensure the effect of statins use.

Targeted delivery as key for the success of small osteoinductive molecules

Molecules such as growth factors, peptides and small molecules can guide cellular behavior and are thus important for tissue engineering. They are rapidly emerging as promising compounds for the regeneration of tissues of the musculoskeletal system. Growth factors have disadvantages such as high cost, short half-life, supraphysiological amounts needed, etc. Therefore, small molecules may be an alternative. These molecules have been discovered using high throughput screening. Small osteoinductive molecules exhibit several advantages over growth factors owing to their small sizes, such as high stability and non-immunogenicity. These molecules may stimulate directly signaling pathways that are important for osteogenesis. However, systemic application doesn't induce osteogenesis in most cases. Therefore, local administration is needed. This may be achieved by using a bone graft material providing additional osteoconductive properties. These graft materials can also act by themselves as a delivery matrix for targeted and local delivery. Furthermore, vascularization is necessary in the process of osteogenesis. Many of the small molecules are also capable of promoting vascularization of the tissue to be regenerated. Thus, in this review, special attention is given to molecules that are capable of inducing both angiogenesis and osteogenesis simultaneously. Finally, more recent preclinical and clinical uses in bone regeneration of those molecules are described, highlighting the needs for the clinical translation of these promising compounds.

Novel applications of statins for bone regeneration

The use of statins for bone regeneration is a promising and growing area of research. Statins, originally developed to treat high cholesterol, are inhibitors of the enzyme 3-hydroxy-3-methylglutaryl, the rate-limiting enzyme of the mevalonate pathway. Because the mevalonate pathway is responsible for the synthesis of a wide variety of important biochemical molecules, including cholesterol and other isoprenoids, the effects of statins are pleiotropic. In particular, statins can greatly affect the process of bone turnover and regeneration via effects on important cell types, including mesenchymal stem cells, osteoblasts, endothelial cells, and osteoclasts. Statins have also been shown to have anti-inflammatory and antimicrobial properties that may be useful since infection can derail normal bone healing. This review will explore the pleiotropic effects of statins, discuss the current use of statins for bone regeneration, particularly with regard to biomaterials-based controlled delivery, and offer perspectives on the challenges and future directions of this emerging area of bone tissue engineering.

Genetic analysis of high bone mass cases from the BARCOS cohort of Spanish postmenopausal women

The aims of the study were to establish the prevalence of high bone mass (HBM) in a cohort of Spanish postmenopausal women (BARCOS) and to assess the contribution of LRP5 and DKK1 mutations and of common bone mineral density (BMD) variants to a HBM phenotype. Furthermore, we describe the expression of several osteoblast-specific and Wnt-pathway genes in primary osteoblasts from two HBM cases. A 0.6% of individuals (10/1600) displayed Z-scores in the HBM range (sum Z-score >4). While no mutation in the relevant exons of LRP5 was detected, a rare missense change in DKK1 was found (p.Y74F), which cosegregated with the phenotype in a small pedigree. Fifty-five BMD SNPs from Estrada et al. [NatGenet 44:491-501,2012] were genotyped in the HBM cases to obtain risk scores for each individual. In this small group of samples, Z-scores were found inversely related to risk scores, suggestive of a polygenic etiology. There was a single exception, which may be explained by a rare penetrant genetic variant, counterbalancing the additive effect of the risk alleles. The expression analysis in primary osteoblasts from two HBM cases and five controls suggested that IL6R, DLX3, TWIST1 and PPARG are negatively related to Z-score. One HBM case presented with high levels of RUNX2, while the other displayed very low SOX6. In conclusion, we provide evidence of lack of LRP5 mutations and of a putative HBM-causing mutation in DKK1. Additionally, we present SNP genotyping and expression results that suggest additive effects of several genes for HBM.

