Up-regulation of vascular endothelial growth factor (VEGF) in small-for-size liver grafts enhances macrophage activities through VEGF receptor 2-dependent pathway.
This study aims to investigate the potential role of vascular endothelial growth factor (VEGF) and VEGF-R2 (fetal liver kinase (Flk)-1) in mediating macrophage activities in small-for-size liver transplantation. A rat orthotopic liver transplantation model was performed using either whole, 50, or 30% liver grafts (both 50 and 30% were regarded as small-for-size) in syngeneic or allogeneic combinations, respectively. Firstly, the mRNA and protein levels of VEGF and Flk-1 in liver grafts were detected by RT-PCR and Western blot, and the number of Flk-1(+) macrophages (labeled by ED1) was determined by flow cytometry. It was found that the small-for-size isografts and allografts presented higher levels of VEGF and Flk-1 expression than the whole isograft and allograft. In addition, a higher number of Flk-1(+)ED1(+) cells were detected in the small-for-size isografts and allografts than the whole isograft and allograft. Secondly, our study revealed that macrophage cell lines did not initially express detectable Flk-1, but could be induced by VEGF, and the inducible expression of Flk-1 in macrophages was related to their migration and proliferation activities. Finally, our study demonstrated that the induction of Flk-1 expression on macrophages by VEGF was associated with the expression of NF-kappaB and heat shock protein 90. In conclusion, the present study showed that the up-regulated expression of VEGF and its interaction with Flk-1 in small-for-size liver grafts might facilitate the activities of macrophages.
Yang
Zhen Fan
ZF
Center for the Study of Liver Disease and Department of Surgery, University of Hong Kong, Hong Kong, China.
Poon
Ronnie T
RT
Luo
Ying
Y
Cheung
Cindy K
CK
Ho
David W
DW
Lo
Chung Mau
CM
Fan
Sheung Tat
ST
D000818:Animals; D015153:Blotting, Western; D002455:Cell Division / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D018841:HSP90 Heat-Shock Proteins / Q000276:immunology / Q000378:metabolism; D016031:Liver Transplantation / Q000276:immunology*; D008262:Macrophage Activation / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D008297:Male; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014184:Transplantation, Homologous; D014185:Transplantation, Isogeneic; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000276:immunology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000096:biosynthesis* / Q000276:immunology
D018841:HSP90 Heat-Shock Proteins; D016328:NF-kappa B; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2