Ghrelin induces cardiac lineage differentiation of human embryonic stem cells through ERK1/2 pathway.
BACKGROUND
Ghrelin, an endogenous ligand for growth hormone secretagogue receptor (GHS-R), shows cardioprotective activity and regulates the differentiation of several mesoderm-derived cells, including myocytes, adipocytes and osteoblasts. The effect of ghrelin on cardiogenesis and its underlying mechanism, however, have not been studied in detail.


METHODS
The effects of ghrelin on cardiomyocyte differentiation were tested both in human embryonic stem cells (hESCs) cultured in embryoid body (EB)-based differentiation protocol, and in hESCs transplanted into rat hearts. The signaling mechanisms of ghrelin were further investigated under the EB-based culture condition.


RESULTS
The generation of beating EBs and the expression of cardiac-specific markers including cardiac troponin I (cTnI) and α-myosin heavy chain (α-MHC) were 2 to 3-fold upregulated by ghrelin. Although GHS-R1α protein was expressed in differentiated EBs, the effects of exogenous ghrelin were unchanged by D-[lys(3)]-GHRP-6, a specific GHS-R1α antagonist. Moreover, des-acyl ghrelin, which does not bind to GHS-R1α, displayed similar effects with ghrelin. Importantly, activation of ERK1/2, but not Akt, was induced by ghrelin in the newly-formed EBs, and the ghrelin-induced effects of cardiomyocyte differentiation were abolished by adding specific ERK1/2 inhibitor PD98059, but not specific PI3K inhibitor Wortmannin. In addition, ghrelin promoted the differentiation of grafted hESCs into Sox9- and Flk1-positive mesodermal/cardiac progenitor cells in rat hearts.


CONCLUSIONS
These results suggest that ghrelin induces cardiomyocyte differentiation from hESCs via the activation of the ERK1/2 signaling pathway. Our study, therefore, indicates that using ghrelin may be an effective strategy to promote the differentiation of hESCs into cardiomyocytes.
Department of Endocrinology and Metabolism, Peking University Third Hospital, Beijing 100191, China.
Meijuan
M
Gao
Jin
J
Yang
Rui
R
Wei
Guoqiang
G
Liu
Lin
L
Zhang
Haining
H
Wang
Guang
G
Wang
Hongwei
H
Gao
Guian
G
Chen
Tianpei
T
Hong
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D019070:Cell Lineage / Q000187:drug effects / Q000502:physiology*; D053595:Embryonic Stem Cells / Q000187:drug effects / Q000201:enzymology*; D054439:Ghrelin / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D054439:Ghrelin