Highly efficient release of simvastatin from simvastatin-loaded calcium sulphate scaffolds enhances segmental bone regeneration in rabbits

Statins-Their Role in Bone Tissue Metabolism and Local Applications with Different Carriers

Statins, widely prescribed for lipid disorders, primarily target 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase competitively and reversibly, resulting in reduced low-density lipoprotein cholesterol (LDL-C). This mechanism proves effective in lowering the risk of lipid-related diseases such as ischemic cerebrovascular and coronary artery diseases. Beyond their established use, statins are under scrutiny for potential applications in treating bone diseases. The focus of research centers mainly on simvastatin, a lipophilic statin demonstrating efficacy in preventing osteoporosis and aiding in fracture and bone defect healing. Notably, these effects manifest at elevated doses (20 mg/kg/day) of statins, posing challenges for systematic administration due to their limited bone affinity. Current investigations explore intraosseous statin delivery facilitated by specialized carriers. This paper outlines various carrier types, characterizing their structures and underscoring various statins' potential as local treatments for bone diseases.

Efficacy of spongy xenogeneic scaffold loaded with simvastatin in the treatment of severe alveolar horizontal defect: A clinical and histological study

Background

Bone tissue engineering offers several advantages for repairing skeletal defects. In this study, we designed and fabricated a scaffold for bone tissue engineering in patients with horizontal alveolar defect.

Aim

The items included in the fabrication of the scaffold were xenogenic bone graft, gelatin as a substrate to improve the physical integrity of scaffold, and simvastatin to stimulate osteogenesis (10 mg per 1 g of xenograft).

Methods

Fourteen patients with a horizontal defect in the alveolar ridge were enrolled in the study. Seven patients underwent routinely guided bone regeneration (GBR) using xenogenic bone graft plus collagenous membrane, and seven patients were treated with the scaffolds. After four months of follow-up after surgery, both the scaffold and GBR groups were examined for changes in the width of alveolar ridge and histologically for the quantity of newly produced bone.

Results

The newly designed scaffold showed superior osteoconduction characteristics to routine GBR materials, which were used in this study. The difference in the quantity of the newly produced bone between the scaffold group and GBR group was significant and higher for the scaffold group. Regarding newly produced bone percentage, the scaffold group showed a mean of 20.93 and the GBR group presented a mean of 13.25% (P = 0.004). Also, the mean value for the duration of surgery for GBR was 45 minutes and for scaffold was 22 minutes, which was significantly lower in the scaffold group (P < 0.001).

Conclusions

The newly designed scaffold is a suitable treatment modality for bone tissue engineering.

Fabrication of Silk Scaffold Containing Simvastatin-Loaded Silk Fibroin Nanoparticles for Regenerating Bone Defects

BACKGROUND

In the present study, a tissue engineered silk fibroin (SF) scaffold containing simvastatin-loaded silk fibroin nanoparticles (SFNPs) were used to stimulate the regeneration of the defected bone.

METHODS

At first, the porous SF scaffold was prepared using freeze-drying. Then simvastatin-loaded SFNPs were made by dissolvation method and embedded in the SF scaffold. Afterwards, the scaffold and the NPs were characterized in terms of physicochemical properties and the ability to release the simvastatin small molecule.

RESULTS

The results exhibited that the SF scaffold had a porous structure suitable for releasing the small molecule and inducing the proliferation and attachment of osteoblast cells. SFNPs containing simvastatin had spherical morphology and were 174 ± 4 nm in size with -24.5 zeta potential. Simvastatin was also successfully encapsulated within the SFNPs with 68% encapsulation efficiency. Moreover, the small molecule revealed a sustained release profile from the NPs during 35 days. The results obtained from the in vitro cell-based studies indicated that simvastatin-loaded SFNPs embedded in the scaffold had acceptable capacity to promote the proliferation and alkaline phosphatase production of osteoblast cells while inducing osteogenic matrix precipitation.

CONCLUSION

The SF scaffold containing simvastatin-loaded SFNPs could have a good potential to be used as a bone tissue-engineered construct.

