sdc4 siRNA and retro-orbital injection

To knockdown sdc4 in adult zebrafish hearts, zebrafish sdc4 siRNA (GenePharma, Shanghai, China) was used. The sdc4 siRNA sequence is shown in Table S1. The following protocol was performed as previously described with some modifications [15]. For preparing the sdc4 siRNA/SilenceMag nanoparticle mix, 40 μL of 10 nM sdc4 siRNA was mixed with 1.1 μL SilenceMag agent (OZ Bioscience, Marseille, France). The experimental procedure and the knockdown efficiency of sdc4 siRNA are shown in Fig. S2.

The retro-orbital injection was used to deliver siRNA-loaded magneto-nanoparticles into the zebrafish bloodstream. The anesthetized zebrafish were placed on the Petri dish and covered with wetted tissue paper. The needle was inserted into the zebrafish eye socket with 1–2 mm depth by a 7 o'clock position and at a 45-degree angle and injected with 2 μL sdc4 siRNA/SilenceMag nanoparticle mix into the zebrafish blood vessel. The treated zebrafish were then transferred into a recovery tank with fresh water.