A comparative study of Sr-incorporated mesoporous bioactive glass scaffolds for regeneration of osteopenic bone defects

Cell Instructive Behavior of Composite Scaffolds in a Co-Culture of Human Mesenchymal Stem Cells and Peripheral Blood Mononuclear Cells

The in vitro evaluation of 3D scaffolds for bone tissue engineering in mono-cultures is a common practice; however, it does not represent the native complex nature of bone tissue. Co-cultures of osteoblasts and osteoclasts, without the addition of stimulating agents for monitoring cellular cross-talk, remains a challenge. In this study, a growth factor-free co-culture of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and human peripheral blood mononuclear cells (hPBMCs) has been established and used for the evaluation of 3D-printed scaffolds for bone tissue engineering. The scaffolds were produced from PLLA/PCL/PHBV polymeric blends, with two composite materials produced through the addition of 2.5% w/v nanohydroxyapatite (nHA) or strontium-substituted nanohydroxyapatite (Sr-nHA). Cell morphology data showed that hPBMCs remained undifferentiated in co-culture, while no obvious differences were observed in the mono- and co-cultures of hBM-MSCs. A significantly increased alkaline phosphatase (ALP) activity and osteogenic gene expression was observed in co-culture on Sr-nHA-containing scaffolds. Tartrate-resistant acid phosphatase (TRAP) activity and osteoclastogenic gene expression displayed significantly suppressed levels in co-culture on Sr-nHA-containing scaffolds. Interestingly, mono-cultures of hPBMCs on Sr-nHA-containing scaffolds indicated a delay in osteoclasts formation, as evidenced from TRAP activity and gene expression, demonstrating that strontium acts as an osteoclastogenesis inhibitor. This co-culture study presents an effective 3D model to evaluate the regenerative capacity of scaffolds for bone tissue engineering, thus minimizing time-consuming and costly in vivo experiments.

Zinc- and Fluoride-Releasing Bioactive Glass as a Novel Bone Substitute

Bioglass 45S5, a silica-based glass, has pioneered a new field of biomaterials. Bioglass 45S5 promotes mineralization through calcium ion release and is widely used in the dental field, including toothpaste formulations. However, the use of Bioglass 45S5 for bone grafting is limited owing to the induction of inflammation, as well as reduced degradation and ion release. Phosphate-based glasses exhibit higher solubility and ion release than silica-based glass. Given that these glasses can be synthesized at low temperatures (approximately 1,000°C), they can easily be doped with various metal oxides to confer therapeutic properties. Herein, we fabricated zinc- and fluoride-doped phosphate-based glass (multicomponent phosphate [MP] bioactive glass) and further doped aluminum oxide into the MP glass (4% Al-MP glass) to overcome the striking solubility of phosphate-based glass. Increased amounts of zinc and fluoride ions were detected in water containing the MP glass. Doping of aluminum oxide into the MP glass suppressed the striking dissolution in water, with 4% Al-MP glass exhibiting the highest stability in water. Compared with Bioglass 45S5, 4% Al-MP glass in water had a notably reduced particle size, supporting the abundant ion release of 4% Al-MP glass. Compared with Bioglass 45S5, 4% Al-MP glass enhanced the osteogenesis of mouse bone marrow-derived mesenchymal stem cells. Mouse macrophages cultured with 4% Al-MP glass displayed enhanced induction of anti-inflammatory M2 macrophages and reduced proinflammatory M1 macrophages, indicating M2 polarization. Upon implanting 4% Al-MP glass or Bioglass 45S5 in a mouse calvarial defect, 4% Al-MP glass promoted significant bone regeneration when compared with Bioglass 45S5. Hence, we successfully fabricated zinc- and fluoride-releasing bioactive glasses with improved osteogenic and anti-inflammatory properties, which could serve as a promising biomaterial for bone regeneration.

Influence of Strontium on the Biological Behavior of Bioactive Glasses for Bone Regeneration

Bioactive glasses (BGs) can potentially be applied in biomedicine, mainly for bone repair and replacement, given their unique ability to connect to natural bone tissue and stimulate bone regeneration. Since their discovery, several glass compositions have been developed to improve the properties and clinical abilities of traditional bioactive glass. Different inorganic ions, such as strontium (Sr2+), have been incorporated in BG due to their ability to perform therapeutic functions. Sr2+ has been gaining prominence due to its ability to stimulate osteogenesis, providing an appropriate environment to improve bone regeneration, in addition to its antibacterial potential. However, as there are still points in the literature that are not well consolidated, such as the influence of ionic concentrations and the BG production technique, this review aims to collect information on the state of the art of the biological behavior of BGs containing Sr2+. It also aims to gather data on different types of BGs doped with different concentrations of Sr2+, and to highlight the manufacturing techniques used in order to analyze the influence of the incorporation of this ion for bone regeneration purposes.

Alendronate modified mPEG-PLGA nano-micelle drug delivery system loaded with astragaloside has anti-osteoporotic effect in rats

Astragaloside (AS) has an anti-osteoporotic effect, but its poor water solubility and low bioavailability limit its application. In this study, a novel nano-carrier with bone targeting was prepared by modifying mPEG-PLGA with alendronate (AL) before incorporation into astragaloside nano-micelles (AS-AL-mPEG-PLGA) to enhance the oral bioavailability, bone targeting and anti-osteoporosis effect of AS. The release behavior of AS-AL-mPEG-PLGA in vitro was investigated via dialysis. The pharmacokinetics of AS-AL-mPEG-PLGA was studied in Sprague-Dawley (SD) rats. The cytotoxicity of AS-AL-mPEG-PLGA in vitro (via MTT method), coupled with bone targeting ability in vitro and in vivo were evaluated. The therapeutic effects of free AS and AS-AL-mPEG-PLGA (ELISA, micro-CT, H&E staining) were compared in osteoporotic rats. AS-AL-mPEG-PLGA with smaller particle size (45.3 ± 3.8 nm) and high absolute zeta potential (−23.02 ± 0.51 mV) were successfully prepared, wherein it demonstrated higher entrapment efficiency (96.16 ± 0.18%), a significant sustained-release effect for 96 h and acceptable safety within 10–200 μg/mL. AS-AL-mPEG-PLGA could enhance the hydroxyapatite affinity and bone tissue concentration of AS. The relative bioavailability of AS-AL-mPEG-PLGA was 233.90% compared with free AS. In addition, the effect of AS in reducing serum levels of bone metabolism-related indicators, restoring the bone microarchitecture and improving bone injury could be enhanced by AS-AL-mPEG-PLGA. AS-AL-mPEG-PLGA with small particle size, good stability, remarkable sustained-release effect, safety and bone targeting was successfully constructed in this experiment to potentially improve the oral bioavailability and anti-osteoporosis effect of AS. Thus, AS-AL-mPEG-PLGA may be a promising strategy to prevent and treat osteoporosis.