Simvastatin-Incorporated Drug Delivery Systems for Bone Regeneration

Local drug delivery systems composed of biomaterials and osteogenic substances provide promising strategies for the reconstruction of large bone defects. In recent years, simvastatin has been studied extensively for its pleiotropic effects other than lowering of cholesterol, including its ability to induce osteogenesis and angiogenesis. Accordingly, several studies of simvastatin incorporated drug delivery systems have been performed to demonstrate the feasibility of such systems in enhancing bone regeneration. Therefore, this review explores the molecular mechanisms by which simvastatin affects bone metabolism and angiogenesis. The simvastatin concentrations that promote osteogenic differentiation are analyzed. Furthermore, we summarize and discuss a variety of simvastatin-loaded drug delivery systems that use different loading methods and materials. Finally, current shortcomings of and future development directions for simvastatin-loaded drug delivery systems are summarized. This review provides various advanced design strategies for simvastatin-incorporated drug delivery systems that can enhance bone regeneration.

Modified electrospun chitosan membranes for controlled release of simvastatin

Chitosan nanofibrous membranes have immense potential in tissue engineering and drug delivery applications because of their increased surface area, high degree of biocompatibility, and their ability to mimic the extracellular matrix. However, their use is often limited due to their extreme hydrophilic nature causing them to lose their nanofibrous structure in vivo. In the present study, chitosan membranes were modified either by acylation reactions using fatty acids of different chain lengths or tert-butyloxycarbonyl (tBOC) protecting groups to increase the hydrophobicity of the membranes and protect the nanofibrous structure. The modified membranes were characterized using scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, water contact angle and elemental analysis to confirm the addition of the modification groups. These membranes were then evaluated to control the release of a hydrophobic osteogenic drug-simvastatin (SMV). The interaction between SMV and the polymer was determined using molecular modeling. Pure SMV and SMV loaded membranes were examined for their in vitro cytotoxicity and osteogenic potential using preosteoblast mouse bone marrow stromal cells. From results, it was evident that as the fatty acid chain length increased from two to six methylene groups, the hydrophobicity of the membranes increased (59.2 ± 8.2° to 94.3 ± 8.5° water contact angle). The amount of drug released from the membranes could be controlled by changing the amount of initial drug loaded and/or the type of modifications. After 4 weeks, for a 500 μg loading, the short chain fatty acid modified membranes released 17.8 ± 3.2% of the drug whereas a long chain fatty acid released only 4.8 ± 0.8%. Similarly, for a 50 μg loading, short chain modified membranes released more (73.3 ± 33.3%) of the loaded drug as compared to the long chain membranes (43.0 ± 3.5%). The long chain fatty acid membranes released SMV for extended time periods of up to 90 days. This data was further supported by molecular modeling, which revealed that SMV was more compatible with more hydrophobic membranes. Cell studies showed that pure SMV from 75 to 600 ng/ml range possessed osteogenic potential in a dose dependent manner and the amount of SMV released from the most hydrophobic FA treated membranes was not cytotoxic and supported osteogenic differentiation. Therefore, this study demonstrates our ability to control the release of a hydrophobic drug from modified chitosan membranes as per the clinical need.

Adjuvant Drug-Assisted Bone Healing: Advances and Challenges in Drug Delivery Approaches

Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.

Adjuvant drug-assisted bone healing: Part III - Further strategies for local and systemic modulation

In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is pursued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.

Effects of statins on the biological features of mesenchymal stem cells and therapeutic implications

Statins are well-known lipid-lowering drugs. The pleiotropic effects of statins have brought about some beneficial effects on improving the therapeutic outcomes of cell therapy and tissue engineering approaches. In this review, the impact of statins on mesenchymal stem cell behaviors including differentiation, apoptosis, proliferation, migration, and angiogenesis, as well as molecular pathways which are responsible for such phenomena, are discussed. A better understanding of pathways and mechanisms of statin-mediated effects on mesenchymal stem cells will pave the way for the expansion of statin applications. Furthermore, since designing a suitable carrier for statins is required to maintain a sufficient dose of active statins at the desired site of the body, different systems for local delivery of statins are also reviewed.

