Alendronate promotes bone formation by inhibiting protein prenylation in osteoblasts in rat tooth replantation model

Alendronate treatment rescues the effects of compressive loading of TMJ in osteogenesis imperfecta mice

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue caused by mutations associated with type I collagen, which results in defective extracellular matrix in temporomandibular joint (TMJ) cartilage and subchondral bone. TMJ is a fibrocartilaginous joint expressing type I collagen both in the cartilage and the subchondral bone. In the present study the effects of alendronate and altered loading of the TMJ was analyzed both in male and female OI mice.

MATERIALS AND METHODS

Forty-eight, 10-weeks-old male and female OI mice were divided into 3 groups: (1) Control group: unloaded group, (2) Saline + Loaded: Saline was injected for 2 weeks and then TMJ of mice was loaded for 5 days, (3) alendronate + loaded: alendronate was injected for 2 weeks and then TMJ of mice was loaded for 5 days. Mice in all the groups were euthanized 24-h after the final loading.

RESULTS

Alendronate pretreatment led to significant increase in bone volume and tissue density. Histomorphometrically, alendronate treatment led to increase in mineralization, cartilage thickness and proteoglycan distribution. Increased mineralization paralleled decreased osteoclastic activity. Our immunohistochemistry revealed decreased expression of matrix metallopeptidase 13 and ADAM metallopeptidase with thrombospondin type 1 motif 5.

CONCLUSION

The findings of this research support that alendronate prevented the detrimental effects of loading on the extracellular matrix of the TMJ cartilage and subchondral bone.

Myricitrin: A promising herbal therapy for periodontitis in immunosuppressed status

Background

Periodontitis is a complex chronic inflammatory disease aggravated in immunosuppressed patients. However, adjuvant therapies can alleviate severe inflammation and slow down disease progression.

Objective

To evaluate the efficacy of myricitrin, a herbal flavonoid glycoside, in reducing immunosuppression-associated periodontitis and compare its effects with that of alendronate on alveolar bone regeneration.

Methods

Fifty albino Wistar rats were randomly allocated to the control, periodontitis, immunosuppressant, myricitrin, and alendronate groups. Ligature-associated periodontitis was induced in all groups, except the control group. Cyclosporin A (CsA) was administered subcutaneously in the immunosuppressant group for immunosuppression. The myricitrin group received CsA and myricitrin, whereas the alendronate group received CsA and alendronate. The therapeutic efficacies of myricitrin and alendronate were compared histologically, morphometrically, and biochemically.

Results

Myricitrin reversed bone destruction in the periodontitis and immunosuppressant groups. Morphometrically, myricitrin showed comparable improvements to alendronate in terms of gaining more bone area to 49.4 ± 4.6 and 59.5 ± 2%, respectively (P < 0.001 in relation to the untreated periodontitis group). Concomitantly, myricitrin increased osteoblast count significantly to 28.4 ± 4.7 closer to the 34.5 ± 2.4 count in the alendronate group (P < 0.001 compared with 22.5 ± 2.6 count of the immunosuppressant group). Moreover, myricitrin restored the serum calcium to 9.4 ± 0.6 mg/dL and alkaline phosphatase up to 112.9 ± 2.9 IU/L, which were almost normal levels similar to the control cohort (P > 0.05).

Conclusion

Myricitrin showed beneficial effects in counteracting bone resorption in subjects with immunosuppression-associated periodontitis. Its efficacy in slowing down disease progression was comparable to that of alendronate.

The administration of bovine hydroxyapatite-alendronate implant accelerates bone defect healing in an osteoporotic rat

BACKGROUND

Bone fracture is the main consequence of osteoporosis, which may become a neglected disease.

OBJECTIVE

This study aims to fabricate bovine hydroxyapatite-gelatine (BHA-GEL) based bone-implant with alendronate (ALE) in vivo.

METHODS

Wistar rats were used for an osteoporotic animal model induced by ovariectomy. There were three groups: negative control, BHA-GEL implant, and BHA-GEL-ALE implant. Each group performed a defect by drilling the femur (diameter of 2.2 mm and depth of 2 mm). Observations on the closure of bone defects were performed by X-ray radiography at the second and sixth week after surgery. The mechanism of bone healing was observed by using hematoxylin-eosin (HE) staining and immunohistochemical technique with anti-vascular endothelial growth factor (VEGF) and anti-alkaline phosphatase (ALP) antibodies.

