Problem: The purpose of this study was the isolation and characterization of decidual extract proteins that exhibit mitogenicity on endothelial cells.
Method of study: A partially purified extract (F1 fraction) was obtained from human decidua of the first trimester of pregnancy. F1 was separated by heparin-sepharose column and showed significant mitogenicity on bovine brain capillary endothelial (BBCE) cells in vitro, using methylene blue stain nuclear assay. Sodium-dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed four fractions with MW less than 30 KDa.
Results: Mitogenic fraction, E11-12 (eluted at 1.5 M NaCl) was identified as basic fibroblast growth factor (bFGF). Vascular endothelial growth factor (VEGF) and acidic (a)FGF were not identified as one of the mitogenic fractions. However, fractions E5-6, and E7-8 induced statistically significant mitogenicity at concentration of 1 pg/mL, which is 10(3) times lower than bFGF. Sequencing of E5-6 fraction identified NKG5 protein, a putative secreted polypeptide derived from human natural killer (NK) cells and activated T cells of unknown function.
Conclusion: This work demonstrates that NKG5 stimulates mitogenicity of endothelial cells and may be involved in angiogenesis.