Phosphoinositide 3-kinases (PI3Ks) and PKC are important mediators of many transmembrane signaling receptors, and may be involved in cardiovascular differentiation of ES cells. Preincubation of ES cells with wortmannin and LY294002 which are potent and non-selective PI3K inhibitors resulted in an inhibition of angiogenesis and cardiac differentiation as well. By using specific pharmacological inhibitors for class IA PI3K catalytic subunit p110a (Compound 15e) and p110d (IC-87114) a significant inhibition of cardiomyocyte differentiation was observed, while angiogenesis was powerful affected by Compound 15e. Pharmacological inhibitors for class IA PI3K catalytic subunit p110ß (TGX-221 (1mM)) and for catalytic subunit p110d (IC-87114 (1mM)) did not inhibit angiogenesis, as demonstrated by PCR studies. The preincubation of embryoid bodies with inhibitors of the PKC family bisindolylmaleimide-1 (BIM-1) and GÖ6976 significantly inhibited PECAM-1 expression but did not impair VE-Cadherin expression. Cardiac differentiation remained unimpaired following treatment with inhibitors of the PKC family bisindolylmaleimide-1 (BIM-1) and GÖ6976. However at the used concentration of bisindolylmaleimide-1 (10nM) and GÖ6976 (2,3nM) an exclusive inhibition of PKCa and PKCß is assumed. The involvement of novel PKC, has to be elucidated.

In the present study, we conclude that class IA PI3K catalytic subunit p110a control angiogenesis in ES-cell derived embryoid bodies and class IA PI3K catalytic subunit p110a and p110d control cardiomyogenesis in embryoid bodies. Inhibitors of classical PKC suppress PECAM-1 expression in embryoid bodies.