Guided bone regeneration in osteoporotic conditions following treatment with zoledronic acid

Evaluation of Peri-Implant Bone Repair in Ovariectomized Rats Submitted to the Implant Placement Functionalized with Anti-Sclerostin

(1) Background: The challenges in Implantology involve the development of alternative methods to enhance bone repair in patients with systemic conditions, such as osteoporosis. This study aimed to evaluate the effect of a local anti-sclerostin monoclonal antibody (Scl-Ab) on the functionalization of titanium implant surfaces through a dip-coating technique in peri-implant bone repair. (2) Methods: A total of 32 female rats were separated into four groups (n = 8): SHAM NT (Sham surgery), OVX NT (ovariectomy), SHAM Scl-Ab (SHAM; implants functionalized with Scl-Ab), and OVX Scl-Ab (OVX; implants functionalized with Scl-Ab). Implant surgery was executed 30 days after ovariectomy, and the rats were euthanized 28 days postoperatively. The right tibia was used for removal torque and RT-PCR, while the left tibia was collected for micro-CT and laser confocal microscopy. (3) Results: Functionalization with Scl-Ab significantly increased the gene expression of bone markers, especially ALP, in the SHAM Scl-Ab group compared to the other groups (p < 0.05). (4) Conclusions: Some parameters of this study indicate that implants functionalized with anti-sclerostin bone anabolic drug enhance peri-implant bone repair, especially in healthy rats. However, more studies must be carried out to confirm the therapeutic benefits of this approach.

Cone beam computed tomography outcomes in patients diagnosed with compromised bone health undergoing dental implant therapy and bone augmentation

STATEMENT OF PROBLEM

Studies examining mid-term treatment outcomes of implant placement with bone augmentation in patients with compromised bone health are lacking.

PURPOSE

The purpose of this prospective, nonrandomized cohort study was to evaluate the cone bean computed tomography (CBCT) outcomes of implant placement with bone augmentation in postmenopausal women.

MATERIAL AND METHODS

For this best practice, standard of care study, 78 participants received 1 test implant along with 1 or a combination of 3 bone augmentation procedures: particulate graft, expansion, or block graft. Participants were categorized as healthy (n=49) or bone compromised (n=29). Using CBCT scans made preoperatively, immediately postoperatively, and 2 years postoperatively, the augmented alveolar ridge widths were measured in a buccolingual (BL) dimension 2 mm and 6 mm apical to the coronal aspect of the implant's rough surface. Additionally, peri-implant bone height was measured on the mesial and distal implant surfaces at the mid-alveolar aspect of the ridge using a coronal panoramic view.

RESULTS

Both study groups exhibited an increase in horizontal BL measurements at the 2-mm and 6-mm landmarks from preoperative to immediate postoperative time points and a minimal decrease from intermediate postoperative to 2 years postoperative. The mean proximal height decreased over time in healthy participants but did not show a significant change in participants with compromised bone. The linear mixed effects model results revealed that the mean difference between groups significantly decreased over time at the 2-mm landmark (P<.05); however, no significant group-time interactions were found for the BL width at the 6-mm landmark and proximal height measurements (P=.627).

CONCLUSIONS

Mid-term CBCT measurements showed significant bone augmentation immediately after surgery and 2 years after surgery and stable proximal bone adjacent to implants in postmenopausal women diagnosed with compromised bone health.

Zoledronic Acid Inhibits Lipopolysaccharide-Induced Osteoclastogenesis by Suppressing Macrophage NLRP3-Mediated Autophagy Pathway

INTRODUCTION

Inflammatory factors leading to bone loss significantly increase the risk of tooth loosening or implantation failure. Zoledronic acid (ZOL) is a widely used medication for effectively inhibiting excessive bone destruction, but its effect on alleviating inflammatory bone loss remains to be elucidated. In this study, we investigated whether ZOL alleviates inflammatory bone resorption through immunomodulatory effect.