Applications of Calcium-Based Nanomaterials in Osteoporosis Treatment

With rapidly aging populations worldwide, osteoporosis has become a serious global public health problem. Caused by disordered systemic bone remodeling, osteoporosis manifests as progressive loss of bone mass and microarchitectural deterioration of bone tissue, increasing the risk of fractures and eventually leading to osteoporotic fragility fractures. As fracture risk increases, antiosteoporosis treatments transition from nonpharmacological management to pharmacological intervention, and finally to the treatment of fragility fractures. Calcium-based nanomaterials (CBNMs) have unique advantages in osteoporosis treatment because of several characteristics including similarity to natural bone, excellent biocompatibility, easy preparation and functionalization, low pH-responsive disaggregation, and inherent pro-osteogenic properties. By combining additional ingredients, CBNMs can play multiple roles to construct antiosteoporotic biomaterials with different forms. This review covers recent advances in CBNMs for osteoporosis treatment. For ease of understanding, CBNMs for antiosteoporosis treatment can be classified as locally applied CBNMs, such as implant coatings and filling materials for osteoporotic bone regeneration, and systemically administered CBNMs for antiosteoporosis treatment. Locally applied CBNMs for osteoporotic bone regeneration develop faster than the systemically administered CBNMs, an important consideration given the serious outcomes of fragility fractures. Nevertheless, many innovations in construction strategies and preparation methods have been applied to build systemically administered CBNMs. Furthermore, with increasing interest in delaying osteoporosis progression and avoiding fragility fracture occurrence, research into systemic administration of CBNMs for antiosteoporosis treatment will have more development prospects. Deep understanding of the CBNM preparation process and optimizing CBNM properties will allow for increased application of CBNMs in osteoporosis treatments in the future.

Nanoceria provides antioxidant and osteogenic properties to mesoporous silica nanoparticles for osteoporosis treatment

Osteoporosis, a chronic metabolic bone disease, is the most common cause of fractures. Drugs for treating osteoporosis generally inhibit osteoclast (OC) activity, but are rarely aimed at encouraging new bone growth and often cause severe systemic side effects. Reactive oxygen species (ROS) are one of the key triggers of osteoporosis, by inducing osteoblast (OB) and osteocyte apoptosis and promoting osteoclastogenesis. Here we tested the capability of the ROS-scavenger nanoceria encapsulated within mesoporous silica nanoparticles (Ce@MSNs) to treat osteoporosis using a pre-osteoblast MC3T3-E1 cell monoculture in stressed and normal conditions. Ce@MSNs (diameter of 80 ± 10 nm) were synthesised following a scalable two-step process involving sol-gel and wet impregnation methods. The Ce@MSNs at concentration of 100 μg mL^-1 induced a significant reduction in oxidative stress produced by t-butyl hydroperoxide and did not alter cell viability significantly. Confocal microscopy showed that MSNs and Ce@MsNs were internalised into the cytoplasm of the pre-osteoblasts after 24 h but were not in the nucleus, avoiding any DNA and RNA modifications. Ce@MSNs provoked mineralisation of the pre-osteoablasts without osteogenic supplements, which did not occur when the cells were exposed to MSN without nanoceria. In a co-culture system of MC3T3-E1 and RAW264.7 macrophages, the Ce@MSNs exhibited antioxidant capability and stimulated cell proliferation and osteogenic responses without adding osteogenic supplements to the culture. The work brings forward an effective platform based for facile synthesis of Ce@MSNs to interact with both OBs and OCs for treatment of osteoporosis.

Effects of ultrasound, radial extracorporeal shock waves, and electrical stimulation on rat bone defect healing

Fractures associated with osteoporosis are a major public health concern. Current treatments for fractures are limited to surgery or fixation, leading to long-term bedrest, which is linked to increased mortality. Alternatively, utilization of physical agents has been suggested as a promising therapeutic approach for fractures. Here, we examined the effects of ultrasound, radial extracorporeal shock waves, and electrical stimulation on normal or osteoporotic fracture healing. Femoral bone defects were created in normal or ovariectomized rats. Rats were divided into four groups: untreated, and treated with ultrasound, shock waves, or electrical stimulation after surgery. Samples were collected at 2 or 4 weeks after surgery, and the healing process was evaluated with micro-CT, histological, and immunohistochemical analyses. Ultrasound at intensities of 0.5 and 1.0 W/cm² , but not 0.05 W/cm² , accelerated new bone formation. Shock wave exposure also increased newly formed bone, but formed abnormal periosteal callus around the defect site. Conversely, electrical stimulation did not affect the healing process. Ultrasound exposure increased osteoblast activity and cell proliferation and decreased sclerostin-positive osteocytes. We demonstrated that higher-intensity ultrasound and radial extracorporeal shock waves accelerate fracture healing, but shock wave treatment may increase the risk of periosteal callus formation.

Efficacy of strontium supplementation on implant osseointegration under osteoporotic conditions: A systematic review

STATEMENT OF PROBLEM

Strontium has been validated for potent bone-seeking and antiosteoporotic properties and elicits a potentially beneficial impact on implant osseointegration in patients with osteoporosis. However, the efficacy of strontium supplementation on improving new bone formation and implant osseointegration in the presence of osteoporotic bone is still unclear.

PURPOSE

The purpose of this systematic review was to comprehensively assess the efficacy of strontium supplementation, encompassing oral intake and local delivery of strontium, on implant osseointegration in patients with osteoporosis.

MATERIAL AND METHODS

Searches on electronic databases (MEDLINE or PubMed, Web of Science, EBSCO, Embase, and Clinicaltrials.gov) and manual searches were conducted to identify relevant preclinical animal trials up to June 2020. The primary outcomes were the percentage of bone-implant contact and bone area; the secondary outcomes were quantitative parameters of biomechanical tests and microcomputed tomography (μCT).

RESULTS

Fourteen preclinical trials (1 rabbit, 1 sheep, and 12 rat), with a total of 404 ovariectomized animals and 798 implants, were eligible for analysis. The results revealed a significant 17.1% increase in bone-implant contact and 13.5% increase in bone area, favoring strontium supplementation despite considerable heterogeneity. Subgroup analyses of both bone-implant contact and bone area exhibited similar outcomes with low to moderate heterogeneity. Results of biomechanical and μCT tests showed that strontium-enriched implantation tended to optimize the mechanical strength and microarchitecture of newly formed bone despite moderate to generally high heterogeneity.

CONCLUSIONS

Based on the available preclinical evidence, strontium supplementation, including local and systemic delivery, showed promising results for enhancing implant osseointegration in the presence of osteoporosis during 4 to 12 weeks of healing. Future well-designed standardized studies are necessary to validate the efficacy and safety of strontium supplementation and to establish a standard methodology for incorporating Sr into implant surfaces in a clinical setting.

