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

Novel insights into the pharmacological modulation of human periodontal ligament stem cells by the amino-bisphosphonate Alendronate

Alendronate (ALN) is a second-generation bisphosphonate widely used for osteoporosis and cancer-induced bone lesions. Many studies have confirmed a strong relationship between osteonecrosis of the jaws (ONJ) development and oral bisphosphonates, especially ALN, although the molecular mechanisms underlying this pathology have not yet been elucidated. The reduction in bone turnover and vascularization usually observed in ONJ are the result of ALN action on different cell types harboured in oral microenvironment, such as osteoclasts, endothelial cells, and periodontal ligament stem cells (PDLSCs). In this perspective, the present study aims to investigate the effects of different ALN concentrations (2 μM, 5 μM, 10 μM, 25 μM, 50 μM) on the phenotype and functional properties of human PDLSCs (hPDLSCs). hPDLSCs showed a decrease in cell viability (MTT assay) only when treated with ALN concentration of 10 μM or larger for 48 h and 72 h. Cell cycle analysis revealed a moderate increase in proportion of S-phase cells after exposure to low ALN concentration (2-5 μM), an effect that was reverted after exposure to 10-50 μM ALN. Conversely, cell death was evidenced via Annexin V/PI assay at very high concentration of ALN (50 μM) after 4 days of treatment. In addition, we explored whether the effects of ALN on hPDLSCs growth and survival can be mediated by its ability to modulate oxidative stress. To this, we quantified the intracellular ROS amount and lipid peroxidation by using DCF probe and Bodipy staining, respectively. Flow cytometry analysis showed that ALN induced a dose-dependent reduction of intracellular oxidative stress and lipid peroxidation upon treatment with low concentrations at both 48 h and 72 h. Increased levels of oxidative stress was reported at 50 μM ALN and was also confirmed via TEM analysis. Despite the stability of the cellular immunophenotype, hPDLSCs showed impaired mobility after ALN exposure. Chronic exposure (7-14 days) to ALN in the range of 2-10 μM significantly decreased the expression of the differentiation-related factors ALP, RUNX2, COLI, and OPN as well as the osteogenic ability of hPDLSCs compared with untreated cells. Conversely, higher doses were found to be neutral. Our findings indicated that the effects of ALN on hPDLSCs behavior are dose-dependent and suggest a role for oxidative stress in ALN-induced cell death that may lead to novel therapeutic approaches for ONJ.

Fabrication and characterization of bovine hydroxyapatite-gelatin-alendronate scaffold cross-linked by glutaraldehyde for bone regeneration

OBJECTIVES

Alendronate are widely used in the treatment of bone disorders characterized by inhibit osteoclast-mediated bone resorption such as Paget's disease, fibrous dysplasia, myeloma, bone metastases and osteoporosis. In recent studies alendronate improves proliferation and differentiation of osteoblasts, thereby facilitating for bone regeneration. The disadvantages of this class are their poor bioavailability and side effects on oral and intravenous application such as stomach irritation and osteonecrosis in jaw. Thus, local treatment of alendronate is needed in order to achieve high concentration of drug. Bovine hydroxyapatite-gelatin scaffold with alendronate was studied. Glutaraldehyde was used as cross-linking agent, increase the characteristics of this scaffold. The objectives of this study were to manufacture and characterize alendronate scaffold using bovine hydroxyapatite-gelatin and crosslinked by glutaraldehyde.

METHODS

Preparation of cross-linked bovine hydroxyapatite-gelatin and alendronate scaffold with different concentration of glutaraldehyde (0.00, 0.50, 0.75, and 1.00%). The scaffolds were characterized for compressive strength, porosity, density, swelling ratio, in vitro degradation, and cytotoxicity (the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay, shorted as MTT assay).

RESULTS

Bovine hydroxyapatite-gelatin-alendronate scaffold cross-linked with glutaraldehyde showed lower density than without glutaraldehyde. As glutaraldehyde concentration increased, porosity also increased. Eventually, it reduced compressive strength. Swelling ratio and in vitro degradation was negatively dependent on glutaraldehyde concentration. In addition, the scaffold has a good safety by MTT assay.