Enhanced in vitro osteoblast differentiation on TiO2 scaffold coated with alginate hydrogel containing simvastatin

The aim of this study was to develop a three-dimensional porous bone graft material as vehicle for simvastatin delivery and to investigate its effect on primary human osteoblasts from three donors. Highly porous titanium dioxide (TiO₂) scaffolds were submerged into simvastatin containing alginate solution. Microstructure of scaffolds, visualized by scanning electron microscopy and micro-computed tomography, revealed an evenly distributed alginate layer covering the surface of TiO₂ scaffold struts. Progressive and sustained simvastatin release was observed for up to 19 days. No cytotoxic effects on osteoblasts were observed by scaffolds with simvastatin when compared to scaffolds without simvastatin. Expression of osteoblast markers (collagen type I alpha 1, alkaline phosphatase, bone morphogenetic protein 2, osteoprotegerin, vascular endothelial growth factor A and osteocalcin) was quantified using real-time reverse transcriptase–polymerase chain reaction. Secretion of osteoprotegerin, vascular endothelial growth factor A and osteocalcin was analysed by multiplex immunoassay (Luminex). The relative expression and secretion of osteocalcin was significantly increased by cells cultured on scaffolds with 10 µM simvastatin when compared to scaffolds without simvastatin after 21 days. In addition, secretion of vascular endothelial growth factor A was significantly enhanced from cells cultured on scaffolds with both 10 nM and 10 µM simvastatin when compared to scaffolds without simvastatin at day 21. In conclusion, the results indicate that simvastatin-coated TiO₂ scaffolds can support a sustained release of simvastatin and induce osteoblast differentiation. The combination of the physical properties of TiO₂ scaffolds with the osteogenic effect of simvastatin may represent a new strategy for bone regeneration in defects where immediate load is wanted or unavailable.

Should we abandon statins in the prevention of bone fractures?

Osteoporosis increases dramatically with age. About 40 % of women in developed countries will experience an osteoporosis-related fracture in the course of their lifetime, with men experiencing approximately one-third to one-half the risk of women. The "lipid hypothesis of osteoporosis" claims for a role of oxidized lipids as a contributing factor in osteoporosis. On the other hand, statins are supposed to exert anabolic effects on the bone, either through their lipid-lowering action or signal pathways that are independent of their effects on lipid levels. The epidemiological evidence seems to suggest that higher triglycerides may give some protection against fracture, although no association with reduced fracture risk has been reported between lipid-lowering drug (except statins) users and non-users. The epidemiological evidence for a role of statins in osteoporosis is strong, with a lower fracture risk ranging from 30 to 40 % in statin users versus non-users. However, some pitfalls inherent to observational studies (high heterogeneity, residual confounding, potential publication bias) and the lack of association in randomized trials suggest caution. At the moment, the evidence for a role of statins in prevention of osteoporosis is insufficient to recommend starting statin therapy with the aim to prevent osteoporosis.

Encapsulation of simvastatin in PLGA microspheres loaded into hydrogel loaded BCP porous spongy scaffold as a controlled drug delivery system for bone tissue regeneration

The main objective of this study was to fabricate a controlled drug delivery which is simultaneously effective for bone regeneration. We have encapsulated simvastatin, which enhances osteoblastic activity, in the poly (lactic-co-glycolic acid) microspheres. Loading of these microspheres inside the spongy scaffold of biphasic calcium phosphate with the help of Gelatin (Gel) hydrogel controls the delivery of the drug, and ensures a more favorable drug release profile. As a result, some significant benefits have been achieved, such as higher mechanical strength, excellent biocompatibility in in vitro experiments. For determining the characteristics of the composite scaffold, several analysis, such as scanning electron microscope, EDX, X-ray diffraction, FT-IR, and porosity were carried out. The in vitro drug release profile clearly indicates that simvastatin release from the microsphere was more controlled and prolonged after loading in the scaffold. Biocompatibility was certainly higher for the final composite scaffold compared to drug unloaded scaffold, as assessed through MTT assay and Confocal imaging with MC3T3-E1 pre-osteoblast cells. Cell attachment and proliferation were certainly higher in the presence of drug loaded microspheres. Bone remodeling gene and protein expression were observed by real-time polymerase chain reaction and Western blot respectively. Simvastatin loaded scaffold exhibited the best results in every determination which was carried out.

