Figure 3

Figure 3: IGF-1 induces intracellular Ca²⁺ oscillations in SSEA-1+ cardiac stem cells. Human SSEA-1+ cells were loaded with Fluo-4 and dynamic Ca²⁺ measurements were performed using fluorescence Ca²⁺ imaging. (A) Representative basal Ca²⁺ levels in SSEA-1⁺ cells maintained in Ca²⁺-containing recording medium (n=28, from 3 independent cultures). (B) Representative basal Ca²⁺ level in SSEA-1⁺ cells maintained in Ca²⁺-free recording medium (n=32, from 3 independent culture). (C) Sequence of pseudocolor fluorescence images of a Fluo-4-preloaded SSEA-1⁺ cell stimulated in the presence of extracellular Ca²⁺ with IGF-1 10 nM as indicated. Representative Ca²⁺ oscillations are presented. Time and fluorescence intensity scales as shown. (D) Relative Ca²⁺ levels in SSEA-1⁺ cells stimulated with IGF-1 10 nM in a Ca²⁺-containing recording medium (n=36, from 3 independent cultures). (E) Spectral analysis of Ca²⁺ oscillations induced by IGF-1 in SSEA-1⁺ cells. The analysis was performed into a previously described spectral analysis software tool implemented in MATLAB, to characterize the temporal properties of Ca²⁺ oscillations. Average frequency obtained was 2.40 ± 0.37 mHz, which represent a periodicity 7.0 ± 1.1 minutes. (n=16, from 3 independent cultures). (F) Relative Ca²⁺ levels in SSEA-1⁺ cells stimulated with IGF-1 10 nM in a Ca²⁺-free recording medium (n=25, from 3 independent cultures).