Myostatin (MSTN), a member of the TGF-β superfamily, negatively regulates muscle growth. MSTN inhibition has been known to cause a double-muscled phenotype in skeletal muscle and fibrosis reduction in the heart. However, the role of MSTN in the cardiac extracellular matrix (ECM) needs more studies in various species of animal models to draw more objective conclusions. The main objective of the present study was to investigate whether loss of MSTN affects the cardiac extracellular matrix in pigs. Three MSTN knockouts (MSTN−/−) and three wild type (WT) male pigs were generated by crossing MSTN ± heterozygous gilts and boars. Cardiac ECM and underlying mechanisms were determined post-mortem. The role of MSTN on collagen expression was investigated by treating cardiac fibroblasts with active MSTN protein in vitro. MSTN protein was detected in WT hearts, while no expression was detected in MSTN−/− hearts. The heart-to-body weight ratio was significantly decreased in MSTN−/− pigs. The morphometric analyses, including picrosirius red staining, immunofluorescent staining, and ultra-structural thickness examination of the endomysium, revealed a significant reduction of connective tissue content in MSTN−/− hearts compared to WT. Hydroxyproline, type I collagen (Col1A), and p-Smad3/Smad3 levels were significantly lower in MSTN−/− hearts in vivo. On the contrary, cardiac fibroblasts treated with exogenous MSTN protein overexpressed Col1A and activated Smad and AKT signaling pathways in vitro. The present study suggests that inhibition of MSTN decreases cardiac extracellular matrix.

肌肉生长抑制素 (MSTN) 是 TGF-β 超家族的成员，负向调节肌肉生长。已知 MSTN 抑制会导致骨骼肌中的双肌表型和心脏中的纤维化减少。然而，MSTN 在心脏细胞外基质 (ECM) 中的作用需要在各种动物模型中进行更多研究，以得出更客观的结论。本研究的主要目的是调查 MSTN 的丢失是否会影响猪的心脏细胞外基质。三头MSTN基因敲除 ( MSTN -/-) 和三头野生型 (WT) 雄性猪通过MSTN杂交产生 ± 杂合的后备母猪和公猪。心脏 ECM 和潜在机制在死后确定。通过在体外用活性 MSTN 蛋白处理心脏成纤维细胞来研究 MSTN 对胶原蛋白表达的作用。在 WT 心脏中检测到 MSTN 蛋白，而在 MSTN-/- 心脏中未检测到表达。MSTN-/- 猪的心脏体重比显着降低。形态测量分析，包括天狼星红染色、免疫荧光染色和肌内膜超微结构厚度检查，显示与 WT 相比， MSTN -/- 心脏中的结缔组织含量显着降低。MSTN中的羟脯氨酸、I 型胶原蛋白 (Col1A) 和 p-Smad3/Smad3 水平显着降低-/- 体内的心脏。相反，用外源性 MSTN 蛋白处理的心脏成纤维细胞在体外过表达 Col1A 并激活 Smad 和 AKT 信号通路。本研究表明，抑制 MSTN 会降低心脏细胞外基质。