Mesenchymal stem cell sheet transplantation combined with locally released simvastatin enhances bone formation in a rat tibia osteotomy model

Nonunion of fractured bones is a common clinical problem for orthopedic surgeons. This study aimed to investigate the effects of simvastatin locally applied from calcium sulfate (CS) combined with a mesenchymal stem cell (MSC) sheet on fracture healing. In vitro, the proliferation and differentiation of rat bone marrow-derived MSCs stimulated by simvastatin were investigated. In vivo, an osteotomy model was made in rat tibia, and fractured tibias were treated with CS, CS/simvastatin, CS/MSC sheet or simvastatin-loaded CS with MSC or untreated (control). Tibias were harvested at 2 or 8 weeks and underwent real-time quantitative polymerase chain reaction, x-ray, micro-CT and histological analysis. The expression levels of bone morphogenetic protein 2, alkaline phosphatase, osteocalcin, osteoprotegerin and vascular endothelial growth factor of simvastatin-induced MSCs increased with the concentrations of the simvastatin, significantly higher than those in the MSCs group. At 2 weeks, the CS/simvastatin/MSC sheet group showed significantly higher expressions of bone morphogenetic protein 2, alkaline phosphatase, osteocalcin, osteoprotegerin and vascular endothelial growth factor, with more callus formation around the fracture site compared with the other four groups. At 8 weeks, complete bone union was obtained in the CS/simvastatin/MSC sheet group. By contrast, newly regenerated bone tissue partially bridged the gap in the CS/simvastatin group and the CS/MSC sheet group; the control and CS group showed nonunion of the tibia. These results show that both simvastatin and the MSC sheet contributed to the formation of new bone and that the tibia fracture was completely healed by transplantation of the MSC sheet with locally applied simvastatin. Such MSC sheet with locally applied simvastatin might contribute to the treatment of fractures, bone delayed unions or nonunions in clinical practice.

Mechanisms of bone anabolism regulated by statins

Osteoporosis is a common disease in the elderly population. The progress of this disease results in the reduction of bone mass and can increase the incidence of fractures. Drugs presently used clinically can block the aggravation of this disease. However, these drugs cannot increase the bone mass and may result in certain side effects. Statins, also known as HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase inhibitors, have been widely prescribed for CVD (cardiovascular disease) for decades. Nonetheless, several studies have demonstrated that statins exert bone anabolic effect and may be helpful for the treatment of osteoporosis. Several experiments have analysed the mechanisms of bone anabolism regulated by statins. In the present paper, we review the mechanisms of promoting osteogenesis, suppressing osteoblast apoptosis and inhibiting osteoclastogenesis.

The role of small molecules in musculoskeletal regeneration

The uses of bone morphogenetic proteins and parathyroid hormone therapeutics are fraught with several fundamental problems, such as cost, protein stability, immunogenicity, contamination and supraphysiological dosage. These downsides may effectively limit their more universal use. Therefore, there is a clear need for alternative forms of biofactors to obviate the drawbacks of protein-based inductive factors for bone repair and regeneration. Our group has studied small molecules with the capacity to regulate osteoblast differentiation and mineralization because their inherent physical properties minimize limitations observed in protein growth factors. For instance, in general, small molecule inducers are usually more stable, highly soluble, nonimmunogenic, more affordable and require lower dosages. Small molecules with the ability to induce osteoblastic differentiation may represent the next generation of bone regenerative medicine. This review describes efforts to develop small molecule-based biofactors for induction, paying specific attention to their novel roles in bone regeneration.

