Endothelial precursor cells promote angiogenesis in hepatocellular carcinoma

AIM:To investigate the role of bone marrow-derived endothelial progenitor cells(EPCs) in the angiogenesis of hepatocellular carcinoma(HCC).METHODS:The bone marrow of HCC mice was reconstructed by transplanting green fluorescent protein(GFP) + bone marrow cells.The concentration of circulating EPCs was determined by colony-forming assays and fluorescence-activated cell sorting.Serum and tissue levels of vascular endothelial growth factor(VEGF) and colony-stimulating factor(CSF) were quantified by enzyme-linked immunosorbent assay.The distribution of EPCs in tumor and tumor-free tissues was detected by immunohistochemistry and real-time polymerase chain reaction.The incorporation of EPCs into hepatic vessels was examined by immunofluorescence and immunohistochemistry.The proportion of EPCs in vessels was then calculated.RESULTS:The HCC model was successful established.The flow cytometry analysis showed the mean percentage of CD133CD34 and CD133VEGFR2 double positive cells in HCC mice was 0.45% ± 0.16% and 0.20% ± 0.09% respectively.These values are much higher than in the sham-operation group(0.11% ± 0.13%,0.05% ± 0.11%,n = 9) at 14 d after modeling.At 21 d,the mean percentage of circulating CD133CD34 and CD133VEGFR2 cells is 0.23% ± 0.19%,0.25% ± 0.15% in HCC model vs 0.05% ± 0.04%,0.12% ± 0.11% in control.Compared to the transient increase observed in controls,the higher level of circulating EPCs were induced by HCC.In addition,the level of serum VEGF and CSF increased gradually in HCC,reaching its peak 14 d after modeling,then slowly decreased.Consecutive sections stained for the CD133 and CD34 antigens showed that the CD133+ and CD34+ VEGFR2 cells were mostly recruited to HCC tissue and concentrated in tumor microvessels.Under fluorescence microscopy,the bone-marrow(BM)-derived cells labeled with GFP were concentrated in the same area.The relative levels of CD133 and CD34 gene expression were elevated in tumors,around 5.0 and 3.8 times that of the tumor free area.In frozen liver sections from HCC mice,cells co-expressing CD133 and VEGFR2 were identified by immunohistochemical staining using anti-CD133 and VEGFR2 antibodies.In tumor tissue,the double-positive cells were incorporated into vessel walls.In immunofluorescent staining.These CD31 and GFP double positive cells are direct evidence that tumor vascular endothelial cells(VECs) come partly from BM-derived EPCs.The proportion of GFP CD31 double positive VECs(out of all VECs) on day 21 was around 35.3% ± 21.2%.This is much higher than the value recorded on day 7 group(17.1% ± 8.9%).The expression of intercellular adhesion molecule 1,vascular adhesion molecule 1,and VEGF was higher in tumor areas than in tumor-free tissues.CONCLUSION:Mobilized EPCs were found to participate in tumor vasculogenesis of HCC.Inhibiting EPC mobilization or recruitment to tumor tissue may be an efficient strategy for treating HCC.

加权残数法分析前屈曲变形对正交各向异性层迭圆柱壳屈曲载荷的影响

用加权残数法求解考虑前屈曲变形影响时正交各向异性层迭圆柱壳的屈曲载荷。文中采用满足边界条件的三角级数作为试函数,然后用最小二乘法得到特征方程,求得屈曲载荷,并与差分法的结果作一对比,得到了一些满意的结论。