Figure 1.

Human cardiotrophin 1 (hCT1) induces morphologic changes in primary cardiomyocytes with reversion upon removal of hCT1 stimulation. (A) Primary neonatal cardiomyocytes were stimulated for 24 h with hCT1 (0.5 nM), PE (100 μM), hCT1 and PE, or control serum-free medium (Ctrl, SF) followed by morphometric analysis (cell area and length:width ratio). Cells were stained with α-actinin (red) and nuclei were stained with DAPI (blue). Scale bar, 40 μm. (B, C) Morphometric analysis of (A) above. Treatment with hCT1, PE, and hCT1+PE induced a significant increase in cell area versus control (n = 3; ^*P < 0.05 and ^**P < 0.01). However, only hCT1 (or hCT1+PE) stimulation resulted in elongated/eccentric growth versus control (n = 3; ^*P < 0.05 and ^**P < 0.01). (D) Cardiomyocytes were stimulated as in (A) above, but for 2 days followed by removal for 4 days. After 2 days, both hCT1 and PE induced hypertrophy versus control at day 2 (n = 3; ^*P < 0.05 and ^****P < 0.0001). Cells reverted to pre-treatment dimensions upon removal of hCT1, whereas removal of PE caused cells to remain hypertrophied versus Control at day 6 (n = 3; ^***P < 0.001). (E-G) Length:width ratio population frequency analysis of (D) above. The majority of cardiomyocytes (∼ 60%) display a length:width ratio of 1.0-2.0 (Day 0); however, upon treatment with hCT1 (Day 2), a significant shift in length:width ratio of 3.0-9.0 was observed versus control at day 2 (n = 3; ^**P < 0.01 and ^***P < 0.001) with reversion occurring at day 6 upon hCT1 removal.