An approach to evaluate the effect of inflammatory microvesicles on Ca2+ handling in human-induced pluripotent stem cell-derived cardiomyocytes

Microvesicles (MV) isolated from septic individuals were observed to impact systemic hemodynamics and cardiac function. The aim of this <i>in vitro</i> study was to analyze the effects of TNFα-induced endothelial MV (TMV) and MV from septic patients (SMV) on beating frequency and Ca²⁺ transient kinetics of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM). MV were isolated from supernatants of TNFα-stimulated primary human pulmonary microvascular endothelial cells (HPMEC) and plasma from 20 sepsis patients by ultracentrifugation and quantified using flow cytometry. Spontaneous Ca²⁺ transients were measured in hiPSC-CM using the Ca²⁺-sensitive ratiometric indicator fura-2 at different time points of incubation with different MV concentrations. At 16 h of incubation, higher MV concentrations showed significant differences, especially regarding decay and beating frequency. Despite high variability, at 10 × 10⁶ MV/mL and 16 h of incubation, TMV significantly decreased frequency compared to control MV (CMV). SMV from septic patients did not reveal any significant effects on Ca²⁺ transients under these experimental settings. MV isolated from control or TNFα-treated HPMEC affected Ca²⁺ handling and spontaneous activity of hiPSC-CM, however, the measured effects were not consistent throughout the different conditions. Further refinement of the experiment conditions is needed to specify the exact conditions for crosstalk between endothelium-derived MV and cardiomyocytes.