Department of Animal Sciences, University of Florida, Gainesville, FL 32611, USA.
J Anim Sci. 2013 May;91(5):2083-90. doi: 10.2527/jas.2012-5732. Epub 2013 Mar 5.
Satellite cells support efficient postnatal skeletal muscle hypertrophy through fusion into the adjacent muscle fiber. Nuclear contribution allows for maintenance of the fiber myonuclear domain and proficient transcription of myogenic genes. Niche growth factors affect satellite cell biology; however, the interplay between fiber elasticity and microenvironment proteins remains largely unknown. The objective of the experiment was to examine the effects of hepatocyte growth factor (HGF) and surface elasticity on bovine satellite cell (BSC) activation kinetics in vitro. Young's elastic modulus was calculated for the semimembranosus (SM) and LM muscles of young bulls (5 d; n = 8) and adult cows (27 mo; n = 4) cattle. Results indicate that LM elasticity decreased (P < 0.05) with age; no difference in Young's modulus for the SM was noted. Bovine satellite cells were seeded atop polyacrylamide bioscaffolds with surface elasticities that mimic young bull and adult cow LM or traditional cultureware. Cells were maintained in low-serum media supplemented with 5 ng/mL HGF or vehicle only for 24 or 48 h. Activation was evaluated by proliferating cell nuclear antigen (PCNA) immunocytochemistry. Results indicate that BSC maintained on rigid surfaces were activated at 24 h and refractive to HGF supplementation. By contrast, fewer (P < 0.05) BSC had exited quiescence after 24 h of culture on surfaces reflective of either young bull (8.1 ± 1.7 kPa) or adult cow (14.6 ± 1.6 kPa) LM. Supplementation with HGF promoted activation of BSC cultured on bioscaffolds as measured by an increase (P < 0.05) in PCNA immunopositive cells. Culture on pliant surfaces affected neither activation kinetics nor numbers of Paired box 7 (Pax7) immunopositive muscle stem cells (P > 0.05). However, with increasing surface elasticity, an increase (P < 0.05) in the numbers of muscle progenitors was observed. These results confirm that biophysical and biochemical signals regulate BSC activation.
卫星细胞通过融合到相邻的肌肉纤维中支持出生后骨骼肌的高效肥大。核贡献允许维持纤维的肌核域和肌生成基因的有效转录。生态位生长因子影响卫星细胞生物学；然而，纤维弹性和微环境蛋白之间的相互作用在很大程度上仍然未知。实验的目的是研究肝细胞生长因子（HGF）和表面弹性对牛卫星细胞（BSC）体外激活动力学的影响。为了计算幼公牛（5 天；n = 8）和成年牛（27 个月；n = 4）半膜肌（SM）和腰大肌（LM）的杨氏弹性模量。结果表明，随着年龄的增长，LM 的弹性降低（P < 0.05）；SM 的杨氏模量没有差异。将牛卫星细胞接种在具有模仿幼公牛和成年牛 LM 或传统培养皿的表面弹性的聚丙酰胺生物支架上。细胞在补充有 5 ng/mL HGF 或仅载体的低血清培养基中维持 24 或 48 小时。通过增殖细胞核抗原（PCNA）免疫细胞化学评估激活。结果表明，在刚性表面上维持的 BSC 在 24 小时时被激活，并且对 HGF 补充不敏感。相比之下，在表面上培养 24 小时后，更少的（P < 0.05）BSC 已经从静止中退出，该表面反映了幼公牛（8.1 ± 1.7 kPa）或成年牛（14.6 ± 1.6 kPa）LM。用 HGF 补充促进了生物支架上培养的 BSC 的激活，这表现为 PCNA 免疫阳性细胞的数量增加（P < 0.05）。在柔软的表面上培养既不影响激活动力学，也不影响配对盒 7（Pax7）免疫阳性肌肉干细胞的数量（P > 0.05）。然而，随着表面弹性的增加，观察到肌肉祖细胞的数量增加（P < 0.05）。这些结果证实生物物理和生化信号调节 BSC 的激活。
