Figure 4. RA treatment increases Pod1 and decreases SM22α expression in intact chick E7 hearts.

(A–H) Chick E7 whole hearts were treated with vehicle controls (Ctrl) MeOH+DMSO (A,E), RA (B,F), DEAB (C,G), or RA+DEAB (D,H) in vitro. Expression of Pod1 and SM22α was detected by IF using anti-Pod1 antibody or anti-SM22α antibody, respectively. (A–D) Pod1 (red) is expressed in epicardium (arrows) and in EPDCs (arrowheads). (E–H) Expression of the smooth muscle (SM) marker SM22α (red) is indicated in the epicardium (arrows) and EPDCs (arrowheads). Nuclei are labeled with DAPI (blue). Asterisks indicate Pod1 or SM22α-negative cells. (I,J) Quantification of the average number of Pod1⁺ EPDCs (I) or SM22α⁺ EPDCs (J) per microscopic field is shown. Note that panels (A–H) are cropped and magnified regions of the microscopic fields. (K) A negative (no primary) control section has little background labeling. Statistical significance of observed differences relative to control was determined by Student’s t-test (n=6). *P•0.01, #P•0.05.