Lianyi Xu

Biofunctionalization of a titanium surface with a nano-sawtooth structure regulates the behavior of rat bone marrow mesenchymal stem cells.

Background: The topography of an implant surface can serve as a powerful signaling cue for attached cells and can enhance the quality of osseointegration. A series of improved implant surfaces functionalized with nanoscale structures have been fabricated using various methods. Methods: In this study, using an H2O2 process, we fabricated two size-controllable sawtooth-like nanostructures with different dimensions on a titanium surface. The effects of the two nano-sawtooth structures on rat bone marrow mesenchymal stem cells (BMMSCs) were evaluated without the addition of osteoinductive chemical factors. Results: These new surface modifications did not adversely affect cell viability, and rat BMMSCs demonstrated a greater increase in proliferation ability on the surfaces of the nano-sawtooth structures than on a control plate. Furthermore, upregulated expression of osteogenic-related genes and proteins indicated that the nano-sawtooth structures promote osteoblastic differentiation of rat BMMSCs. Importantly, the large nano-sawtooth structure resulted in the greatest cell responses, including increased adhesion, proliferation, and differentiation. Conclusion: The enhanced adhesion, proliferation, and osteogenic differentiation abilities of rat BMMSCs on the nano-sawtooth structures suggest the potential to induce improvements in bone-titanium integration in vivo. Our study reveals the key role played by the nano-sawtooth structures on a titanium surface for the fate of rat BMMSCs and provides insights into the study of stem cell-nanostructure relationships and the related design of improved biomedical implant surfaces.

Comparison of the Use of Adipose Tissue–Derived and Bone Marrow–Derived Stem Cells for Rapid Bone Regeneration

Stem cell–based bone tissue engineering has been recognized as a new strategy for maxillary sinus floor elevation. More rapid bone formation may enhance this technique when simultaneous dental implant placement is desired. Adipose tissue–derived stem cells (ADSCs) and bone marrow stem cells (BMSCs) are the most well-characterized cell sources for bone regeneration, but comparative studies on the osteogenic potential of these cells have yielded conflicting conclusions. This study aimed to compare the rapid bone formation capacity of ADSCs and BMSCs in a canine sinus floor augmentation model. In in vitro studies, BMSCs had a higher proliferative ability and greater osteogenic differentiation potential at both the mRNA and protein levels. When GFP-labeled cells on calcium phosphate cement (CPC) scaffolds were implanted subcutaneously into nude mice, both ADSCs and BMSCs survived for 4 wks, but only BMSCs formed new bone. Furthermore, according to sequential fluorescence labeling results for the canine sinus, BMSCs promoted rapid and greater bone regeneration during the entire observation period. In contrast, obvious mineralization was detected starting from 3 wks after implantation in the ADSC group. These results suggest that BMSCs might be more useful than ADSCs for rapid bone regeneration for sinus augmentation with simultaneous implant placement.

Magnesium ion implantation on a micro/nanostructured titanium surface promotes its bioactivity and osteogenic differentiation function

As one of the important ions associated with bone osseointegration, magnesium was incorporated into a micro/nanostructured titanium surface using a magnesium plasma immersion ion-implantation method. Hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 30 minutes (Mg30) and hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 60 minutes (Mg60) were used as test groups. The surface morphology, chemical properties, and amount of magnesium ions released were evaluated by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, field-emission transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used to evaluate cell responses, including proliferation, spreading, and osteogenic differentiation on the surface of the material or in their medium extraction. Greater increases in the spreading and proliferation ability of rBMMSCs were observed on the surfaces of magnesium-implanted micro/nanostructures compared with the control plates. Furthermore, the osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) genes were upregulated on both surfaces and in their medium extractions. The enhanced cell responses were correlated with increasing concentrations of magnesium ions, indicating that the osteoblastic differentiation of rBMMSCs was stimulated through the magnesium ion function. The magnesium ion-implanted micro/nanostructured titanium surfaces could enhance the proliferation, spreading, and osteogenic differentiation activity of rBMMSCs, suggesting they have potential application in improving bone-titanium integration.

