Key Engineering Materials Vols. 361-363

Abstract: Hydroxyapatite (HA) is a bioactive ceramic material with a chemical composition similar to natural bone, and carbon nano tubes (CNT) is able to enhance the brittle ceramic matrix without detrimental to the bioactivity. This study reported an attempt to use a commercially multiwalled CNT strengthen brittle hydroxyapatite bioceramics. Using iTRAQ-coupled 2D LCMS/ MS analysis, we report the first study of protein profile in osteoblasts from human osteoblastic cell line incubated separately on HA with and without strengthening multiwall CNT surfaces. Sixty proteins were identified and quantified simultaneously at the initial culturing stage of 3 days. The results were validated by Western blotting for selected proteins: Fetuin-A, Elongation factor II and Peroxiredoxin VI. Fetuin-A showed up-regulation, and Peroxiredoxin VI gave down-regulation in the osteoblasts cultured on HA based ceramic surfaces. Similar regulation was expressed by the protein of Elongation factor II on the phase pure HA surfaces as compared to the control group cultured on the polystyrene substrate. Relatively high EF 2 expression was detected on the phase the surfaces of CNT strengthen HA samples.

Abstract: In this work we examine the effect of the ionic exchange in cell behaviour of two apatite substrates with the same chemical composition but different microstructures (Coarse and Fine) by culturing cells with their extracts. A higher decrease in Ca and a higher increase in P concentrations were detected in the culture medium extracts from the finer apatite substrate in accordance with its higher specific surface area. A decrease in cell proliferation was observed when cells were cultured with the Fine extract in comparison with cells in contact with the Coarse extract or the control group. Although the higher ionic exchange, this could not explain the drastic decrease in cell proliferation observed on Fine apatite substrates, so a strong interaction with the underlying microstructure that modulates cell behaviour is also present.

Abstract: The osteoblast adhesion to the substrates are recognized to play a fundamental role in osteoconduction process. The purpose of this study was to evaluate the in vitro behavior of osteoblasts cultured on polarized hydroxyapatite (HA), having the enhanced osteobonding abilities. Osteoblast-like cells were seeded onto the polarized HA and investigated the adhesion and motility. The polarization had no effects on the percentage of the number of the spreaded cells against all the adhered cells, but had significant effects on the elongation of adhered cells from fluorescent observation and on the cell motility showed by the wound healing assay. The charges induced on the HA surface accelerated the cytoskeleton reorganization of the adhered cells cultured on HA specimens. The acceleration was emerged as the cells shape, actin filament pattern such as stress fiber formation, and the prolongation of the cell movement distances.

Abstract: This work aimed at preparing dense and monophasic silicated hydroxyapatite ceramics over the range 0 ≤ x ≤ 1.0 mol of silicon. The synthesis of the powder via an aqueous precipitation process followed by an adapted thermal treatment showed that it was possible to obtain dense single-phased apatite ceramics containing up to 0.6 mol of silicon. The in vitro biological characterization of these materials was performed.

Abstract: The decrease in bone mass caused by wear debris-induced osteolysis could have been compensated through osteoblasts secreting enough new bone matrix. However, the normal osteoblastic population depends on the regular differentiation of their progenitor cells, the bone marrow mesenchymal stem cells (BMSCs). It is not possible to predict whether wear particles will affect the BMSCs’ viability, and subsequently their differentiation. Furthermore, little is known about the extent to which the sizes of the wear particles loading can impact the viability the most. This study has, therefore, concentrated on the potential mechanism for rat BMSCs’ (rBMSCs) viability influenced by different-sized titanium particle (Ti) loading in vitro.rBMSCs were harvested and loaded with circular Ti particles having three different mean diameters, 0.9, 2.7 and 6.9 .m respectively. The results showed that different-sized titanium particles all inhibited rBMSCs’ proliferation and induced rBMSCs’ apoptosis response , but this influence varied with the size of the Ti particles, their concentration and the duration of loading. The smallest Ti particles (0.9.m) exhibited the earliest and largest suppression on the proliferation and the most powerful induction on the apoptotic response of rBMSCs. qRT-PCR analysis demonstrated that those apoptotic effects were association with the abnormal accentuation of inducible nitric oxide synthase(iNOS) activity. The size of titanium particles generated through wear of a prosthetic device and the osteoblastic progenitor BMSCs may be both important considerations in the development of superior implant technology.

