Combination of calcium sulfate and simvastatin-controlled release microspheres enhances bone repair in critical-sized rat calvarial bone defects

PLGA+HA/βTCP Scaffold Incorporating Simvastatin: A Promising Biomaterial for Bone Tissue Engineering

The aim of this study was to synthesize, characterize, and evaluate degradation and biocompatibility of poly(lactic-co-glycolic acid) + hydroxyapatite/β-tricalcium phosphate (PLGA+HA/βTCP) scaffolds incorporating simvastatin (SIM) to verify if this biomaterial might be promising for bone tissue engineering. Samples were obtained by the solvent evaporation technique. Biphasic ceramic particles (70% HA, 30% βTCP) were added to PLGA in a ratio of 1:1. Samples with SIM received 1% (m/m) of this medication. Scaffolds were synthesized in a cylindric shape and sterilized by ethylene oxide. For degradation analysis, samples were immersed in phosphate-buffered saline at 37°C under constant stirring for 7, 14, 21, and 28 days. Nondegraded samples were taken as reference. Mass variation, scanning electron microscopy, porosity analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetry were performed to evaluate physico-chemical properties. Wettability and cytotoxicity tests were conducted to evaluate the biocompatibility. Microscopic images revealed the presence of macro-, meso-, and micropores in the polymer structure with HA/βTCP particles homogeneously dispersed. Chemical and thermal analyses presented similar results for both PLGA+HA/βTCP and PLGA+HA/βTCP+SIM. The incorporation of simvastatin improved the hydrophilicity of scaffolds. Additionally, PLGA+HA/βTCP and PLGA+HA/βTCP+SIM scaffolds were biocompatible for osteoblasts and mesenchymal stem cells. In summary, PLGA+HA/βTCP scaffolds incorporating simvastatin presented adequate structural, chemical, thermal, and biological properties for bone tissue engineering.

Copper-Loaded Biodegradable Bone Wax with Antibacterial and Angiogenic Properties in Early Bone Repair

Traditional bone wax has lots of shortcomings such as the risk of infection and inflammation and the ability to hinder osteogenesis that limit its clinical applications. In this study, we designed a novel biodegradable bone wax with desirable angiogenic and antibacterial ability and low foreign body reaction by mixing calcium sulfate, poloxamer, and cupric ions. To evaluate its biocompatibility and angiogenetic effect in vitro, we cultured human umbilical vein endothelial cells (HUVECs) with the indicated bone wax to observe cell viability and vessel-like tubular formation. The bone wax was then implanted in a critical-sized bone defect rat model for 4 and 8 weeks to successfully stimulate angiogenesis in vivo. Finally, the bone wax extract was incubated with Gram-positive Staphylococcus aureus to confirm its antibacterial ability. The copper-loaded biodegradable bone wax overcomes the drawbacks of traditional bone wax and provides a new approach for the treatment of bone injuries.

Clinical Application of Bone Marrow Mesenchymal Stem/Stromal Cells to Repair Skeletal Tissue

There has been an escalation in reports over the last decade examining the efficacy of bone marrow derived mesenchymal stem/stromal cells (BMSC) in bone tissue engineering and regenerative medicine-based applications. The multipotent differentiation potential, myelosupportive capacity, anti-inflammatory and immune-modulatory properties of BMSC underpins their versatile nature as therapeutic agents. This review addresses the current limitations and challenges of exogenous autologous and allogeneic BMSC based regenerative skeletal therapies in combination with bioactive molecules, cellular derivatives, genetic manipulation, biocompatible hydrogels, solid and composite scaffolds. The review highlights the current approaches and recent developments in utilizing endogenous BMSC activation or exogenous BMSC for the repair of long bone and vertebrae fractures due to osteoporosis or trauma. Current advances employing BMSC based therapies for bone regeneration of craniofacial defects is also discussed. Moreover, this review discusses the latest developments utilizing BMSC therapies in the preclinical and clinical settings, including the treatment of bone related diseases such as Osteogenesis Imperfecta.

