Fei Wei

Blood clot formed on rough titanium surface induces early cell recruitment

OBJECTIVES The initial contact of blood with biomaterials and subsequent recruitment of inflammatory and marrow-derived stromal cells are among the first phases of bone regeneration. The aim of this study was to investigate the migratory potential of mesenchymal stem cells by treating rat bone marrow mesenchymal stromal cells (rBMSCs) with the extract of the blood clot formed on implant surfaces. MATERIALS AND METHODS Cell attachment and morphology on the blood clot was observed using scanning electron microscopy. The cell metabolism was reflected by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, and the cell proliferation was assessed by the CyQuant(®) assay based on DNA content. Cytokine profiles in the incubation medium derived from different blood-titanium surface were detected using the rat cytokine antibody array. Scratch wound assay and transwell migration assay were performed to determine the effect of blood-implant conditioned medium on cell migration and movement. RESULTS No significant difference was found in cell attachment and morphology on the blood clot formed on smooth and rough surfaces. Increased rBMSC proliferation was induced by the blood clot on rough surfaces. Comparison of cytokine secretion showed a significant increase of CINC-2α, IL-2, L-selectin, MCP-1, prolactin AA and VEGF levels in the elution of blood clot formed on rough titanium surfaces, which led to significantly improved mobility and wound healing ability of rBMSCs. CONCLUSIONS Rough titanium surfaces could influence the blood clot formation and properties, which will induce cell recruitment and stimulate wound healing.

Effect of nano-structural properties of biomimetic hydroxyapatite on osteoimmunomodulation

Immune cells are sensitive to the microstructural and textural properties of materials. Tuning the structural features of synthetic bone grafts could be a valuable strategy to regulate the specific response of the immune system, which in turn modulates the activity of bone cells. The aim of this study was to analyse the effect of the structural characteristics of biomimetic calcium deficient hydroxyapatite (CDHA) on the innate immune response of macrophages and the subsequent impact on osteogenesis and osteoclastogenesis. Murine RAW 264.7 cells were cultured, under standard and inflammatory conditions, on chemically identical CDHA substrates that varied in microstructure and porosity. The impact on osteogenesis was evaluated by incubating osteoblastic cells (SaOS-2) with RAW-CDHA conditioned extracts. The results showed that macrophages were sensitive to different textural and structural properties of CDHA. Under standard conditions, the impact of inflammatory cytokine production by RAW cells cultured on CDHA played a significant role in the degradation of substrates, suggesting the impact of resorptive behaviour of RAW cells on biomimetic surfaces. Osteoblast differentiation was stimulated by the conditioned media collected from RAW cells cultured on needle-like nanostructured CDHA. The results demonstrated that needle-like nanostructured CDHA was able to generate a favourable osteoimmune environment to regulate osteoblast differentiation and osteogenesis. Under inflammatory conditions, the incubation of RAW cells with less porous CDHA resulted in a decreased gene expression and release of pro-inflammatory cytokines.