RESULTS

The radiograph examination showed the implanted group had accelerated bone growth. In addition, the osteoblast, osteoclast and osteocyte had accelerated migration to the defect area. Moreover, the immunoreactive score (IRS) of VEGF at the sixth week in the BHA-GEL-ALE group was lower than the other groups. Meanwhile, the IRS of ALP in BHA-GEL-ALE was higher compared to other groups.

CONCLUSION

The BHA-GEL-ALE implant accelerates the healing of bone defect in the osteoporotic rat by increasing the ALP expression and the total number of cells.

Dual Modification of Porous Ca-P/PLA Composites with APTES and Alendronate Improves Their Mechanical Strength and Cytobiocompatibility towards Human Osteoblasts

Synthetic implants are used to treat large bone defects that are often unable to regenerate, for example those caused by osteoporosis. It is necessary that the materials used to manufacture them are biocompatible and resorbable. Polymer-ceramic composites, such as those based on poly(L-lactide) (PLLA) and calcium phosphate ceramics (Ca-P), are often used for these purposes. In this study, we attempted to investigate an innovative strategy for two-step (dual) modification of composites and their components to improve the compatibility of composite components and the adhesion between PLA and Ca-P whiskers, and to increase the mechanical strength of the composite, as well as improve osteological bioactivity and prevent bone resorption in composites intended for bone regeneration. In the first step, Ca-P whiskers were modified with a saturated fatty acid namely, lauric acid (LA), or a silane coupling agent γ-aminopropyltriethoxysilane (APTES). Then, the composite, characterized by the best mechanical properties, was modified in the second stage of the work with an active chemical compound used in medicine as a first-line drug in osteoporosis-sodium alendronate, belonging to the group of bisphosphonates (BP). As a result of the research covered in this work, the composite modified with APTES and alendronate was found to be a promising candidate for future biomedical engineering applications.

Tooth transplantation and replantation: Biological insights towards therapeutic improvements

Transplantation and replantation of teeth are effective therapeutic approaches for tooth repositioning and avulsion, respectively. Transplantation involves transplanting an extracted tooth from the original site into another site, regenerating tissue including the periodontal ligament (PDL) and alveolar bone, around the transplanted tooth. Replantation places the avulsed tooth back to its original site, regenerating functional periodontal tissue. In clinical settings, transplantation and replantation result in favorable outcomes with regenerated PDL tissue in many cases. However, they often result in poor outcomes with two major complications: tooth ankylosis and root resorption. In tooth ankylosis, the root surface and alveolar bone are fused, reducing the PDL tissue between them. The root is subjected to remodeling processes and is partially replaced by bone. In severe cases, the resorbed root is completely replaced by bone tissue, which is called as "replacement resorption." Resorption is sometimes accompanied by infection-mediated inflammation. The molecular mechanisms of ankylosis and root resorption remain unclear, although some signaling mechanisms have been proposed. In this mini-review, we summarized the biological basis of repair mechanisms of tissues in transplantation and replantation and the pathogenesis of their healing failure. We also discussed possible therapeutic interventions to improve treatment success rates.

Platelet-derived growth factor-BB regenerates functional periodontal ligament in the tooth replantation

Tooth ankylosis is a pathological condition of periodontal ligament (PDL) restoration after tooth replantation. Platelet-derived growth factor-BB (PDGF-BB) has been proposed as a promising factor for preventing tooth ankylosis. Using rat tooth replantation model, we investigated whether PDGF-BB accelerates the repair of PDL after tooth replantation without ankylosis, and its molecular mechanisms. In PDGF-BB pretreated replanted teeth (PDGF-BB group), ankylosis was markedly reduced and functionally organized PDL collagen fibers were restored; the mechanical strength of the healing PDL was restored to an average of 76% of that in non-replanted normal teeth at 21 days. The numbers of PDGF-Rβ- and BrdU-positive cells in the periodontal tissues of the PDGF-BB group were greater than those of atelocollagen pretreated replanted teeth (AC group). Moreover, in the PDGF-BB group, the periodontal tissues had fewer osteocalcin-positive cells and decreased number of nuclear β-catenin-positive cells compared to those in the AC group. In vitro analyses showed that PDGF-BB increased the proliferation and migration of human periodontal fibroblasts. PDGF-BB downregulated mRNA expressions of RUNX2 and ALP, and inhibited upregulatory effects of Wnt3a on β-catenin, AXIN2, RUNX2, COL1A1, and ALP mRNA expressions. These findings indicate that in tooth replantation, topical PDGF-BB treatment enhances cell proliferation and migration, and inhibits canonical Wnt signaling activation in bone-tooth ankylosis, leading to occlusal loading of the PDL tissues and subsequent functional restoration of the healing PDL. This suggests a possible clinical application of PDGF-BB to reduce ankylosis after tooth replantation and promote proper regeneration of PDL.