The Role of Structure and Biophysical Properties in the Pleiotropic Effects of Statins

Statins are a class of drugs used to lower low-density lipoprotein cholesterol and are amongst the most prescribed medications worldwide. Most statins work as a competitive inhibitor of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR), but statin intolerance from pleiotropic effects have been proposed to arise from non-specific binding due to poor enzyme-ligand sensitivity. Yet, research into the physicochemical properties of statins, and their interactions with off-target sites, has not progressed much over the past few decades. Here, we present a concise perspective on the role of statins in lowering serum cholesterol levels, and how their reported interactions with phospholipid membranes offer a crucial insight into the mechanism of some of the more commonly observed pleiotropic effects of statin administration. Lipophilicity, which governs hepatoselectivity, is directly related to the molecular structure of statins, which dictates interaction with and transport through membranes. The structure of statins is therefore a clinically important consideration in the treatment of hypercholesterolaemia. This review integrates the recent biophysical studies of statins with the literature on the physiological effects and provides new insights into the mechanistic cause of statin pleiotropy, and prospective means of understanding the cholesterol-independent effects of statins.

Development and Biocompatibility Analysis of NBD Peptide Sustained- Release Microsphere Scaffold Nanoparticle SP-Sr-CaS/NBD

BACKGROUND

In clinical treatment, it is difficult to carry out effective bone tissue transplantation and anti-inflammatory treatment at the same time due to bone defects and osteomyelitis where the tissue is contaminated or infected. As a downstream target of TNF-α, NF-κB has an inhibition effect on the proliferation and differentiation of cells surrounding the lesion. As a negative effect, it leads to a reduction in bone growth and development.

METHODS

In this study, the small molecule NBD polypeptide and bone conduction matrix Sr-CaS are microspheres, formed to prepare Sr-CaS, NBD drug-loaded sustained-release microspheres in order to achieve a Sr-CaS/NBD peptide drug-loaded sustained release microsphere scaffold material (SP-Sr-CaS/NBD). We prepared the microspheres and optimized the production process to obtain particles with stable morphological properties and sustained release properties.

RESULT

In vitro experiments demonstrated that SP-Sr-CaS/NBD could reduce TNF-α-induced cell growth inhibition, caspase-3 activity and NF-κB transcriptional activation as the function of continuous NBD peptide dosing regimen.

CONCLUSION

Also, the introduction of the Sr-CaS matrix potentiates microspheres to promote cell proliferation and provides a basis to become a promising 3D bone scaffold material in the future.

Bone Healing and Regeneration Potential in Rabbit Cortical Defects Using an Innovative Bioceramic Bone Graft Substitute

This study aimed to elucidate the local effect and micro-computed tomographic (μ-CT) assessment following bone implantation of an innovative bioceramic (α-calcium sulfate hemihydrate; α-CSH) on femur lateral condyle cortical bone of rabbit models. The innovative α-CSH bioceramic was synthesized through a green processing technology (microwave irradiation treatment). The bilateral implantation model was performed among 24 New Zealand White rabbits which were divided into three groups based on the type of filling materials: α-CSH, control, and blank. Treatments were performed in defects with 6 mm diameter and 7 mm depth and observed after 2, 4, 8, and 12 weeks. Material reaction and bone formation after implantation were evaluated radiographically and histopathologically. The μ-CT analysis results showed that the degradation of α-CSH and control material was similar at 4 and 8 weeks. The bone volume in the defects indicated the α-CSH increased most in 8 weeks. In histopathological evaluation, the α-CSH group was repaired with lamellar bone and well-grown bone marrow infiltration similar to the control material. Moreover, the α-CSH revealed a faster degradation rate and better healing progress than the control material under the same conditions. Therefore, the α-CSH was confirmed to be useful in promoting osteoconduction and in controlling the resorption rate in bone defects. Further, the innovative α-CSH could be considered as a promising bone substitute for utilization in bone reconstructive therapy in dental and orthopedic fields.