Strontium ranelate incorporated 3D porous sulfonated PEEK simulating MC3T3-E1 cell differentiation

Polyetheretherketone (PEEK) has been used as an implant material because it has similar mechanical properties to natural bone. However, inferior osseointegration and bioinertness hamper the clinical application of PEEK. In this study, the surfaces of sulfonated three-dimensional (3D) PEEK porous structures were loaded with different concentrations of strontium ranelate, a compound commonly used in the treatment or prevention of osteoporosis by promoting bone formation and inhibiting bone resorption. Field-emission scanning electron microscopy was used to characterize the topography of the structures, elemental carbon, oxygen and strontium contents were measured by X-ray photoelectron spectroscopy, and surface zeta potentials and water-contact angle were also measured. The results indicated that strontium ranelate was successfully loaded onto the 3D porous structures. In vitro cellular results showed that strontium ranelate-treated sulfonated PEEK (SP-SR) strengthened the adhesion of MC3T3-E1 cells. The activity of alkaline phosphatase, collagen secretion and extracellular matrix mineralization deposition of MC3T3-E1 cells were also improved on the surface of SP-SR. These results indicate that SP-SR could serve a new implant candidate for surgical treatment.

Synthesis and Characterization of Mesoporous Mg- and Sr-Doped Nanoparticles for Moxifloxacin Drug Delivery in Promising Tissue Engineering Applications

Mesoporous silica-based nanoparticles (MSNs) are considered promising drug carriers because of their ordered pore structure, which permits high drug loading and release capacity. The dissolution of Si and Ca from MSNs can trigger osteogenic differentiation of stem cells towards extracellular matrix calcification, while Mg and Sr constitute key elements of bone biology and metabolism. The aim of this study was the synthesis and characterization of sol-gel-derived MSNs co-doped with Ca, Mg and Sr. Their physico-chemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), Brunauer Emmett Teller and Brunauer Joyner Halenda (BET/BJH), dynamic light scattering (DLS) and ζ-potential measurements. Moxifloxacin loading and release profiles were assessed with high performance liquid chromatography (HPLC) cell viability on human periodontal ligament fibroblasts and their hemolytic activity in contact with human red blood cells (RBCs) at various concentrations were also investigated. Doped MSNs generally retained their textural characteristics, while different compositions affected particle size, hemolytic activity and moxifloxacin loading/release profiles. All co-doped MSNs revealed the formation of hydroxycarbonate apatite on their surface after immersion in simulated body fluid (SBF) and promoted mitochondrial activity and cell proliferation.

In vitro effects of the co-release of icariin and strontium from bioactive glass submicron spheres on the reduced osteogenic potential of rat osteoporotic bone marrow mesenchymal stem cells

Osteoporosis is a metabolic disease that affects bone tissue and is highly associated with bone fractures. Typical osteoporosis fracture treatments, such as bisphosphonates and hormone replacement, present important challenges because of their low bioavailability on the site of action. Options to overcome this issue are systems for the local release of therapeutic agents such as bioactive glasses containing therapeutic molecules and ions. These agents are released during the dissolution process, combining the drugs and ion therapeutic effects for osteoporosis treatment. Among the therapeutic agents that can be applied for bone repair are strontium (Sr) ion and phytopharmaceutical icariin, which have shown potential to promote healthy bone marrow stem cells osteogenic differentiation, increase bone formation and prevent bone loss. Submicron Sr-containing bioactive glass mesoporous spheres with sustained ion release capacity were obtained. Icariin was successfully incorporated into the particles, and the glass composition influenced the icariin incorporation efficiency and release rates. In this work, for the first time, Sr and icariin were incorporated into bioactive glass submicron mesoporous spheres and the in vitro effects of the therapeutic agents release were evaluated on the reduced osteogenic potential of rat osteoporotic bone marrow mesenchymal stem cells, and results showed an improvement on the reduced differentiation potential.

Enhanced osteogenesis and therapy of osteoporosis using simvastatin loaded hybrid system

Postmenopausal osteoporosis is a common chronic dynamic bone disorder, caused by estrogen deficiency. To address this issue, we constructed a controlled drug-release system composed of poly (N-isopropylacrylamide) brush modified mesoporous hydroxyapatite (MHA-SIM-P) loaded with simvastatin (SIM) using an ovariectomised (OVX) rat model. Quantitative alkaline phosphatase activity assay, alizarin red staining and RT-PCR were tested to evaluate the osteogenic ability in vitro. The results showed that the MHA-SIM-P nanoparticles significantly improved the osteogenic differentiation of OVX bone marrow stromal cells (BMSCs) in vitro. In osteoporotic animal model, the therapeutic efficiency for bone defect was evaluated by μCT analysis, tartrate-resistant acid phosphatase, haematoxylin and eosin staining, which showed improved bone formation and less osteoclastic response in OVX rats after surgery for 3 and 6 weeks. This polymer brush modified MHA system provided a sustained release system of hydrophobic SIM to inhibit osteoporosis together with MHA nanoparticle promoting the osteogenesis. Thus, this novel strategy exhibited great potential for promoting osteogenic ability and treating local osteoporotic defects.

Nonunion - consensus from the 4th annual meeting of the Danish Orthopaedic Trauma Society

Nonunions are a relevant economic burden affecting about 1.9% of all fractures. Rather than specifying a certain time frame, a nonunion is better defined as a fracture that will not heal without further intervention.

Successful fracture healing depends on local biology, biomechanics and a variety of systemic factors. All components can principally be decisive and determine the classification of atrophic, oligotrophic or hypertrophic nonunions. Treatment prioritizes mechanics before biology.

The degree of motion between fracture parts is the key for healing and is described by strain theory. If the change of length at a given load is > 10%, fibrous tissue and not bone is formed. Therefore, simple fractures require absolute and complex fractures relative stability.

The main characteristics of a nonunion are pain while weight bearing, and persistent fracture lines on X-ray.

Treatment concepts such as ‘mechanobiology’ or the ‘diamond concept’ determine the applied osteosynthesis considering soft tissue, local biology and stability. Fine wire circular external fixation is considered the only form of true biologic fixation due to its ability to eliminate parasitic motions while maintaining load-dependent axial stiffness. Nailing provides intramedullary stability and biology via reaming. Plates are successful when complex fractures turn into simple nonunions demanding absolute stability. Despite available alternatives, autograft is the gold standard for providing osteoinductive and osteoconductive stimuli.

The infected nonunion remains a challenge. Bacteria, especially staphylococcus species, have developed mechanisms to survive such as biofilm formation, inactive forms and internalization. Therefore, radical debridement and specific antibiotics are necessary prior to reconstruction.