Selective responses of human gingival fibroblasts and bacteria on carbon fiber reinforced polyetheretherketone with multilevel nanostructured TiO2

The long-term success of dental implants relies not only on stable osseointegration but also on the integration of implant surfaces with surrounding soft tissues. In our previous work, titanium plasma immersion ion implantation (PIII) technique was applied to modify the carbon-fiber-reinforced polyetheretherketone (CFRPEEK) surface, constructing a unique multilevel TiO2 nanostructure thus enhancing certain osteogenic properties. However, the interactions between the modified surface and soft-tissue cells are still not clear. Here, we fully investigate the biological behaviors of human gingival fibroblasts (HGFs) and oral pathogens on the structured surface, which determine the early peri-implant soft tissue integration. Scanning electron microscopy (SEM) shows the formation of nanopores with TiO2 nanoparticles embedded on both the sidewall and bottom. In vitro studies including cell adhesion, viability assay, wound healing assay, real-time PCR, western blot and enzyme-linked immunosorbent assay (ELISA) disclose improved adhesion, migration, proliferation, and collagen secretion ability of HGFs on the modified CFRPEEK. Moreover, the structured surface exhibits sustainable antibacterial properties towards Streptococcus mutans, Fusobacterium nucleatum and Porphyromonas gingivalis. Our results reveal that the multilevel TiO2 nanostructures can selectively enhance soft tissue integration and inhibit bacterial reproduction, which will further support and broaden the adoption of CFRPEEK materials in dental fields.

Strontium delivery on topographical titanium to enhance bioactivity and osseointegration in osteoporotic rats

Osseointegration remains a major clinical challenge in osteoporotic patients. Strontium (Sr) has been shown to be a significant therapy to favor bone growth by both increasing new bone formation and reducing bone resorption. In this study, we attempt to chemically functionalize Ti implants by micro-arc oxidation, alkali treatment and ion exchange. This functionalized Ti surface possessed a hierarchical topography with Sr incorporation, which can release Sr ions at a slow rate. To our knowledge, this work is the first to use this type of Sr-doped Ti surface to address osteoporotic bone mesenchymal stem cells (BMSCs) in the dual directions of bone regeneration, bone formation and bone resorption. The modified surface was demonstrated to remarkably enhance the adhesion, spreading, and osteogenic differentiation of BMSCs in vitro. The effect of the wash-out solution from various groups on osteoporotic BMSCs was also investigated. The Sr-doped group can improve the ALP activity and osteogenic gene expression. Moreover, the Sr-doped group and the wash-out solution show the most inhibition in osteoclast formation and maturation. Furthermore, the increased bioactivity of the hierarchical structure was also confirmed with the ovariectomized rat femur model in vivo. The outcome of fluorescence labeling, histology and histomorphometric analysis demonstrated a significant promotion of osseointegration in ovariectomized rats. Altogether, the experimental data indicate that the fabrication of a Sr-doped hierarchical Ti surface is a meaningful attempt to incorporate the Sr nutrient element into Ti-based implants, and it is expected to be exploited in developing better osseointegration for osteoporotic patients.

Curculigoside promotes osteogenic differentiation of bone marrow stromal cells from ovariectomized rats

Curculigoside, a natural compound isolated from the medicinal plant Curculigo orchioides has been reported to prevent bone loss in ovariectomized rats. However, the underlying molecular mechanisms are largely unknown. This study investigated the effects of curculigoside on proliferation and osteogenic differentiation of bone marrow stromal cells (BMSCs).

rhPDGF-BB via ERK pathway osteogenesis and adipogenesis balancing in ADSCs for critical-sized calvarial defect repair.

Adipose-derived stem cells (ADSCs) with the capacity of differentiating into osteo-like cells have been widely investigated for bone tissue engineering as a novel seed cell source. Recombinant human platelet-derived growth factor (rhPDGF-BB) is a clinically proven growth factor with the potential of promoting cell proliferation and osteogenic differentiation during the bone regeneration process. In this study, we investigated the effects of rhPDGF-BB on the proliferation and osteogenic and adipogenic differentiation of rat ADSCs and explored whether the extracellular signal-related kinase (ERK) signaling pathway might be involved. We found that rhPDGF-BB significantly enhanced ADSCs proliferation and osteogenic differentiation, as detected by MTT, real-time polymerase chain reaction (PCR), ALP activity assays, and calcium deposition in vitro, in concert with ERK pathway activation. In contrast, the adipogenesis of ADSCs, as detected by real-time PCR and Oil Red O staining, was suppressed in the presence of rhPDGF-BB. Furthermore, with the supplement of the ERK inhibitor PD98059, cell proliferation and osteogenesis were reduced; as expected, adipogenesis was enhanced. Subsequently, for the first time, we evaluated the effect of ADSCs associated with rhPDGF-BB on bone regeneration in a critical-sized rat calvarial defect model with silk scaffold as a carrier. Micro-computed tomography and histological analyses exhibited dramatically more new bone formation and trabecular number in the Silk/PDGF/ADSC group. These data indicated that rhPDGF-BB promoted cell proliferation and osteogenic differentiation and suppressed adipogenic differentiation in vitro via ERK pathway and that ADSCs associated with rhPDGF-BB could be a promising tissue-engineered construct for craniofacial bone regeneration in vivo.