Green Tea Catechin (-)-Epigallocatechin-3-Gallate (EGCG) Facilitates Fracture Healing

Green tea drinking can ameliorate postmenopausal osteoporosis by increasing the bone mineral density. (-)-Epigallocatechin-3-gallate (EGCG), the abundant and active compound of tea catechin, was proven to be able to reduce bone loss and ameliorate microarchitecture in female ovariectomized rats. EGCG can also enhance the osteogenic differentiation of murine bone marrow mesenchymal stem cells and inhibit the osteoclastogenesis in RAW264.7 cells by modulation of the receptor activator of nuclear factor-kB (RANK)/RANK ligand (RANKL)/osteoprotegrin (OPG) (RANK/RANKL/OPG) pathway. Our previous study also found that EGCG can promote bone defect healing in the distal femur partially via bone morphogenetic protein-2 (BMP-2). Considering the osteoinduction property of BMP-2, we hypothesized that EGCG could accelerate the bone healing process with an increased expression of BMP-2. In this manuscript, we studied whether the local use of EGCG can facilitate tibial fracture healing. Fifty-six 4-month-old rats were randomly assigned to two groups after being weight-matched: a control group with vehicle treatment (Ctrl) and a study group with 10 µmol/L, 40 µL, EGCG treatment (EGCG). Two days after the operation, the rats were treated daily with EGCG or vehicle by percutaneous local injection for 2 weeks. The application of EGCG enhanced callus formation by increasing the bone volume and subsequently improved the mechanical properties of the tibial bone, including the maximal load, break load, stiffness, and Young’s modulus. The results of the histology and BMP-2 immunohistochemistry staining showed that EGCG treatment accelerated the bone matrix formation and produced a stronger expression of BMP-2. Taken together, this study for the first time demonstrated that local treatment of EGCG can accelerate the fracture healing process at least partly via BMP-2.

Local effect of simvastatin combined with different osteoconductive biomaterials and collagen sponge on new bone formation in critical defects in rat calvaria

Purpose

To evaluate the local effect of simvastatin (SVT) combined with deproteinized bovine bone (DBB) with hydroxyapatite/β-tricalcium phosphate biphasic ceramics (HA/TCP) and with collagen sponge (CS) on bone repair in critical size defects (CSDs) in rat calvaria.

Methods

Forty-two 5-mm diameter CSDs were made bilaterally in the calvaria of 18 rats. The animals were allocated according to the type of biomaterial and associations used to fill the CSD. After 8 weeks, the animals were euthanized, and their calvaria were evaluated for repaired tissue composition using histologic and histometric analyses.

Results

In the histometric analysis, the use of SVT showed to increase bone formation in the CSDs when combined with all the bone substitutes tested in this study (p<0.05). Greater bone formation was observed in the groups with SVT compared to the groups without SVT.

Conclusions

The use of SVT without the need for a vehicle and combined with a commercially available biomaterial may be a cheaper way to potentiate the formation of bone tissue without the need to produce new biomaterials. Therefore, SVT combined with DBB induced significantly greater new bone formation than did the other treatments.

The effect of graft application and allopurinol treatment on calvarial bone defect in rats1

Purpose

To investigate the effects of allopurinol administration on osteoinductive reaction and bone development with graft material.

Methods

Thirty-six Wistar albino rats were divided into 3 groups. In the control group, calvarial bone defect was only created without any treatment. In the Defect + Graft group, allograft treatment was performed by forming 8 mm calvarial bone defect. In the Defect + Graft + Allopurinol group, alloplastic bone graft was placed in the calvarial bone defect and then, allopurinol (50 mg/kg/day) treatment was intraperitoneally applied for 28 days.

Results

Histopathological examination revealed inflammation, congestion in the vessels, and an increase in osteoclast cells in the defect area. We also observed that new osteocyte cells, increase in connective tissue fibers, and new bone trabeculae. Osteopontin expression was positive in osteoblast cells and lacunated osteocyte cells were located in the periphery of the new bone trabeculae. Osteopontin expression was also positive in osteoblasts and osteocytes cells of new bone trabeculae in the graft site.

Conclusion

It has been shown that allopurinol treatment in rat calvaria defects may induce osteoblastic activity, matrix development, mature bone cell formation and new bone formation when used with autogenous grafts.