Dose-dependent effects of pharmaceutical treatments on bone matrix properties in ovariectomized rats

As both anabolic and anti-catabolic osteoporosis drugs affect bone formation and resorption processes, they may contribute to bone's overall mechanical behavior by altering the quality of the bone matrix. We used an ovariectomized rat model and a novel fracture mechanics approach to investigate whether treatment with an anabolic (parathyroid hormone) or anti-catabolic (alendronate) osteoporosis drugs will alter the organic and mineral matrix components and consequently cortical bone fracture toughness. Ovariectomized (at 5 months age) rats were treated with either parathyroid hormone or alendronate at low and high doses for 6 months (age 6–12 months). Specifically, treatment groups included untreated ovariectomized controls (n = 9), high-dose alendronate (n = 10), low-dose alendronate (n = 9), high-dose parathyroid hormone (n = 10), and low-dose parathyroid hormone (n = 9). After euthanasia, cortical microbeams from the lateral quadrant were extracted, notched, and tested in 3-point bending to measure fracture toughness. Portions of the bone were used to measure changes in the 1) organic matrix through quantification of advanced glycation end-products (AGEs) and non-collagenous proteins, and 2) mineral matrix through assessment of mineral crystallinity. Compared to the ovariectomized group, rats treated with high doses of parathyroid hormone and alendronate had significantly increased cortical bone fracture toughness, which corresponded primarily to increased non-collagenous proteins while there was no change in AGEs. Additionally, low-dose PTH treatment increased matrix crystallinity and decreased AGE levels. In summary, ovariectomized rats treated with pharmaceutical drugs had increased non-collagenous matrix proteins and improved fracture toughness compared to controls. Further investigation is required for different doses and longer treatment periods.

•

Alendronate increases non-collagenous proteins and improves fracture toughness.

•

Parathyroid hormone also increases collagen maturity and mineral crystallinity.

•

Both treatments minimize accumulation of advanced glycation end-products.

Multiple Porous Synthetic Bone Graft Comprising EngineeredMicro-Channel for Drug Carrier and Bone Regeneration

Due to high demand but limited supply, there has been an increase in the need to replace autologous bone grafts with alternatives that fulfill osteogenic requirements. In this study, two different types of bone grafts were tested for their drug carrying abilities along with their osteogenic properties. Two different types of alendronate-loaded bone grafts, Bio-Oss (bovine bone graft) and InRoad (biphasic synthetic bone graft) were observed to see how different concentrations of alendronate would affect the sustained release to enhance osteogenesis. In this study, defected ovariectomize-induced osteoporotic rat calvarias were observed for 28 days with three different concentrations of alendronate (0 mg, 1 mg, 5 mg) for both Bio-Oss and InRoad. A higher concentration (5 mg) allowed for a more controlled and sustained release throughout the 28-day comparison to those of lower concentrations (0 mg, 1 mg). When comparing Bio-Oss and InRoad through histology and Micro-CT, InRoad showed higher enhancement in osteogenesis. Through this study, it was observed that alendronate not only brings out robust osteogenesis with InRoad bone grafts, but also enhances bone regeneration in an alendronate-concentration-dependent manner. The combination of higher concentration of alendronate and multiple porous bone graft containing internal micro-channel structure of InRoad resulted in higher osteogenesis with a sustained release of alendronate.

Sequential release of double drug (graded distribution) loaded gelatin microspheres/PMMA bone cement

Drugs are loaded into PMMA bone cement to reduce the risk of infection in freshly implanted prostheses or to promote the differentiation and growth of osteoblasts. However, the same method of loading of drugs in the bone cement cannot simultaneously achieve an effective antibacterial response and long-term treatment outcomes for osteoporosis based on a patient's clinical needs. In the present study, gentamicin sulfate (GS)/alendronate (ALN)-dual-loaded gelatin modified PMMA bone cement (GAPBC) was fabricated to provide rapid and continuous antibiotic release and long-term anti-osteoporotic therapy. Specifically, the gelatin microspheres were loaded with the drugs using separate methodologies, namely, ALN was loaded during fabrication of the gelatin microspheres after which GS was absorbed onto the gelatin from solution. The results demonstrate that sequential release of the GS and ALN was achieved, GS release playing a major role over the first 24 hours and ALN release dominant after 3 weeks of immersion in PBS, resulting from the graded distribution within the gelatin microspheres, and the final drug release ratio of GS (73.6%) and ALN (68.5%) from the modified bone cement was significantly higher than from PMMA bone cement. Therefore, GAPBC represents a potential drug carrier for future clinical applications.