Cite this article: EFORT Open Rev 2020;5:46-57. DOI: 10.1302/2058-5241.5.190037

Chemoreactive Nanotherapeutics by Metal Peroxide Based Nanomedicine

The advances of nanobiotechnology and nanomedicine enable the triggering of in situ chemical reactions in disease microenvironment for achieving disease-specific nanotherapeutics with both intriguing therapeutic efficacy and mitigated side effects. Metal peroxide based nanoparticles, as one of the important but generally ignored categories of metal-involved nanosystems, can function as the solid precursors to produce oxygen (O2) and hydrogen peroxide (H2O2) through simple chemical reactions, both of which are the important chemical species for enhancing the therapeutic outcome of versatile modalities, accompanied with the unique bioactivity of metal ion based components. This progress report summarizes and discusses the most representative paradigms of metal peroxides in chemoreactive nanomedicine, including copper peroxide (CuO2), calcium peroxide (CaO2), magnesium peroxide (MgO2), zinc peroxide (ZnO2), barium peroxide (BaO2), and titanium peroxide (TiOx) nanosystems. Their reactions and corresponding products have been broadly explored in versatile disease treatments, including catalytic nanotherapeutics, photodynamic therapy, radiation therapy, antibacterial infection, tissue regeneration, and some synergistically therapeutic applications. This progress report particularly focuses on the underlying reaction mechanisms on enhancing the therapeutic efficacy of these modalities, accompanied with the discussion on their biological effects and biosafety. The existing gap between fundamental research and clinical translation of these metal peroxide based nanotherapeutic technologies is finally discussed in depth.

Multiple and Promising Applications of Strontium (Sr)-Containing Bioactive Glasses in Bone Tissue Engineering

Improving and accelerating bone repair still are partially unmet needs in bone regenerative therapies. In this regard, strontium (Sr)-containing bioactive glasses (BGs) are highly-promising materials to tackle this challenge. The positive impacts of Sr on the osteogenesis makes it routinely used in the form of strontium ranelate (SR) in the clinical setting, especially for patients suffering from osteoporosis. Therefore, a large number of silicate-, borate-, and phosphate-based BGs doped with Sr and produced in different shapes have been developed and characterized, in order to be used in the most advanced therapeutic strategies designed for the management of bone defects and injuries. Although the influence of Sr incorporation in the glass is debated regarding the obtained physicochemical and mechanical properties, the biological improvements have been found to be substantial both in vitro and in vivo. In the present study, we provide a comprehensive overview of Sr-containing glasses along with the current state of their clinical use. For this purpose, different types of Sr-doped BG systems are described, including composites, coatings and porous scaffolds, and their applications are discussed in the light of existing experimental data along with the significant challenges ahead.

Biomaterial based treatment of osteoclastic/osteoblastic cell imbalance - Gelatin-modified calcium/strontium phosphates

Osteoporotic bone represents - particularly in case of fractures - difficult conditions for its regeneration. In the present study, the focus was put on a degradable bone substitute material of gelatin-modified calcium and strontium phosphates facing the special demands of osteoporotic bone. The release of strontium ions from the material ought to stimulate osteoblastogenesis either direct by ion release or indirect after material resorption by increased presence and activity of osteoclasts, which subsequently stimulate osteoblasts. A new porous material was produced from calcium phosphate, strontium phosphate and a mixed phase of calcium/strontium phosphate precipitated in presence of gelatin. Initially, ion release was analyzed in standard‑calcium containing (2.0 mM) and low-calcium (0.4 mM) minimum essential medium. The cultivation of human peripheral blood mononuclear cells next to the material led to formation of osteoclast-like cells, able to migrate, fuse, and differentiate. Especially, the mixed gelatin-modified calcium/strontium phosphate allowed osteoclastogenesis as proven morphologically and by real-time quantitative polymerase chain reaction (RT-qPCR). It was precisely this material that led to the best osteoblastic reaction of human bone marrow stromal cells cultured on the material. The investigations of the bone substitute material indicate active involvement in the balance of cells of the bone morphogenetic unit.

Polyhydroxyalkanoate (PHA): applications in drug delivery and tissue engineering

INTRODUCTION

The applications of naturally obtained polymers are tremendously increased due to them being biocompatible, biodegradable, environmentally friendly and renewable in nature. Among them, polyhydroxyalkanoates are widely studied and they can be utilized in many areas of human life research such as drug delivery, tissue engineering, and other medical applications.

AREAS COVERED

This review provides an overview of the polyhydroxyalkanoates biosynthesis and their possible applications in drug delivery in the range of micro- and nano-size. Moreover, the possible applications in tissue engineering are covered considering macro- and microporous scaffolds and extracellular matrix analogs.

EXPERT COMMENTARY

The majority of synthetic plastics are non-biodegradable so, in the last years, a renewed interest is growing to develop alternative processes to produce biologically derived polymers. Among them, PHAs present good properties such as high immunotolerance, low toxicity, biodegradability, so, they are promisingly using as biomaterials in biomedical applications.

HnRNPL inhibits the osteogenic differentiation of PDLCs stimulated by SrCl2 through repressing Setd2

Osteoporosis has been shown to intensify bone loss caused by periodontitis and both share common risk factors. One strategy utilized to manage the disease has been via the release of Sr ions by Strontium Ranelate having a direct effect on preventing osteoclast activation and promoting osteoblast differentiation. Previously we have developed and characterized porous Sr-mesoporous bioactive glass (Sr-MBG) scaffolds and demonstrated their ability to promote periodontal regeneration when compared to MBG alone. Our group further discovered a splicing factor, heterogeneous nuclear ribonucleoprotein L (hnRNPL), was drastically down-regulated in periodontal ligament stem cells (PDLCs) stimulated by Sr through the activation of AKT pathway. Furthermore, hnRNPL restrained the osteogenic differentiation of PDLCs through down-regulating H3K36me3-specific methyltransferase Setd2. The goal of the present study was to investigate the mechanism of periodontal regeneration stimulated by Sr It was first found that the epigenetic mechanism of splicing factor hnRNPL participated in the osteogenesis processing of PDLCs stimulated by SrCl2 . Meanwhile, the different role of hnRNPL and SET domain containing 2 (Setd2) may provide some implication of the treatment of periodontitis patients simultaneously suffering from osteoporosis.

Strontium-releasing fluorapatite glass-ceramics: Crystallization behavior, microstructure, and solubility

The purpose of this work was to investigate the effect of strontium partial replacement for calcium on the crystallization behavior, microstructure and solubility of fluorapatite glass-ceramics. Four glass compositions were prepared with increasing amounts of strontium partially replacing calcium. The crystallization behavior was analyzed by differential scanning calorimetry and X-ray diffraction (XRD). The microstructure was investigated by scanning electron microscopy. The chemical solubility was quantified according to ISO standard 10993-14. The amount of strontium released in solution after incubation in TRIS-HCl or citric acid buffer was measured by atomic absorption spectroscopy. XRD analyses revealed that partially substituted strontium-fluorapatite and strontium-åkermanite crystallized after strontium additions. The lattice cell volume of both phases increased linearly with the amount of strontium in the composition. Strontium additions led to a reduction in crystal size and an increase in crystal number density. The chemical solubility and amount of strontium released in solution increased linearly with the amount of strontium present in the composition in both TRIS-HCl and citric acid buffers. Total amounts of strontium released reached a maximum of 547 ± 80 ppm in TRIS-HCl and 1252 ± 290 ppm in citric acid buffer for the glass composition with the highest amount of strontium. For all strontium-containing compositions, the amount released in TRIS-HCl continued to increase between 70 and 120 h, indicating sustained release rather than burst release. © 2017 Wiley Periodicals, Inc. J Biomater Res Part B: 106B: 1421-1430, 2018.

