The cardiac and skeletal muscle tissues are both striated and contractile but their intrinsic cellular properties are distinct. The minimal cardiomyocyte proliferation and the lack of cardiac stem cells directly leads to poor heart repair in adult mammals. But in skeletal muscle, the robust proliferation of widespread muscle stem cells support efficient muscle regeneration. The endogenous cardiomyocyte and muscle stem cell proliferation has been analyzed in common laboratory animals but not in large mammals including pigs, which are more comparable to human. In this study, we rigorously examined the cell cycle dynamics of porcine cardiomyocytes and muscle stem cells through different developmental stages. Proliferative cardiomyocytes and muscle stem cells were broadly observed in the embryonic heart and limb muscle respectively. Muscle stem cells continue to proliferate postnatally but cardiomyocyte proliferation was drastically reduced after birth. However, robust cardiomyocyte cell cycle activity was detected around postnatal day 20, which could be attributed to the binucleation but not cell division. Increased proliferating cells were detected in maternal heart during early pregnancy but they represent non-cardiomyocyte cell types. The islet1 expressing cells were only identified in the embryonic and new born porcine hearts. Furthermore, the accumulated oxidative DNA damage in the cardiac but not skeletal muscle during development could be responsible for the diminished cardiomyocyte proliferation in adult pig. Similarities and differences in the proliferation of heart and skeletal muscle cells are identified in pigs across different developmental stages. Such cellular proliferative features must be taken into account when using porcine models for cardiovascular and muscular research.

中文翻译：

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猪心肌细胞和肌肉干细胞增殖的动力学。

心肌和骨骼肌组织均横纹和收缩，但其固有的细胞特性却不同。最小的心肌细胞增殖和心脏干细胞的缺乏直接导致成年哺乳动物心脏修复不良。但是在骨骼肌中，广泛分布的肌肉干细胞的强劲增殖支持有效的肌肉再生。已经在普通的实验动物中分析了内源性心肌细胞和肌肉干细胞的增殖，但在包括猪在内的大型哺乳动物中没有进行过分析，后者与人的可比性更高。在这项研究中，我们严格检查了猪心肌细胞和肌肉干细胞在不同发育阶段的细胞周期动态。在胚胎心脏和四肢肌肉中分别广泛观察到增殖性心肌细胞和肌肉干细胞。肌肉干细胞在出生后继续增殖，但是出生后心肌细胞的增殖急剧减少。然而，出生后第20天左右检测到强大的心肌细胞周期活性，这可能归因于双核而不是细胞分裂。孕早期在母体心脏中检测到增殖细胞增加，但是它们代表了非心肌细胞类型。仅在胚胎和新生猪心脏中鉴定出表达islet1的细胞。此外，成年猪心肌而不是骨骼肌中积累的氧化DNA损伤可能是成年猪心肌细胞增殖减少的原因。在不同发育阶段的猪中，发现了心脏和骨骼肌细胞增殖的异同。