SDF-1α decreased apoptosis in neonate cardiomyocytes.

<p>(A) 5 µM SDF-1α reduced apoptosis induced by hypoxia (n = 4) compared to normoxia (n = 4). (B) 5 µM SDF-1α protected against apoptosis induced by hypoxia combined to staurosporine 1 µM (n = 3). All data are expressed as fold change in Caspase-3 activity fluorescence (F) compared to normoxia (F0) *P<0.05, **P<0.01, ***P<0.001. ST: staurosporine, CASP3I: Caspase-3 inhibitor.</p

SDF-1α increased cardiomyocyte calcium transients through CXCR4.

<p>Ca²⁺ transients were evoked by 0.05 µM, 0.5 µM, 1 µM, 2 µM, 5 µM and 10 µM SDF-1α (n = 2), 5 µM SDF-1α 5 min after 0.5 mg/ml anti-CXCR4 preincubation (n = 4), 10 µM ATP (n = 5), ATP after 5 min anti-CXCR4 preincubation (n = 2) and finally 5 µM SDF-1α in the non-myocyte enriched fraction (n = 3). (A) Dose-response curve of the Ca²⁺ transient (Fmax-F₀)/F₀ induced by SDF-1α. (B, C) Time course of the Ca²⁺ fluorescent signal in a representative experiment. (D) Comparison of the Ca²⁺ transients (Fmax-F₀)/F₀ between groups. (E) Comparison of the time to peak. All data are presented as mean ± SEM, *P<0.05, **P<0.01, ***P<0.001.</p

The cultured cardiomyocytes were immunostained in green for CXCR4 and counterstained with DAPI for nuclei (blue).

<p>The cardiomyocyte enriched fraction showed increased expressions of CXCR4 (B and C) compared to the non-myocyte enriched fraction (E and F). OM: Bright field for CXCR4 (A: cardiomyocyte enriched fraction, D: non-myocyte enriched fraction).</p

Forskolin induced calcium transients in neonatal cardiomyocytes.

<p>Ca²⁺ transients were evoked by application of 10 µM forskolin alone (n = 3) or in addition to 5 µM SDF-1α (n = 3). (A, B) Time course of the Ca²⁺ fluorescent signal in a representative experiment. (C) Comparison of the Ca²⁺ transient (Fmax-F₀)/F₀ between groups.(D) Comparison of the time to peak. All data are presented as mean ± SEM, **P<0.01. FSK: forskolin.</p

Relative gene expression of (A) CXCR4 and (B) IP₃Rs and RyRs measured by QRT-PCR in the cardiomyocyte enriched fraction compared to the non-myocyte enriched fraction (n = 3).

<p>Data are presented as mean ± SEM, *P<0.05.</p

Activation of RyRs increased neonatal cardiomyocyte calcium transients.

<p>Ca²⁺ transients were evoked by 10 mM caffeine (n = 4), caffeine 5 min after preincubation with 1 mM tetracaine (n = 3) or 2 µM 2-APB (n = 3). (A, B) Time course of the Ca²⁺ fluorescent signal in a representative experiment. (C) Comparison of the Ca²⁺ transients (Fmax-F₀)/F₀ between groups.(D) Comparison of the time to peak. All data are presented as mean ± SEM, *P<0.05, **P<0.01. 2-APB: 2-aminoethyl-diphenyl-borinate, Tet: tetracaine, Caff: caffeine.</p

Cardiomyocyte and non-myocyte enriched fractions co-immunstained for troponin I (green) to mark myocytes, vimentin (red) to mark fibroblasts and with DAPI (blue) to mark the nuclei.

<p>The cardiomyocyte enriched fraction was troponin I positive (D and E) and vimentin negative (B–E) and the non-myocyte enriched fraction was vimentin positive (I and J) but troponin negative (G and H).</p