Superior bone-inducing potential of rhBMP9 compared to rhBMP2

Recombinant human bone morphogenic protein (rhBMP) 9 has recently been reported to have more osteopromotive potential in vitro when compared to rhBMP2. The aim of the present study was to investigate the bone-inducing potential of rhBMP2 and rhBMP9. We compared rhBMP2, rhBMP7, and rhBMP9 at five different concentrations and showed convincingly that rhBMP9 possesses much greater potential for osteoblast differentiation even at 20 times lower concentrations in vitro. We further show that Noggin, an inhibitor for rhBMP2-induced osteogenesis, did not alter rhBMP9-induced osteogenesis. Thereafter, we show for the first time that rhBMP9 loaded onto atelo-collagen membranes is osteoinductive and has greater potential to form ectopic bone formation when compared to rhBMP2 even at four times lower doses. Similarly new bone formation of rhBMP2 and 9 when loaded on deproteinized bovine bone mineral (DBBM) was investigated in a rabbit calvarial defect. At 8 weeks, both rhBMP2 and rhBMP9 induced significantly higher new bone formation when compared to DBBM alone samples. Interestingly, once again four times lower dose of rhBMP9 group induced comparable or even greater levels of new bone height and new bone area when compared to the rhBMP2 group. The present study revealed that (1) rhBMP9 is capable of inducing ectopic new bone formation in vivo and (2) up to four times lower doses of rhBMP9 may be utilized to regenerate same-size bone defects when compared to rhBMP2. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1561-1574, 2018.

[Research and application progress of bioactive glass in bone repair]

Objective

To review the research and application progress of bioactive glass in bone repair.

Methods

The recently published literature concerning bioactive glass in bone repair was reviewed and summarized.

Results

Bioactive glass can classified different types, such as bioactive glass particulate, bioactive glass scaffold, bioactive glass coating, injectable bioactive glass cement, and bioactive glass delivery system. Bioactive glass has been well studied in the field of bone repair due to its excellent biological properties. Also, the remarkable progress has been made in various aspects.

Conclusion

Bioactive glass is a reliable material of bone repair and will play an even more important role in the future.

The Effect of Strontium Ranelate Gel on Bone Formation in Calvarial Critical Size Defects

AIM:

The current study was designed to investigate the effectiveness of locally applied Strontium ranelate to induce bone formation.

MATERIALS AND METHODS:

Forty-eight female rats were divided into six groups (eight rats in each group): The three test groups included Strontium (SR) 2.5 mg, 5 mg and 10 mg that was dissolved in methylcellulose gel. The control groups included methylcellulose, simvastatin 5 mg and a negative control where the defect was left to heal without any intervention. At 44 days the groups were sacrificed, and the bone defects were assessed histomorphometically to assess bone formation. The data was statistically analysed.

RESULTS:

There was a statistically significant difference in the amount of new bone formation between all groups, where the 2.5 mg SR group showed the highest median bone percentage, is 41.95 %, followed by the 5, and 10 mg SR demonstrating a median bone are a percentage of 39.89%, and 30.19% respectively. Simvastatin showed a median bone percentage of 36.07 %, while the methylcellulose and the negative control groups demonstrated the lowest median area percentage of 23.12 and 20.70 % respectively.

CONCLUSIONS:

The study showed that the local application of an SR could up-regulate the bone formation and may prove to be a cost-effective method of bone regeneration.

Effect of titanium implants with strontium incorporation on bone apposition in animal models: A systematic review and meta-analysis

This systematic review aims to assess the efficacy of titanium (Ti) implant surfaces with or without strontium (Sr) incorporation on osseointegration in animal experimental studies. An electronic search was conducted using databases of PubMed and EMBASE up to November 2016 to identify studies focusing on osseointegration of strontium-modified titanium implants following PRISMA criteria. The primary outcome was the percentage of bone-to-implant contact (BIC) around the implants with or without strontium-modified surface. Of the 1320 studies, 17 studies fulfilling the inclusion criteria were finally included. A random effect meta-analysis was conducted based on BIC in 17 studies, and the results demonstrated considerable heterogeneity (I² = 79%). A sensitivity analysis found that three studies using the same surface modification method were the major source of the heterogeneity. Therefore, exploratory subgroup analysis was performed. Subgroup one including 14 studies showed a standard mean differences (SMD) of 1.42 (95% CI, 1.13-1.71) with no heterogeneity (I² = 0.0%), while subgroup two including the other three studies showed a SMD of 9.49.95% CI, 7.51-11.47) with low heterogeneity (I² = 0.1%). Sr-modified implants in both subgroups showed significantly higher BIC than unmodified implants (P < 0.01). The results showed a statistically significant effect of Sr-modified titanium implant surfaces on osseointegration and bone apposition in animal models.

Regenerating bone with bioactive glass scaffolds: A review of in vivo studies in bone defect models

Large bone defects resulting from fractures and disease are a medical concern, being often unable to heal spontaneously by the body's repair mechanisms. Bone tissue engineering (BTE) is a promising approach for treating bone defects through providing a template to guide osseous regeneration. 3D scaffolds with microstructure mimicking host bone are necessary in common BTE strategies. Bioactive glasses (BGs) attract researchers' attention as BTE scaffolds as they are osteoconductive and osteoinductive in certain formulations. In vivo animal models allow understanding and evaluation of materials' performance in the complex physiological environment, being an inevitable step before clinical trials. The aim of this paper is to review for the first time published research investigating the in vivo osseous regenerative capacity of 3D BG scaffolds in bone defect animal models, to better understand and evaluate the progress and future outlook of the use of such scaffolds in BTE. The literature analysis reveals that the regenerative capacity of BG scaffolds depends on several factors; including BG composition, fabrication method, scaffold microstructure and pore characteristics, in addition to scaffold pretreatment and whether or not the scaffolds are loaded with growth factors. In addition, animal species selected, defect size and implantation time affect the scaffold in vivo behavior and outcomes. The review of the literature also makes clear the difficulty encountered to compare different types of bioactive glass scaffolds in their bone forming ability. Even considering such limitations of the current state-of-the-art, results generated from animal bone defect models provide an essential source of information to guide the design of BG scaffolds in future.

STATEMENT OF SIGNIFICANCE

Bioactive glasses are at the centre of increasing research efforts in bone tissue engineering as the number of research groups around the world carrying out research on this type of biomaterials continues to increase. However, there are no previous reviews in literature which specifically cover investigations of the performance of bioactive glass scaffolds in bone defect animal models. This is the topic of the present review, in which we have analysed comprehensively all available literature in the field. The review thus fills a gap in the biomaterials literature providing a broad platform of information for researchers interested in bioactive glasses in general and specifically in the outcomes of in vivo models. Bioactive glass scaffolds of different compositions tested in relevant bone defect models are covered.