METHODS

The viability of the cells was evaluated by Cell Counting Kit 8 (CCK8) assay. Osteoclast (OC) differentiation and function were determined by tartrate-resistant acid phosphatase (TRAP) staining and bone resorption pits assays, respectively. Autophagosomes and actin ring structures of OC were observed using transmission electron microscopy (TEM) and F-actin ring staining, respectively. The microstructure in mice maxillary alveolar bone model was observed by micro computed tomography (Miro-CT). Reverse transcription-quantitative PCR (RT-qPCR) to detect the mRNA expression of osteoclast-related genes and Western blot (WB) analysis to evaluate the protein expression levels of autophagy-related proteins and the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3)-related proteins in pre-OCs.

RESULTS

The findings indicated that ZOL hindered lipopolysaccharide (LPS)-mediated OC differentiation, formation, bone resorption activity and autophagosome levels. Furthermore, ZOL diminished the expression of genes associated with OC. And the expression of proteins ATG7, LC3II, Beclin1, NLRP3-related proteins and tumor necrosis factor-α (TNF-α) protein were markedly decreased while P62 was increased, especially in the 1 μM ZOL group or MCC950 + ZOL group.

CONCLUSIONS

ZOL has a certain immunomodulatory effect that exhibits anti-inflammatory properties at lower concentrations, which can weaken LPS-induced OCs differentiation and function, and NLRP3-mediated autophagy pathway may participate in this process.

Sonification of Deproteinized Bovine Bone Functionalized with Genistein Enhances Bone Repair in Peri-Implant Bone Defects in Ovariectomized Rats

Estrogen deficiency is one of several contributing factors to catabolic changes in bone surrounding dental implants, impairing bone repair in defects requiring bone regeneration. Functionalizing bone substitutes is an alternative approach among various strategies to address this challenge. In this study, the aim was to evaluate the effect of functionalizing deproteinized bovine bone (Bio-Oss®, BO) with genistein via sonication on peri-implant bone defects in ovariectomized rats. The animals were randomly distributed according to the treatment into the following four groups (n = 10): BO sonicated with genistein (BOS + GEN), BO sonicated alone (BOS), untreated BO (BO), and blood clot only (CLOT). After twenty-eight days, implant removal torque was determined, and the peri-implant bone parameters were calculated based on computed microtomography. Additionally, the gene expression of bone turnover markers was evaluated. As a main result, the functionalization with genistein increased implant removal torque and the peri-implant bone volume in the BOS + GEN group compared to both BOS and BO groups (both p < 0.05). These findings suggest that the sonification of deproteinized bovine bone functionalized with genistein improves bone repair in peri-implant bone defects in ovariectomized rats.

CREB1 alleviates the apoptosis and potentiates the osteogenic differentiation of zoledronic acid-treated human periodontal ligament stem cells via up-regulating VEGF

Periodontitis represents a severe inflammatory illness in tooth supporting tissue. It has been supported that cAMP response element binding protein 1 (CREB1), a common transcription factor, extensively participates in osteogenic differentiation. Here, the current study was to look into the impacts of CREB1 on the process of periodontitis and its possible action mechanism. After human periodontal ligament stem cells (PDLSCs) were challenged with zoledronic acid (ZA), CREB1 expression was examined with RT-qPCR and western blotting. CCK-8 assay appraised cell activity. Following CREB1 elevation or/and vascular endothelial growth factor (VEGF) silencing in ZA-treated PDLSCs, CCK-8 and TUNEL assays separately estimated cell viability and apoptosis. Western blotting tested the expression of apoptosis- and osteogenic differentiation-associated proteins. ALP staining measured PDLSCs osteogenic ability and ARS staining estimated mineralized nodule formation. JASPAR predicted the potential binding of CREB1 with VEGF promoter, which was then testified by ChIP and luciferase reporter assays. RT-qPCR and western blotting tested VEGF expression. CREB1 expression was declined in ZA-exposed PDLSCs and CREB1 elevation exacerbated the viability and osteogenic differentiation while obstructed the apoptosis of PDLSCs. Additionally, CREB1 bond to VEGF promoter and transcriptionally activated VEGF expression. Further, VEGF absence partially stimulated the apoptosis while suppressed the osteogenic differentiation of CREB1-overexpressing PDLSCs treated by ZA. To be concluded, CREB1 might activate VEGF transcription to obstruct the apoptosis while contribute to the osteogenic differentiation of ZA-treated PDLSCs.

