Embryotoxicity of pyrethroid insecticides and their mixtures in a human induced pluripotent stem cell-based model in...

Pyrethroid insecticides are used worldwide, yet their potential effects on early human development remain poorly understood. We applied the PluriLum assay, a human induced pluripotent stem cell-based 3D in vitro model, to evaluate the embryotoxicity of three commonly used pyrethroids (α-cypermethrin, deltamethrin, and etofenprox), and their shared metabolite 3-phenoxybenzoic acid (3-PBA). Embryoid bodies (EBs) were repeatedly exposed to these compounds throughout their differentiation into cardiomyocytes, and effects on cardiomyocyte beating, expression of the early cardiac marker NKX2.5, as well as their impact at a transcriptional level was assessed. The three pyrethroids were tested in combination at two different mixture compositions to investigate their potential for additivity. All three pyrethroids impaired cardiomyocyte differentiation at micromolar levels, with the following potency ranking: α-cypermethrin > etofenprox > deltamethrin. At higher concentrations, α-cypermethrin also reduced cardiomyocyte contractility. In contrast, 3-PBA showed no significant effects on neither differentiation nor contractile function. The pyrethroid mixtures followed the principle of concentration addition. An exploratory transcriptomic analysis revealed that α-cypermethrin and deltamethrin significantly altered the EBs gene expression profiles, affecting pathways related to ion channel activity, receptor signalling, and extracellular matrix organization. These findings suggest that exposure to pyrethroids may interfere with early human cardiac development through effects on multiple molecular targets. This study also highlights the value of the PluriLum assay as a human-relevant platform for assessing the embryotoxic potential of environmental chemicals.