Intramedullary injury combined with osteoporosis therapeutics regulates targeted local osteogenesis

Bone marrow ablation prompts transient bone formation in nearly the entire medullary cavity before marrow regeneration occurs. Here, we establish a procedure to direct bone formation in a desired particular site within the medullary cavity for support of biomedical devices. Local intramedullary injury was performed in the tibiae of rats and parathyroid hormone (PTH), alendronate, or saline was administered. Newly generated bone in the medulla was assessed by micro-CT and histology. To evaluate the function of newly generated bone, animals received intramedullary injury in tibiae followed by daily PTH. At day-14, implants were placed in the endocortical bone and the bone response to the implants was assessed. The fate of newly generated bone was compared with and without implants. We found that neither intramedullary injury nor medication alone resulted in bone formation. However, when combined, substantial bone was generated locally inside the diaphyseal medulla. Newly formed bone disappeared without implant placement but was retained with implants. Bone was especially retained around and between the implants. This study found that local bone marrow disruption followed by PTH or alendronate generated substantial cancellous bone locally in the diaphyseal medulla. This approach offers promise as a tissue engineering tool in medicine and dentistry.

Long-term evaluation of alendronate treatment on the healing of calvaria bone defects in rats. Biochemical, histological and immunohistochemical analyses

OBJECTIVE

The aim of this study was to investigate the effects of the long-term alendronate administration on bone healing in defects created in rat calvarias.

MATERIALS AND METHODS

Female Wistar rats were randomly distributed into 2 groups: Control (CTL): animals received saline solution once a week; and Alendronate (ALD): rats underwent alendronate treatment (1 mg/kg/weekly). After 120 days from the commencement of treatment, a critical size defect was created in all animals, and 10 animals from each group were sacrificed at 5, 10, 15, 20, 25, 30, 45 and 60-days after the defect creation. On the day of sacrifice, urine and blood samples were collected for determination of the serum levels of bone resorption and formation markers by enzyme linked immunosorbent assay, and the urinary concentration of deoxypyridinoline. Bone mineral density (BMD) in the femurs, descriptive histology, tartrate-resistant acid-phosphatase staining and immunohistochemical analyzes were assessed in the calvaria.

RESULTS

Alendronate group showed increased BMD compared to the test group. The concentration of C-terminal telopeptide of type I collagen and deoxypyridinoline decreased significantly, and the concentration of aminoterminal propeptide of procollagen type 1 and osteocalcin were significant lower in the alendronate group. Immunohistochemical analysis showed significant downregulation in the inducible nitric oxide synthase, runt-related transcription factor-2, cathepsin-K and receptor activator of nuclear factor kappa-B ligand expression in the alendronate group. Vascular endothelial growth factor and osteopontin were upregulated in the later periods of alendronate group.

CONCLUSIONS

Our results suggest that long-term treatment with alendronate did not compromise the repair processing of critical size defects in rat.

Bisphosphonate-Functionalized Scaffolds for Enhanced Bone Regeneration

The local sustained release of bioactive substances are attracting increasing attention in bone tissue engineering, which is beneficial to bone tissue formation and helps to improve the bone ingrowth ability of a scaffold. Bisphosphonates (BPs), as a representative kind of osteoclast inhibitors, are proven to possess excellent osteogenic induction capability. Accordingly, various physical and chemical strategies are developed to functionalize bone tissue scaffolds with BPs to achieve controlled release profiles. Compared with traditional treatment modalities, local release of BPs from these composite scaffolds will contribute to continuous bone integration without the risk of many complications. This review explores the molecular mechanisms of BPs on bone metabolism and analyzes the appropriate concentrations of BPs that promote bone regeneration. The advanced BP loading strategies, implant modification technologies, and BP-loaded composite scaffolds based on different matrices are summarized. Finally, the latest advances and the future development of BP-modified scaffolds for enhanced bone regeneration are discussed. This article provides leading-edge design strategies of the BP-functionalized bone engineering scaffolds for improved bone repairability.

