This indicated different cyclooxygenase (COX)-downstream synthases and metabolizing enzymes are involved in the AA products' signaling through the COX-1 and COX-2 pathways. The presence of many enzymes' and receptors' [(COX-1, COX-2, microsomal prostaglandin E synthase (mPGES), cytosolic prostaglandin E synthase (cPGES), prostaglandin I synthase (PGIS), the PGE(2) subtype receptors (EP(1), EP(2), and EP(4)) and the prostacyclin receptor (IP)] involvement in the prostanoid biosynthesis and activity was confirmed by western blot. The studies implied the negative effects of NSAIDs, such as aspirin and COX-2 inhibitors, which suppress prostanoid production during tissue regeneration for infarcted heart when using hESCs.