Simvastatin prevents the induction of interleukin-6 gene expression by titanium particles in human osteoblastic cells

One of the most important complications of total joint arthroplasty is failure associated with periprosthetic osteolysis, a process mainly initiated by the biological response to wear-derived products from the biomaterials in service. The inflammatory mediator interleukin-6 (IL-6) plays a key role in the establishment and progression of aseptic loosening. Metal particles specifically up-regulate IL-6 production in bone-forming cells and implant-bone interfacial tissues. The use of statins has been recently associated with a significantly reduced risk of revision in patients that undergo total hip arthroplasty. We hypothesized that simvastatin (Simv) could modulate the osteoblastic response to titanium particles (Ti) by attenuating the production of IL-6. Pre-treatment of human osteoblastic cells with Simv down-regulated Ti particle-induced IL-6 gene expression at mRNA and protein levels. The effect of Simv on Ti-induced IL-6 production in osteoblastic cells could not be explained by inhibition of the internalization of metal particles. The mechanism involved in this down-regulation is based in the inhibition of the HMG-CoA/GGPP/RhoA/ROCK pathway, independently of Simv effects in the cholesterol synthesis. The cytokine-lowering property of Simv has been observed in Saos-2 cells and human primary osteoblasts (hOBs) exposed to Ti particles, and was further enhanced when hOBs were co-cultured with macrophages.

Relationship of serum osteocalcin levels with blood glucose, insulin resistance and lipid profile in central Indian men with type 2 diabetes

OBJECTIVE

To assess the relationship of serum osteocalcin levels with blood glucose, insulin resistance and lipid profile in central Indian men with type 2 diabetes.

METHODS

Anthropometric and biochemical parameters were measured in 56 newly diagnosed type 2 diabetic men and in 56 age and body mass index (BMI) matched controls. Insulin resistance was calculated by homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

After adjustment for age and BMI, osteocalcin levels were negatively correlated with fasting plasma glucose (p = 0.0004), fasting insulin (p = 0.0311), HOMA-IR (p = 0.0023), and triglycerides (p = 0.0095), and positively correlated with high density lipoprotein (HDL)-cholesterol (p = 0.0042) in type 2 diabetic patients. In multivariate logistic regression analyses that adjusted for age, BMI, waist circumference and waist-to-hip ratio, osteocalcin was inversely associated with the presence of type 2 diabetes (p < 0.0001).

CONCLUSION

Osteocalcin may play a protective role in the pathogenesis of type 2 diabetes, not only through direct involvement in glucose homeostasis, but also through improving lipid profile.

Iron excess limits HHIPL-2 gene expression and decreases osteoblastic activity in human MG-63 cells

In order to understand mechanisms involved in osteoporosis observed during iron overload diseases, we analyzed the impact of iron on a human osteoblast-like cell line. Iron exposure decreases osteoblast phenotype. HHIPL-2 is an iron-modulated gene which could contribute to these alterations. Our results suggest osteoblast impairment in iron-related osteoporosis.

INTRODUCTION

Iron overload may cause osteoporosis. An iron-related decrease in osteoblast activity has been suggested.

METHODS

We investigated the effect of iron exposure on human osteoblast cells (MG-63) by analyzing the impact of ferric ammonium citrate (FAC) and iron citrate (FeCi) on the expression of genes involved in iron metabolism or associated with osteoblast phenotype. A transcriptomic analysis was performed to identify iron-modulated genes.

RESULTS

FAC and FeCi exposure modulated cellular iron status with a decrease in TFRC mRNA level and an increase in intracellular ferritin level. FAC increased ROS level and caspase 3 activity. Ferroportin, HFE and TFR2 mRNAs were expressed in MG-63 cells under basal conditions. The level of ferroportin mRNA was increased by iron, whereas HFE mRNA level was decreased. The level of mRNA alpha 1 collagen type I chain, osteocalcin and the transcriptional factor RUNX2 were decreased by iron. Transcriptomic analysis revealed that the mRNA level of HedgeHog Interacting Protein Like-2 (HHIPL-2) gene, encoding an inhibitor of the hedgehog signaling pathway, was decreased in the presence of FAC. Specific inhibition of HHIPL-2 expression decreased osteoblast marker mRNA levels. Purmorphamine, hedgehog pathway activator, increased the mRNA level of GLI1, a target gene for the hedgehog pathway, and decreased osteoblast marker levels. GLI1 mRNA level was increased under iron exposure.