Geranylgeraniol (GGOH) as a Mevalonate Pathway Activator in the Rescue of Bone Cells Treated with Zoledronic Acid: An In Vitro Study

Bisphosphonates (BPs) are the keystone to treat bone disorders. Despite the great benefits of BPs, medication-related osteonecrosis of the jaw (MRONJ) arouse as a potential side effect. Nitrogen-containing BPs (N-BPs) as zoledronate (ZA) act by the inhibition of specific enzymes of the mevalonate pathway resulting in altering protein prenylation which is required for the posttranslational maturation of the small GTP-binding proteins. Geranylgeraniol (GGOH) is an intermediate product in the mevalonate pathway having positive effects on different cell types treated with BPs by salvaging protein prenylation improving cell viability and proliferation in tissue regeneration, thus overcoming N-BP-induced apoptosis. Here, the effect of different concentrations of zoledronate (ZA) on the bone cells has been investigated by cell viability assay, live/dead staining, and western blot to understand if GGOH was able to rescue bone cells and levels of statistical significance were indicated at ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001, and ^∗∗∗∗P < 0.0001. Although the high concentration of ZA had significantly decreased the cell viability in the bone cells, GGOH reversed the action of ZA on the cells while at very high concentration; it caused severe reduction in the cell viability. Rap1A, a member of the GTPases family, was expressed in the negative controls but was absent in cells treated with high concentrations of ZA. The addition of GGOH had increased the expression of Rap1A up to a certain limit. The experiments proved that ZA acts directly on the mevalonate pathway and protein prenylation and that GGOH could be applied as a future local therapy to MRONJ.

Annexin A5 Involvement in Bone Overgrowth at the Enthesis

Little is known about the molecular mechanisms of enthesis formation in mature animals. Here, we report that annexin A5 (Anxa5) plays a critical role in the regulation of bone ridge outgrowth at the entheses. We found that Anxa5 is highly expressed in the entheses of postnatal and adult mice. In Anxa5-deficient (Anxa5^-/- ) mice, the sizes of bone ridge outgrowths at the entheses of the tibias and femur were increased after age 7 weeks. Bone overgrowth was not observed at the fibrous enthesis where the fibrocartilage layer does not exist. More ALP-expressing cells were observed in the fibrocartilage layer in Anxa5^-/- mice than in wild-type (WT) mice. Calcein and Alizarin Red double labeling revealed more mineralized areas in Anxa5^-/- mice than WT mice. To examine the effects of mechanical forces, we performed tenotomy in which transmission of contractile forces by the tibial muscle was impaired by surgical muscle release. In tenotomized mice, bone overgrowth at the enthesis in Anxa5^-/- mice was decreased to a level comparable to that in WT mice at 8 weeks after the operation. The tail-suspended mice also showed a decrease in bone overgrowth to similar levels in Anxa5^-/- and WT mice at 8 weeks after hindlimb unloading. These results suggest that bone overgrowth at the enthesis requires mechanical forces. We further examined effects of Anxa5 gene knockdown (KD) in primary cultures of osteoblasts, chondrocytes, and tenocytes in vitro. Anxa5 KD increased ALP expression in tenocytes and chondrocytes but not in osteoblasts, suggesting that increased ALP activity in the fibrocartilaginous tissue in Anxa5^-/- mice is directly caused by Anxa5 deletion in tenocytes or fibrocartilage cells. These data indicate that Anxa5 prevents bone overgrowth at the enthesis, whose formation is mediated through mechanical forces and modulating expression of mineralization regulators. © 2018 American Society for Bone and Mineral Research.

Development of nanomaterials for bone-targeted drug delivery

Bone is one of the major organs of the human body; it supports and protects other organs, produces blood cells, stores minerals, and regulates hormones. Therefore, disorders in bone can cause serious morbidity, complications, or mortality of patients. However, despite the significant occurrence of bone diseases, such as osteoarthritis (OA), osteoporosis (OP), non-union bone defects, bone cancer, and myeloma-related bone disease, their effective treatments remain a challenge. In this review, we highlight recent progress in the development of nanotechnology-based drug delivery for bone treatment, based on its improved delivery efficiency and safety. We summarize the most commonly used nanomaterials for bone drug delivery. We then discuss the targeting strategies of these nanomaterials to the diseased sites of bone tissue. We also highlight nanotechnology-based drug delivery to bone cells and subcellular organelles. We envision that nanotechnology-based drug delivery will serve as a powerful tool for developing treatments for currently incurable bone diseases.

