RESUMO
The aim of this study was to develop chitosan composite scaffolds with high strength and controlled pore structures by homogenously dispersed nano-sized hydroxyapatite (nano-HAp) powders. In the fabrication of composite scaffolds, nano-HAp powders distributed in an alginate (AG) solution with a pH higher than 10 were mixed with a chitosan (CS) solution and then freeze dried. While the HAp content increased up to 70 wt.%, the compressive strength and the elastic modulus of the composite scaffolds significantly increased from 0.27 MPa and 4.42 MPa to 0.68 MPa and 13.35 MPa, respectively. Higher content of the HAp also helped develop more differentiation and mineralization of the MC3T3-E1 cells on the composite scaffolds. The uniform pore structure and the excellent mechanical properties of the HAp/CS composite scaffolds likely resulted from the use of the AG solution at pH 10 as a dispersant for the nano-HAp powders.
Assuntos
Alginatos/química , Materiais Biocompatíveis/química , Desenvolvimento Ósseo , Quitosana/química , Durapatita/química , Engenharia Tecidual/métodos , Alicerces Teciduais/química , Células 3T3 , Animais , Diferenciação Celular , Força Compressiva , Liofilização , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Concentração de Íons de Hidrogênio , Camundongos , Nanoestruturas/química , Osteoblastos/citologia , Osteoblastos/metabolismo , Tamanho da Partícula , PorosidadeRESUMO
PURPOSE: The aim of this in vitro study was to investigate the adhesion of initial colonizer, Streptococcus sanguis, on resin, titanium and zirconia under the same surface polishing condition. MATERIALS AND METHODS: Specimens were prepared from Z-250, cp-Ti and 3Y-TZP and polished with 1 µm diamond paste. After coating with saliva, each specimen was incubated with Streptococcus sanguis. Scanning electron microscope, crystal violet staining and measurement of fluorescence intensity resulting from resazurin reduction were performed for quantifying the bacterial adhesion. RESULTS: Surface of resin composite was significantly rougher than that of titanium and zirconia, although all tested specimens are classified as smooth. The resin specimens showed lower value of contact angle compared with titanium and zirconia specimens, and had hydrophilic surfaces. The result of scanning electron microscopy demonstrated that bound bacteria were more abundant on resin in comparison with titanium and zirconia. When total biofilm mass determined by crystal violet, absorbance value of resin was significantly higher than that of titanium or zirconia. The result of relative fluorescence intensities also demonstrated that the highest fluorescence intensity was found on the surface of resin. Absorbance value and fluorescence intensity on titanium was not significantly different from those on zirconia. CONCLUSION: Resin specimens showed the roughest surface and have a significantly higher susceptibility to adhere Streptococcus sanguis than titanium and zirconia when surfaces of each specimen were polished under same condition. There was no significant difference in bacteria adhesion between titanium and zirconia in vitro.
RESUMO
Kindlins are focal adhesion proteins that regulate integrin signaling. Although integrin activation is critical for bone development, little is known about the expression and role of kindlins in osteoblasts. We therefore investigated the function of kindlin-2 in osteoblast adhesion, spreading, and proliferation using small interfering RNA. In MC3T3-E1 cells, only kindlin-2 is highly expressed and localizes to focal adhesion. We found that kindlin-2 was involved in integrin activation in MC3T3-E1 cells and that kindlin-2 knockdown osteoblasts resulted in diminished cell adhesion, spreading, and proliferation. In this process, kindlin-2 knockdown impaired transient Rac1 activation, influencing Akt activation and AP-1 activity. In agreement with these data, pharmacological inhibition of Rac1 reduced MC3T3-E1 cell adhesion, spreading, and proliferation. Overall, these findings demonstrated that kindlin-2 governs Rac1 activation, which controls osteoblast function. Our findings provide the first insights concerning the function of kindlin-2 in osteoblast, and suggest that kindlin-2 is a critical mediator for osteoblast physiology.
Assuntos
Adesão Celular , Proliferação de Células , Proteínas do Citoesqueleto/metabolismo , Ativação Enzimática , Proteínas Musculares/metabolismo , Neuropeptídeos/metabolismo , Osteoblastos/fisiologia , Proteínas rac de Ligação ao GTP/metabolismo , Aminoquinolinas/farmacologia , Animais , Linhagem Celular , Proteínas do Citoesqueleto/genética , Expressão Gênica , Técnicas de Silenciamento de Genes , Integrina beta1/metabolismo , Camundongos , Proteínas Musculares/genética , Neuropeptídeos/antagonistas & inibidores , Osteoblastos/citologia , Osteoblastos/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Pirimidinas/farmacologia , Interferência de RNA , Fator de Transcrição AP-1/metabolismo , Proteínas rac de Ligação ao GTP/antagonistas & inibidores , Proteínas rac1 de Ligação ao GTPRESUMO
Hydroxyapatite (HA) is a widely used calcium phosphate implant substitute and has dissolution property. Although HA has been shown a beneficial effect on osteoblast differentiation, the exact mechanism is still unclear. In the present study, we proposed that Ca(2+) released from HA activated the expression bone associated proteins, OPN and BSP, mediated by L-type calcium channel and calcium/calmodulin-dependent protein kinase (CaMK) 2 which resulted into improved osteoblast differentiation. Results showed that HA elevated ALP expression as well as OPN and BSP expression in MC3T3-E1 cells. The result from western blot of CaMK2alpha indicated that HA released Ca(2+) activated CaMK2 through L-type calcium channel. Furthermore, upregulation of OPN and BSP mRNA expression was significantly inhibited when blocking both the L-type calcium channel and CaMK2. These findings suggested that HA accelerated the osteoblast differentiation by releasing Ca(2+).
