Optimizing an Intermittent Stretch Paradigm Using ERK1/2 Phosphorylation Results in Increased Collagen Synthesis in Engineered Ligaments
Optimizing an Intermittent Stretch Paradigm Using ERK1/2 Phosphorylation Results in Increased Collagen Synthesis in Engineered Ligaments
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DOI：
10.1089/ten.tea.2011.0336
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发表时间：
2012-02-01
影响因子：
4.1
通讯作者：
Baar, Keith
中科院分区：
文献类型：
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作者：
Paxton, Jennifer Z.;Hagerty, Paul;Baar, Keith
动态机械输入被认为在功能性肌肉骨骼组织的发育中起关键作用。为了研究这种现象，使用定制的生物反应器将循环单轴机械拉伸施加到工程化韧带，并确定不同拉伸频率、振幅和持续时间的影响。牵张使p38（3.5 +/- 0.74倍）、S6 K1（3.9 +/- 0.19倍）和ERK 1/2（2.45 +/- 0.32倍）的磷酸化急剧增加。在这些结构中，ERK 1/2的磷酸化依赖于时间，而不是频率或振幅。在频率为0.1 - 1Hz，振幅为2.5%-15%的牵张后，ERK 1/2磷酸化水平相似，而磷酸化水平在牵张10分钟时达到最高，并在牵张60分钟内恢复到基础水平。在一次10分钟的循环拉伸后，细胞对第二次拉伸保持不反应长达6小时。使用ERK 1/2的磷酸化作为指导，假设最佳拉伸范例为每6小时重复2.5%静息长度的拉伸10分钟。与该假设一致，使用该优化的间歇拉伸程序拉伸7天使移植物的胶原蛋白含量增加超过连续拉伸程序（CTL = 3.1% +/- 0.44%; CONT=4.8% +/- 0.30%;和INT = 5.9% +/- 0.56%）。这些结果表明，短而不频繁的负荷是最佳的改善工程肌腱和韧带的生理。
Dynamic mechanical input is believed to play a critical role in the development of functional musculoskeletal tissues. To study this phenomenon, cyclic uniaxial mechanical stretch was applied to engineered ligaments using a custom-built bioreactor and the effects of different stretch frequency, amplitude, and duration were determined. Stretch acutely increased the phosphorylation of p38 (3.5 +/- 0.74-fold), S6K1 (3.9 +/- 0.19- fold), and ERK1/2 (2.45 +/- 0.32-fold). The phosphorylation of ERK1/2 was dependent on time, rather than on frequency or amplitude, within these constructs. ERK1/2 phosphorylation was similar following stretch at frequencies from 0.1 to 1Hz and amplitudes from 2.5% to 15%, whereas phosphorylation reached maximal levels at 10 min of stretch and returned toward basal within 60 min of stretch. Following a single 10-min bout of cyclic stretch, the cells remained refractory to a second stretch for up to 6 h. Using the phosphorylation of ERK1/2 as a guide, the optimum stretch paradigm was hypothesized to be 10 min of stretch at 2.5% of resting length repeated every 6 h. Consistent with this hypothesis, 7 days of stretch using this optimized intermittent stretch program increased the collagen content of the grafts more than a continuous stretch program (CTL = 3.1% +/- 0.44%; CONT=4.8% +/- 0.30%; and INT = 5.9% +/- 0.56%). These results suggest that short infrequent bouts of loading are optimal for improving engineered tendon and ligament physiology.