Influence of bisphosphonate treatment on bone substitute performance in osteoporotic conditions

OBJECTIVE

Considering the elevated number of osteoporotic patients in need of bone graft procedures, we here evaluated the effect of alendronate (ALN) treatment on the regeneration of bone defects in osteoporotic rats. Bone formation was histologically and histomorphometrically assessed in rat femoral condyle bone defects filled with bone graft (Bio-Oss®) or left empty.

METHODS

Male Wistar rats were induced osteoporotic through orchidectomy (ORX) and SHAM-operated. The animals were divided into three groups: osteoporotic (ORX), osteoporotic treated with ALN (ORX + ALN) and healthy (SHAM). Six weeks after ORX or SHAM surgeries, bone defects were created bilaterally in femoral condyles; one defect was filled with Bio-Oss® and the other one left empty. Bone regeneration within the defects was analyzed by histology and histomorphometry after 4 and 12 weeks.

RESULTS

Histological samples showed new bone surrounding Bio-Oss® particles from week 4 onward in all three groups. At week 12, the data further showed that ALN treatment of osteoporotic animals enhanced bone formation to a 10-fold increase compared to non-treated osteoporotic control. Bio-Oss® filling of the defects promoted bone formation at both implantation periods compared to empty controls.

CONCLUSION

Our histological and histomorphometric results demonstrate that the enteral administration of alendronate under osteoporotic bone conditions leverages bone defect regeneration to a level comparable to that in healthy bone. Additionally, Bio-Oss® is an effective bone substitute, increasing bone formation, and acting as an osteoconductive scaffold guiding bone growth in both healthy and osteoporotic bone conditions.

SIGNIFICANCE

Based on the results of this study, enteral use of ALN mitigates adverse effects of an osteoporotic condition on bone defect regeneration.

Dental implants osseointegration in patients with osteoporosis

The successful use of surgical and medical methods of jaw bone tissue restoration has been convincingly confirmed in clinical practice. At the same time, technologies are being developed to improve the osseointegration of dental implants in patients with osteoporosis. The use of various implant coatings, as well as systemic therapy, demonstrate the emergence of new directions in the treatment of patients with partial or complete secondary edentulism with concomitant osteoporosis. This trend is relevant in modern medicine . Information was obtained from the PubMed database, using the keywords «osteoporosis» and «osseointegration» and «dental implantation» and «zoledronic acid» from 2016 to 2022. Articles were selected based on experimental work. Numerous studies have shown that bone tissue is an effective indicator of osteoporotic changes. The main changes in bone tissue in osteoporosis are emphasized - a decrease in bone volume, deterioration of the microarchitecture of the trabecular bone and processes that prevent osseointegration - loss of bone mass, a significant decrease in the percentage of contact in the implant-bone complex. Methods of dealing with the negative impact on the operation of dental implantation have been identified. In a review of studies on the systemic administration of drugs based on bisphosphonates, an increase in the osseointegration of dental implants was revealed, the systemic administration of zoledronic acid preparations significantly increased the formation of new bone, which in turn contributed to the elimination of such a negative effect of osteoporosis as bone resorption. In addition to the systemic administration of bisphosphonates, experimental studies describe the topical application of bisphosphonates in the form of various implant coatings. Topical application of bisphosphonates also contributed to increased osseointegration. Microstructured coated implants showed less marginal bone loss compared to uncoated implants. Conclusion. The use of dental implants with modified macro- and microrelief, as well as systemic drug therapy, remains the main direction of scientific research that contributes to the optimization of osseointegration of dental implants.

Volumetric analysis of the periodontal microstructure under antiresorptive therapy: an experimental study in rabbits

OBJECTIVES

The objective of this study was to volumetrically assess changes in the periodontal microstructure under antiresorptive therapy.

MATERIALS AND METHODS

Microtomographic scans from a total of 9 Dutch Belted rabbits having been randomly allocated to either the intravenous administration of amino-bisphosphonate (zoledronic acid) (Za) (n = 5) or a negative control group (nZa) (n = 4) were obtained at 10 months following a repeated drug administration. A quantification of the periodontal space thickness (P.Th) of both maxillary and mandibular most posterior premolars, as well as of the 2nd molars was performed. Bone micromorphometry was assessed by means of bone volume per total volume (BV/TV), the bone mineral density (BMD), trabecular thickness (Tb.Th), trabecular number (Tb.N), bone surface (BS), and the specific bone surface (BS/BV).

