Nanoscale Modification of Titanium Implants Improves Behaviors of Bone Mesenchymal Stem Cells and Osteogenesis In Vivo

The surficial micro/nanotopography and physiochemical properties of titanium implants are essential for osteogenesis. However, these surface characters’ influence on stem cell behaviors and osteogenesis is still not fully understood. In this study, titanium implants with different surface roughness, nanostructure, and wettability were fabricated by further nanoscale modification of sandblasted and acid-etched titanium (SLA: sandblasted and acid-etched) by H2O2 treatment (hSLAs: H2O2 treated SLA). The rat bone mesenchymal stem cells (rBMSCs: rat bone mesenchymal stem cells) are cultured on SLA and hSLA surfaces, and the cell behaviors of attachment, spreading, proliferation, and osteogenic differentiation are further analyzed. Measurements of surface characteristics show hSLA surface is equipped with nanoscale pores on microcavities and appeared to be hydrophilic. In vitro cell studies demonstrated that the hSLA titanium significantly enhances cell response to attachment, spreading, and proliferation. The hSLAs with proper degree of H2O2 etching (h1SLA: treating SLA with H2O2 for 1 hour) harvest the best improvement of differentiation of rBMSCs. Finally, the osteogenesis in beagle dogs was tested, and the h1SLA implants perform much better bone formation than SLA implants. These results indicate that the nanoscale modification of SLA titanium surface endowing nanostructures, roughness, and wettability could significantly improve the behaviors of bone mesenchymal stem cells and osteogenesis on the scaffold surface. These nanoscale modified SLA titanium scaffolds, fabricated in our study with enhanced cell affinity and osteogenesis, had great potential for implant dentistry.

Recombinant Human Bone Morphogenic Protein-2 Immobilized Fabrication of Magnesium Functionalized Injectable Hydrogels for Controlled-Delivery and Osteogenic Differentiation of Rat Bone Marrow-Derived Mesenchymal Stem Cells in Femoral Head Necrosis Repair

Femoral head necrosis (FHN) is a clinically progressive disease that leads to overwhelming complications without an effective therapeutic approach. In recent decades, transplantation of mesenchymal stem cells (MSCs) has played a promising role in the treatment of FHN in the initial stage; however, the success rate is still low because of unsuitable cell carriers and abridged osteogenic differentiation of the transplanted MSCs. Biopolymeric-derived hydrogels have been extensively applied as effective cell carriers and drug vesicles; they provide the most promising contributions in the fields of tissue engineering and regenerative medicine. However, the clinical potential of hydrogels may be limited because of inappropriate gelation, swelling, mechanical characteristics, toxicity in the cross-linking process, and self-healing ability. Naturally, gelated commercial hydrogels are not suitable for cell injection and infiltration because of their static network structure. In this study, we designed a novel thermogelling injectable hydrogel using natural silk fibroin-blended chitosan (CS) incorporated with magnesium (Mg) substitutes to improve physical cross-linking, stability, and cell osteogenic compatibility. The presented observations demonstrate that the developed injectable hydrogels can facilitate the controlled delivery of immobilized recombinant human bone morphogenic protein-2 (rhBMP-2) and rat bone marrow-derived MSCs (rBMSCs) with greater cell encapsulation efficiency, compatibility, and osteogenic differentiation. In addition, outcomes of in vivo animal studies established promising osteoinductive, bone mineral density, and bone formation rate after implantation of the injectable hydrogel scaffolds. Therefore, the developed hydrogels have great potential for clinical applications of FHN therapy.

Relationship of Matrix Stiffness and Cell Morphology in Regulation of Osteo Genesis and Adipogenesis of BMSCs

Backgrounds: Both matrix stiffness and cell morphology have been found as important factors directing MSCs (mesenchymal stem cells) differentiation, but cells also spontaneously adapt their morphology under matrix stiffness stimulation. This study aimed to investigate the interplay of cell morphology and matrix stiffness on osteogenesis and adipogenesis of rBMSCs(rat bone BMSCs) on 2D substrates. Methods and Results: First, we modulated MSCs morphology through different fibronectin (FN) concentrations on tissue culture plates (TCPs). We found FN promoted and osteogenesis of BMSCs while suppressing adipogenesis, mediated by FN-induced F-actin polymerization and cell spreading. Based on these findings, we modulated BMSCs morphology on 0.5 kPa and 32 kPa CytoSoft® plates through FN concentrations. We found BMSCs on 0.5 kPa substrates coated with 300μg/ml of FN manifested similarly spreading morphology with cells on 32 kPa substrates coated with 100 μg/ml of FN, and cells in both groups dominantly commit osteogenesis. On the other hand, BMSCs on 32 kPa substrates coated with 30μg/ml of FN manifested similarly restricted morphology with cells in on 0.5 kPa substrates with 100μg/ml of FN, and in both groups cells mainly commit adipogenesis. Immunofluorescence staining indicated YAP/TAZ mainly located in cytoplasm when cells exhibited restricted morphology on stiff matrices, while exhibiting significant nuclear translocation when cells spread on soft matrices. Conclusions: Cell morphology overrode effects of matrix stiffness on BMSCs differentiation through more robust regulation of YAP/TAZ. Matrix stiffness depended on cell morphology to regulate osteogenesis and adipogenesis of BMSCs.