Sustained raloxifene release from hyaluronan-alendronate-functionalized titanium nanotube arrays capable of enhancing osseointegration in osteoporotic rabbits

To enhance the localized bone remodeling at titanium-based implants under osteoporotic conditions, TiO₂ nanotube arrays (TNT) were used as nanoreserviors for raloxifene (Ral) and then covered with the hybrid multilayered coating of chitosan and alendronate grafted hyaluronic acid (HA-Aln) via a spin-assisted layer-by-layer technique. The fabrication of this system (TNT/Ral/LBL-Aln) was characterized by field emission scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The release test showed that the composited multilayers onto Ral-loaded TiO₂ nanotube substrate (TNT/Ral) could prevent the burst release of Ral from TiO₂ nanotube arrays and maintain stable Ral concentration at the implant site even after 192h. The TNT/Ral/LBL-Aln system demonstrated higher alkaline phosphatase (ALP) activity, mineralization capability in osteoblasts as well as lower tartrate-resistant acid phosphatase (TRAP) activity in osteoclasts compared to both bare TiO₂ nanotube and TNT/Ral substrate, respectively. Moreover, the in vivo tests of micro-CT, histological staining and push-out testing showed that TNT/Ral/LBL-Aln implant could efficiently enhance the formation of new bone around the implant and promote bone binding in osteoporotic rabbits. The study indicated the potential application of TNT/Ral/LBL-Aln system for bone remodeling under osteoporotic condition.

Osteoblast as a target of anti-osteoporotic treatment

Osteoblasts are mesenchymal cells that play a key role in maintaining bone homeostasis; they are responsible for the production of extracellular matrix proteins, regulation of matrix mineralization, control of bone remodeling and regulate osteoclast differentiation. Osteoblasts have an essential role in the pathogenesis of many bone diseases, particularly osteoporosis. For many decades, the main current available treatments for osteoporosis have been represented by anti-resorptive drugs, such as bisphosphonates, which act mainly by inhibiting osteoclasts maturation, proliferation and activity; nevertheless, in recent years much attention has been paid on anabolic aspects of osteoporosis treatment. Many experimental evidences support the hypothesis of direct effects of the classical anti-resorptive drugs also on osteoblasts, and recent progress in understanding bone physiology have led to the development of new pharmacological agents such as anti-sclerostin antibodies and teriparatide which directly target osteoblasts, inducing anabolic effects and promoting bone formation.

The osteogenesis-promoting effects of alpha-lipoic acid against glucocorticoid-induced osteoporosis through the NOX4, NF-kappaB, JNK and PI3K/AKT pathways

Recently, accumulating evidence has indicated that glucocorticoid-induced osteoporosis (GIOP) is closely related to oxidative stress and apoptosis. Alpha-lipoic acid (LA), a naturally endogenous anti-oxidant, possesses anti-oxidative and anti-apoptosis activities, implicating LA as a therapeutic agent for the treatment of GIOP. In this study, the osteogenesis-promoting effects of LA against GIOP were investigated and the mechanisms were further probed. Here, the results showed that LA inhibited oxidative stress, suppressed apoptosis and improved osteopenia by promoting the expression of osteogenesis markers, including ALP, COL-I, OCN, BMP-2, RUNX2 and OSX. Further study revealed that the osteogenesis-promoting effects of LA likely occur via the regulation of the NOX4, NF-kappaB, JNK and PI3K/AKT pathways. The present study indicated that LA may prevent GIOP and promote osteogenesis and might be a candidate for the treatment of GIOP.

In Vitro and In Vivo Evaluation of Commercially Available Fibrin Gel as a Carrier of Alendronate for Bone Tissue Engineering

Alendronate (ALN) is a bisphosphonate drug that is widely used for the treatment of osteoporosis. Furthermore, local delivery of ALN has the potential to improve the bone regeneration. This study was designed to investigate an ALN-containing fibrin (fibrin/ALN) gel and evaluate the effect of this gel on both in vitro cellular behavior using human mesenchymal stem cells (hMSCs) and in vivo bone regenerative capacity. Fibrin hydrogels were fabricated using various ALN concentrations (10-7-10-4 M) with fibrin glue and the morphology, mechanical properties, and ALN release kinetics were characterized. Proliferation and osteogenic differentiation of and cytotoxicity in fibrin/ALN gel-embedded hMSCs were examined. In vivo bone formation was evaluated using a rabbit calvarial defect model. The fabricated fibrin/ALN gel was transparent with Young's modulus of ~13 kPa, and these properties were not affected by ALN concentration. The in vitro studies showed sustained release of ALN from the fibrin gel and revealed that hMSCs cultured in fibrin/ALN gel showed significantly increased proliferation and osteogenic differentiation. In addition, microcomputed tomography and histological analysis revealed that the newly formed bone was significantly enhanced by implantation of fibrin/ALN gel in a calvarial defect model. These results suggest that fibrin/ALN has the potential to improve bone regeneration.

