sdc4 inhibition resulted in a decrease in cell proliferation at the injury site. Expression patterns of PCNA (red) and Hoechst (blue) immunostaining were analyzed after cryoinjury. PCNA (proliferating cell nuclear antigen) was used as a marker for cell proliferation, and Hoechst was used to label nuclei. Dashed line: injury site. Double-headed arrow: compact myocardium. A–F The PCNA signals of the negative control group were significantly higher than the sdc4 siRNA group at 3 dpci. G–L At 7 dpci, the expression levels of PCNA were the same at the injury site in both groups. Moreover, the Hoechst signals of the sdc4 siRNA group were weaker at the injury site than the negative control group. M The statistics indicated the cell numbers of PCNA-positive cells at the injury site. Knockdown of sdc4 significantly reduced the cell proliferation at the injury site at 3 dpci, but no significant difference compared to the negative control at 7 dpci. Scale bar: 100 μm (*p < 0.05 vs. negative control; n = 2–4 per group) (dpci: days post cryoinjury)
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