Propionic Acidemia‐Induced Proarrhythmic Electrophysiological Alterations in Human iPSC ‐Derived Cardiomyocytes

Figures

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  FIGURE 1. Characteristics of spontaneous APs recorded in hiPSC‐CMs. (A and B) Series of spontaneous APs generated by hiPSC‐CMs obtained from the healthy donor (A) or the PCCA‐deficient patient (B). In panel B, the appearance of delayed afterdepolarizations is indicated by arrows. (C, D) Mean values of spontaneous frequency (C) and RMP (D) measured in both experimental groups. In panels C and D, each bar represents the mean ± SEM of the “n” experiments/cells indicated in each corresponding figure, and each dot represents one experiment/cell. In C and D, the p values from Student's t comparisons are indicated.

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  FIGURE 2. Characteristics of APs recorded in hiPSC‐CMs driven at 1 Hz. (A, B) Representative traces of APs generated by hiPSC‐CMs obtained from the healthy donor (A) or the PCCA‐deficient patient (B). The inset shows a trace of an AP generated by a cell driven at 0.5 Hz. In panel B, the inset, the respective transient and slow depolarization phases just after repolarization are highlighted by arrows. (C–G) Mean values of RMP (C), APA (D), APD20 (E), APD50 (F), and APD90 (G). In panels C–G, each bar represents the mean ± SEM of the “n” experiments/cells indicated in each corresponding figure and each dot represents one experiment/cell. In panels C–G, the p values from Student's t comparisons are indicated.

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  FIGURE 3. PCC deficiency reduces peak I Na. (A) Family of I Na traces recorded by applying the pulse protocol shown at the top in a hiPSC‐CM from the healthy donor or the PCCA‐deficient patient. (B) Density–voltage curves of the I Na recorded in hiPSC‐CMs from the healthy donor or the PCCA‐deficient patient. (C) Normalized conductance–voltage curves recorded in both experimental groups. (D) Fast (τ fast) and slow (τ slow) time constants of inactivation yielded by the biexponential fit to the decay phase of maximum peak I Na traces. In panels B–D, each point/bar represents the mean ± SEM of the “n” experiments/cells indicated in each corresponding figure and in D, each dot represents one experiment. In panel B, *p < 0.05 versus healthy cells, and in panel D, the p values from Student's t comparisons are indicated.

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  FIGURE 4. PCC deficiency increases I NaL. (A) I Na traces recorded by applying 500‐ms pulses to −30 mV in a hiPSC‐CM from the healthy donor before and after superfusion with TTX. (B) I NaL, expressed as % of peak I Na, measured at the end of 500‐ms pulses to −30 mV (Total I NaL) and as TTX‐sensitive current in hiPSC‐CMs from the healthy donor or the PCCA‐deficient patient. In panel B, each bar represents the mean ± SEM of the “n” experiments indicated in the figure, and each dot represents one single experiment. In panel B, the p values from Student's t comparisons are indicated.

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  FIGURE 5. PCC deficiency decreases the I CaL density. (A) Representative traces of I CaL recorded in hiPSC‐CMs obtained from the healthy donor or the PCCA‐deficient patient by applying the pulse protocol shown at the top. Only the first 200 ms of the trace are shown for the sake of clarity. (B, C) Mean I CaL density–voltage (B) and normalized conductance–voltage (C) curves recorded in both experimental groups. (D) Fast (τ fast) and slow (τ slow) time constants of inactivation yielded by the biexponential fit to the decay phase of I CaL traces recorded at +10 mV. In panels B–D, each point/bar represents the mean ± SEM of 7 and 6 experiments/cells, and in panel D, each dot represents one experiment. In panel B, *p < 0.05 versus healthy cells, and in panel D, the p values from Student's t comparisons are indicated.

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  FIGURE 6. PCC deficiency increases the I NCX. (A) Representative traces of the currents recorded by applying the pulse protocol shown at the top in a hiPSC‐CM derived from the healthy donor under control conditions (left) and after superfusion with a 0 Ca2+ solution supplemented with 5 mM Ni2+ (right). (B) Density of the current sensitive to Ni2+ (I NCX) calculated by the subtraction of the current in the presence of Ni2+ from the current measured in control conditions. The curves were corrected according to the calculated LJP. In B, each point represents the mean ± SEM of the “n” experiments indicated in the figure. *p < 0.05 versus healthy cells.