Injectable hybrid system for strontium local delivery promotes bone regeneration in a rat critical-sized defect model

Strontium (Sr) has been described as having beneficial influence in bone strength and architecture. However, negative systemic effects have been reported on oral administration of Sr ranelate, leading to strict restrictions in clinical application. We hypothesized that local delivery of Sr improves osteogenesis without eliciting detrimental side effects. Therefore, the in vivo response to an injectable Sr-hybrid system composed of RGD-alginate hydrogel cross-linked in situ with Sr and reinforced with Sr-doped hydroxyapatite microspheres, was investigated. The system was injected in a critical-sized bone defect model and compared to a similar Sr-free material. Micro-CT results show a trend towards higher new bone formed in Sr-hybrid group and major histological differences were observed between groups. Higher cell invasion was detected at the center of the defect of Sr-hybrid group after 15 days with earlier bone formation. Higher material degradation with increase of collagen fibers and bone formation in the center of the defect after 60 days was observed as opposed to bone formation restricted to the periphery of the defect in the control. These histological findings support the evidence of an improved response with the Sr enriched material. Importantly, no alterations were observed in the Sr levels in systemic organs or serum.

In vivo and clinical application of strontium-enriched biomaterials for bone regeneration: A systematic review

OBJECTIVES

This systematic review aimed to assess the in vivo and clinical effect of strontium (Sr)-enriched biomaterials in bone formation and/or remodelling.

METHODS

A systematic search was performed in Pubmed, followed by a two-step selection process. We included in vivo original studies on Sr-containing biomaterials used for bone support or regeneration, comparing at least two groups that only differ in Sr addition in the experimental group.

RESULTS

A total of 572 references were retrieved and 27 were included. Animal models were used in 26 articles, and one article described a human study. Osteoporotic models were included in 11 papers. All articles showed similar or increased effect of Sr in bone formation and/or regeneration, in both healthy and osteoporotic models. No study found a decreased effect. Adverse effects were assessed in 17 articles, 13 on local and four on systemic adverse effects. From these, only one reported a systemic impact from Sr addition. Data on gene and/or protein expression were available from seven studies.

CONCLUSIONS

This review showed the safety and effectiveness of Sr-enriched biomaterials for stimulating bone formation and remodelling in animal models. The effect seems to increase over time and is impacted by the concentration used. However, included studies present a wide range of study methods. Future work should focus on consistent models and guidelines when developing a future clinical application of this element.Cite this article: N. Neves, D. Linhares, G. Costa, C. C. Ribeiro, M. A. Barbosa. In vivo and clinical application of strontium-enriched biomaterials for bone regeneration: A systematic review. Bone Joint Res 2017;6:366-375. DOI: 10.1302/2046-3758.66.BJR-2016-0311.R1.

Setd2 is associated with strontium-induced bone regeneration

Strontium Ranelate has been utilized as a preventative treatment option for osteoporosis with the release of Sr ions having a direct effect on preventing osteoclast activation and promoting osteoblast differentiation. Previously our group has prepared and characterized a porous Sr-mesoporous bioactive glass (Sr-MBG) scaffold demonstrating its ability to enhance new bone formation when compared to MBG alone. The goal of the present study was to elucidate the bone-inducing properties of Sr by utilizing RNA-seq on in vivo tissue samples to investigate potential target genes responsible for Sr-induced new bone formation. The results demonstrated an increased expression and affiliation of Setd2 in the Sr-MBG group when compared to MBG group alone. Immunofluorescent staining further demonstrated a localization of Setd2 and H3K36me3 in Runx2-positive cells in defects treated with Sr-MBG scaffolds. It was detected that specifically MAPK pathway was activated in MG63 stimulated by Sr. To verify the role of Setd2 in bone formation in the presence of SrCl₂, Setd2 was knocked-down and overexpressed in MG63 with/without SrCl₂ stimulation. The result showed that Setd2 plays a positive role in osteoblast differentiation which was enhanced by SrCl₂. Furthermore, it was found that Setd2 regulated the activation of ERK, which set up a positive feedback in the osteoblast differentiation process. Based on these findings, it was shown that Setd2 has an active role in osteoblast differentiation. As a histone methylase, Setd2 may also turn to be an epigenetic target for new treatment options of osteoporosis.

STATEMENT OF SIGNIFICANCE

Our research group recently demonstrated that the combination of MBG scaffolds with Sr, efficiently promoted bone regeneration in rat femoral defects even in severely compromised osteoporotic animals, however, the epigenetic mechanism by which Sr ions function to promote bone generation remains unclear. This study showed an increased expression and affiliation of Setd2 and H3K36me3. In vitro, the increased expression of Setd2 promoted osteoblastic differentiation of MG63 stimulated by SrCl2 in MAPK-dependent way, which activated ERK in turn leading to a positive feedback. Based on these findings, it was shown that Setd2 has an active role in osteoblast differentiation and may also turn to be an epigenetic target for new treatment options of osteoporosis and the development of novel bone regeneration scaffold.

Strontium Ranelate Effect on the Repair of Bone Defects and Molecular Components of the Cortical Bone of Rats

This study was conducted to evaluate the effects of treatment with strontium ranelate (SR) on the repair of bone defects and molecular components of bones in femurs. Adult female rats (n=27) were subjected to ovariectomy (OVX) or Sham surgery. Thirty days after surgery, a defect was made in the femur and the animals were then divided into three groups: OVX, SHAM and OVX+SR. Euthanasia was performed four weeks after the bone defect surgery. Repair in bone defect was assessed by computed microtomography (μCT) and chemical composition of cortical bone was analyzed by Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray spectroscopy (EDS). The trabecular thickness (Tb.Th) of the newly formed bone in the OVX+SR group was significantly higher than that for the OVX group. The collagen maturity in the OVX+SR group was smaller than in the other two groups. In this group, a significant increase in the amount of strontium (Sr) and a decrease in the amount of calcium (Ca) embedded to bone tissue were also observed. Systemic treatment with SR improved microarchitecture of the newly formed bone inside the defect, but decreased cross-linking of mature collagen in cortical bone.

Nanogel-based scaffolds fabricated for bone regeneration with mesoporous bioactive glass and strontium: In vitro and in vivo characterization

The delivery of novel bioactive scaffolds for the repair of bone defects remains a prominent challenge worldwide. Currently osteoporosis, a disease caused by low bone mineral density affects over 200 million people worldwide with up to half of this population experiencing at least one fracture within their lifetime. Recently temperature-sensitive p(N-isopropylacrylamide-co-butyl methylacrylate) nanogel (PIB nanogel) scaffolds have emerged as biomaterial candidate for regenerative therapies. It has the advantage of being injected from syringes as a soluble gel form (capable of delivering growth and/or living progenitor cells) yet hardens once it reaches body temperatures. Although this material demonstrates optimal clinical delivery of scaffolds, its main drawback is its low osteoconductivity and bioactivity. Recently we have demonstrated that mesoporous bioactive glass (MBG) loaded with strontium was able to regenerate osteoporotic defects in vivo and enhance osteoblast differentiation in vitro. The aim of this study was to combine the advantages of these two therapies and prepare PIB-nanogel scaffolds containing Sr-MBG and investigate their ability to regenerate femur defects created in ovarectamized rats. The results demonstrate that groups containing Sr-MBG within the nanogel formulation had significantly higher new bone formation when compared with other modalities. We further demonstrate that although nanogel demonstrated poor osteogenic ability, the addition of osteoblasts worked synergistically with Sr-MBG particles to enhance the regeneration of the created femur defects in osteoporotic animals. In conclusion, PIB nanogel scaffolds are a viable treatment modality for bone tissue engineering and may serve as a carrier-scaffold for osteogenic cells and/or bioactive scaffolds such as Sr-MBG. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1175-1183, 2017.

