Papers by Author: Jie Feng

Abstract: Biomimetic nanoapatite coatings was developed by functionally modified methods with a combination of topographic, chemical and biomimetic treatments on the surface of titanium (Ti) substrate. The biological behavior and bioactivity of functionally modified SLA implants with chemical and biomimetic treatments (SCB-treated Ti) using body like solution were investigated to compare with untreated Ti and SLA Ti plates as controls. The cell attachment, proliferation, alkaline phosphotatse (AKP) activity, cell morphology and differentiation were evaluated by using MTT, RT-PCR, scanning electron microscopy (SEM) and confocal laser-scanning microscope (CLSM) analysis system. The results showed that the cell adhesion and proliferation was enhanced on functionalized titanium surface with nano-scale apatite compared to the controls. SEM micrographs also revealed that the osteoblast-like cells spreadly grew along the surface. Cell morphology and differentiation could be further observed distinctly by CLSM graphs. Moreover, mRNA expression of alkaline phosphotatse in nucleus on the SCB-treated Ti increased obviously on the third day compared with the controls. The in vitro results demonstrated the remarkable improvement on cell adhesion and proliferation of the biomimetic nanoapatite on SCB-treated Ti, which could be used for orthopaedic/dental implants.

Abstract: To evaluate the effectiveness of the cell-material in situ on joint resurfacing, a woven fabric polyglycolic acid (PGA) treated with fresh chondrocytes was used for repairing cartilage defects. Full-thickness defects were created in the weight-bearing surfaces of the femoral intercondylar fossa in a rabbit model. The defect was filled with and without PGA under surgical condition. Before implantation, chondrocytes were co-cultured with PGA for one day. The animals were sacrificed at eight weeks after implantation and evaluated grossly and histological score. Morphological examination showed that for PGA/chondrocytes group, the repaired tissue appeared similar in color and texture to the surrounding articular surface. While for the untreated control, no cartilage-like tissue was observed at all defects, but connective fibrous tissue. Histological analysis revealed neochondrogenesis and clusters of cartilage matrix with specific safranin-O staining for the PGA/cell group. The Gross and histological evaluation indicated a significantly higher score for PGA/cell group than for PGA and control group. These results suggest that the woven fabric PGA may facilitate the formation of cartilage tissues by providing a biodegradable and good-handle vehicle for the delivery to and retention of organized cell matrix constructs in vivo site. It might therefore enhance neochondrogenesis because of the superior biodegradable and biocompatible of PGA scaffold sheet, while the more suitable biological environment might sustain cell growth and in situ cell function, suggesting a promising candidate for functional tissue engineering of clinical environment.

Abstract: Bone grafts have been used to fill bone defects caused by disease or trauma. The amount of autografts is limited and allogenic bone grafts may transmit diseases and cause immune responses. Numerous materials have been proposed and used as scaffolds for bone tissue reconstruction. In this study, we tested nanophase PLGA/HA composite with mesenchymal stem cells in vitro to examine its biological response and cellular activity. The nanophase composite was compared to conventional polystyrene on cytocompatibility by cell attachment, proliferation, alkaline phosphotase activity test and scanning electron microscopy (SEM) analysis. The results demonstrated that human mesenchymal cells showed more cell attachment and higher cell proliferation rate when growing on nanophase PLGA/HA composite than those growing on polystyrene alone. And the composite also promoted MSC cells differentiate to osteoblast cells as compared with control. It was suggested that the combination of bone marrow mesenchymal cells with artificial materials or differentiation factors may enhance bone formation and regeneration, nanophase PLGA/HA composite might therefore be a promising scaffold material for bone tissue substitute in clinical application.

Abstract: A novel composite of biodegradable Poly-L-lactic acid (PLLA) with the deposition of the nanosized amorphous calcium phosphate (NCP) particles was developed as tissue engineering scaffold. To improve the minor intrinsic healing capacity of cartilage tissue, the porous composite with desired degradation rate was incorporated with basic fibroblast growth factor (bFGF) and evaluated in the in vivo environment. Full-thickness defects were created in the weight-bearing surface of the femoral condyles in a rabbit model. The defect was filled with and without NCP/PLLA scaffold as a carrier of bFGF. Gross morphology for the test implant showed that the defect was filled with regenerated tissue. It resembled cartilaginous tissue and restored the contour of the condyle at 8 weeks after operation. For the untreated control, no cartilage-like tissue was observed at all defects. Histological analysis revealed neochondrogenesis and clusters of cartilaginous extracellular matrix observed with safranin-O staining at 4 weeks for the NCP/PLLA with bFGF treated defects. At 8 weeks after operation, well-formed and mature cartilage was resurfaced the defects. While only fibrous tissue replacement was observed for the control either at 4 or 8 weeks. Special staining for cartilage indicated the presence of highly sulfated glycosaminoglycans and collagen, which were the major extracellular matrices of cartilage. This investigation showed the potential of NCP/PLLA loaded with bFGF in the study of in situ-transplantable carrier to improve healing of cartilage tissue lesion.

Abstract: The objective of this study was to evaluate the interface shear strength and the responses of osteoblast-like cells to titanium implants with a sandblasted and acid-etched surface modified by alkali and heat treatments (SLA-AH). The implants with machined and SLA surface served as controls. Each type of implant was characterized by scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) analysis. In vitro assays were made using human osteoblast-like cell culture on different surfaces. The rectangle plates were also transcortically implanted into the proximal metaphysis of New Zealand White rabbit tibiae. After 4, 8 and 12 weeks implantation, mechanical and histological assessments were performed to evaluate biomechanical and biological behavior in vivo. By SEM examination, SLA surface combined with AH treatments revealed a macro-rough surface with finely microporous structure. The in vitro assays showed that the SLA-AH surfaces exhibited more extensive cell deposition and improved cell proliferation as compared with controls. Pull-out test demonstrated that the SLA-AH treated implants had a higher mechanical strength than the controls at all interval time after implantation. Histologically, the test implants revealed a significantly greater percentage of bone-implant contact when compared with controls. The results of this study suggest that a useful approach by combined processes could optimize implant surfaces for bone deposition and produce distinct biological surface features.

Abstract: Stimulation of bone healing through local application of growth factors from implants may improve the clinical outcome in fracture treatments. However, the growth factors in reconstructive application require supraphysiologic dosing and considerable expense while hampering their clinical application. Genetic modification of mesenchymal stem cells (MSCs) to both produce and respond to osteogenic factors may have potential for use in enhancing bone healing. In this study, MSCs were genetically modified by a recombinant adenoviral containing the gene for human bone morphogenetic protein 2 (hBMP-2). The gene-transduced cells were incorporated with a porous beta-tricalcium phosphate (TCP) as a novel complex. We investigated osteogeneic potential of gene-transduced MSCs/ceramic and the ability of the complex on facilitating bone formation in a radius segmental defect of rabbits. In vitro results showed that there were apparent hBMP2 gene expression and protein synthesis in MSCs with hBMP2 stably transfection, whereas negative expression of hBMP2 in controls. Histological studies demonstrated that gene-transfected MSCs/ceramic composite appeared an ability of heterotopic osteogenesis. In the segmental bone defects, endochondrial ossification at fracture sites was found in both transfected and untransfected MSCs-ceramic composites. While the composite with hBMP2 transfection showed the earliest and the most effective healing of the segmental bone defects both radiographically and morphologically. Our results show that genetically modified MSCs/ceramics had enhanced osteogeneic capacity relative to unmodified MSCs or only ceramic implants. This study suggests that use of cell-and gene-activated bioceramics may offer promise for molecular design of implants to induce osteogenesis and enhance bone regeneration.