Bone tumor-targeted delivery of theranostic 195mPt-bisphosphonate complexes promotes killing of metastatic tumor cells.

Platinum-based drugs such as cisplatin are very potent chemotherapeutics, whereas radioactive platinum (195mPt) is a rich source of low-energy Auger electrons, which kills tumor cells by damaging DNA. Auger electrons damage cells over a very short range. Consequently, 195mPt-based radiopharmaceuticals should be targeted toward â€‹tumors to maximize radiotherapeutic efficacy and minimize Pt-based systemic toxicity. Herein, we show that systemically administered radioactive bisphosphonate-functionalized platinum (195mPt-BP) complexes specifically accumulate in intratibial bone metastatic lesions in mice. The 195mPt-BP complexes accumulate 7.3-fold more effectively in bone 7 days after systemic delivery compared to 195mPt-cisplatin lacking bone-targeting bisphosphonate ligands. Therapeutically, 195mPt-BP treatment causes 4.5-fold more γ-H2AX formation, a biomarker for DNA damage in metastatic tumor cells compared to 195mPt-cisplatin. We show that systemically administered 195mPt-BP is radiotherapeutically active, as evidenced by an 11-fold increased DNA damage in metastatic tumor cells compared to non-radioactive Pt-BP controls. Moreover, apoptosis in metastatic tumor cells is enhanced more than 3.4-fold upon systemic administration of 195mPt-BP vs. radioactive 195mPt-cisplatin or non-radioactive Pt-BP controls. These results provide the first preclinical evidence for specific accumulation and strong radiotherapeutic activity of 195mPt-BP in bone metastatic lesions, which offers new avenues of research on radiotherapeutic killing of tumor cells in bone metastases by Auger electrons.

Calcium phosphate cements: Optimization toward biodegradability.

Synthetic calcium phosphate (CaP) ceramics represent the most widely used biomaterials for bone regenerative treatments due to their biological performance that is characterized by bioactivity and osteoconductive properties. From a clinical perspective, injectable CaP cements (CPCs) are highly appealing, as CPCs can be applied using minimally invasive surgery and can be molded to optimally fill irregular bone defects. Such CPCs are prepared from a powder and a liquid component, which upon mixing form a paste that can be injected into a bone defect and hardens in situ within an appropriate clinical time window. However, a major drawback of CPCs is their poor degradability. Ideally, CPCs should degrade at a suitable pace to allow for concomitant new bone to form. To overcome this shortcoming, control over CPC degradation has been explored using multiple approaches that introduce macroporosity within CPCs. This strategy enables faster degradation of CPC by increasing the surface area available to interact with the biological surroundings, leading to accelerated new bone formation. For a comprehensive overview of the path to degradable CPCs, this review presents the experimental procedures followed for their development with specific emphasis on (bio)material properties and biological performance in pre-clinical bone defect models.

Complement proteins regulating macrophage polarisation on biomaterials.

One of the events occurring when a biomaterial is implanted in an host is the protein deposition onto its surface, which might regulate cell responses. When a biomaterial displays a compromised biocompatibility, distinct complement pathways can be activated to produce a foreign body reaction. In this article, we have designed different types of biomaterial surfaces to study the inflammation process. Here, we used different concentrations of (3-glycidoxypropyl)-trimethoxysilane (GPTMS), an organically-modified alkoxysilane as a precursor for the synthesis of various types of sol-gel materials functionalizing coatings for titanium implants to regulate biological responses. Our results showed that greater GPTMS surface concentrations induced greater secretion of TNF-α and IL-10 on RAW 264.7 macrophages. When implanted into rabbit tibia, osseointegration decreased with higher GPTMS concentrations. Interestingly, higher deposition of complement-related proteins C-reactive protein (CRP) and ficolin-2 (FCN2), two main activators of distinct complement pathways, was observed. Taking all together, inflammatory potential increase seems to be GPTMS concentration-dependent. Our results show that a greater adsorption of complement proteins can condition macrophage polarization.

Comparison of a resorbable magnesium implant in small and large growing-animal models.

