Hepatocyte growth factor secreted by cultured adipocytes promotes tube formation of vascular endothelial cells in vitro.
OBJECTIVE
Adipose tissue is closely associated with angiogenesis, but the mechanisms are not fully understood. Some of the adipocyte-derived cytokines are hypothesized to play an important role in angiogenesis. We evaluated tube formation of human umbilical vascular endothelial cells (HUVECs) cultured in type I collagen gel when overlaid with the supernatant of 3T3-L1 cell culture, and expression of tube-forming factor(s) in 3T3-L1 cells with or without pioglitazone. We also studied plasma growth factor levels in patients with type 2 diabetes mellitus treated with pioglitazone.


RESULTS
The supernatant of 3T3-L1 cells increased tube formation of HUVECs by 9.03-fold of control. Reverse transcription-polymerase chain reaction showed that hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) mRNA were expressed in 3T3-L1 cells. Western blot analysis also demonstrated HGF and VEGF protein expression. When 3T3-L1 cells were treated with 100 nM small interfering RNAs (siRNAs) for HGF, the HGF mRNA and protein were suppressed. The VEGF mRNA and protein in the cells were also suppressed by siRNA for VEGF. The supernatant of 3T3-L1 cells treated with HGF siRNA suppressed tube formation of HUVECs by 61% compared with the supernatant of cells treated with control siRNA. Addition of VEGF siRNA resulted in no significant changes. The supernatant conditioned with pioglitazone further promoted the tube formation. Pioglitazone enhanced HGF mRNA expression in 3T3-L1 cells. After 12 weeks of pioglitazone treatment, the changes of plasma HGF levels in patients treated with pioglitazone were significantly higher than those in control.


CONCLUSIONS
These results suggest that HGF secreted from 3T3-L1 cells may be the major factor regulating the tube formation, and agents that enhance the differentiation of adipocytes may promote tube formation of HUVECs mediated by HGF secreted by adipocytes.
Center of Diabetes, Endocrine and Metabolism, Sakura Hospital, School of Medicine, Toho University, Chiba, Japan.
A
A
Saiki
F
F
Watanabe
T
T
Murano
Y
Y
Miyashita
K
K
Shirai
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D003470:Culture Media; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology*; D005260:Female; D017228:Hepatocyte Growth Factor / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use; D008297:Male; D051379:Mice; D008875:Middle Aged; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D000077205:Pioglitazone; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000494:pharmacology; D045162:Thiazolidinediones / Q000494:pharmacology / Q000627:therapeutic use; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis
D003470:Culture Media; D007004:Hypoglycemic Agents; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D045162:Thiazolidinediones; D042461:Vascular Endothelial Growth Factor A; D017228:Hepatocyte Growth Factor; D000077205:Pioglitazone