Bone scaffolds loaded with siRNA-Semaphorin4d for the treatment of osteoporosis related bone defects

Osteoporosis is a prominent disorder affecting over 200 million people worldwide. Recently, semaphorins have been implicated in the cell-cell communication between osteoclasts and osteoblasts and have been associated with the progression of osteoporosis. Previously, we demonstrated that knockdown of semaphorin4d (Sema4d) using siRNA delivered with a bone-targeting system prevented bone loss in an osteoporotic animal model. Here, we used this bone-specific technology containing siRNA-Sema4d and fabricated a PLLA scaffold capable of enhancing bone repair following fracture. We investigated the ability of the implant to release siRNA-Sema4d into the surrounding tissues over time and to influence new bone formation in a 3 mm femur osteoporotic defect model in ovariectomized rats. Delivery of the bone-targeting system released from PLLA scaffolds began 2 hours post-implantation, peaked at 1 day, and was sustained over a 21 day period. μCT analysis demonstrated a significantly higher bone volume/total volume bone mineral density and number of osteoblasts in the rats that were transplanted with scaffolds loaded with siRNA-Sema4d. These results confirm the specific role of Sema4d in bone remodeling and demonstrate that significant increases in the speed and quality of new bone formation occur when siRNA-Sema4d is delivered via a PLLA scaffold.

A comparative study of strontium-substituted hydroxyapatite coating on implant's osseointegration for osteopenic rats

Surface modification techniques have been applied to generate titanium implant surfaces that promote osseointegration for the implants in cementless arthroplasty. However, its effect is not sufficient for osteoporotic bone. Strontium (Sr) promotes osteoblast proliferation and inhibits osteoclast proliferation and positively affects bone regeneration. The aim of this study was to confirm the effects of strontium-substituted hydroxyapatite (Sr-HA) coating via electrochemical deposition on implant's osseointegration in the osteoporotic condition. Female Sprague Dawley rats were used for this study. Twelve weeks after bilateral ovariectomy, all animals were randomly divided into four groups: group HA; group 5 % Sr-HA; group 10 % Sr-HA; and group 20 % Sr-HA. Afterward, all rats from groups HA, 5 % Sr-HA, 10 % Sr-HA, and 20 % Sr-HA received implants with hydroxyapatite coating containing 0, 5, 10, and 20 % Sr. Implants were inserted bilaterally in all animals until death at 12 weeks. The bilateral femurs of rats were harvested for evaluation. All treatment groups increased new bone formation around the surface of titanium rods and push-out force; group 20 % Sr-HA showed the strongest effects on new bone formation and biomechanical strength. Additionally, these are significant differences in bone formation and push-out force was observed between groups 5 % Sr-HA and 10 % Sr-HA. This finding suggests that Sr-HA coating can improve implant osseointegration, and the 20 % Sr coating exhibited the best properties for implant osseointegration among the tested coatings in osteoporosis rats.

Strontium ranelate increases osteoblast activity

Strontium ranelate (SR) is the first generation of a new class of medication for osteoporosis, which is capable of inducing bone formation and, to a certain extent, inhibiting bone resorption. The aim of this study was to evaluate the in vitro effects of SR on osteoblastic cell cultures. MC3TE-E1 cells were seeded in 24-well plates at a density of 2×10(4) cells/well and exposed to SR at 0.05, 0.1, and 0.5mM. The following parameters were assayed: 1) Cell proliferation by hemocytometer counting after 24, 48 and 72h, 2) Cell viability by MTT assay after 24, 48 and 72h, 3) Type I Collagen and Osteopontin (OPN) quantification by Western Blotting, ELISA, and Real Time PCR after 48h, 3) Immunolocalization of fibronectin (FN) by epifluorescence, and 4) matrix mineralization by Alizarin Red staining after 14days. After 24, 48 and 72h, the cell proliferation and viability were not affected by SR at 0.05 and 0.1mM (p>0.05). However, cell cultures exposed to SR at 0.5mM exhibited a decrease in both cell proliferation and cell viability in all time points assayed (p<0.05). High levels of protein and mRNA for Type I Collagen and OPN were detected in cultures exposed to SR, particularly at 0.5mM (p<0.05). SR allowed the expression of FN in osteoblastic cell cultures as observed by epifluorescence analysis. The mineralized bone-like nodule formation was affected in a concentration-dependent manner by SR, with large bone-like nodules being detected in osteoblastic cell cultures exposed to SR at 0.5mM. In conclusion, these results suggest that SR can accelerate acquisition of the osteoblastic phenotype, which explains, at least in part, the rebalancing of bone turnover in favor of bone formation.

Systemic Treatment with Strontium Ranelate Does Not Influence the Healing of Femoral Mid-shaft Defects in Rats

Strontium ranelate (SrR) has both bone anabolic and anti-resorption properties and has therefore the potential to increase the healing of bone defects. The aim of the present study was to investigate the effect of systemic treatment with SrR during the healing of cortical bone defects in rats. In addition, the vertebral bodies were examined in order to elucidate the effect of short-term treatment with SrR on intact trabecular bone. Sixty 16-week-old female Wistar rats were randomized into four groups. A cylindrical defect was drilled through the anterior cortex of the mid-femoral diaphysis in both hind limbs. Two of the groups were treated with SrR (900 mg/kg b.w.) mixed into the food and two groups served as controls. The animals were euthanized after either 3 or 8 weeks of treatment. Healing of the defects was analyzed with µCT, mechanical testing, and stereology. Treatment with SrR resulted in increased thickness of the defects after 3 weeks of treatment, whereas no effect on bone volume fraction (BV/TV), mechanical properties (maximum strength and maximum stiffness), periosteal callus volume, or osteoclast-covered bone surfaces (Oc.S/BS) after either 3 or 8 weeks of treatment was found. Furthermore, SrR increased the bone material density (ρ) of the vertebral bodies, and tended to increase BV/TV after 8 weeks of treatment (p = 0.087). The mechanical properties of the vertebral bodies were not influenced by SrR treatment. In conclusion, 3 weeks of treatment with SrR increased the thickness of the healing mid-femoral cortical bone defects in rats, but did not influence BV/TV, mechanical properties, periosteal callus volume, or Oc.S/BS after either 3 or 8 weeks. Furthermore, SrR had no effect on the microstructure and mechanical properties of the vertebral bodies.

Strontium folate loaded biohybrid scaffolds seeded with dental pulp stem cells induce in vivo bone regeneration in critical sized defects

Strontium folate loaded biohybrid scaffolds enhance dental pulp stem cells replication and differentiation, promoting complete regeneration of critical bone defects.

