Background Natural articular cartilage has a limited capacity for spontaneous regeneration. Controlled release of transforming growth factor-β1 （TGF-β1） to cartilage defects can enhance chondrogenesis. In this study, we assessed the feasibility of using biodegradable chitosan microspheres as carriers for controlled TGF-β1 delivery and the effect of released TGF-β1 on the chondrogenic potential of chondrocytes. Methods Chitosan scaffolds and chitosan microspheres loaded with TGF-β1 were prepared by the freeze-drying and the emulsion-crosslinking method respectively. In vitro drug release kinetics, as measured by enzyme-linked immunosorbent assay, was monitored for 7 days. Lysozyme degradation was performed for 4 weeks to detect in vitro degradability of the scaffolds and the microspheres. Rabbit chondrocytes were seeded on the scaffolds containing TGF-β1 microspheres and incubated in vitro for 3 weeks. Histological examination and type Ⅱ collagen immunohistochemical staining was performed to evaluate the effects of released TGF-β1 on cell adhesivity, proliferation and synthesis of the extracellular matrix. Results TGF-β1 was encapsulated into chitosan microspheres and the encapsulation efficiency of TGF-β1 was high （90.1%）. During 4 weeks of incubation in lysozyme solution for in vitro degradation, the mass of both the scaffolds and the microspheres decreased continuously and significant morphological changes was noticed. From the release experiments, it was found that TGF-β1 could be released from the microspheres in a multiphasic fashion including an initial burst phase, a slow linear release phase and a plateau phase. The release amount of TGF-β1 was 37.4%, 50.7%, 61.3%, and 63.5% for 1, 3, 5, and 7 days respectively. At 21 days after cultivation, type II collagen immunohistochemical staining was performed. The mean percentage of positive cells for collagen type II in control group （32.7%± 10.4%） was significantly lower than that in the controlled TGF-β1 release group （92.4%±4.8%,
CAI Dao-zhangZENG ChunQUAN Da-pingBU Li-siWANG KunLU Hua-dingLI Xiao-feng
Objective To investigate the effects of rhubarb extracts,i.e.rhein and emodin,on the neuronal hyperexcitability and synaptic transmission,and to further reveal the mechanism of the secondary brain damage.Methods The fluid percussion injury(FPI) rat model and extracellular recording method were used.The evoked field potentials by stimulating Schaffer collaterals were collected from the ipsilateral(impact side) and the contralateral hippocampal CA1 areas of rat in vitro.And the field potentials,including the field excitatory postsynaptic potential and the population spike,were analyzed.Results After the impact was performed on the rat parietal cortex,the evoked field potentials in the ipsilateral hippocampus CA1 area were enhanced obviously.Rhubarb extracts reduced the slope of the field excitatory postsynaptic potential and the number of the population spike significantly while rhein and emodin increased the latency of the population spike obviously.Conclusion Rhubarb extracts,i.e. rhein and emodin,can depress the neuronal hyperexcitability,which suggests that rhein and emodin play an important role in protecting the central nervous system from neuronal damage after traumatic brain injury.FPI produces hyperexcitability of hippocampal CA1 neurons,probably by enhancing excitatory synaptic transmission.