RESULTS

Za was associated with significantly higher P.Th (P = 0.010), which was most pronounced in the upper jaw. Bone micromorphometry revealed no significant differences among the two groups, i.e., Za and nZa, for all the investigated parameters.

CONCLUSIONS

Volumetric analysis revealed that antiresorptive therapy was associated with periodontal space widening, whereas major effects on the bone micro-morphology could not be observed.

CLINICAL RELEVANCE

A deep understanding of specific periodontal and alveolar bone alterations in patients under antiresorptive therapy might help to prevent the onset of medication-related osteonecrosis of the jaw.

A long-lasting guided bone regeneration membrane from sequentially functionalised photoactive atelocollagen

The fast degradation of collagen-based membranes in the biological environment remains a critical challenge, resulting in underperforming Guided Bone Regeneration (GBR) therapy leading to compromised clinical results. Photoactive atelocollagen (AC) systems functionalised with ethylenically unsaturated monomers, such as 4-vinylbenzyl chloride (4VBC), have been shown to generate mechanically competent materials for wound healing, inflammation control and drug delivery, whereby control of the molecular architecture of the AC network is key. Building on this platform, the sequential functionalisation with 4VBC and methacrylic anhydride (MA) was hypothesised to generate UV-cured AC hydrogels with reduced swelling ratio, increased proteolytic stability and barrier functionality for GBR therapy. The sequentially functionalised atelocollagen precursor (SAP) was characterised via TNBS and ninhydrin colourimetric assays, circular dichroism and UV-curing rheometry, which confirmed nearly complete consumption of collagen's primary amino groups, preserved triple helices and fast (< 180 s) gelation kinetics, respectively. Hydrogel's swelling ratio and compression modulus were adjusted depending on the aqueous environment used for UV-curing, whilst the sequential functionalisation of AC successfully generated hydrogels with superior proteolytic stability in vitro compared to both 4VBC-functionalised control and the commercial dental membrane Bio-Gide®. These in vitro results were confirmed in vivo via both subcutaneous implantation and a proof-of-concept study in a GBR calvarial model, indicating integrity of the hydrogel and barrier defect, as well as tissue formation following 1-month implantation in rats. STATEMENT OF SIGNIFICANCE: Collagen-based membranes remain a key component in Guided Bone Regeneration (GBR) therapy, but their properties, e.g. proteolytic stability and soft tissue barrier functionality, are still far from optimal. This is largely attributed to the complex molecular configuration of collagen, which makes chemical accessibility and structure-function relations challenging. Here, we fabricated a UV-cured hydrogel network of atelocollagen, whereby triple helices were sequentially functionalised with two distinct ethylenically unsaturated monomers. The effects of the sequential functionalisation and UV-curing on the macroscopic properties, degradation behaviour and GBR capability were investigated in vitro and in vivo. The results highlight the key role of the sequential functionalisation and provide important insights for the design of future, longer-lasting resorbable membranes for GBR therapy.

Texturized P(VDF-TrFE)/BT membrane enhances bone neoformation in calvaria defects regardless of the association with photobiomodulation therapy in ovariectomized rats

OBJECTIVES

The purpose of this investigation was to evaluate in vivo the response of bone tissue to photobiomodulation when associated with texturized P(VDF-TrFE)/BT in calvaria defects of ovariectomized rats.

MATERIALS AND METHODS

Wistar Hannover rats were submitted to ovariectomy/control surgery. Calvaria bone defects of 5-mm diameter were performed after 90 days of ovariectomy. The animals were divided into OVX (without laser (L) and membrane), OVX + P(VDF-TrFE)/BT, OVX + P(VDF-TrFE)/BT + L, and OVX + PTFE + L. It was utilized a low-intensity gallium-aluminum-arsenide laser (GaAlAs) with 780-nm wavelength and 30-J/cm² energy density in 12 sessions (120 s). Thirty days after the bone defect the animals were euthanized for histological, microtomographic, and molecular evaluation. Quantitative analysis was analyzed by statistical software for p < 0.05.

