Osteoporosis and biomaterial osteointegration

The relevance of biomaterials to the prevention and treatment of osteoporosis

Osteoporosis is a worldwide disease with a very high prevalence in humans older than 50. The main clinical consequences are bone fractures, which often lead to patient disability or even death. A number of commercial biomaterials are currently used to treat osteoporotic bone fractures, but most of these have not been specifically designed for that purpose. Many drug- or cell-loaded biomaterials have been proposed in research laboratories, but very few have received approval for commercial use. In order to analyze this scenario and propose alternatives to overcome it, the Spanish and European Network of Excellence for the Prevention and Treatment of Osteoporotic Fractures, "Ageing", was created. This network integrates three communities, e.g. clinicians, materials scientists and industrial advisors, tackling the same problem from three different points of view. Keeping in mind the premise "living longer, living better", this commentary is the result of the thoughts, proposals and conclusions obtained after one year working in the framework of this network.

Nanocrystalline silicon substituted hydroxyapatite effects on osteoclast differentiation and resorptive activity

In the present study, the effects of nanocrystalline hydroxyapatite (nano-HA) and nanocrystalline Si-substituted hydroxyapatite (nano-SiHA) on osteoclast differentiation and resorptive activity have been evaluated in vitro using osteoclast-like cells. The action of these materials on proinflammatory and reparative macrophage populations was also studied. Nano-SiHA disks delayed the osteoclast differentiation and decreased the resorptive activity of these cells on their surface, as compared to nano-HA samples, without affecting cell viability. Powdered nano-SiHA also induced an increase of the reparative macrophage population. These results along with the beneficial effects on osteoblasts previously observed with powdered nano-SiHA suggest the potential of this biomaterial for modulating the fundamental processes of bone formation and turnover, preventing bone resorption and enhancing bone formation at implantation sites in treatment of osteoporotic bone and in bone repair and regeneration.

A Standardized Critical Size Defect Model in Normal and Osteoporotic Rats to Evaluate Bone Tissue Engineered Constructs

Tissue engineered constructs should be tested for their efficacy not only in normal but also in osteoporotic bone. The rat is an established animal model for osteoporosis and is used often for bone healing studies. In this study a defined and standardized critical size defect model in the rat suitable for screening new tissue engineered constructs in normal and osteoporotic bone is described and validated. Normal and ovariectomised Wistar rats received a unilateral middiaphyseal 5 mm defect in the femur, which was instrumented with a radiolucent PEEK plate fixed with angular stable titanium screws and left untreated. All animals were euthanized eight weeks after defect surgery and the bone healing was evaluated using radiographs, computed tomography measurements, and histology. The developed fixation system provided good stability, even in osteoporotic bone. The implants and ancillary instruments ensured consistent and facile placement of the PEEK plates. The untreated defects did not heal without intervention making the model a well-defined and standardized critical size defect model highly useful for evaluating tissue engineered solutions in normal and osteoporotic bone.

Effect of concentrated growth factors on beagle periodontal ligament stem cells in vitro

Identifying a reliable and effective cytokine or growth factor group has been the focus of stem cell osteogenic induction studies. Concentrated growth factors (CGFs) as the novel generation of platelet concentrate products, appear to exhibit a superior clinical and biotechnological application potential, however, there are few studies that have demonstrated this effect. This study investigated the proliferation and differentiation of periodontal ligament stem cells (PDLSCs) co‑cultured with CGFs. The rate of proliferation was analyzed by cell counting and an MTT assay. Mineralization nodule counts, alkaline phosphatase activity detection, qPCR, western blot analysis and immunohistochemistry were used to analyze mineralization effects. The results showed that CGF significantly promoted the proliferation of PDLSCs, and exhibited a dose‑dependent effect on the activation and differentiation of the stem cells. The application of CGF on PDLSC proliferation and osteoinduction may offer numerous clinical and biotechnological application strategies.

