Effects of cannabidiol on the viability and neuronal differentiation of human iPS cells

Cannabidiol (CBD) is a non-psychoactive cannabinoid with increasing global use, yet safety data during pregnancy remain limited. Preclinical studies suggest possible developmental neurotoxicity. Here, we examined the effects of CBD (0.001-100 μM) on human induced pluripotent stem cells (hiPSCs) using cell counting, morphology, flow cytometry, and qRT-PCR. Acute exposure to CBD (≥10 μM) markedly reduced hiPSC viability, accompanied by morphological disruptions and upregulation of caspase-3 and -7 within 3-5 h. These effects were significantly attenuated by the pan-caspase inhibitor Z-VAD-FMK, indicating caspase-dependent apoptosis as a key mechanism. Chronic exposure to CBD (0.001-1 μM) for 7 days did not alter transcriptional profiles of Nanog, Pax6, or Map2 during neural ectodermal induction, and immunocytochemical analyses further confirmed that early neuroectodermal morphology was preserved, with comparable PAX6- and NESTIN-positive populations in CBD-treated and control cultures. However, higher CBD concentrations caused marked cytotoxicity and impaired colony formation. These findings define a narrow concentration window between safe and toxic levels, highlighting stage-specific vulnerability to CBD during early development. Use of CBD in pregnancy should therefore be approached cautiously, considering potential risks to fetal neural development.