RESULTS

Histological parameters showed bone tissue formation at the borders of all group defects. The association of photobiomodulation and texturized P(VDF-TrFE)/BT was not synergistic and did not show significant changes in morphometric analysis and biomarkers gene expression. Nevertheless, texturized P(VDF-TrFE)/BT membrane enhanced bone repair regardless of the association with photobiomodulation therapy, with an increase of connectivity density when compared to the OVX + PTFE + L group. The association of photobiomodulation therapy and PTFE was synergistic, increasing the expression of Runx2, Alp, Bsp, Bglap, Sp7, and Rankl, even though not enough to reflect significance in the morphometric parameters.

CONCLUSIONS

The utilization of texturized P (VDF-TrFE)/BT, regardless of the association with photobiomodulation therapy, enhanced bone repair in an experimental model of osteoporosis.

Zoledronic acid modulates osteoclast apoptosis through activation of the NF-κB signaling pathway in ovariectomized rats

Bone mass loss (osteoporosis) seen in postmenopausal women is an adverse factor for implant denture. Using an ovariectomized rat model, we studied the mechanism of estrogen-deficiency-caused bone loss and the therapeutic effect of Zoledronic acid. We observed that ovariectomized-caused resorption of bone tissue in the mandible was evident at four weeks and had not fully recovered by 12 weeks post-ovariectomized compared with the sham-operated controls. Further evaluation with a TUNEL assay showed ovariectomized enhanced apoptosis of osteoblasts but inhibited apoptosis of osteoclasts in the mandible. Zoledronic acid given subcutaneously as a single low dose was shown to counteract both of these ovariectomized effects. Immunohistochemical staining showed that ovariectomized induced the protein levels of RANKL and the 65-kD subunit of the NF-κB complex mainly in osteoclasts, as confirmed by staining for TRAP, a marker for osteoclasts, whereas zoledronic acid inhibited these inductions. Western blotting showed that the levels of RANKL, p65, as well as the phosphorylated form of p65, and IκB-α were all higher in the ovariectomized group than in the sham and ovariectomized + zoledronic acid groups at both the 4th- and 12th-week time points in the mandible. These data collectively suggest that ovariectomized causes bone mass loss by enhancing apoptosis of osteoblasts and inhibiting apoptosis of osteoclasts. In osteoclasts, these cellular effects may be achieved by activating RANKL-NF-κB signalling. Moreover, zoledronic acid elicits its therapeutic effects in the mandible by counteracting these cellular and molecular consequences of ovariectomized.

The Bone Regeneration Capacity of BMP-2 + MMP-10 Loaded Scaffolds Depends on the Tissue Status

Biomaterials-mediated bone formation in osteoporosis (OP) is challenging as it requires tissue growth promotion and adequate mineralization. Based on our previous findings, the development of scaffolds combining bone morphogenetic protein 2 (BMP-2) and matrix metalloproteinase 10 (MMP-10) shows promise for OP management. To test our hypothesis, scaffolds containing BMP-2 + MMP-10 at variable ratios or BMP-2 + Alendronate (ALD) were prepared. Systems were characterized and tested in vitro on healthy and OP mesenchymal stem cells and in vivo bone formation was studied on healthy and OP animals. Therapeutic molecules were efficiently encapsulated into PLGA microspheres and embedded into chitosan foams. The use of PLGA (poly(lactic-co-glycolic acid)) microspheres as therapeutic molecule reservoirs allowed them to achieve an in vitro and in vivo controlled release. A beneficial effect on the alkaline phosphatase activity of non-OP cells was observed for both combinations when compared with BMP-2 alone. This effect was not detected on OP cells where all treatments promoted a similar increase in ALP activity compared with control. The in vivo results indicated a positive effect of the BMP-2 + MMP-10 combination at both of the doses tested on tissue repair for OP mice while it had the opposite effect on non-OP animals. This fact can be explained by the scaffold’s slow-release rate and degradation that could be beneficial for delayed bone regeneration conditions but had the reverse effect on healthy animals. Therefore, the development of adequate scaffolds for bone regeneration requires consideration of the tissue catabolic/anabolic balance to obtain biomaterials with degradation/release behaviors suited for the existing tissue status.