Fracture treatment in children needs new implant materials to overcome disadvantages associated with removal surgery. Magnesium-based implants constitute a biocompatible and bioresorbable alternative. In adults and especially in children, implant safety needs to be evaluated. In children the bone turnover rate is higher and implant material might influence growth capacity, and the long-term effect of accumulated particles or ions is more critical due to the host's prolonged post-surgery lifespan. In this study we aimed to investigate the degradation behavior of ZX00 (Mg-0.45Zn-0.45Ca; in wt.%) in a small and a large animal model to find out whether there is a difference between the two models (i) in degradation rate and (ii) in bone formation and in-growth. Our results 6, 12 and 24 weeks after ZX00 implantation showed no negative effects on bone formation and in-growth, and no adverse effects such as fibrotic or sclerotic encapsulation. The degradation rate did not significantly differ between the two growing-animal models, and both showed slow and homogeneous degradation performance. Our conclusion is that small animal models may be sufficient to investigate degradation rates and provide preliminary evidence on bone formation and in-growth of implant materials in a growing-animal model. STATEMENT OF SIGNIFICANCE: The safety of implant material is of the utmost importance, especially in children, who have enhanced bone turnover, more growth capacity and longer postoperative lifespans. Magnesium (Mg)-based implants have long been of great interest in pediatric orthopedic and trauma surgery, due to their good biocompatibility, biodegradability and biomechanics. In the study documented in this manuscript we investigated Mg-Zn-Ca implant material without rare-earth elements, and compared its outcome in a small and a large growing-animal model. In both models we observed bone formation and in-growth which featured no adverse effects such as fibrotic or sclerotic encapsulation, and slow homogeneous degradation performance of the Mg-based implant material.

Porous titanium scaffolds with injectable hyaluronic acid-DBM gel for bone substitution in a rat critical-sized calvarial defect model.

Demineralized bone matrix (DBM) is an allograft bone substitute used for bone repair surgery to overcome drawbacks of autologous bone grafting, such as limited supply and donor-site comorbidities. In view of different demineralization treatments to obtain DBM, we examined the biological performance of two differently demineralized types of DBM, i.e. by acidic treatment using hydrochloric acid (HCl) or treatment with the chelating agent ethylene diamine tetra-acetate (EDTA). First, we evaluated the osteo-inductive properties of both DBMs by implanting the materials subcutaneously in rats. Second, we evaluated the effects on bone formation by incorporating DBM in a hyaluronic acid (HA) gel to fill a porous titanium scaffold for use in a critical-sized calvarial defect model in 36 male Wistar rats. These porous titanium scaffolds were implanted empty or filled with HA gel containing either DBM HCl or DBM EDTA. Ectopically implanted DBM HCl and DBM EDTA did not induce ectopic bone formation over the course of 12 weeks. For the calvarial defects, mean percentages of newly formed bone at 2 weeks were significantly higher for Ti-Empty compared to Ti-HA + DBM HCl, but not compared to Ti-HA + DBM EDTA. Significant temporal bone formation was observed for Ti-Empty and Ti-HA + DBM HCl, but not for Ti-HA + DBM EDTA. At 8 weeks there were no significant differences in values of bone formation between the three experimental constructs. In conclusion, these results showed that, under the current experimental conditions, neither DBM HCl nor DBM EDTA possess osteo-inductive properties. Additionally, in combination with an HA gel loaded in a porous titanium scaffold, DBM HCl and DBM EDTA showed similar amounts of new bone formation after 8 weeks, which were lower than using the empty porous titanium scaffold. Copyright © 2016 John Wiley & Sons, Ltd.

A systematic review on the long-term success of calcium phosphate plasma-spray-coated dental implants.

The objectives of the current review were (1) to systematically appraise, and (2) to evaluate long-term success data of calcium phosphate (CaP) plasma-spray-coated dental implants in clinical trials with at least 5 years of follow-up. To describe the long-term efficacy of functional implants, the outcome variables were (a) percentage annual complication rate (ACR) and (b) cumulative success rate (CSR), as presented in the selected articles. The electronic search yielded 645 titles. On the basis of the inclusion criteria, 8 studies were finally included. The percentage of implants in function after the first year was estimated to be 98.4 % in the maxilla and 99.2 % in the mandible. The estimates of the weighted mean ACR-percentage increased over the years up to 2.6 (SE 0.7) during the fifth year of function for the maxilla and to 9.4 (SE 8.4) for the mandible in the tenth year of function. After 10 years, the mean percentage of successful implants was estimated to be 71.1 % in the maxilla and 72.2 % in the mandible. The estimates seem to confirm the proposed, long-term progressive bone loss pattern of CaP-ceramic-coated dental implants. Within the limits of this meta-analytic approach to the literature, we conclude that: (1) published long-term success data for calcium phosphate plasma-spray-coated dental implants are limited, (2) comparison of the data is difficult due to differences in success criteria among the studies, and (3) long-term CSRs demonstrate very weak evidence for progressive complications around calcium phosphate plasma-spray-coated dental implants.

