[Ghrelin stimulates in vitro angiogenic capacity of rat cardiac microvascular endothelial cells]

To clarify whether ghrelin could promote in vitro rat cardiac microvascular endothelial cells (CMECs) angiogenesis and related mechanisms.

CMECs were isolated from myocardial tissue of adult male SD rats and characterized by the immunocytochemistry staining with Factor VIII and the capacity of in vitro capillary tube-like formation. The mRNAs and protein expressions of ghrelin and its receptor (growth hormone secretagogue receptor, GHS-R) of CMECs were determined by RT-PCR, Immunofluorescence, ELISA and Western blot. Proliferation, migration and in vitro angiogenesis as well as ERK2 phosphorylation of CMECs were tested in the presence of ghrelin (10(-9) - 10(-7) mol/L) with or without pretreatment with specific MAPK/ERK2 inhibitor PD98059.

Purity of CMECs characterized by immunocytochemistry staining with Factor VIII was about 95%, and the cells showed a high ability to form the capillary tube-like structures on Matrigel. Ghrelin and GHS-R were constitutively expressed in CMECs. Proliferation, migration and in vitro angiogenesis capacities of CMECs (72.20 ± 5.72 vs. 28.60 ± 5.13, P < 0.001; 71.00 ± 7.78 vs. 28.60 ± 5.13, P < 0.001) as well as ERK2 phosphorylation (0.92 ± 0.13 vs. 0.29 ± 0.04, P < 0.001; 1.15 ± 0.16 vs. 0.29 ± 0.04, P < 0.001) were significantly enhanced by exogenous ghrelin (10(-8) - 10(-7) mol/L). PD98059 abolished ghrelin-induced ERK2 phosphorylation and in vitro angiogenesis.

Ghrelin and its receptor are expressed in CMECs and ghrelin could stimulate CMECs in vitro angiogenesis through activation of MAPK/ERK2 signaling pathway.