CONCLUSIONS

Bovine hydroxyapatite-gelatin-alendronate scaffold was fabricated with various concentrations of glutaraldehyde. The presence of glutaraldehyde on bovine hydroxyapatite-gelatin-alendronate is safe and suitable candidate scaffold for bone regeneration.

Sustained delivery of alendronate by engineered collagen scaffold for the repair of osteoporotic bone defects and resistance to bone loss

Researches of biomaterials for osteoporotic bone defects focus on the improvement of its anti-osteoporosis ability, due to osteoporosis is a kind of systemic and long-range bone metabolism disorder. Nevertheless, how to steadily deliver anti-osteoporosis drugs in osteoporotic bone defects is rarely studied. Reported evidences have shown that alendronate (Aln) is known to not only restrain osteoclasts from mediating bone resorption but also stimulate osteoblasts to regenerate bone tissue. Here, we developed an engineered implantable scaffold that could sustainably release Aln for osteoporotic bone defects. Briefly, Aln was added into 2% collagen (Col) solution to form a 5 mg/ml mixture. Then the mixture was filled into pre-designed round models (diameter: 5 mm, height: 2 mm) and crosslinked to obtain engineered Col-Aln scaffolds. The release kinetics showed that Aln was released at an average rate of 2.99 μg/d in the initial 8 days and could sustainably release for 1 month. To detect the repair effects of the Col-Aln scaffolds for osteoporotic defects, the Col and Col-Aln scaffolds were implanted into 5 mm cranial defects in ovariectomized rats. After 3 months, the cranial defects implanted with Col-Aln scaffolds achieved more bone regeneration in defect area (11.74 ± 3.82%) than Col scaffold (5.12 ± 1.15%) (p < .05). Moreover, ovariectomized rats in Col-Aln scaffold group possessed more trabecular bone in femur metaphysis than Col scaffold group as analyzed by Micro-CT. This study demonstrated the engineered Col-Aln scaffold has the potential to repair osteoporotic bone defects and resist bone loss in osteoporosis.

In vitro effects of alendronate on fibroblasts of the human rotator cuff tendon

Background

Bone mineral density of the humeral head is an independent determining factor for postoperative rotator cuff tendon healing. Bisphosphonates, which are commonly used to treat osteoporosis, have raised concerns regarding their relationships to osteonecrosis of the jaw and to atypical fracture of the femur. In view of the prevalence of rotator cuff tear in osteoporotic elderly people, it is important to determine whether bisphosphonates affect rotator cuff tendon healing. However, no studies have investigated bisphosphonates’ cytotoxicity to human rotator cuff tendon fibroblasts (HRFs) or bisphosphonates’ effects on rotator cuff tendon healing. The purpose of this study was to evaluate the cytotoxicity of alendronate (Ald), a bisphosphonate, and its effects on HRF wound healing.

Methods

HRFs were obtained from human supraspinatus tendons, using primary cell cultures. The experimental groups were control, 0.1 μM Ald, 1 μM Ald, 10 μM Ald, and 100 μM Ald. Alendronate exposure was for 48 h, except during a cell viability analysis with durations from 1 day to 6 days. The experimental groups were evaluated for cell viability, cell cycle and cell proliferation, type of cell death, caspase activity, and wound-healing ability.

Results

The following findings regarding the 100 μM Ald group contrasted with those for all the other experimental groups: a significantly lower rate of live cells (p < 0.01), a higher rate of subG1 population, a lower rate of Ki-67 positive cells, higher rates of apoptosis and necrosis, a higher number of cells with DNA fragmentation, higher caspase-3/7 activity (p < 0.001), and a higher number of caspase-3 positive staining cells. In scratch-wound healing analyses of all the experimental groups, all the wounds healed within 48 h, except in the 100 μM Ald group (p < 0.001).

Conclusions

Low concentrations of alendronate appear to have little effect on HRF viability, proliferation, migration, and wound healing. However, high concentrations are significantly cytotoxic, impairing cellular proliferation, cellular migration, and wound healing in vitro.

