Department of Animal Sciences, Washington State University, Pullman 99164, USA.
J Anim Sci. 2013 Mar;91(3):1419-27. doi: 10.2527/jas.2012-5670. Epub 2012 Oct 16.
Beef cattle are raised for their lean tissue, and excessive fat accumulation accounts for large amounts of waste. On the other hand, intramuscular fat or marbling is essential for the palatability of beef. In addition, tender beef is demanded by consumers, and connective tissue contributes to the background toughness of beef. Recent studies show that myocytes, adipocytes, and fibroblasts are all derived from a common pool of progenitor cells during embryonic development. It appears that during early embryogenesis, multipotent mesenchymal stem cells first diverge into either myogenic or adipogenic-fibrogenic lineages; myogenic progenitor cells further develop into muscle fibers and satellite cells whereas adipogenic-fibrogenic lineage cells develop into the stromal-vascular fraction of skeletal muscle where reside adipocytes, fibroblasts, and resident fibro-adipogenic progenitor cells (the counterpart of satellite cells). Strengthening myogenesis (i.e., formation of muscle cells) enhances lean growth, promoting intramuscular adipogenesis (i.e., formation of fat cells) increases marbling, and reducing intramuscular fibrogenesis (i.e., formation of fibroblasts and synthesis of connective tissue) improves overall tenderness of beef. Because the abundance of progenitor cells declines as animals age, it is more effective to manipulate progenitor cell differentiation at an early developmental stage. Nutritional, environmental, and genetic factors shape progenitor cell differentiation; however, up to now, our knowledge regarding mechanisms governing progenitor cell differentiation remains rudimentary. In summary, altering mesenchymal progenitor cell differentiation through nutritional management of cows, or fetal programming, is a promising method to improve cattle performance and carcass value.
肉牛养殖是为了获取其瘦肉组织，而过量的脂肪积累会造成大量浪费。另一方面，肌肉内脂肪或大理石纹对于牛肉的美味至关重要。此外，消费者对嫩牛肉的需求也很高，而结缔组织是牛肉口感韧性的基础。最近的研究表明，在胚胎发育过程中，肌细胞、脂肪细胞和成纤维细胞都来源于一个共同的祖细胞池。似乎在早期胚胎发生过程中，多能间充质干细胞首先分化为成肌或成脂成纤维谱系；成肌祖细胞进一步发育成肌纤维和卫星细胞，而成脂成纤维谱系细胞则发育成骨骼肌的基质血管部分，其中存在脂肪细胞、成纤维细胞和驻留成纤维脂肪祖细胞（卫星细胞的对应物）。加强成肌作用（即肌肉细胞的形成）可促进瘦肉生长，促进肌内脂肪生成（即脂肪细胞的形成）可增加大理石纹，减少肌内纤维生成（即成纤维细胞的形成和结缔组织的合成）可提高牛肉的整体嫩度。由于随着动物年龄的增长，祖细胞的丰度下降，因此在早期发育阶段更有效地操纵祖细胞分化。营养、环境和遗传因素影响祖细胞的分化；然而，到目前为止，我们对于控制祖细胞分化的机制的了解还很基础。总之，通过对奶牛进行营养管理或胎儿编程来改变间充质祖细胞的分化是提高牛的生产性能和胴体价值的一种很有前景的方法。