Evaluation of Osteogenesis and Angiogenesis of Icariin in Local Controlled Release and Systemic Delivery for Calvarial Defect in Ovariectomized Rats

Typically, bone regenerative medicine is applied to repair bone defects in patients with osteoporosis. Meanwhile, there is an urgent need to develop safe and cheap drugs that induce bone formation. Icariin, which is reported to promote the osteogenesis of stem cells in vitro, is the main active component of Herba Epimedii. However, whether icariin could repair bone defects caused by osteoporosis remains unknown. In this study, an osteoporosis model in rats was established by an ovariectomy first, and then, the osteogenic and angiogenic differentiation of bone mesenchymal stem cells (BMSCs) treated with icariin was evaluated. Furthermore, calcium phosphate cement (CPC) scaffolds loaded with icariin were constructed and then implanted into nude mice to determine the optimal construction. To evaluate its osteogenic and angiogenic ability in vivo, this construction was applied to calvarial defect of the ovariectomized (OVX) rats accompanied with an icariin gavage. This demonstrated that icariin could up-regulate the expression of osteogenic and angiogenic genes in BMSCs. Meanwhile, osteoclast formation was inhibited. Moreover, CPC could act as a suitable icariin delivery system for repairing bone defects by enhancing osteogenesis and angiogenesis, while the systemic administration of icariin has an antiosteoporotic effect that promotes bone defect repair.

In Vitro and in Vivo Evaluation of Silicate-Coated Polyetheretherketone Fabricated by Electron Beam Evaporation

Intrinsic bioinertness severely hampers the application of polyetheretherketone (PEEK), although in the field of dentistry it is considered to be an ideal titanium substitute implanting material. In this study, a bioactive silicate coating was successfully introduced onto PEEK surface by using electron beam evaporation (EBE) technology to improve its bioactivity and osseointegration of PEEK. Through controlling the duration of EBE, the incorporated amounts of silicon (Si) could be exquisitely adjusted to obtain proper biofunctionality, as assessed by cell adhesion, proliferation, osteogenic gene expression, and protein detection. In vivo, the samples were then tested in a femur implantation model to assay osseointegration effects in ovariectomized (OVX) rats. Remarkable enhancement of adhesion, spreading, osteogenesis, and differentiation of bone marrow stem cells (rBMSCs-OVX) were noted on silicate-coated samples. In particular, the group that was processed for 5 min with EBE (EBE-5 min) showed the most improvements in ALP activity and osteogenic-related gene expression compared to the remaining groups. Better osseointegration of the group that was processed for 8 min with EBE (EBE-8 min) was observed in vivo, as indicated by micro-CT test, fluorescent labeling, and histological and histomorphometric analyses. Collectively, the outcomes of the above experiments demonstrate that the present work is a meaningful attempt to promote osseointegration under osteoporotic conditions with only Si element incorporated to PEEK surface by the application of EBE technique. To the best of our knowledge, this work is the first demonstration of tuning the surface properties of PEEK via the adoption of an EBE-fabricated silicate coating to address an osteoporotic problem both in vitro and in vivo.

The response of human osteoblasts, epithelial cells, fibroblasts, macrophages and oral bacteria to nanostructured titanium surfaces: a systematic study

Nanotopography modification is a major focus of interest in current titanium surface design; however, the influence of the nanostructured surface on human cell/bacterium behavior has rarely been systematically evaluated. In this study, a homogeneous nanofiber structure was prepared on a titanium surface (Nano) by alkali-hydrothermal treatment, and the effects of this Nano surface on the behaviors of human MG-63 osteoblasts, human gingival epithelial cells (HGECs) and human gingival fibroblasts (HGFs) were evaluated in comparison with a smooth titanium surface (Smooth) by polishing and a micro-rough titanium surface (Micro) by sandblasting and acid etching. In addition, the impacts of these different surface morphologies on human THP-1 macrophage polarization and Streptococcus mutans attachment were also assessed. Our findings showed that the nanostructured surface enhanced the osteogenic activity of MG-63 cells (Nano=Micro>Smooth) at the same time that it improved the attachment of HGECs (Nano>Smooth>Micro) and HGFs (Nano=Micro>Smooth). Furthermore, the surface with nanotexture did not affect macrophage polarization (Nano=Micro=Smooth), but did reduce initial bacterial adhesion (Nano<Smooth<Micro). These results suggest that the nanostructured titanium surface may promote bone and soft tissue healing, and thereby increase the success and survival of dental implants.