Development of Zoledronic Acid Containing Biomaterials for Enhanced Guided Bone Regeneration

In recent years, biomaterial-based treatments, also called guided bone regeneration (GBR), which aim to establish a bone regeneration site and prevent the migration of gingival connective tissue and / or peripheral epithelium through the defective area during periodontal surgical procedures have come to the fore. In this report, we have developed a nanoparticle bearing thermosensitive in situ gel formulation of Pluronic F127 and poly(D,L-lactic acid) based membrane to reveal their utilization at GBR by in-vivo applications. In addition, the encouragement of the bone formation in defect area via inhibition of osteoclastic activity is intended by fabrication these biodegradable biomaterials at a lowered Zoledronic Acid (ZA) dose. Both of the developed materials remained stable under specified stability conditions (25 °C, 6 months) and provided the extended release profile of ZA. The in-vivo efficacy of nanoparticle bearing in situ gel formulation, membrane formulation and simultaneous application for guided bone regeneration was investigated in New Zealand female rabbits with a critical size defect of 0.5 × 0.5 cm in the tibia bone for eight weeks. Based on the histopathological findings, lamellar bone and primarily woven bone formations were observed after 8 weeks of post-implantation of both formulations, while fibrosis was detected only in the untreated group. Lamellar bone growth was remarkably achieved just four weeks after the simultaneous application of formulations. Consequently, the simultaneous application of ZA-membrane and ZA-nanoparticles loaded in-situ gel formulations offers enhanced and faster GBR therapy alternatives.

Hydrophilic titanium surface modulates early stages of osseointegration in osteoporosis

OBJECTIVE

Using a mouse osteoporotic model, this study aimed to determine the influence of hydrophilic titanium surfaces on gene expression and bone formation during the osseointegration process.

BACKGROUND

Based on the previous evidence, it is plausible to assume that osteoporotic bone has a different potential of bone healing. Therefore, implant surface modification study that aims at enhancing bone formation to further improve short- and long-term clinical outcomes in osteoporosis is necessary.

MATERIAL AND METHODS

Fifty female, 3-month-old mice were included in this study. Osteoporosis was induced by ovariectomy (OVX, test group) in 25 mice. The further 25 mice had ovaries exposed but not removed (SHAM, control group). Seven weeks following the ovariectomy procedures, one customized implant (0.7 × 8 mm) of each surface was placed in each femur for both groups. Implants had either a hydrophobic surface (SAE) or a hydrophilic treatment surface (SAE-HD). Calcium (Ca) and phosphorus (P) content was measured by energy-dispersive X-ray spectroscopy (EDS) after 7 days. The femurs were analyzed for bone-to-implant contact (BIC) and bone volume fraction (BV) by nano-computed tomography (nano-CT) after 14 and 28 days. Same specimens were further submitted to histological analysis. Additionally, after 3 and 7 days, implants were removed and cells were collected around the implant to access gene expression profile of key osteogenic (Runx2, Alp, Sp7, Bsp, Sost, Ocn) and inflammatory genes (IL-1β, IL-10, Tnf-α, and Nos2) by qRT-PCR assay. Statistical analysis was performed by ANOVA and paired t test with significance at P < .05.

RESULTS

The amount of Ca and P deposited on the surface due to the mineralization process was higher for SAE-HD compared to SAE on the intra-group analysis. Nano-CT and histology revealed more BV and BIC for SAE-HD in SHAM and OVX groups compared to SAE. Analysis in OVX group showed that most genes (ie, ALP, Runx2) involved in the bone morphogenetic protein (BMP) signaling were significantly activated in the hydrophilic treatment.

CONCLUSION

Both surfaces were able to modulate bone responses toward osteoblast differentiation. SAE-HD presented a faster response in terms of bone formation and osteogenic gene expression compared to SAE. Hydrophilic surface in situations of osteoporosis seems to provide additional benefits in the early stages of osseointegration.