Toward accelerated bone regeneration by altering poly(D,L-lactic-co-glycolic) acid porogen content in calcium phosphate cement.

This work aimed to compare in vitro degradation of dense PLGA microspheres and milled PLGA particles as porogens within CPC, considering that the manufacturing of milled PLGA is more cost-effective when compared with PLGA microspheres. Additionally, we aimed to examine the effect of porogen amount within CPC/PLGA on degradation and bone formation. Our in vitro results showed no differences between both forms of PLGA particles (as porogens in CPC; spherical for microspheres, irregular for milled) regarding morphology, porosity, and degradation. Using milled PLGA as porogens within CPC/PLGA, we evaluated the effect of porogen amount on degradation and bone forming capacity in vivo. Titanium landmarks surrounded by CPC/PLGA with 30 and 50 wt % PLGA, were implanted in forty femoral bone defects of twenty male Wistar rats. Histomorphometrical results showed a significant temporal decrease in the amount of CPC, for both formulas, and confirmed that 50 wt % PLGA degrades faster than 30 wt%, and allows for a 1.5-fold higher amount of newly formed bone. Taken together, this study demonstrated that (i) milled PLGA particles perform equal to PLGA microspheres, and (ii) tuning of the PLGA content in CPC/PLGA is a feasible approach to leverage material degradation and bone formation.

Influence of surface microstructure and chemistry on osteoinduction and osteoclastogenesis by biphasic calcium phosphate discs.

It has been reported that surface microstructural dimensions can influence the osteoinductivity of calcium phosphates (CaPs), and osteoclasts may play a role in this process. We hypothesised that surface structural dimensions of ≤ 1 µm trigger osteoinduction and osteoclast formation irrespective of macrostructure (e.g., concavities, interconnected macropores, interparticle space) or surface chemistry. To test this, planar discs made of biphasic calcium phosphate (BCP: 80% hydroxyapatite, 20% tricalcium phosphate) were prepared with different surface structural dimensions - either ~ 1 µm (BCP1150) or ~ 2-4 µm (BCP1300) - and no macropores or concavities. A third material was made by sputter coating BCP1150 with titanium (BCP1150Ti), thereby changing its surface chemistry but preserving its surface structure and chemical reactivity. After intramuscular implantation in 5 dogs for 12 weeks, BCP1150 formed ectopic bone in 4 out of 5 samples, BCP1150Ti formed ectopic bone in 3 out of 5 samples, and BCP1300 formed no ectopic bone in any of the 5 samples. In vivo, large multinucleated osteoclast-like cells densely colonised BCP1150, smaller osteoclast-like cells formed on BCP1150Ti, and osteoclast-like cells scarcely formed on BCP1300. In vitro, RAW264.7 cells cultured on the surface of BCP1150 and BCP1150Ti in the presence of osteoclast differentiation factor RANKL (receptor activator for NF-κB ligand) proliferated then differentiated into multinucleated osteoclast-like cells with positive tartrate resistant acid phosphatase (TRAP) activity. However, cell proliferation, fusion, and TRAP activity were all significantly inhibited on BCP1300. These results indicate that of the material parameters tested - namely, surface microstructure, macrostructure, and surface chemistry - microstructural dimensions are critical in promoting osteoclastogenesis and triggering ectopic bone formation.

Osteochondral defect repair using bilayered hydrogels encapsulating both chondrogenically and osteogenically pre-differentiated mesenchymal stem cells in a rabbit model.

