Poly(lactide-co-glycolide)-bilayered scaffolds with the same porosity or different ones on the two layers were fabricated,and the porosity effect on in vivo repairing of the osteochondral defect was examined in a comparative way for the first time.The constructs of scaffolds and bone marrow-derived mesenchymal stem cells were implanted into pre-created osteochondral defects in the femoral condyle of New Zealand white rabbits.After 12 weeks,all experimental groups exhibited good cartilage repairing according to macroscopic appearance,cross-section view,haematoxylin and eosin staining,toluidine blue staining,immunohistochemical staining and real-time polymerase chain reaction of characteristic genes.The group of 92%porosity in the cartilage layer and 77%porosity in the bone layer resulted in the best efficacy,which was understood by more biomechanical mimicking of the natural cartilage and subchondral bone.This study illustrates unambiguously that cartilage tissue engineering allows for a wide range of scaffold porosity,yet some porosity group is optimal.It is also revealed that the biomechanical matching with the natural composite tissue should be taken into consideration in the design of practical biomaterials,which is especially important for porosities of a multi-compartment scaffold concerning connected tissues.
The purpose of this paper is to utilize the signaling pathway polymerase chain reaction(PCR)arrays to investigate the activation of two important biological signaling pathways in endothelial cell adhesion and growth mediated by adsorbed serum protein on the surface of bare and titanium nitride(TiN)-coated nickel titanium(NiTi)alloys.First,the endothelial cells were cultured on the bare and TiN-coated NiTi alloys and chitosan films as control for 4 h and 24 h,respectively.Then,the total RNA of the cells was collected and the PCR arrays were performed.After that,the differentially expressed genes in the transforming growth factor beta(TGF-b)signaling pathway and the regulation of actin cytoskeleton pathway were screened out;and the further bioinformatics analyses were performed.The results showed that both TGF-b signaling pathway and regulation of actin cytoskeleton pathway were activated in the cells after 4 h and 24 h culturing on the surface of bare and TiN-coated NiTi alloys compared to the chitosan group.The activated TGF-b signaling pathway promoted cell adhesion;the activated regulation of actin cytoskeleton pathway promoted cell adhesion,spreading,growth and motility.In addition,the activation of both pathways was much stronger in the cells cultured for 24 h versus 4 h,which indicated that cell adhesion and growth became more favorable with longer time on the surface of two NiTi alloy materials.
Poly(lactic acid) (PLA) and other aliphatic polyesters containing the unit of lactic acid are very popular biodegradable materials. While the degradation products, lactic acids, have been worried to bring with negative influence on biocompatibility, the focused experimental studies are less reported. This study is aimed at an in vitro examination of cytotoxicity of both L-lactic acid and D,L-lactic acid. Mesenchymal stem cells (MSCs) derived from rat bone marrow are employed to test the cytotoxicity of the lactic acids. Considering that the addition of lactic acids not only introduces lactate groups but also alters medium pH and ion strength, these three candidate effects are examined in a decoupled way by setting different comparison groups. The results confirm that the change of medium pH is the predominant factor. It has also been found that D-lactate is more cytotoxic than L-lactate at high concentrations. Yet, either L-or D,L-lactic acids seem acceptable in most of medical applications, because the cytotoxicity is significant only when the concentrations are as high as 20 mmol/L for both of them.