Calcium-phosphate-coated Oral Implants Promote Osseointegration in Osteoporosis

Osteoporotic conditions are anticipated to affect the osseointegration of dental implants. This study aimed to evaluate the effect of a radiofrequent magnetron-sputtered calcium phosphate (CaP) coating on dental implant integration upon installment in the femoral condyles of both healthy and osteoporotic rats. At 8 weeks post-implantation, bone volume and histomorphometric bone area were lower around non-coated implants in osteoporotic rats compared with healthy rats. Interestingly, push-out tests revealed significantly enhanced implant fixation for CaP-coated compared with non-coated implants in both osteoporotic ( i.e., 2.9-fold) and healthy rats ( i.e., 1.5-fold), with similar implant fixation for CaP-coated implants in osteoporotic conditions compared with that of non-coated implants in healthy conditions. Further, the presence of a CaP coating significantly increased bone-to-implant contact compared with that in non-coated implants in both osteoporotic ( i.e., 1.3-fold) and healthy rats ( i.e., 1.4-fold). Sequential administration of fluorochrome labels showed significantly increased bone dynamics close to CaP-coated implants at 3 weeks of implantation in osteoporotic conditions and significantly decreased bone dynamics in osteoporotic compared with healthy conditions. In conclusion, analysis of the data obtained demonstrated that dental implant modification with a thin CaP coating effectively improves osseointegration in both healthy and osteoporotic conditions.

History and design considerations for arthroplasty around the wrist

The history and evolution of both soft tissue and implant arthroplasty about the wrist are discussed, including carpometacarpal, radiocarpal, and distal radioulnar joints. Technical considerations for arthroplasty are reviewed, including factors affecting implant osseointegration, implant articulation/constraint, and management of complications.

Effect of reactive oxygen species overproduction on osteogenesis of porous titanium implant in the present of diabetes mellitus

Clinical evidence indicates diabetes as a majorrisk factor for titaniumimplant treatment with high failure rates and poor osteointegration, but the underlying mechanism involved remains elusive.We hypothesize that reactive oxygen species (ROS) overproduction may contribute to the impaired osteogenesis of porous titanium implants (pTi) under diabetic conditions. To test this hypothesis, we culturedprimary rabbit osteoblasts onto pTi and studied the cellular performance when subjected to normal serum (NS), diabetic serum (DS), DS + NAC (a potent ROS inhibitor) and NS + H(2)O(2)(an oxidant).In-vivo performance of pTi was investigated by transplanting them intofemoral condyledefects of diabetic rabbits, which received vehicle or NAC treatment respectively.Results showed that diabetic conditions induced significant cellular apoptosis, depressedosteoblast function evidenced by impairedcell attachment and morphology, decreased cell proliferation anddifferentiation, andcompromised in-vivo osteogenesis ofpTi, while cellular ROSgeneration was increased derived from mitochondrial dysfunction. Scavenging ROS with NAC markedly attenuated cell apoptosis and osteoblast dysfunction, and improved bone ingrowth within pTi. Furthermore, treatment withH(2)O(2) exerted similar adverse effect on cellular behavior as diabetes. This study furthers our knowledge on the potential role of ROS overproduction in the diabetes-induced impaired osteogenesis of titanium implants, and indicates anti-oxidative treatment as a promising strategy to promote the treatment efficacy of pTi in diabetic patients.

Bone tissue response to BMP-2 adsorbed on amorphous microporous silica implants

AIM

To evaluate bone regeneration potential of bone morphogenetic protein-2 (BMP-2) adsorbed on amorphous microporous silica (AMS).

MATERIALS & METHODS

Four implants [titanium as control (CTR); AMS-coated titanium (AMS), BMP-2 adsorbed on titanium (CTR+BMP) and AMS (AMS+BMP)] were implanted randomly in the tibiae of 20 New Zealand white rabbits. Bone specimens with implants were retrieved 2/4 weeks post implantation and analysed histologically and histomorphometrically. Bone fraction was measured in initial bone-free area (bone regeneration area, BRA) and in the area with initial bone-implant contact [bone adaptation area (BAA)] (BF(BRA) & BF(BAA) ). Bone-implant contact was measured in BRA (BIC(BRA) ). In vitro BMP-2 release profiles were determined to evaluate the impact of the carrier surface. Mixed models were used for statistical analysis.

RESULTS

BMP-2 release profiles were different for CTR+BMP and AMS+BMP. BIC(BRA) and BF(BRA) were significantly increased after 4 weeks compared to 2 weeks for AMS, CTR+BMP and AMS+BMP. However, no differences between the implant types were observed within both healing periods. BF(BAA) for CTR+BMP was smaller than that for CTR and AMS+BMP after 4 weeks. Despite slower BMP-2 release, AMS+BMP did not stimulate bone regeneration. CTR+BMP caused bone resorption at the bone-implant interface.