The Antioxidant Effects of Ginger Extract on Bioavailability and Oxidative Stress-induced Apoptosis in Mesenchymal Stem Cells of Human Adipose Tissue and Rat Bone Marrow

Background and Aim: Proliferate potential differentiate into different cell lineages and high self-renewal of Mesenchymal Stem Cells (MSCs); thus, they are ideal tools for regenerative medicine. However, a leading problem is an oxidative stress in the target tissue and the apoptosis of transplanted stem cells before tissue repair. The pretreatment of stem cells with antioxidants may make them resistant to oxidative stress. Ginger is the main medicinal plant with antioxidant properties. This study explored the antioxidant effects of ginger extract on bioavailability and oxidative stress-induced apoptosis in human adipose tissue-derived mesenchymal stem cells and rat bone marrow examined. Methods & Materials: In this study, human adipose tissue-derived mesenchymal stem cells and rat bone marrow were cultured in a DMEM medium with 20% FBS. The explored cells were incubated for 4 and 6 hours for pretreatment with different concentrations of ginger extract (50, 100, 200, & 400 mg/mL); then, they were treated with 200 μM H2O2 for 2 hours. Bioavailability was analyzed by ELISA reader using an MTS kit and apoptosis was analyzed by flow cytometry using an Annexin V-FITC/PI kit into the manufacturer’s protocol at both times. The obtained data were analyzed by Analysis of Variance (ANOVA) using SPSS. Ethical Considerations: This study was approved by the Ethics Research Committee of Shahrekord Branch, Islamic Azad University (Code: IR.IAU.SHK.REC.1397.028). Results: The MTS results indicated a dose- and time-dependent manner increase in the bioavailability of human adipose tissue-derived mesenchymal treated stem cells. Ginger extract treatment also dose- and time-dependently decreased the rate of apoptosis in rat bone marrow mesenchymal stem cells. Conclusion: Ginger extract, by reducing the oxidative stress in mesenchymal stem cells, elevates their lifespan in the target tissue, and increases the efficiency of these cells in tissue regeneration.

Behavior of rat bone marrow stem cells on titanium surfaces modified by laser-beam and deposition of calcium phosphate

Objectives The aim of this study was to evaluate the behavior of rat bone marrow stem cells seeded on a Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition. Materials and methods A total of four groups were evaluated: polished commercially pure titanium (cpTi): Ti-P; laser irradiation + calcium phosphate deposition on cpTi: Ti-LCP; polished Ti-15Mo alloy: Ti15Mo-P; and laser irradiation + calcium phosphate deposition on Ti-15Mo alloy: Ti15Mo-LCP. Before and after laser irradiation and calcium phosphate deposition on the surfaces, physicochemical and morphological analyses were performed: Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDX). The wettability of the samples was evaluated by contact angle measurement. In addition, the behavior of osteoblast-like cells to these surfaces was evaluated for cell morphology, adhesion, proliferation and viability, evaluation of alkaline phosphatase formation and gene expression of osteogenesis markers. Results Surfaces wet-abrade with grit paper (P) showed oriented groves, while the laser irradiation and calcium phosphate deposition (LCP) produced porosity on both cpTi and Ti15Mo alloy groups with deposits of hydroxyapatite (HA) crystals (SEM). EDX showed no contamination after surface modification in both metal samples. A complete wetting was observed for both LCP groups, whereas P surfaces exhibited high degree of hydrophobicity. There was a statistical difference in the intragroup comparison of proliferation and viability (p < 0.05). The ALP activity showed higher values in the Ti15Mo alloy at 10 days of culture. The gene expression of bone related molecules did not present significant differences at 7 and 14 days among different metals and surface treatments. Conclusion Ti15-Mo seems to be an alternative alloy to cpTi for dental implants. Surface treatment by laser irradiation followed by phosphate deposition seems to positively interact with bone cells. Clinical relevance Ti-15Mo alloy surface modified by laser-beam irradiation followed by calcium phosphate deposition may improve and accelerate the osseointegration process of dental implants.