3D plotting of highly uniform Sr5(PO4)2SiO4 bioceramic scaffolds for bone tissue engineering

Novel bioactive ceramic scaffolds were 3D-plotted with controlled pore structures and the ions released from the scaffolds stimulated both osteogenesis and angiogenesis of tissue cells.

Comparative study of the effect of PTH (1-84) and strontium ranelate in an experimental model of atrophic nonunion

This study aimed to set up an experimental model of long bone atrophic nonunion and to explore the potential role of PTH-1-84 (PTH 1-84) and strontium ranelate (SrR). A model of atrophic nonunion was created in Sprague-Dawley rats at the femoral midshaft level. The animals were randomised into four groups. Group A1: control rodents, fracture without bone gap; Group A2: rodents with subtraction osteotomy (non-union model control) treated with saline; Group B: rodents with subtraction osteotomy treated with human-PTH (PTH 1-84); and Group C: rodents with subtraction osteotomy treated with strontium ranelate (SrR). The groups were followed for 12 weeks. X-rays were be obtained at weeks 1, 6 and 12. After sacrificing the animals, we proceeded to the biomechanical study and four point bending tests to evaluate the resistance of the callus and histological study. In second phase, the expression of genes related to osteoblast function was analysed by reverse transcription-quantitative PCR in rats subjected to substraction osteotomy and treated for 2 weeks. The animals were randomised into three groups: Group A2: rodents treated with saline; Group B: rodents treated with PTH 1-84 and Group C: rodents treated with SrR.

RESULTS

No significant histological differences were found between animals subjected to subtraction osteotomy and treated with either saline or PTH (p=0.628), but significant difference existed between animals receiving saline or SrR (p=0.005). There were no significant differences in X-ray score between the saline and PTH groups at either 6 or 12 weeks (p=0.33 and 0.36, respectively). On the other hand, better X-ray scores were found in the SrR group (p=0.047 and 0.006 in comparison with saline, at 6 and 12 weeks, respectively). In line with this, biomechanical tests revealed improved results in the SrR group. Gene expression analysis revealed a slightly decreased levels of DKK1, a Wnt pathway inhibitor, in rats treated with SrR.

CONCLUSIONS

SrR increases has a beneficial effect in this atrophic non-union model in rats. This suggests that it might have a role may have important implications for the potential clinical role in the treatment of fracture nonunion.

Addition of a Synthetically Fabricated Osteoinductive Biphasic Calcium Phosphate Bone Graft to BMP2 Improves New Bone Formation

BACKGROUND

Bone morphogenetic protein-2 (BMP2) has been successfully utilized in dentistry to promote new bone formation because of its osteoinductive ability to recruit mesenchymal progenitor cells and induce their differentiation to bone-forming osteoblasts. Recently, novel biphasic calcium phosphate scaffolds have been developed with similar osteoinductive properties capable of forming ectopic bone formation.

PURPOSE

The aim of the present study was to assess whether the combination of BMP2 with this novel Biphasic Calcium Phosphate (BCP) scaffold may additionally promote new bone regeneration.

MATERIALS AND METHODS

Cylindrical bone defects measuring 2.5 mm were created bilaterally in the femurs of 18 Wistar rats. After 4 weeks, the following six groups were assessed for new bone formation by micro-computed tomography (CT) as well as histological assessment: 1) collagen scaffolds + 20 μg of BMP2; 2) collagen scaffolds + 50 μg of BMP2; 3) collagen scaffolds + 100 μg of BMP2; 4) BCP scaffolds + 20 μg of BMP2; 5) BCP scaffolds + 50 μg of BMP2; and 6) BCP scaffolds + 100 μg of BMP2. Furthermore, tartrate-resistant acid phosphatase (TRAP) staining was utilized to assess osteoclast activity and osteoclast number. The release kinetics of BMP2 from both BCP and collagen scaffolds was investigated over a 14-day period.

RESULTS

The results from present study demonstrate that BMP2 is able to promote new bone formation in a concentration dependant manner when loaded with either a collagen scaffolds or BCP scaffolds. Micro-CT analysis demonstrated significantly higher levels of new bone formation in groups containing BCP + BMP2 when compared with collagen scaffolds + BMP2. BMP2 had little effect on osteoclast activity; however, less TRAP staining and osteoclast number was observed in the defects receiving collagen scaffolds when compared with BCP scaffolds. The release of BMP2 over time was rapidly released after 1 day on BCP scaffolds whereas a gradually release over time was observed for collagen scaffolds up to 14 days.

CONCLUSION

The osteoinductive properties of BMP2 may further be enhanced by its combination with a novel synthetically fabricated osteoinductive BCP scaffold. Future clinical testing is required to further assess these preliminary findings.

Effect of teriparatide on repair of femoral metaphyseal defect in ovariectomized rats

OBJECTIVE

This study aimed to investigate the effect exerted by teriparatide on the repair of femoral metaphyseal defect in ovariectomized rats.

METHOD

Female Sprague-Dawley rats were ovariectomized and after 3 months a critically sized defect of 3 mm in diameter-a through-hole bone defect-was drilled into each distal femur of the ovariectomized rats. The rats were injected with teriparatide (30 μg/kg) parathyroid hormone (PTH) in the peritoneum three times per week. After 4 and 8 weeks the animals were killed and the blood and bilateral femora were harvested for biochemical analysis, histopathological observation, and micro-computed tomography (CT) examination.

RESULTS

The PTH group and control group were compared 4  and 8 weeks after surgery. PTH increased bone formation in the defect area. Moreover, PTH showed the strongest effects on bone volume per total volume, trabecular number, trabecular thickness, trabecular separation, and total fluorescence-marked new bone area. Additionally, the PTH treatment group showed inhibited serum concentrations of C-terminal telopeptide of type I collagen and enhanced expression of calcium, phosphorus, and bone alkaline phosphatase.

CONCLUSION

Our findings suggest a positive effect of PTH on defect healing in ovariectomized rats.

Improvement of bioactivity, degradability, and cytocompatibility of biocement by addition of mesoporous magnesium silicate into sodium-magnesium phosphate cement

A novel mesoporous magnesium-based cement (MBC) was fabricated by using the mixed powders of magnesium oxide, sodium dihydrogen phosphate, and mesoporous magnesium silicate (m-MS). The results indicate that the setting time and water absorption of the MBC increased as a function of increasing m-MS content, while compressive strength decreased. In addition, the degradability of the MBC in a solution of Tris-HCl and the ability of apatite formation on the MBC were significantly improved with the increase in m-MS content. In cell culture experiments, the results show that the attachment, proliferation, and alkaline phosphatase activity of the MC3T3-E1 cells on the MBC were significantly enhanced with the increase of the content of m-MS. It can be suggested that the MBC with good cytocompatibility could promote the proliferation and differentiation of the MC3T3-E1 cells. In short, our findings indicate that the MBC containing m-MS had promising potential as a new biocement for bone regeneration and repair applications.