Combination of a Bioceramic Scaffold and Simvastatin Nanoparticles as a Synthetic Alternative to Autologous Bone Grafting

The fragile nature of porous bioceramic substitutes cannot match the toughness of bone, which limits the use of these materials in clinical load-bearing applications. Statins can enhance bone healing, but it could show rhabdomyolysis/inflammatory response after overdosing. In this study, the drug-containing bone grafts were developed from poly(lactic acid-co-glycolic acid)-polyethylene glycol (PLGA-PEG) nanoparticles encapsulating simvastatin (SIM) (SIM-PP NPs) loaded within an appropriately mechanical bioceramic scaffold (BC). The combination bone graft provides dual functions of osteoconduction and osteoinduction. The mechanical properties of the bioceramic are enhanced mainly based on the admixture of a combustible reverse-negative thermoresponsive hydrogel (poly(N-isopropylacrylamide base). We showed that SIM-PP NPs can increase the activity of alkaline phosphatase and osteogenic differentiation of bone marrow stem cells. To verify the bone-healing efficacy of this drug-containing bone grafts, a nonunion radial endochondral ossification bone defect rabbit model (N = 3/group) and a nonunion calvarial intramembranous defect Sprague Dawley (SD) rat model (N = 5/group) were used. The results indicated that SIM-PP NPs combined with BC can improve the healing of nonunion bone defects of the radial bone and calvarial bone. Therefore, the BC containing SIM-PP NPs may be appropriate for clinical use as a synthetic alternative to autologous bone grafting that can overcome the problem of determining the clinical dosage of simvastatin drugs to promote bone healing.

Study of mesenchymal stem cells cultured on a poly(lactic-co-glycolic acid) scaffold containing simvastatin for bone healing

BACKGROUND

Tissue engineering is a promising alternative for the development of bone substitutes; for this purpose, three things are necessary: stem cells, a scaffold to allow tissue growth and factors that induce tissue regeneration.

METHODS

To congregate such efforts, we used the bioresorbable and biocompatible polymer poly(lactic-co-glycolic acid) (PLGA) as scaffold. For the osteoinductive factor, we used simvastatin (SIM), a drug with a pleiotropic effect on bone growth. Mesenchymal stem cells (MSCs) were cultured in PLGA containing SIM, and the bone substitute of PLGA/SIM/MSC was grafted into critical defects of rat calvaria.

RESULTS

The in vitro results showed that SIM directly interfered with the proliferation of MSC promoting cell death, while in the pure PLGA scaffold the MSC grew continuously. Scaffolds were implanted in the calvaria of rats and separated into groups: control (empty defect), PLGA pure, PLGA/SIM, PLGA/MSC and PLGA/SIM/MSC. The increase in bone growth was higher in the PLGA/SIM group.

CONCLUSIONS

We observed no improvement in the growth of bone tissue after implantation of the PLGA/SIM/MSC scaffold. As compared with in vitro results, our main hypothesis is that the microarchitecture of PLGA associated with low SIM release would have created an in vivo microenvironment of concentrated SIM that might have induced MSC death. However, our findings indicate that once implanted, both PLGA/SIM and PLGA/MSC contributed to bone formation. We suggest that strategies to maintain the viability of MSCs after cultivation in PLGA/SIM will contribute to improvement of bone regeneration.

Combination of simvastatin, calcium silicate/gypsum, and gelatin and bone regeneration in rabbit calvarial defects

The present study was performed to determine whether simvastatin improves bone regeneration when combined with calcium silicate/gypsum and gelatin (CS-GEL). The surface morphology was determined using field-emission scanning electron microscopy (FSEM). Degradation in vitro was evaluated by monitoring the weight change of the composites soaked in phosphate buffered saline (PBS). Drug release was evaluated using high-performance liquid chromatography (HPLC). Cytotoxicity testing was performed to assess the biocompatibility of composites. Four 5 mm-diameter bone defects were created in rabbit calvaria. Three sites were filled with CS-GEL, 0.5 mg simvastatin-loaded CS-GEL (SIM-0.5) and 1.0 mg simvastatin-loaded CS-GEL (SIM-1.0), respectively, and the fourth was left empty as the control group. Micro-computed tomography (micro-CT) and histological analysis were carried out at 4 and 12 weeks postoperatively. The composites all exhibited three-dimensional structures and showed the residue with nearly 80% after 4 weeks of immersion. Drug release was explosive on the first day and then the release rate remained stable. The composites did not induce any cytotoxicity. The results in vivo demonstrated that the new bone formation and the expressions of BMP-2, OC and type I collagen were improved in the simvastatin-loaded CS-GEL group. It was concluded that the simvastatin-loaded CS-GEL may improve bone regeneration.