OBJECTIVE: To investigate the ability of cell-laden bilayered hydrogels encapsulating chondrogenically and osteogenically (OS) pre-differentiated mesenchymal stem cells (MSCs) to effect osteochondral defect repair in a rabbit model. By varying the period of chondrogenic pre-differentiation from 7 (CG7) to 14 days (CG14), the effect of chondrogenic differentiation stage on osteochondral tissue repair was also investigated. METHODS: Rabbit MSCs were subjected to either chondrogenic or osteogenic pre-differentiation, encapsulated within respective chondral/subchondral layers of a bilayered hydrogel construct, and then implanted into femoral condyle osteochondral defects. Rabbits were randomized into one of four groups (MSC/MSC, MSC/OS, CG7/OS, and CG14/OS; chondral/subchondral) and received two similar constructs bilaterally. Defects were evaluated after 12 weeks. RESULTS: All groups exhibited similar overall neo-tissue filling. The delivery of OS cells when compared to undifferentiated MSCs in the subchondral construct layer resulted in improvements in neo-cartilage thickness and regularity. However, the addition of CG cells in the chondral layer, with OS cells in the subchondral layer, did not augment tissue repair as influenced by the latter when compared to the control. Instead, CG7/OS implants resulted in more irregular neo-tissue surfaces when compared to MSC/OS implants. Notably, the delivery of CG7 cells, when compared to CG14 cells, with OS cells stimulated morphologically superior cartilage repair. However, neither osteogenic nor chondrogenic pre-differentiation affected detectable changes in subchondral tissue repair. CONCLUSIONS: Cartilage regeneration in osteochondral defects can be enhanced by MSCs that are chondrogenically and osteogenically pre-differentiated prior to implantation. Longer chondrogenic pre-differentiation periods, however, lead to diminished cartilage repair.

Gelation and biocompatibility of injectable alginate-calcium phosphate gels for bone regeneration.

An emerging approach toward development of injectable, self-setting, and fully biodegradable bone substitutes involves the combination of injectable hydrogel matrices with a dispersed phase consisting of nanosized calcium phosphate particles. Here, novel injectable composites for bone regeneration have been developed based on the combination of ultrapure alginate as the matrix phase, crystalline CaP [monetite and poorly crystalline hydroxyapatite (HA)] powders as both a dispersed mineral phase and a source of calcium for cross-linking alginate, glucono-delta-lactone (GDL) as acidifier and glycerol as both plasticizer and temporary sequestrant. The composites were maximized with respect to CaP content to obtain the highest amount of osteoconductive filler. The viscoelastic and physicochemical properties of the precursor compounds and composites were analyzed using rheometry, elemental analysis (for calcium release and uptake), acidity [by measuring pH in simulated body fluid (SBF)], general biocompatibility (subcutaneous implantation in rabbits), and osteocompatibility (implantation in femoral condyle bone defect of rabbits). The gelation of the resulting composites could be controlled from seconds to tens of minutes by varying the solubility of the CaP phase (HA vs. monetite) or amount of GDL. All composites mineralized extensively in SBF for up to 11 days. In vivo, the composites also disintegrated upon implantation in subcutaneous or bone tissue, leaving behind less degradable but osteoconductive CaP particles. Although the composites need to be optimized with respect to the available amount of calcium for cross-linking of alginate, the beneficial bone response as observed in the in vivo studies render these gels promising for minimally invasive applications as bone-filling material.

Porous calcium phosphate cement for alveolar bone regeneration.

The present study aimed to provide information on material degradation and subsequent alveolar bone formation, using composites consisting of calcium phosphate cement (CPC) and poly(lactic-co-glycolic) acid (PLGA) with different microsphere morphology (hollow vs dense). In addition to the plain CPC-PLGA composites, loading the microspheres with the growth factors platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF) was investigated. A total of four different CPC composites were applied into one-wall mandible bone defects in beagle dogs in order to evaluate them as candidates for alveolar bone regeneration. These composites consisted of CPC and hollow or dense PLGA microspheres, with or without the addition of PDGF-IGF growth factor combination (CPC-hPLGA, CPC-dPLGA, CPC-hPLGAGF , CPC-dPLGAGF ). Histological evaluation revealed significantly more bone formation in CPC-dPLGA than in CPC-hPLGA composites. The combination PDGF-IGF enhanced bone formation in CPC-hPLGA materials, but significantly more bone formation occurred when CPC-dPLGA was used, with or without the addition of growth factors. The findings demonstrated that CPC-dPLGA composite was the biologically superior material for use as an off-the-shelf material, due to its good biocompatibility, enhanced degradability and superior bone formation.