CONCLUSION

We showed that in human MG-63 cells, iron exposure impacts iron metabolism and osteoblast gene expression. HHIPL-2 gene expression modulation may contribute to these alterations. Our results support a role of osteoblast impairment in iron-related osteoporosis.

High bone density and bone health

The aim of this paper is to review the main aspects related to high bone density (HBD) as well as to discuss the physiologic mechanisms involved in bone health. There are still no well-defined criteria for identification of individuals with HBD and there are few studies on the topic. Most studies demonstrate that overweight, male gender, black ethnic background, physical activity, calcium and fluoride intake and use of medications such as statins and thiazide diuretics play a relevant and positive role on bone mineral density. Moreover, it is known that individuals with certain diseases such as obesity, diabetes, estrogen receptor-positive breast or endometrial cancer have greater bone density than healthy individuals, as well as athletes having higher bone density than non-athletes does not necessarily mean that they have healthy bones. A better understanding of risk and protective factors may help in the management of patients with bone frailty and have applicability in the treatment and in the prevention of osteoporosis, especially intervening on non-modifiable risk factors.

Geranylgeranyl pyrophosphate stimulates PPARγ expression and adipogenesis through the inhibition of osteoblast differentiation

Osteoblasts and adipocytes are derived from mesenchymal stem cells and play important roles in skeletal homeostasis. Osteoblast differentiation results in a decrease in the cellular concentration of the isoprenoid geranylgeranyl pyrophosphate (GGPP), and the statin-mediated depletion of GGPP stimulates osteoblast differentiation. Adipogenic differentiation, in contrast, results in increased expression of GGPP synthase (GGPPS), and GGPP lowering agents inhibit adipogenesis in vitro. In this study, we tested the hypothesis that GGPP inhibits osteoblast differentiation and enhances adipogenesis. We found that treatment with exogenous GGPP reduced osteoblastic gene expression and matrix mineralization in primary calvarial osteoblast cultures. GGPP treatment of primary calvarial osteoblasts and bone marrow stromal cells (BMSCs) led to increased expression of total peroxisome proliferator activated receptor (PPAR)-γ as well as the adipocyte specific splice variant PPARγ2. Inhibition of PPARγ transcriptional activity did not prevent the effects of GGPP on osteoblasts, suggesting that enhanced PPARγ expression is secondary to the inhibition of osteoblast differentiation. Enhanced PPARγ expression correlated with the increased formation of Oil Red O-positive cells in osteoblast cultures. Additionally, primary calvarial osteoblasts treated with GGPP exhibited increased expression of the adipokine adiponectin. Consistent with a role for GGPP in adipogenesis, adipogenic differentiation of BMSCs could be impaired by specific depletion of cellular GGPP. In contrast to previous reports utilizing other cell types, treatment of osteoblasts with GGPP did not increase geranylgeranylation, suggesting that GGPP itself may be acting as a signaling molecule. GGPP treatment of MC3T3-E1 pre-osteoblasts and primary calvarial osteoblasts led to enhanced insulin-induced Erk signaling which has been previously demonstrated to inhibit insulin receptor substrate (IRS)-1 activity. Additionally, GGPP treatment of MC3T3-E1 pre-osteoblasts resulted in a decrease in the insulin-induced phosphorylation of the insulin receptor. Altogether these findings demonstrate a negative role for GGPP in osteoblast differentiation, leading to increased adipogenesis. Additionally, the effects of GGPP on insulin signaling suggest a potential mechanism for inhibition of osteoblast differentiation and also implicate a role for this isoprenoid in physiological energy homeostasis.

