Commitment of human pluripotent stem cells to a neural lineage is induced by the pro-estrogenic flavonoid apigenin

Flavonoids are polyphenolic compounds that are ubiquitous in plants and have biological effects on cancer cells and other cell types. In particular, apigenin (API) has been shown to bind to estrogen receptors, which affect the development, maturation, function, and plasticity of the nervous system. The aim of this study was to investigate the effects of 4′,5,7-trihydroxyflavone (API) upon the neural differentiation of human pluripotent stem cells. Treatment of both human embryonic stem cells and human induced pluripotent stem cells with API increased the number of nestin (NES+) neural progenitor cells compared to untreated controls. API also induced the expression of neuronal markers, such as β-tubulin-III (TUBB3), microtubule-associated protein 2 (MAP2), polysialylated-neural cell adhesion molecule (PSA-NCAM), synapsin 1 (SYN1), neurofilament (NEF), choline acetyltransferase (CHAT), glutamate decarboxylase (GAD1), and parvalbumin (PVALB) proteins. Antagonists of estrogen receptors (ESR1 and ESR2) suppressed the effects of API. API-induced differentiation was followed by increased expression of retinoic acid (RA) receptors (RARA and RARB) and retinoic X receptor (RXR) G, but not RARG1 or RXRB. Neural differentiation induced by API was drastically reduced by the inhibition of RARs. In addition, API also increased synaptogenesis in RA-differentiated neurons. These findings suggest that API induces neural differentiation of human pluripotent stem cells through estrogen receptor and RAR signaling and improves their functional differentiation into neurons.