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.

Incorporation of bioactive glass in calcium phosphate cement: material characterization and in vitro degradation.

Calcium phosphate cements (CPCs) have been widely used as an alternative to biological grafts due to their excellent osteoconductive properties. Although degradation has been improved by using poly(D,L-lactic-co-glycolic) acid (PLGA) microspheres as porogens, the biological performance of CPC/PLGA composites is insufficient to stimulate bone healing in large bone defects. In this context, the aim of this study was to investigate the effect of incorporating osteopromotive bioactive glass (BG; up to 50 wt %) on setting properties, in vitro degradation behavior and morphological characteristics of CPC/BG and CPC/PLGA/BG. The results revealed that the initial and final setting time of the composites increased with increasing amounts of incorporated BG. The degradation test showed a BG-dependent increasing effect on pH of CPC/BG and CPC/PLGA/BG pre-set scaffolds immersed in PBS compared to CPC and CPC/PLGA equivalents. Whereas no effects on mass loss were observed for CPC and CPC/BG pre-set scaffolds, CPC/PLGA/BG pre-set scaffolds showed an accelerated mass loss compared with CPC/PLGA equivalents. Morphologically, no changes were observed for CPC and CPC/BG pre-set scaffolds. In contrast, CPC/PLGA and CPC/PLGA/BG showed apparent degradation of PLGA microspheres and faster loss of integrity for CPC/PLGA/BG pre-set scaffolds compared with CPC/PLGA equivalents. Based on the present in vitro results, it can be concluded that BG can be successfully introduced into CPC and CPC/PLGA without exceeding the setting time beyond clinically acceptable values. All injectable composites containing BG had suitable handling properties and specifically CPC/PLGA/BG showed an increased rate of mass loss. Future investigations should focus on translating these findings to in vivo applications.

Incorporation of bioactive glass in calcium phosphate cement: An evaluation.

Bioactive glasses (BGs) are known for their unique ability to bond to living bone. Consequently, the incorporation of BGs into calcium phosphate cement (CPC) was hypothesized to be a feasible approach to improve the biological performance of CPC. Previously, it has been demonstrated that BGs can successfully be introduced into CPC, with or without poly(d,l-lactic-co-glycolic) acid (PLGA) microparticles. Although an in vitro physicochemical study on the introduction of BG into CPC was encouraging, the biocompatibility and in vivo bone response to these formulations are still unknown. Therefore, the present study aimed to evaluate the in vivo performance of BG supplemented CPC, either pure or supplemented with PLGA microparticles, via both ectopic and orthotopic implantation models in rats. Pre-set scaffolds in four different formulations (1: CPC; 2: CPC/BG; 3: CPC/PLGA; and 4: CPC/PLGA/BG) were implanted subcutaneously and into femoral condyle defects of rats for 2 and 6 weeks. Upon ectopic implantation, incorporation of BG into CPC improved the soft tissue response by improving capsule and interface quality. Additionally, the incorporation of BG into CPC and CPC/PLGA showed 1.8- and 4.7-fold higher degradation and 2.2- and 1.3-fold higher bone formation in a femoral condyle defect in rats compared to pure CPC and CPC/PLGA, respectively. Consequently, these results highlight the potential of BG to be used as an additive to CPC to improve the biological performance for bone regeneration applications. Nevertheless, further confirmation is necessary regarding long-term in vivo studies, which also have to be performed under compromised wound-healing conditions.

Non-glycosylated BMP-2 can induce ectopic bone formation at lower concentrations compared to glycosylated BMP-2.

