Papers by Keyword: Osteoblast

Abstract: Similar to other glucocorticoids, dexamethasone (DEX) induces osteoblast differentiation. At high concentrations, glucocorticoids may induce osteoporosis as a side effect. However, the exact mechanism of these two opposing effects has not been elucidated. To understand the mechanism of DEX-induced osteoblast differentiation, we developed a real-time osteoblast differentiation detection system using dual labeling of cells with fluorescent proteins. The promoter sequences of type I collagen and osteocalcin were ligated with mCherry and green fluorescent protein (GFP), respectively. Type I collagen is an early marker of osteoblast differentiation, and osteocalcin is a terminal differentiation marker. We investigated the effects of DEX on cell proliferation and differentiation using cells transformed with both constructs. Low DEX concentrations (<10 μM) induced calcification, as determined by alizarin-red staining, whereas calcification was inhibited at higher concentrations (>100 μM). Consistent with these results, mCherry-associated red fluorescence as an early marker was evident under both conditions, whereas green fluorescence associated with terminal differentiation was evident only at lower DEX concentrations. The level of green fluorescence diminished in a DEX-concentration-dependent manner. Thus, DEX does not inhibit the early stages of osteoblast differentiation but instead inhibits terminal differentiation.

Abstract: We have previously established a wet synthesis method of octacalcium phosphate (OCP) in a relatively large scale and found that OCP enhances bone formation more than synthetic hydroxyapatite (HA) if implanted onto bone surface and various bone defects. The present paper reviews, based on our studies, as to how OCP controls in vitro cellular activities of bone-related cells, such as bone marrow stromal cells, and how OCP enhances bone repair in critical sized bone defect experimentally created in animal models. OCP tends to progressively convert to HA in culture media and in rat calvaria defects. OCP is capable of enhancing in vitro osteoblast differentiation and osteoclast formation in the presence of osteoblasts. Recent our studies also indicated that OCP enhances odontoblast differentiation while suppresses chondrogenic differentiation. The physicochemical properties, such as chemical composition and adsorption affinity of serum proteins, vary depending on the advancement of conversion from OCP to HA, which suggests that the change on the surface property during the conversion of OCP may affect the cellular responses in vitro and tissue reaction in vivo. OCP could be used as a scaffold material that can control the activity of bone-related cells.

Abstract: Constructing biomimetic tissue architecture in vitro holds the key to the realization of tissue engineering. To control the anisotropic microstructure of bone tissue which governs the mechanical properties of bone, especially, is imperative for the establishment of ideal bone regeneration process. In this study, highly aligned collagen scaffolds were fabricated to control osteoblast alignment. Collagen fibrillogenesis were regulated by an extrusion process, resulting in formation of biomimetic, hierarchically-aligned bony microstructure. Osteoblasts adhered to the fabricated scaffolds showed aligned morphology along the collagen orientation. In the present method, the degree of scaffold orientation is regulatable, which suggests that the designing of the appropriate scaffolds depending on the tissue anisotropy is possible. Interestingly, the bone matrix produced by the aligned osteoblasts exhibited anisotropic microstructure along the cell alignment. Our findings imply that controlling the osteoblast alignment by oriented collagen scaffolds could be an initiator to establish the anisotropic bone structural development or regeneration.

Abstract: Bone microstructure is dominantly composed of anisotropic extracellular matrix (ECM) in which collagen fibers and epitaxially-oriented biological apatite (BAp) crystals are preferentially aligned depending on the bone anatomical position, resulting in exerting appropriate mechanical function. The regenerative bone in bony defects is however produced without the preferential alignment of collagen fibers and the c-axis of BAp crystals, and subsequently reproduced to recover toward intact alignment. Thus, it is necessary to produce the anisotropic bone-mimetic tissue for the quick recovery of original bone tissue and the related mechanical ability in the early stage of bone regeneration. Our group is focusing on the methodology for regulating the arrangement of bone cells, the following secretion of collagen and the self-assembled mineralization by oriented BAp crystallites. Cyclic stretching in vitro to bone cells, principal-stress loading in vivo on scaffolds, step formation by slip traces on Ti single crystal, surface modification by laser induced periodic surface structure (LIPSS), anisotropic collagen substrate with the different degree of orientation, etc. can dominate bone cell arrangement and lead to the construction of the oriented ECM similar to the bone tissue architecture. This suggests that stress/strain loading, surface topography and chemical anisotropy are useful to produce bone-like microstructure in order to promote the regeneration of anisotropic bone tissue and to understand the controlling parameters for anisotropic osteogenesis induction.