The role of strontium ranelate and guided bone regeneration in osteoporotic and healthy conditions

BACKGROUND/ OBJECTIVES

SR is a chemical agent developed for the treatment of osteoporosis. In vitro, SR enhanced replication of osteoprogenitor cells and bone formation. In vivo, in ovariectomized rats SR prevented the biomechanical deterioration of bone while in non-ovariectomized rats, enhanced bone architecture and increased trabecular and cortical bone mass. The aim of this study was to evaluate the effect of SR on bone healing of calvarial critical size defects treated with a deproteinized bovine bone mineral (DBBM) and a collagen barrier (CM), in healthy and osteoporotic rats.

MATERIAL AND METHODS

Sixty-four, 4-month-old Wistar female rats were used. Osteoporosis was induced by ovariectomy and calcium-deficient diet in half of them. Sixteen ovariectomized (OSR) and 16 healthy (HSR) rats were treated with SR while no medication was administered in the remaining 16 healthy (H) and 16 ovariectomized (O) rats. At 6 weeks after ovariectomy, a 5mm defect was created in each parietal bone of every animal. One defect was treated with DBBM and CM, while the contralateral was left untreated. Qualitative and quantitative histological analysis was performed at 30 and 60 days of healing. A generalized estimating equations test was performed to evaluate the effect of SR and osteoporosis, on new bone formation (NB).

RESULTS

After 30 days of healing, NB in the untreated defects was 3.4%±1.7%, 4.3%±6.2%, 3.2±4.5%, 15.9±23.5% in O, OSR, H and HSR groups, respectively; after 60 days, NB was 4.7%±4.3%, 11.3%±7%, 7.1%±13.2, 12.1%±13.5%, respectively. In the GBR-treated defects, after 30 days, NB was 2.6%±1.4%, 2.4%±1.6%, 4.5%±4.1%, 10.3%±14.4% in O, OSR, H and HSR groups, respectively; after 60 days, NB was 2.2%±1.6%, 4.3%±4.2%, 7%±5.1%, 10.8%±17.4%, respectively. Osteoporosis (p=0.008) and the absence of strontium ranelate treatment (p=0.01) had a negative impact on NB.

CONCLUSION

SR may promote bone formation in calvarial defects in healthy and osteoporotic rats, albeit in a moderate extent.

Photobiomodulation as adjunctive therapy for guided bone regeneration. A microCT study in osteoporotic rat model

Regeneration of diseased bone is challenging. Guided bone regeneration (GBR) has been applied to favor the bone repair. Photobiomodulation (PBM) is also a recognized therapy able to improve bone repair in healthy and diseased individuals. Thus, with the hypothesis that PBM therapy could improve the GBR of diseased bone, this study evaluated the effect of PBM as adjunctive therapy to GBR in osteoporotic rats. Osteoporosis was induced in rats using the oophorectomy model. Then, 5-mm calvaria bone defects were created and treated according to the experimental groups, as follows: with no further treatment (Control); conventional GBR (Membrane), GBR and PBM applied with 3 s, 4 J/cm² and 0.12 J per point (PBM-1) and GBR and PBM applied with 10s, 14 J/cm², 0.4 J per point (PBM-2). PBM therapy (808 nm, 40 mW, 1.42 W/cm²) was applied immediately, 48 and 96 h postoperatively. Four and eight weeks later, the samples were harvested and processed for micro-computerized tomography (Micro CT). Data were statistically compared (p < 0.05). From 4 to 8 weeks mostly significant changes were observed in the PBM groups. The bone volume fraction and number of trabeculae of the PBM groups, especially the PBM-1, were significantly higher than those of Control (p < 0.0001). The values of thickness and separation of the trabeculae and structural model index of the PBM groups were significantly smaller than Control (p < 0.0001). The connectivity density was significantly higher on Membrane and PBM groups than Control (p < 0.0004). The application of PBM as adjunctive therapy to GBR results in enhanced bone formation and maturation in comparison to the conventional GBR in the regeneration of lesions of osteoporotic bone in rats. Overviewing the challenges that face bone regeneration in patients with osteoporosis, our findings open new perspectives on the treatment of bone defects under osteoporotic conditions.