Effect of bisphosphonates on root resorption after tooth replantation - a systematic review

BACKGROUND/AIM

Replantation of avulsed teeth may lead to root resorption. Bisphosphonates (BPs), a class of drugs of used to treat resorptive diseases of the bone such as osteoporosis and Paget's disease, have been observed to exert an antiresorptive effect on periodontal bone as well. The antiresorptive properties of BPs could prove them useful in preventing root resorption of replanted avulsed teeth. The aim of this systematic review was to analyze and summarize the currently available literature concerning the use of BPs in preventing root resorption of avulsed teeth.

MATERIALS AND METHODS

PubMed/MEDLINE, Google Scholar, ISI Web of Knowledge, and Embase databases were searched using keywords 'bisphosphonate', 'replantation', and 'tooth'. Quality assessment of each study was carried out. In addition, general characteristics and outcomes of each study were summarized.

RESULTS

After exclusion of 116 irrelevant articles, 10 animal studies were included in this review. The majority of the studies suggest that surface application of zoledronate or alendronate reduces root resorption of replanted teeth in animal models. Surface treatment with etidronate had no significant effect on root resorption, and intracanal etidronate accelerated resorption.

CONCLUSION

Surface application of zoledronate and alendronate reduces root resorption of replanted teeth in animal models. However, the efficacy of intracanal usage of BPs is still debatable.

RETRACTED: Potential role of andrographolide in the proliferation of osteoblasts mediated by the ERK signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. The authors contacted the journal to request a retraction: "We found some errors in reviewing the original data, the current results could not fully support the conclusions". Concern was also raised about the reliability of the Western blot results in Figure 8A+E, which appear to have a similar phenotype as contained within other publications, as detailed here: https://pubpeer.com/publications/CC36842602D94EB300623ED982FBFA; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Concerns were also raised about suspected image duplications within Figure 1C. The journal requested the corresponding author comment on these concerns and provide the raw data. The author did not fulfil this request and the Editor-in-Chief decided to retract the article.

Bone-targeted delivery of nanodiamond-based drug carriers conjugated with alendronate for potential osteoporosis treatment

This paper describes the design of alendronate-conjugated nanodiamonds (Alen-NDs) and evaluation of their feasibility for bone-targeted delivery. Alen-NDs exhibited a high affinity to hydroxyapatite (HAp, the mineral component of bone) due to the presence of Alen. Unlike NDs (without Alen), Alen-NDs were preferentially taken up by MC3T3-E1 osteoblast-like cells, compared to NIH3T3 and HepG2 cells, suggesting their cellular specificity. In addition, NDs itself increased ALP activity of MC3T3-E1 cells, compared to control group (osteogenic medium) and Alen-NDs exhibited more enhanced ALP activity. In addition, an in vivo study revealed that Alen-NDs effectively accumulated in bone tissues after intravenous tail vein injection. These results confirm the superior properties of Alen-NDs with advantages of high HAp affinity, specific uptake for MC3T3-E1 cells, positive synergistic effect for ALP activity, and in vivo bone targeting ability. The Alen-NDs can potentially be employed for osteoporosis treatment by delivering both NDs and Alen to bone tissue.

Alendronate-loaded hydroxyapatite-TiO2 nanotubes for improved bone formation in osteoporotic rabbits

Alendronate-loaded hydroxyapatite-TiO₂ nanotubes were fabricated for locally improving new bone formation at the bone–implant interface in osteoporotic rabbits.

Regulation of local bone remodeling mediated by hybrid multilayer coating embedded with hyaluronan-alendronate/BMP-2 nanoparticles on Ti6Al7Nb implants

Hyaluronate-alendronate/BMP-2 nanoparticles were inserted into Gel/Chi multilayers on Ti6Al7Nb for enhancing BMP-2 stability and promoting local osteogenesis under osteoporosis.

