In lab-grown stem cells, adding the peptide ghrelin helped more cells turn into beating heart cells, but this effect didn't work through the usual ghrelin receptor and the study didn't test any real‑world dosing or benefits for people.

Ghrelin is involved in regulating the differentiation of mesoderm-derived precursor cells. The aim of this study was to investigate whether ghrelin modulated the differentiation of human embryonic stem (hES) cells into cardiomyocytes and, if so, whether the effect was mediated by growth hormone secretagogue receptor 1α (GHS-R1α). Cardiomyocyte differentiation from hES cells was performed according to an embryoid body (EB)-based protocol. The cumulative percentage of beating EBs was calculated. The expression of cardiac-specific markers including cardiac troponin I (cTnI) and α-myosin heavy chain (α-MHC) was detected using RT-PCR, real-time PCR and Western blot. The dispersed beating EBs were examined using immunofluorescent staining. The percentage of beating EBs and the expression of cTnI were significantly increased after ghrelin (0.1 and 1 nmol/L) added into the differentiation medium. From 6 to 18 d of differentiation, the increased expression of cTnI and α-MHC by ghrelin (1 nmol/L) was time-dependent, and in line with the alteration of the percentages of beating EBs. Furthermore, the dispersed beating EBs were double-positively immunostained with antibodies against cTnI and α-actinin. However, blockage of GHS-R1α with its specific antagonist D-[lys(3)]-GHRP-6 (1 μmol/L) did not alter the effects of ghrelin on cardiomyocyte differentiation. Our data show that ghrelin enhances the generation of cardiomyocytes from hES cells, which is not mediated via GHS-R1α.