Abstract: Hydroxyapatite (HA) ceramics together with various kinds of osteogenic cells have been used in bone tissue engineering. It is well known that the ceramics structure and composition affect cell proliferation / differentiation. In this study, three different types of HA ceramics were used to investigate initial cell attachment followed by osteoblastic differentiation of human mesenchymal stromal cells (MSCs). The results indicated that micro-pore affected the cell attachment and porosity (pore diameter and inter-pore connection) was the key to allow spacious distribution of the viable cells in the ceramics. This study also confirmed that surface pore areas of HA ceramics support the differentiation of human MSCs and thus the ceramics have the capability to regenerate damaged bone tissue.

Abstract: MC3T3-E1 mouse osteoblast-like cells were seeded at high cell density to form confluent monolayer on rough surfaced culture substrates. Osteoblastic gene and protein expressions and matrix mineralization were investigated to clarify the effect of surface roughness on differentiation of MC3T3-E1 cells.

Abstract: Appropriate culture conditions cause bone marrow stem cells to differentiate into multilineage cells such as adipocytes, chondrocytes, and osteoblasts. One key factor that regulates intercellular signaling and cell differentiation is the extracellular matrix microenvironment. The composition of the extracellular matrix influences cellular functions. In the present study, we investigated the effects of a microenvironment comprising a three-dimensional apatite-fiber scaffold (AFS) that has two kinds of pores (micro- and macro pores) on proliferation and subsequent differentiation of bone marrow stem cells. Morphologic observation revealed that osteoblastic cells in the AFS were distributed primarily in the same location on the fibrous scaffold and formed bridges within micro- and macro pores. We used molecular approaches to evaluate cell proliferation and differentiation in detail. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that culturing bone marrow cells on AFS increases expression of osteocalcin (OC) mRNA compared with culture in a dish. Furthermore, cells cultured in AFS expressed type X collagen (Col X), which is a marker of hypertrophic cartilage. These data suggest that the three-dimensional microenvironment of AFS facilitates cell proliferation and differentiation, and promotes endochondral ossification of bone marrow cells.

Abstract: The bone-like self-organized hydroxyapatite/collagen (HAp/Col) nanocomposite sponge was prepared from HAp/Col nanocomposite fibers. We analyzed osteogenic activity of human osteoblastic MG63 cells in the HAp/Col sponge under pressure/perfusion culture. Collagen (Col) sponge was used as a control. The MG63 cells were attached well and showed good proliferation in the HAp/Col sponge. The total DNA content in the HAp/Col sponge was approximately 1.8 times greater than that in the Col sponge at 21 days. The MG63 cells showed good osteogenic gene expression in the HAp/Col sponge by reverse transcription-polymerase chain reaction analysis. These result suggested that HAp/Col sponge can be useful for bone tissue engineering scaffold materials.

Abstract: Wollastonite bioceramics prepared from synthetic and natural precursors were implanted in rats in bone and subcutaneous tissues. The implant sites were excised after 7, 30 and 120 days, fixed, dehydrated, embedded in paraffin wax for serial cutting and examined under transmitted light microscope. It was found a very similar behavior for both wollastonite bioceramics. They were biocompatible, bioactive and biodegradable when implanted in rat bone. The synthetic ceramic was more reabsorbable than the one from natural powder. When implanted in subcutaneous rat tissue, both materials elicited a mild initial inflammatory reaction that practically disappeared after 120 days. Both materials were encapsulated with a very thin fibrous capsule and slightly reabsorbed at their surfaces. None of the materials induced ectopic osteogenesis. According to the results, the studied materials seem to be able for manufacturing reabsorbable bone implants.