Simvastatin promotes osteogenic differentiation of mouse embryonic stem cells via canonical Wnt/β-catenin signaling

Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, has been known to reduce cholesterol biosynthesis. However, recent studies demonstrate that simvastatin shows diverse cholesterol-independent functions including cellular differentiation. In this study, we investigated the stimulatory effect of simvastatin on the osteogenic differentiation of mouse embryonic stem cells (ESCs). The osteogenic effect of simvastatin was observed at relatively low doses (ranging from 1 nM to 200 nM). Incubation of ESCs in simvastatin-supplemented osteogenic medium significantly increased alkaline phosphatase (ALP) activity at day 7. The matrix mineralization was also augmented and demonstrated pivotal levels after 14 days incubation of simvastatin. Osteogenic differentiation of ESCs by simvastatin was determined by upregulation of the mRNA expression of runtrelated gene 2 (Runx2), osterix (OSX), and osteocalcin (OCN) as osteogenic transcription factors. Moreover, the increased protein expression of OCN, osteopontin (OPN), and collagen type I (Coll I) was assessed using Western blot analysis and immunocytochemistry. However, the blockage of canonical Wnt signaling by DKK-1 downregulated simvastatin-induced ALP activity and the mRNA expression of each osteogenic transcription factor. Furthermore, the β-catenin specific siRNA transfection decreased the protein levels of OCN, OPN, and Coll I. Collectively, these findings suggest that simvastatin enhances the differentiation of ESCs toward osteogenic lineage through activation of canonical Wnt/β-catenin signaling.

The effects of direct inhibition of geranylgeranyl pyrophosphate synthase on osteoblast differentiation

Statins, drugs commonly used to lower serum cholesterol, have been shown to stimulate osteoblast differentiation and bone formation. These effects have been attributed to the depletion of geranylgeranyl pyrophosphate (GGPP). In this study, we tested whether specific inhibition of GGPP synthase (GGPPS) with digeranyl bisphosphonate (DGBP) would similarly lead to increased osteoblast differentiation. DGBP concentration dependently decreased intracellular GGPP levels in MC3T3-E1 pre-osteoblasts and primary rat calvarial osteoblasts, leading to impaired Rap1a geranylgeranylation. In contrast to our hypothesis, 1 µM DGBP inhibited matrix mineralization in the MC3T3-E1 pre-osteoblasts. Consistent with this, DGBP inhibited the expression of alkaline phosphatase and osteocalcin in primary osteoblasts. By inhibiting GGPPS, DGBP caused an accumulation of the GGPPS substrate farnesyl pyrophosphate (FPP). This effect was observed throughout the time course of MC3T3-E1 pre-osteoblast differentiation. Interestingly, DGBP treatment led to activation of the glucocorticoid receptor in MC3T3-E1 pre-osteoblast cells, consistent with recent findings that FPP activates nuclear hormone receptors. These findings demonstrate that direct inhibition of GGPPS, and the resulting specific depletion of GGPP, does not stimulate osteoblast differentiation. This suggests that in addition to depletion of GGPP, statin-stimulated osteoblast differentiation may depend on the depletion of upstream isoprenoids, including FPP.

Effects of farnesyl pyrophosphate accumulation on calvarial osteoblast differentiation

Statins, drugs commonly used to lower serum cholesterol, have been shown to stimulate osteoblast differentiation and bone formation. Statins inhibit 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A reductase (HMGCR), the first step of the isoprenoid biosynthetic pathway, leading to the depletion of the isoprenoids farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). The effects of statins on bone have previously been attributed to the depletion of GGPP, because the addition of exogenous GGPP prevented statin-stimulated osteoblast differentiation in vitro. However, in a recent report, we demonstrated that the specific depletion of GGPP did not stimulate but, in fact, inhibited osteoblast differentiation. This led us to hypothesize that isoprenoids upstream of GGPP play a role in the regulation of osteoblast differentiation. We demonstrate here that the expression of HMGCR and FPP synthase decreased during primary calvarial osteoblast differentiation, correlating with decreased FPP and GGPP levels during differentiation. Zaragozic acid (ZGA) inhibits the isoprenoid biosynthetic pathway enzyme squalene synthase, leading to an accumulation of the squalene synthase substrate FPP. ZGA treatment of calvarial osteoblasts led to a significant increase in intracellular FPP and resulted in inhibition of osteoblast differentiation as measured by osteoblastic gene expression, alkaline phosphatase activity, and matrix mineralization. Simultaneous HMGCR inhibition prevented the accumulation of FPP and restored osteoblast differentiation. In contrast, specifically inhibiting GGPPS to lower the ZGA-induced increase in GGPP did not restore osteoblast differentiation. The specificity of HMGCR inhibition to restore osteoblast differentiation of ZGA-treated cultures through the reduction in isoprenoid accumulation was confirmed with the addition of exogenous mevalonate. Similar to ZGA treatment, exogenous FPP inhibited the mineralization of primary calvarial osteoblasts. Interestingly, the effects of FPP accumulation on osteoblasts were found to be independent of protein farnesylation. Our findings are the first to demonstrate that the accumulation of FPP impairs osteoblast differentiation and suggests that the depletion of this isoprenoid may be necessary for normal and statin-induced bone formation.