CONCLUSIONS

BMP-2 functionalized implant surfaces failed to stimulate bone regeneration and osseointegration.

Enhancement of osteoblast biocompatibility on titanium surface with Terrein treatment

Titanium is biocompatible with bodily tissues. However, the formation of ROS on the titanium surfaces might have negative response of the activity of the surroundings cells. Terrein was isolated from Penicullium sp. 20135 and found to reduce the effects of LPS-induced inflammation. This study examined the role of Terrein on the biocompatibility of titanium to determine if it can help improve osseointegration. MC-3T3 E1 cells were grown on titanium surfaces. The biocompatibility of Terrein was examined by adding it directly to the culture media at the indicated concentration. The cells on the titanium surface produced excessive ROS and decreased the activity of Cu/Zn SOD and Mn SOD. Moreover, the cells had higher activity towards oxidative stress molecules, such as MAPK, FAK and iNOS expression. In addition, MC-3T3 E1 osteoblast-like cells promoted osteoclast differentiation but reduced osteoblast differentiation and mineralization on the titanium surface. Interestingly, the cells given the Terrein treatment showed higher resistance towards oxidative stress through the up-regulation of ERK1/2 and FAK activity but the down-regulation of SAPK/JNK and iNOS activity. Moreover, Terrein promoted osteoblast differentiation and bone mineralization to elevate the activity of ALP, SPARC and down-regulate RANKL expression after blocking NF-κB translocation from the cytosol to the nucleus. In conclusion, the presence of Terrein on titanium surfaces increases osteoblast cell growth without inflammation. Moreover, Terrein, as a putative antioxidant agent, may enhance osseointegration by decreasing the level of ROS and having a potentially synergistic effect on osteoblast differentiation.

Adverse effects of the amlodipine on bone healing of the mandibular fracture: an experimental study in rats

BACKGROUND

Calcium channel blockers are effective antihypertensive agents, but they may affect many metabolic processes, including bone metabolism.

PURPOSE

The aim of this study was to evaluate by radiographic, histologic, and biochemical analyses the effects of amlodipine on bone healing of a defect simulating a fracture in mandibular ramus of rats.

METHODS

Fifty male Wistar rats were submitted to the same unilateral surgical procedure simulating a mandibular fracture. Experimental group received oral doses of amlodipine 0.04 mg/rat/day starting 12 days before procedure, while control group received water. Animals were sacrificed at 1, 7, 14, 30, and 90 days postoperatively. Numerical values were submitted to statistical analyses.

RESULTS

Radiographic analysis showed larger radiolucent area into bone defect to the experimental group at the periods of 14 (p = 0.016), 30 (p = 0.009), and 90 (p = 0.028) days. In the histological analysis, the experimental group had a slight delay in the chronology of the repair process. In the histomorphometric analysis, the experimental group presented significant lowering of newly formed bone volume at 7 and 14 days periods (p = 0.049). There was a significant decrease of alkaline phosphatase levels in experimental group in the initial periods (p = 0.049).

CONCLUSIONS

It was concluded that chronic use of amlodipine compromised bone neoformation in the repairing process of surgical defect in the mandibular ramus of rats, but no precluded occurrence of fracture consolidation.

Bioactive SrTiO(3) nanotube arrays: strontium delivery platform on Ti-based osteoporotic bone implants

Development of strontium releasing implants capable of stimulating bone formation and inhibiting bone resorption is a desirable solution for curing osteoporosis. In this work, well-ordered SrTiO(3) nanotube arrays capable of Sr release at a slow rate and for a long time are successfully fabricated on titanium by simple hydrothermal treatment of anodized titania nanotubes. This surface architecture combines the functions of nanoscaled topography and Sr release to enhance osseointegration while at the same time leaving space for loading of other functional substances. In vitro experiments reveal that the SrTiO(3) nanotube arrays possess good biocompatibility and can induce precipitation of hydroxyapatite from simulated body fluids (SBF). This Ti-based implant with SrTiO(3) nanotube arrays is an ideal candidate for osteoporotic bone implants. The proposed method can also be extended to load other biologically useful elements such as Mg and Zn.