Abstract: The ozone oxidation can easily produce peroxides with free radicals for the surface modification on biomaterials. This process would be highly efficient and without toxicity. In this research, naringin, a HMG-CoA reductase inhibitor which can promote bone formation, was immobilize onto chitosan film by using the ozone activation process. At first, chitosan films were treated by the ozone activation to produce peroxides for the following immobilization of naringin. The amounts of peroxides produced by ozone treatment were quantified by the iodide assay. The immobilized naringin were identified with UV and FTIR. The results indicated successful immobilization of naringin. The concentration of crosslinkers was also optimized in this study. From SEM images, the surface topography of chitosan film was not changed after the immobilization process. The FTIR spectra indicated the difference in amine bonds of chitosan, revealing that there would be the chemical reaction between chitosan and crosslinkers. In the in vitro delivery, the chitosan substrate with immobilized naringin was immersed in PBS and the released amount of naringin was measured by UV every two days. It was found that the immobilized naringin was slowly released in two weeks, where the naringin concentration was successfully controlled by this delivery process. The results of cell culture showed that cell activity, attachment and proliferation were promoted with immobilized naringin without any cytotoxicity. The early osteoblastic differentiation, ALPase expression, was also enhanced. The results in this research demonstrated the successful immobilization of naringin onto chitosan substrates. With the slow delivery of naringin, the naringin-chitosan substrate was highly osteoconductive without cytoxicity.

Abstract: In this study, we prepared porous nano-hydroxyapatite/ polyamide 66 (n-HA/ PA66) porous scaffolds by injection molding method. The morphology, macrostructure and mechanical strength of the scaffolds were characterized. Osteoblasts (OBs) derived from cranial bone of SD rats were cultured and seeded on n-HA/ PA66 scaffolds. The OB/scaffold constructs were cultured for up to 18 days and the adhesion, proliferation and osteogenic activity of OBs were observed by scanning electron microscope and detected by alkaline phosphatase activity. The results showed that the porous n-HA/PA66 porous scaffolds are biocompatible and have no negative effects on the OBs in vitro. The scaffolds fulfill the basic requirements of bone tissue engineering scaffold, and have the potential application in orthopedic, reconstructive and maxillofacial surgery areas.

Abstract: This study used micro-arc oxidation technology for pure titanium alloy surface modification, which 400μm titanium beads were sintered into porous titanium in vacuum conditions, and produced silicon and calcium coatings. Scanning electron microscope(SEM), X-ray diffraction (XRD) and Energy dispersion spectrometer(EDS) were employed to investigate the surface morphology and phase composition of the coatings. The results are listed as follows: the main component of porous titanium MAO coating is anatase TiO2,and the coating introduced silicon and calcium element successfully. The proliferation ability of osteoblasts on the oxidized and unoxidized surface was determined by CCK-8 method, The results indicated that both the proliferation and adhesion ability of osteoblast on the oxidized surface were better than the unoxidized surface.

Abstract: Three methods have been used to modify the porous titanium surface, which is the alkali heat treatment, alkali heat treatment + SBF solution soak and alkali heat treatment + precalcidied + SBF solution soak. The morphology of different surfaces was observed by scanning electron microscopy (SEM). The MC3T3-E1 osteoblast cell was cultured on the modified and unmodified surface of porous titanium with 3days and 7days, the morphology of osteoblast adhesion and growth on different surface was observed. The results showed that osteoblast adhere on the modified and unmodified surface of the porous titanium. Osteoblast on AHS and HA modified surface can grow and spread, but it cannot grow and spread on unmodified and AH modified surface of the porous titanium. Osteoblast can grow across the different titanium fibers of on HA modified surface of porous titanium. Osteoblast on the HA surface has the very good biological suitability, which is beneficial to the combination of bone tissue and porous titanium.

Abstract: Calcium plays an important role in various stages of bone repair. Surface calcium modification is a common method to improve the biocompatibility of titanium implant. In this work, anovel facile codeposition dopamine/calcium on titanium alloy method for orthopedics applications was developed. SEM-EDS results showed calcium microspheres uniformly deposited on titanium surface with dopamine. Water contact angle showed the dopamine/calcium modification layer improved the bare titanium surface hydrophobic property. And the dopamine/calcium coating enhanced the cell proliferation by MTT test. The ALP gene expression also showed the dopamine/calcium coating may enhance the cell early differentiation. Such facile method has great potential in titanium applications.

Abstract: Micro- and nanotopography as well as the surface chemistry of biomaterials affect cell adhesion, proliferation and cell differentiation. Furthermore, the organization and localization of intracellular adhesion components such as the actin cytoskeleton are also altered dependent on the material surface topography. However, the detailed influence of the material micro-structure on cellular mechanisms on the molecular level is still unknown. This study is intended to elucidate such effects using regular pillar structures to characterize the modulation of cell responses like the regulation of voltage-sensitive calcium channels as well as signaling molecules in human osteoblasts. To analyze cell behavior on defined biomaterial surfaces, human osteoblastic MG 63 cells were cultured on geometrically micro textured titanium coated silicon wafers, as opposed to planar titanium references. Samples were fabricated by a photolithographic process using the negative tone resist SU 8 and sputter-coated with 100 nm titanium. Immunofluorescence staining and flow cytometry are used to detect the expression levels and the function of T type calcium channels. Knowledge about the biocomplexity of cell behavior dependent on topographical characteristics is of clinical relevance for the development of implant designs in tissue engineering.