Membranes for Guided Bone Regeneration: A Road from Bench to Bedside

Bone resorption can negatively influence the osseointegration of dental implants. Barrier membranes for guided bone regeneration (GBR) are used to exclude nonosteogenic tissues from influencing the bone healing process. In addition to the existing barrier membranes available on the market, a growing variety of membranes for GBR with tailorable physicochemical properties are under preclinical evaluation. Hence, the aim of this review is to provide a comprehensive description of materials used for GBR and to report the main industrial and regulatory aspects allowing the commercialization of these medical devices (MDs). In particular, a summary of the main attributes defining a GBR membrane is reported along with a description of commercially available and under development membranes. Finally, strategies for the scaling-up of the manufacturing process and the regulatory framework of the main MD producers (USA, EU, Japan, China, and India) are presented. The description of the regulatory approval process of GBR membranes is representative of the typical path that medium- to high-risk MDs have to follow for an effective medical translation, which is of fundamental importance to increase the impact of biomedical research on public health.

Collagen and mPCL-TCP scaffolds induced differential bone regeneration in ovary-intact and ovariectomized rats

BACKGROUND

The data on biomaterial-mediated bone regeneration directly comparing commercially available scaffolds in aging and osteoporotic conditions remain sparse.

OBJECTIVE

To investigate the effects of an absorbable collagen sponge (ACS) and a medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) scaffold on calvarial defect healing in ovary-intact and ovariectomized rats.

METHODS

Forty-two, 5-month old female Sprague-Dawley rats were divided into sham (OVI) or ovariectomy (OVX) groups (n=21). When rats reached 6 months old, 7 mm diameter calvarial defects were created and treated, further dividing each group into blood clot control, mPCL-TCP, or ACS subgroups (n=7). After four weeks, the calvarial specimens were evaluated using micro-computed tomography for bone volume fraction (BVF), and histopathology.

RESULTS

The effects of ovariectomy were confirmed by changes in body, uterine, and vaginal weight, and osteopenia in the femur. A significant increase in BVF was observed in ACS-subgroups compared with their respective control groups (p<0.05). Histopathological analysis revealed no cellular inflammatory infiltrate in any group. Fibrous tissue encapsulated the mPCL-TCP, while the ACS was well-integrated with the bone matrix. The OVX groups presented more osteoid and enlarged marrow cavities compared with the OVI groups.

CONCLUSION

ACS scaffold enhanced calvarial bone regeneration in OVI and OVX rats after four weeks.

Poly(Vinylidene Fluoride-Trifluorethylene)/barium titanate membrane promotes de novo bone formation and may modulate gene expression in osteoporotic rat model

Osteoporosis is a chronic disease that impairs proper bone remodeling. Guided bone regeneration is a surgical technique that improves bone defect in a particular region through new bone formation, using barrier materials (e.g. membranes) to protect the space adjacent to the bone defect. The polytetrafluorethylene membrane is widely used in guided bone regeneration, however, new membranes are being investigated. The purpose of this study was to evaluate the effect of P(VDFTrFE)/BT [poly(vinylidene fluoride-trifluoroethylene)/barium titanate] membrane on in vivo bone formation. Twenty-three Wistar rats were submitted to bilateral ovariectomy. Five animals were subjected to sham surgery. After 150 days, bone defects were created and filled with P(VDF-TrFE)/BT membrane or PTFE membrane (except for the sham and OVX groups). After 4 weeks, the animals were euthanized and calvaria samples were subjected to histomorphometric and computed microtomography analysis (microCT), besides real time polymerase chain reaction (real time PCR) to evaluate gene expression. The histomorphometric analysis showed that the animals that received the P(VDF-TrFE)/BT membrane presented morphometric parameters similar or even better compared to the animals that received the PTFE membrane. The comparison between groups showed that gene expression of RUNX2, BSP, OPN, OSX and RANKL were lower on P(VDF-TrFE)/BT membrane; the gene expression of ALP, OC, RANK and CTSK were similar and the gene expression of OPG, CALCR and MMP9 were higher when compared to PTFE. The results showed that the P(VDF-TrFE)/BT membrane favors bone formation, and therefore, may be considered a promising biomaterial to support bone repair in a situation of osteoporosis.