ABSTRACT
Cyclic peptide drugs have gradually become an emerging research direction due to their some favorable properties such as high-efficiency binding affinity, high selectivity, lower toxicity, and stable metabolism. In recent years, the number of cyclic peptide drugs under clinical research has continued to increase. Unlike the previous cyclic peptide drugs, which were mostly derived from natural products and their derivatives, these cyclic peptide drugs are designed by genetically encoded display technologies which are based on rational design and in vitro evolution (such as BT1718, PTG-300, POL6326, etc). Among them, phage display technology has some advantages such as mature research system, low cost, and simpler operation that make it well recognized and praised by the majority of researchers in this field. Here, we reviewed the recent progress of applying phage display technology to explore diverse cyclic peptide libraries, which, we believe, will contribute more valuable candidate cyclic peptide drugs in clinical research.
ABSTRACT
OBJECTIVE: To observe whether bone marrow mesenchymal stem cell( BMMSC) could be induced by alveolar epithelial cell( AEC) of rats exposed to silica dust or not. METHODS: BMMSCs were isolated and cultivated from 6specific pathogen free healthy male SD rats through bone marrow adherent method. The AECs from other 6 rats randomly selected from the same batch were cultivated by immune adherent purification method. Three rats were treated with 1. 0 m L( 40 g/L mass concentration) of silicosis dust suspension by one time intratracheal injection as silicosis dust exposure model,and the other 3 rats were given 0. 9% sodium chloride solution as normal. Experimental group was the co-culture of BMMSCs and AECs from silicosis dust exposure rats. Control group A was the co-culture of BMMSCs and AECs from normal rats. Control group B was the culture of BMMSCs alone. The morphology changes were observed by the inverted phase contrast microscope at the time points of the 4th and the 8th day. Double immunofluorescence staining using aquaporin 5( AQP5) and surfactant protein C( SP-C) was performed on the treated BMMSCs. The fluorescence staining was observed using the inverted fluorescence microscope( IFM) and laser scanning confocal microscope( LSCM). Integral optical density( IOD) analysis was conducted on fluorescence of 2 kinds of proteins by Image-pro plus 6. 0 graphic analysis software. RESULTS: After the co-culture,the BMMSCs in experimental group and control group A changed from long spindle shape to cubic and polygonal shape,the variation of morphology on day 8 was more obvious than that on day 4,and the change in control group A was less obvious than that of experimental group. There was no obvious morphology change in BMMSCs of control group B. By IFM and LSCM,on day 4 and day 8,the expression of green fluorescence AQP5 and red fluorescence SP-C were all observed in BMMSCs of experimental group and control group A. The BMMSCs of control group B only showed a little green fluorescence expression of AQP5,no expression of red SP-C fluorescence was seen. Both by IFM and LSCM,on day 4 and day 8,the 2 kinds of IOD of BMMSCs in experiment group were higher than those of control group A and B at the same time points( P < 0. 01); the IOD of control group A was higher than that of control group B at the same time point( P < 0. 01). The IOD of experiment group and control group A on day 8 were higher than those on day4 in the same group( P < 0. 01). CONCLUSION: AEC of rats exposed to silica dust can effectively induce BMMSC to be differentiated into AEC.