Figure 5.

Activation of the Cox2-PGE₂ circuit stimulates cardiomyocyte proliferation. Zebrafish were subjected to ventricular amputation and treated with daily intraperitoneal (IP) injections of either vehicle control, NS-398 or Celecoxib. Hearts were collected for analysis at 3 dpa. (A) Treatment with NS-398 reduced PGE₂ concentrations in ventricles by ~47%, relative to DMSO controls. (mean ± s.e.m. n = 4 biological replicate for each group; 6 pooled ventricles from weight-matched clutch mates per replicate. Student’s t-test. *P < 0.05). (B,C) Representative images of 3 dpa injured hearts treated daily with a DMSO control (B) or NS-398 (C). Hearts were stained with Mef2 (green), and Pcna (red). Mef2+Pcna+ cells mark proliferating CMs, highlighted by white arrows. Scale bars represent 50 μM. (D-E) CM proliferation indices were calculated as a percentage of Mef2(+)Pcna(+) cells relative to the total number of Mef2(+) cells in a defined area adjacent to the injury. (D) CM proliferation was reduced by more than 69% in animals treated with NS-398 when compared to controls. (E) Reduction of CM proliferation was greater than 54% in animals treated daily with Celecoxib, relative to controls. (mean ± s.e.m. n = 7–9 hearts from clutchmates; three sections were quantified per heart and results averaged. Student’s t-test. *P < 0.05).