Bone morphogenic protein-2 (BMP-2) is a well-known growth factor that can improve the biological performance of bone substitute materials. BMP-2 produced via bacterial expression systems are non-glycosylated (ng) whereas native and recombinant equivalents produced in mammalian cell expression systems are glycosylated (g) proteins. ngBMP-2 is less soluble, resulting in lower BMP-2 release from carriers as used as bone substitute materials. This seems promising for reducing the amount of included growth factor in bone substitute materials. Hence, it was hypothesized that ngBMP-2 would induce formation of the same amount of bone at an ectopic site at lower dosage as gBMP-2. To that end, gBMP-2 and ngBMP-2 were firstly in vitro comparatively evaluated for biological activity and release from a calcium phosphate (CaP) based bone substitute material. Thereafter, an ectopic implantation model in rats was used, in which gBMP-2 and ngBMP2 were loaded in various dosages (2-20 µg/implant) on the CaP-based bone substitute material and implanted for 4 and 12 weeks. The results revealed that both the in vitro biological activity of and the in vitro release of ngBMP-2 are lower compared to gBMP2. Upon ectopic implantation, however, ngBMP-2 loaded implants induced more bone formation at lower concentrations from 4-weeks onward compared to gBMP-2 equivalents, indicating the value of ngBMP-2 as a potential alternative for mammalian produced recombinant BMP-2 for bone regenerative therapies.

Predictive value of ridge dimensions on autologous bone graft resorption in staged maxillary sinus augmentation surgery using Cone-Beam CT.

INTRODUCTION: No studies are available that provide predictive parameters regarding the expected amount of resorption after maxillary sinus augmentation surgery using autologous bone grafts. Therefore, the aim of this study was to determine parameters influencing the outcome of the bone graft resorption process. MATERIAL AND METHODS: In 20 patients, three-dimensional analysis of alveolar ridge dimensions and bone graft volume change in the atrophic posterior maxilla was performed by Cone-Beam Computerized Tomography imaging. Ridge dimensions were assessed before maxillary sinus augmentation surgery. Bone graft volumes were compared after maxillary sinus floor augmentation surgery and a graft healing interval of several months. To analyze the relation between bone volume changes with the independent variables, patients' gender, age, alveolar crest height and width, and graft healing time interval, a multi-level extension of linear regression was applied. RESULTS: A residual bone height of 6.0 mm (SD = 3.6 mm) and 6.2 mm (SD = 3.6 mm) was found at the left and right sides, respectively. Moreover, alveolar bone widths of 6.5 mm (SD = 2.2 mm) and 7.0 mm (SD = 2.3 mm) at the premolars, and 8.8 mm (SD = 2.2 mm) and 8.9 mm (SD = 2.5 mm) at the molars regions were found at the left and right site, respectively. Bone graft volume decreased by 25.0% (SD = 21.0%) after 4.7 months (SD = 2.7, median = 4.0 months) of healing time. The variables "age" (P = 0.009) and mean alveolar crest "bone height" (P = 0.043), showed a significant influence on bone graft resorption. A decrease of 1.0% (SE = 0.3%) of bone graft resorption was found for each year the patient grew older, and an increase in bone graft resorption of 1.8% (SE = 0.8%) was found for each mm of original bone height before sinus floor augmentation. CONCLUSIONS: Graft resorption occurs when using autologous bone grafts for maxillary sinus augmentation. Alveolar crest bone height and patient age have a significant effect on graft resorption, with increased resorption for higher alveolar crest bone height and decreased resorption for older patients. Consequently, patient characteristics that affect the process of bone graft resorption should be given full consideration, when performing sinus augmentation surgery.

Maxillary sinus augmentation with microstructured tricalcium phosphate ceramic in sheep.

OBJECTIVE: The objective of this study was to evaluate the biological performance of osteoinductive microstructured tricalcium phosphate (MSTCP) particles in maxillary sinus floor augmentation surgery in sheep. MATERIAL AND METHODS: Sinus floor augmentation was performed in eight Swifter sheep. In each animal, the maxillary sinus floor was unilaterally augmented with MSTCP particles. Computed tomography (CT) imaging and histological analyses were performed after 12 weeks of implantation. RESULTS: Maxillofacial CT, histology, histomorphometrical analysis and sequential polychrome fluorescent labeling indicated that MSTCP particles provided a scaffold for cell ingrowth and bone formation. After a 12-week implantation period, the sinuses grafted with MSTCP showed an increased bone height of 6 mm and a mean total bone volume of 43%, with significant degradation of MSTCP particles. CONCLUSION: MSTCP particles represent a suitable bone substitute material for maxillary sinus floor augmentation surgery.