The Effect of Alendronate Loaded Biphasic Calcium Phosphate Scaffolds on Bone Regeneration in a Rat Tibial Defect Model

This study investigated the effect of alendronate (Aln) released from biphasic calcium phosphate (BCP) scaffolds. We evaluated the in vitro osteogenic differentiation of Aln/BCP scaffolds using MG-63 cells and the in vivo bone regenerative capability of Aln/BCP scaffolds using a rat tibial defect model with radiography, micro-computed tomography (CT), and histological examination. In vitro studies included the surface morphology of BCP and Aln-loaded BCP scaffolds visualized using field-emission scanning electron microscope, release kinetics of Aln from BCP scaffolds, alkaline phosphatase (ALP) activity, calcium deposition, and gene expression. The in vitro studies showed that sustained release of Aln from the BCP scaffolds consisted of porous microstructures, and revealed that MG-63 cells cultured on Aln-loaded BCP scaffolds showed significantly increased ALP activity, calcium deposition, and gene expression compared to cells cultured on BCP scaffolds. The in vivo studies using radiograph and histology examination revealed abundant callus formation and bone maturation at the site in the Aln/BCP groups compared to the control group. However, solid bony bridge formation was not observed at plain radiographs until 8 weeks. Micro-CT analysis revealed that bone mineral density and bone formation volume were increased over time in an Aln concentration-dependent manner. These results suggested that Aln/BCP scaffolds have the potential for controlling the release of Aln and enhance bone formation and mineralization.

Preparation of an injectable depot system for long-term delivery of alendronate and evaluation of its anti-osteoporotic effect in an ovariectomized rat model

We prepared an injectable depot system for the long-term delivery of alendronate using a solid/water/oil/water multiple emulsion technique with poly(lactic-co-glycolic acid) as a carrier. The microparticles were spherical with smooth surfaces, ranging from 20 to 70 μm in size. The microspheres (ALD-HA-RG504H-MC70) were optimally prepared by introducing a viscous material (hyaluronic acid) and a co-solvent system in the inner aqueous and oil phases, respectively, and showed a significantly increased drug encapsulation efficacy (>70%); the initial burst release was <10% after 1 day. In vitro drug release from ALD-HA-RG504H-MC70 followed zero-order kinetics for approximately 4 weeks and the alendronate plasma level was maintained for more than 1 month after intramuscular injection in rabbits. The ovariectomized (OVX) rats with ALD-HA-RG504H-MC70 injected intramuscularly (0.9 mg alendronate/kg/4 weeks) had 112% and 482% increased bone mineral density and trabecular area in the tibia than the OVX controls, respectively, and showed significant improvements in trabecular microarchitecture and bone strength. Furthermore, the major biomarkers of bone turnover revealed that ALD-HA-RG504H-MC70 suppressed effectively the progression of osteoporosis and facilitated new bone formation. Therefore, this sustained release depot system may improve patient compliance and therapeutic efficacy by reducing dose amounts and frequency with minimal adverse reactions.

The susceptive alendronate-treatment timing and dosage for osteogenesis enhancement in human bone marrow-derived stem cells

Recent studies indicated that alendronate enhanced osteogenesis in osteoblasts and human bone marrow-derived stem cells. However, the time- and dose-dependent effects of Aln on ostegenic differentiation and cytotoxicity of hBMSCs remain undefined. In present study, we investigated the effective dose range and timing of hBMSCs. hBMSCs were treated with various Aln doses (1, 5 and 10 µM) according to the following groups: group A was treated with Aln during the first five days of bone medium, groups B, C and D were treated during the first, second, and final five days of osteo-induction medium and group E was treated throughout the entire experiment. The mineralization level and cytotoxicity were measured by quantified Alizarin Red S staining and MTT assay. In addition, the reversal effects of farnesyl pyrophosphate and geranylgeranyl pyrophosphate replenishment in group B were also investigated. The results showed that Aln treatment in groups A, B and E enhanced hBMSC mineralization in a dose-dependent manner, and the most pronounced effects were observed in groups B and E. The higher dose of Aln simultaneously enhanced mineralization and caused cytotoxicity in groups B, C and E. Replenishment of FPP or GGPP resulted in partial or complete reverse of the Aln-induced mineralization respectively. Furthermore, the addition of FPP or GGPP also eliminated the Aln-induced cytotoxicity. We demonstrated that hBMSCs are susceptible to 5 µM Aln during the initiation stage of osteogenic differentiation and that a 10 µM dose is cytotoxic.