Enhancement of Bone Marrow-Derived Mesenchymal Stem Cell Osteogenesis and New Bone Formation in Rats by Obtusilactone A

The natural pure compound obtusilactone A (OA) was identified in Cinnamomum kotoense Kanehira &amp; Sasaki, and shows effective anti-cancer activity. We studied the effect of OA on osteogenesis of bone marrow-derived mesenchymal stem cells (BMSCs). OA possesses biocompatibility, stimulates Alkaline Phosphatase (ALP) activity and facilitates mineralization of BMSCs. Expression of osteogenesis markers BMP2, Runx2, Collagen I, and Osteocalcin was enhanced in OA-treated BMSCs. An in vivo rat model with local administration of OA via needle implantation to bone marrow-residing BMSCs revealed that OA increased the new bone formation and trabecular bone volume in tibias. Micro-CT images and H&amp;E staining showed more trabecular bone at the needle-implanted site in the OA group than the normal saline group. Thus, OA confers an osteoinductive effect on BMSCs via induction of osteogenic marker gene expression, such as BMP2 and Runx2 expression and subsequently elevates ALP activity and mineralization, followed by enhanced trabecular bone formation in rat tibias. Therefore, OA is a potential osteoinductive drug to stimulate new bone formation by BMSCs.

Reconstruction of Large-scale Defects with a Novel Hybrid Scaffold Made from Poly(L-lactic acid)/Nanohydroxyapatite/Alendronate-loaded Chitosan Microsphere: in vitro and in vivo Studies

A chitosan-based microsphere delivery system has been fabricated for controlled release of alendronate (AL). The present study aimed to incorporate the chitosan/hydroxyapatite microspheres-loaded with AL (CH/nHA-AL) into poly(L-lactic acid)/nanohydroxyapatite (PLLA/nHA) matrix to prepare a novel microspheres-scaffold hybrid system (CM-ALs) for drug delivery and bone tissue engineering application. The characteristics of CM-ALs scaffolds containing 10% and 20% CH/nHA-AL were evaluated in vitro, including surface morphology and porosity, mechanical properties, drug release, degradation, and osteogenic differentiation. The in vivo bone repair for large segmental radius defects (1.5 cm) in a rabbit model was evaluated by radiography and histology. In vitro study showed more sustained drug release of CM-AL-containing scaffolds than these of CM/nHA-AL and PLLA/nHA/AL scaffolds, and the mechanical and degradation properties of CM-ALs (10%) scaffolds were comparable to that of PLLA/nHA control. The osteogenic differentiation of adipose-derived stem cells (ASCs) was significantly enhanced as indicated by increased alkaline phosphates (ALP) activity and calcium deposition. In vivo study further showed better performance of CM-ALs (10%) scaffolds with complete repair of large-sized bone defects within 8 weeks. A microspheres-scaffold-based release system containing AL-encapsulated chitosan microspheres was successfully fabricated in this study. Our results suggested the promising application of CM-ALs (10%) scaffolds for drug delivery and bone tissue engineering.

Nanocomposite scaffolds with tunable mechanical and degradation capabilities: co-delivery of bioactive agents for bone tissue engineering

Novel multifunctional nanocomposite scaffolds made of nanobioactive glass and alginate crosslinked with therapeutic ions such as calcium and copper were developed for delivering therapeutic agents, in a highly controlled and sustainable manner, for bone tissue engineering. Alendronate, a well-known antiresorptive agent, was formulated into microspheres under optimized conditions and effectively loaded within the novel multifunctional scaffolds with a high encapsulation percentage. The size of the cation used for the alginate crosslinking impacted directly on porosity and viscoelastic properties, and thus, on the degradation rate and the release profile of copper, calcium and alendronate. According to this, even though highly porous structures were created with suitable pore sizes for cell ingrowth and vascularization in both cases, copper-crosslinked scaffolds showed higher values of porosity, elastic modulus, degradation rate and the amount of copper and alendronate released, when compared with calcium-crosslinked scaffolds. In addition, in all cases, the scaffolds showed bioactivity and mechanical properties close to the endogenous trabecular bone tissue in terms of viscoelasticity. Furthermore, the scaffolds showed osteogenic and angiogenic properties on bone and endothelial cells, respectively, and the extracts of the biomaterials used promoted the formation of blood vessels in an ex vivo model. These new bioactive nanocomposite scaffolds represent an exciting new class of therapeutic cell delivery carrier with tunable mechanical and degradation properties; potentially useful in the controlled and sustainable delivery of therapeutic agents with active roles in bone formation and angiogenesis, as well as in the support of cell proliferation and osteogenesis for bone tissue engineering.

