Department of Food Science, University of Guelph, 50 Stone Road East, Building 038, Guelph, Ontario, N1G 2W1, Canada.
J Anim Sci. 2010 Dec;88(12):4006-15. doi: 10.2527/jas.2010-3060. Epub 2010 Aug 27.
Different muscles in a beef carcass are known to respond differently to the same stimulus or animal growth pattern or both. This may complicate the search by the meat industry for production methods to render meat tender. One of the major differences between muscles in the same carcass is in the expression of intramuscular connective tissue. Current study investigates the existence of a phenotypic difference among fibroblasts from 3 bovine skeletal muscles as exemplified by the expression of matrix metalloproteinases (MMP) the main enzymes responsible for connective tissue turnover. The sensitivity of phenotypic differences to cell culture conditions (passage number, presence of growth factors from fetal serum) was also examined. Fibroblasts, the main cells responsible for the production and turnover of collagen were isolated from LM, semitendinosus (STN), and sternomandibularis (SMD) muscles from a bull calf and grown in DMEM, 10% fetal bovine serum, and 5% CO(2). Cell doubling times, survival time, resting expression, and activity of MMP and the effect of serum withdrawal in the culture media on MMP expression and activity were determined for each cell line during 15 passages. Fibroblasts isolated from the 3 muscles had different growth potentials. The shortest (P < 0.0001) cell doubling times for almost every passage were found in cells from STN muscle. Cells from the LM had a shorter (P < 0.0001) survival time in comparison with STN and SMD. Cells derived from the STN had greater values (P > 0.05) of MMP-2 activity in comparison with LM and SMD cells until passage 4. At passage 15, no activity was detected for any cell line. Serum withdrawal generally reduced MMP-2 activation but did not eliminate differences in activity between fibroblasts from the 3 muscles. These results suggest that fibroblasts from different locations are phenotypically different and may respond differently to the same growth or nutritional stimulus in vitro. This may be related to in vivo differences in accumulation, maturity, and turnover of collagen, and ultimately meat tenderness. These findings may be important for selecting a management strategy for improving meat tenderness by manipulation of animal growth; a strategy applied to the whole animal may work for some muscles but not for others.
不同部位牛肉中的肌肉对相同刺激或动物生长模式或两者的反应不同。这可能会使肉类行业更难以寻找生产方法来使肉质变嫩。同一胴体中肌肉的主要区别之一在于肌内结缔组织的表达。目前的研究调查了来自 3 种牛骨骼肌的成纤维细胞之间是否存在表型差异，其表现为基质金属蛋白酶 (MMP)，这是负责结缔组织更新的主要酶。还研究了表型差异对细胞培养条件（传代数、胎牛血清中生长因子的存在）的敏感性。成纤维细胞是产生和更新胶原蛋白的主要细胞，从公牛小牛的 LM、半腱肌 (STN) 和胸骨舌骨肌 (SMD) 中分离出来，并在 DMEM、10%胎牛血清和 5%CO(2) 中培养。在 15 次传代过程中，确定了每个细胞系的细胞倍增时间、存活时间、静止表达和 MMP 活性以及培养基中血清去除对 MMP 表达和活性的影响。从 3 种肌肉中分离出的成纤维细胞具有不同的生长潜力。几乎每个传代中最短的（P < 0.0001）细胞倍增时间都在 STN 肌肉的细胞中发现。与 STN 和 SMD 相比，LM 细胞的存活时间更短（P < 0.0001）。与 LM 和 SMD 细胞相比，来自 STN 的细胞具有更高的（P > 0.05）MMP-2 活性值，直到第 4 代。在第 15 代，任何细胞系都没有检测到活性。血清去除通常会降低 MMP-2 的激活，但不会消除来自 3 种肌肉的成纤维细胞之间的活性差异。这些结果表明，来自不同部位的成纤维细胞在表型上存在差异，并且在体外对相同的生长或营养刺激可能会有不同的反应。这可能与胶原蛋白在体内的积累、成熟和更新的差异有关，最终与肉质的嫩度有关。这些发现对于通过动物生长的操纵来选择改善肉质嫩度的管理策略可能很重要；适用于整个动物的策略可能对某些肌肉有效，但对其他肌肉无效。