In vitro and in vivo evaluation of chitosan scaffolds combined with simvastatin-loaded nanoparticles for guided bone regeneration

The objective of this study was to fabricate and characterize chitosan combined with different amounts of simvastatin-loaded nanoparticles and to investigate their potential for guided bone regeneration in vitro and in vivo. Different SIM-CSN formulations were combined into a chitosan scaffold (SIM-CSNs-S), and the morphology, simvastatin release profile, and effect on cell proliferation and differentiation were investigated. For in vivo experiments, ectopic osteogenesis and the critical-size cranial defect model in SD rats were chosen to evaluate bone regeneration potential. All three SIM-CSNs-S formulations had a porous structure and exhibited sustained simvastatin release. CSNs-S showed excellent degradation and biocompatibility characteristics. The 4 mg SIM-CSNs-S formulation stimulated higher BMSC ALP activity levels, demonstrated significantly earlier collagen enhancement, and led to faster bone regeneration than the other formulations. SIM-CSNs-S should have a significant effect on bone regeneration.

Spatiotemporal Control Strategies for Bone Formation through Tissue Engineering and Regenerative Medicine Approaches

Global increases in life expectancy drive increasing demands for bone regeneration. The gold standard for surgical bone repair is autografting, which enjoys excellent clinical outcomes; however, it possesses significant drawbacks including donor site morbidity and limited availability. Although collagen sponges delivered with bone morphogenetic protein, type 2 (BMP2) are a common alternative or supplement, they do not efficiently retain BMP2, necessitating extremely high doses to elicit bone formation. Hence, reports of BMP2 complications are rising, including cancer promotion and ectopic bone formation, the latter inducing complications such as breathing difficulties and neurologic impairments. Thus, efforts to exert spatial control over bone formation are increasing. Several tissue engineering approaches have demonstrated the potential for targeted and controlled bone formation. These approaches include biomaterial scaffolds derived from synthetic sources, e.g., calcium phosphates or polymers; natural sources, e.g., bone or seashell; and immobilized biofactors, e.g., BMP2. Although BMP2 is the only protein clinically approved for use in a surgical device, there are several proteins, small molecules, and growth factors that show promise in tissue engineering applications. This review profiles the tissue engineering advances in achieving control over the location and onset of bone formation (spatiotemporal control) toward avoiding the complications associated with BMP2.

3D bioactive composite scaffolds for bone tissue engineering

Bone is the second most commonly transplanted tissue worldwide, with over four million operations using bone grafts or bone substitute materials annually to treat bone defects. However, significant limitations affect current treatment options and clinical demand for bone grafts continues to rise due to conditions such as trauma, cancer, infection and arthritis. Developing bioactive three-dimensional (3D) scaffolds to support bone regeneration has therefore become a key area of focus within bone tissue engineering (BTE). A variety of materials and manufacturing methods including 3D printing have been used to create novel alternatives to traditional bone grafts. However, individual groups of materials including polymers, ceramics and hydrogels have been unable to fully replicate the properties of bone when used alone. Favourable material properties can be combined and bioactivity improved when groups of materials are used together in composite 3D scaffolds. This review will therefore consider the ideal properties of bioactive composite 3D scaffolds and examine recent use of polymers, hydrogels, metals, ceramics and bio-glasses in BTE. Scaffold fabrication methodology, mechanical performance, biocompatibility, bioactivity, and potential clinical translations will be discussed.

Role of Simvastatin on fracture healing and osteoporosis: a systematic review on in vivo investigations

Simvastatin is a lipid lowering drug whose beneficial role on bone metabolism was discovered in 1999. Several in vivo studies evaluated its role on osteoporosis and fracture healing, however, controversial results are seen in the literature. For this reason, Simvastatin has not been the focus of any clinical trials as yet. This systematic review clears the mechanisms of action of Simvastatin on bone metabolism and focuses on in vivo investigations that have evaluated its role on osteoporosis and fracture repair to find out (i) whether Simvastatin is effective on treatment of osteoporosis and fracture repair, and (ii) which of the many available protocols may have the ability to be translated in the clinical setting. Simvastatin induces osteoinduction by increasing osteoblast activity and differentiation and inhibiting their apoptosis. It also reduces osteoclastogenesis by decreasing both the number and activity of osteoclasts and their differentiation. Controversial results between the in vivo studies are mostly due to the differences in the route of administration, dose, dosage and carrier type. Local delivery of Simvastatin through controlled drug delivery systems with much lower doses and dosages than the systemic route seems to be the most valuable option in fracture healing. However, systemic delivery of Simvastatin with much higher doses and dosages than the clinical ones seems to be effective in managing osteoporosis. Simvastatin, in a particular range of doses and dosages, may be beneficial in managing osteoporosis and fracture injuries. This review showed that Simvastatin is effective in the treatment of osteoporosis and fracture healing.

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.

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.