Alendronate Can Improve Bone Alterations in Experimental Diabetes by Preventing Antiosteogenic, Antichondrogenic, and Proadipocytic Effects of AGEs on Bone Marrow Progenitor Cells

Bisphosphonates such as alendronate are antiosteoporotic drugs that inhibit the activity of bone-resorbing osteoclasts and secondarily promote osteoblastic function. Diabetes increases bone-matrix-associated advanced glycation end products (AGEs) that impair bone marrow progenitor cell (BMPC) osteogenic potential and decrease bone quality. Here we investigated the in vitro effect of alendronate and/or AGEs on the osteoblastogenic, adipogenic, and chondrogenic potential of BMPC isolated from nondiabetic untreated rats. We also evaluated the in vivo effect of alendronate (administered orally to rats with insulin-deficient Diabetes) on long-bone microarchitecture and BMPC multilineage potential. In vitro, the osteogenesis (Runx2, alkaline phosphatase, type 1 collagen, and mineralization) and chondrogenesis (glycosaminoglycan production) of BMPC were both decreased by AGEs, while coincubation with alendronate prevented these effects. The adipogenesis of BMPC (PPARγ, intracellular triglycerides, and lipase) was increased by AGEs, and this was prevented by coincubation with alendronate. In vivo, experimental Diabetes (a) decreased femoral trabecular bone area, osteocyte density, and osteoclastic TRAP activity; (b) increased bone marrow adiposity; and (c) deregulated BMPC phenotypic potential (increasing adipogenesis and decreasing osteogenesis and chondrogenesis). Orally administered alendronate prevented all these Diabetes-induced effects on bone. Thus, alendronate could improve bone alterations in diabetic rats by preventing the antiosteogenic, antichondrogenic, and proadipocytic effects of AGEs on BMPC.

Deletion of RBPJK in Mesenchymal Stem Cells Enhances Osteogenic Activity by Up-Regulation of BMP Signaling

Recently we have demonstrated the importance of RBPjk-dependent Notch signaling in the regulation of mesenchymal stem cell (MSC) differentiation during skeletogenesis both in vivo and in vitro. Here we further performed RBPJK loss-of-function experiments to demonstrate for the first time that RBPJK deficient MSC shows enhanced differentiation and osteogenesis acts via up-regulation of the BMP signaling. In the present study, we first compared the spontaneous and osteogenic differentiation in normal and recombination signal binding protein for immunoglobulin kappa J region (RBPJK) deficient human bone marrow-derived mesenchymal stem cells (MSCs). It was found that RBPJK highly expressed in fresh isolated MSCs and its expression was progressing down-regulated during spontaneous differentiation and even greater in osteogenic media inducted differentiation. Deletion of RBPJK in MSCs not only enhances cell spontaneous differentiation, but also significantly accelerates condition media inducted osteogenic differentiation by showing enhanced alkaline phosphatase (ALP) activity, Alizarin red staining, gene expression of Runx2, Osteopontin (OPN), Type I collagen (COL1a1) in culture. Additionally, BMP signaling responsive reporter activity and phosphor-smad1/5/8 expression were also significantly increased upon removal of RBPJK in MSCs. These data proved that inhibition of Notch signaling in MSCs promotes cell osteogenic differentiation by up-regulation of BMP signaling, and RBPJK deficient MSC maybe a better cell population for cell-based bone tissue engineering.