Simvastatin induces osteogenic differentiation of murine embryonic stem cells

Statins are potent inhibitors of cholesterol synthesis. Several statins are available with different molecular and pharmacokinetic properties. Simvastatin is more lipophilic than pravastatin and has a higher affinity to phospholipid membranes than atorvastatin, allowing its passive diffusion through the cell membrane. In vitro studies on bone marrow stromal cells, osteoblast-like cells, and embryonic stem cells have shown statins to have cholesterol-independent anabolic effects on bone metabolism; alas, statins were supplemented in osteogenic medium, which does not facilitate elucidation of their potential osteoinductive properties. Embryonic stem cells (ESCs), derived from the inner cell mass of the blastocyst, are unique in that they enjoy perpetual self-proliferation, are pluripotent, and are able to differentiate toward all the cellular lineages composing the body, including the osteogenic lineage. Consequently, ESCs represent a potentially potent cell source for future clinical cellular therapies of various bone diseases, even though there are several hurdles that still need to be overcome. Herein we demonstrate, for the first time to our knowledge, that simvastatin induces murine ESC (mESC) differentiation toward the osteogenic lineage in the absence of osteoinductive supplements. Specifically, we found that a simvastatin concentration in the micromolar range and higher was toxic to the cells and that an effective concentration for osteoinduction is 0.1 nM, as shown by increased alizarin red staining as well as increased osteocalcin and osetrix gene expression. These results suggest that in the future, lipophilic simvastatin may provide a novel pharmacologic agent for bone tissue engineering applications.

Statins and the joint: multiple targets for a global protection?

OBJECTIVES

Evidence exists that the pleiotropic properties of the hydroxy-methyl-glutaryl Coenzyme A reductase inhibitors (statins) are not restricted to the cardiovascular system, as they can also favorably affect the joints, with intriguing implications for the treatment of many rheumatic diseases. In the view of the increasing interest on this topic, we here review the current state of the art.

METHODS

The PubMed database was searched for articles published between 1966 and 2010 for key words referring to statins and joint diseases. All relevant English-written articles were reviewed.

RESULTS

Many pivotal studies clearly demonstrated that HMG-CoA reductase inhibitors exert a wide spectrum of beneficial effects on the 3 main compartments of the joint, ie, the synovium, the cartilage, and the subchondral bone. Such (1) anti-inflammatory, (2) immunomodulating, and (3) anabolic effects strongly support a potential role of these drugs in the treatment and/or the prevention of the most important chronic joint diseases. However, although the majority of the in vivo studies with statins on animal models of inflammatory and degenerative joint diseases showed a marked protective activity substantially confirming the in vitro experiments, data arising from clinical trials are less probative and more conflicting.

CONCLUSIONS

Statins display multiple joint-protective effects. Since oral administration of statins could result in a relatively low drug bioavailability to the joints, alternative routes of administration of the drug (transdermal, intra-articular) and/or specific delivery systems should be developed to establish the entire therapeutic potential of statins in this clinical setting.