Biomimetic modification of synthetic hydrogels by incorporation of adhesive peptides and calcium phosphate nanoparticles: in vitro evaluation of cell behavior.

The ultimate goal of this work was to develop a biocompatible and biomimetic in situ crosslinkable hydrogel scaffold with an instructive capacity for bone regenerative treatment. To this end, synthetic hydrogels were functionalized with two key components of the extracellular matrix of native bone tissue, i.e. the three-amino acid peptide sequence RGD (which is the principal integrin-binding domain responsible for cell adhesion and survival of anchorage-dependent cells) and calcium phosphate (CaP) nanoparticles in the form of hydroxyapatite (which are similar to the inorganic phase of bone tissue). Rat bone marrow osteoblast-like cells (OBLCs) were encapsulated in four different biomaterials (plain oligo(poly(ethylene glycol) fumarate) (OPF), RGD-modified OPF, OPF enriched with CaP nanoparticles and RGD-modified OPF enriched with CaP nanoparticles) and cell survival, cell spreading, proliferation and mineralized matrix formation were determined via cell viability assay, histology and biochemical analysis for alkaline phosphatase activity and calcium. This study showed that RGD peptide sequences promoted cell spreading in OPF hydrogels and hence play a crucial role in cell survival during the early stage of culture, whereas CaP nanoparticles significantly enhanced cell-mediated hydrogel mineralization. Although cell spreading and proliferation activity were inhibited, the combined effect of RGD peptide sequences and CaP nanoparticles within OPF hydrogel systems elicited a better biological response than that of the individual components. Specifically, both a sustained cell viability and mineralized matrix production mediated by encapsulated OBLCs were observed within these novel biomimetic composite systems.

A novel implantation model for evaluation of bone healing response to dental implants: the goat iliac crest.

OBJECTIVES: Despite the availability of numerous animal models for testing the biological performance of dental and orthopedic implants, the selection of a suitable model is complex. This paper presents a new model for objective and standardized evaluation of bone responses to implants using the iliac crest in goats. MATERIAL AND METHODS: The feasibility of the iliac crest model regarding anatomy and implant positioning was determined using two cadaveric specimens and the bone structure was evaluated and compared with that of the goat femoral condyle. Additionally, the validity of the model was tested by performing an in vivo study. RESULTS: By means of a rather simple, safe, fast and reproducible surgical procedure, the iliac crest in goats could be approached and allowed the implantation of maximally five dental implants per iliac crest. Because of the bilateral implantation possibility, statistical comparisons between groups on either side of the goat could be performed, resulting in a high statistical power, and hence a reduction in the number of animals required to obtain significant data. CONCLUSIONS: In terms of surgical approach, anatomy and implant positioning, the iliac crest is the preferred model over the femoral condyle model. The iliac crest implantation model is suitable for evaluation of the osteogenic response to bone implant materials and represents a justified and deliberate alternative to the already existing animal models.

Bone regenerative properties of rat, goat and human platelet-rich plasma.

To explore the reported contradictory osteogenic capacity of platelet-rich plasma (PRP), the aim of the study was to examine and compare the bone regenerative effect of: PRPs of different species (rat, goat, human); human bone graft (HB) vs. HB combined with human PRP (HB+hPRP); and HB+hPRP vs. synthetic hydroxyapatite-tricalcium phosphate bone substitute combined with hPRP (HA/TCP+hPRP). For this purpose, 72 implants, divided into 6 groups (n=6) were inserted in critical-sized defects of immunodeficient rats. After 2 and 4 weeks, descriptive and quantitative histological, and micro-CT analyses were performed on the specimens. Rat and goat PRP combined with HA/TCP did not enhance bone regeneration compared with HA/TCP. In contrast, human PRP combined with HA/TCP resulted in significantly increased bone fill compared to HA/TCP. The addition of human PRP to human bone graft increased significantly the amount of newly formed bone after 2 weeks. HB+hPRP demonstrated enhanced bone healing compared to HA/TCP+hPRP. In conclusion, rat and goat PRP had no effect on bone formation. Human PRP improved the initial osteogenic response of human bone graft. Human PRP combined with human bone graft had better osteogenic capacity than human PRP combined with synthetic bone substitute.