1Department of Animal Sciences and Department of Pharmaceutical Sciences,Washington Center for Muscle Biology,Washington State University,Pullman,WA 99164,USA.
2College of Animal Science and Veterinary Medicine,Shanxi Agricultural University,Taigu,Shanxi 030801,P. R. China.
Animal. 2018 May;12(5):990-997. doi: 10.1017/S1751731117002403. Epub 2017 Oct 9.
Mechanisms responsible for excellent marbling in Japanese black cattle, Wagyu, remain to be established. Because both muscle cells and intramuscular adipocytes are developed from mesenchymal progenitor cells during early muscle development, we hypothesized that intramuscular progenitor cells in Wagyu cattle have attenuated myogenic capacity in favor of adipogenesis, leading to high marbling but reduced muscle growth. Biceps femoris muscle biopsy samples were obtained from both Angus (n=3) and Wagyu (n=3) cattle at 12 months of age. Compared with Angus, the density of satellite cells was much lower in Wagyu muscle (by 45.8±10%, P<0.05). Consistently, the formation of myotubes from muscle-derived progenitor cells was also lower (by 64.2±12.9%, P<0.05), but adipogenic capacity was greater in Wagyu. The average muscle fiber diameter was larger in Wagyu (by 23.9±6.8%, P=0.089) despite less muscle mass, suggesting less muscle fiber formation in Wagyu compared with Angus cattle. Because satellite cells are derived from fetal myogenic cells, the reduction in satellite cell density together with lower muscle fiber formation suggests that myogenesis was attenuated during early muscle development in Wagyu cattle. Given the shared pool of mesenchymal progenitor cells, the attenuated myogenesis likely shifts progenitor cells to adipogenesis during early development, which may contribute to high intramuscular adipocyte formation in Wagyu cattle.
导致日本黑牛（和牛）具有极好大理石花纹的机制尚不清楚。因为在早期肌肉发育过程中，肌肉细胞和肌间脂肪细胞均由间充质祖细胞发育而来，所以我们假设和牛的肌间祖细胞的成肌能力减弱，有利于成脂分化，导致大理石花纹高但肌肉生长减少。12 月龄时从安格斯牛（n=3）和和牛（n=3）获得比目鱼肌活检样本。与安格斯牛相比，和牛肌肉中的卫星细胞密度要低得多（低 45.8±10%，P<0.05）。同样，来自肌肉源性祖细胞的肌管形成也较低（低 64.2±12.9%，P<0.05），但成脂能力更强。和牛的平均肌纤维直径较大（大 23.9±6.8%，P=0.089），尽管肌肉量较小，这表明与安格斯牛相比，和牛的肌纤维形成较少。由于卫星细胞来源于胎儿成肌细胞，卫星细胞密度降低加上肌纤维形成减少表明在和牛早期肌肉发育过程中肌肉生成减弱。鉴于间充质祖细胞的共享池，早期发育过程中减弱的成肌作用可能将祖细胞转移到成脂分化，这可能有助于和牛肌肉内大量脂肪细胞的形成。
