Type I collagen is proven to make an important contribution to fish muscle quality. Our previous study has shown the Smad4-dependent regulation of type I collagen expression in the muscle of crisp grass carp fed with faba bean. However, the regulatory roles of TGF-β1 or TGF-β1/Smad4 on type I collagen remain unclear in ordinary grass carp fed with normal diets or in other fish species. To clarify this point, the effect of TGF-β1 and Smad4 over-expression and RNAi knockdown on type I collagen (COL1-α1 and COL1-α2) expression were tested in vitro (zebrafish ZF4 cells) and in vivo (grass carp) along with the TGF-β1/Smad4 co-expression and co-knockdown. The mRNA levels of TGF-β1, Smad4, and type I collagen were upregulated in the groups with over-expressed TGF-β1 and Smad4 and downregulated in the groups of TGF-β1 and Smad4 RNAi in comparison to controls in vitro (P < 0.05). Similarly, in the in vivo experiment, the mRNA abundance of TGF-β1, Smad4, and type I collagen of over-expression group was higher than the controls at 36 h (P < 0.05). Co-injection of TGF-β1/Smad4 over-expression and RNAi vectors generally showed the higher efficacy. This study revealed that TGF-β1 and Smad4 genes regulated type I collagen expression in grass carp muscle and zebrafish. These findings will provide references for the collagen regulation of other freshwater fishes.

事实证明，I 型胶原蛋白对鱼的肌肉质量做出了重要贡献。我们之前的研究表明，用蚕豆喂养的脆草鱼肌肉中 I 型胶原蛋白表达的 Smad4 依赖性调节。然而，TGF-β1 或 TGF-β1/Smad4 对 I 型胶原蛋白的调节作用在普通饲料喂养的普通草鱼或其他鱼类中尚不清楚。为了澄清这一点，在体外（斑马鱼 ZF4 细胞）和体内（草鱼）中测试了 TGF-β1 和 Smad4 过表达和 RNAi 敲低对 I 型胶原（COL1-α1和COL1-α2）表达的影响。与 TGF-β1/Smad4 共表达和共敲除。TGF-β1、Smad4的mRNA水平与体外对照相比，TGF-β1 和 Smad4 过表达组中 I 型胶原蛋白上调，TGF-β1 和 Smad4 RNAi 组下调（P < 0.05）。同样，在体内实验中，过表达组TGF-β1、Smad4和I型胶原的mRNA丰度在36 h时高于对照组（P < 0.05）。TGF-β1/Smad4 过表达和 RNAi 载体的共同注射通常显示出更高的功效。该研究表明，TGF-β1和Smad4基因调节草鱼肌肉和斑马鱼中 I 型胶原蛋白的表达。这些发现将为其他淡水鱼类的胶原蛋白调控提供参考。