Orthopaedics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping, Sweden.
J Appl Physiol (1985). 2013 Jun;114(11):1519-26. doi: 10.1152/japplphysiol.01500.2012. Epub 2013 Mar 21.
Loading can stimulate tendon healing. In healing rat Achilles tendons, we have found more than 150 genes upregulated or downregulated 3 h after one loading episode. We hypothesized that these changes were preceded by a smaller number of regulatory genes and thus performed a microarray 15 min after a short loading episode, to capture the primary response to loading. We transected the Achilles tendon of 54 rats and allowed them to heal. The hind limbs were unloaded by tail-suspension during the entire experiment, except during the loading episode. The healing tendon tissue was analyzed by mechanical testing, microarray, and quantitative real-time polymerase chain reaction (qRT-PCR). Mechanical testing showed that 5 min of loading each day for 4 days created stronger tissue. The microarray analysis after one loading episode identified 15 regulated genes. Ten genes were analyzed in a repeat experiment with new rats using qRT-PCR. This confirmed the increased expression of four genes: early growth response 2 (Egr2), c-Fos, FosB, and regulation of G protein signaling 1 (Rgs1). The other genes were unaltered. We also analyzed the expression of early growth response 1 (Egr1), which is often co-regulated with c-Fos or Egr2, and found that this was also increased after loading. Egr1, Egr2, c-Fos, and FosB are transcription factors that can be triggered by numerous stimuli. However, Egr1 and Egr2 are necessary for normal tendon development, and can induce ectopic expression of tendon markers. The five regulated genes appear to constitute a general activation machinery. The further development of gene regulation might depend on the tissue context.
加载可以刺激肌腱愈合。在对大鼠跟腱进行的愈合研究中，我们发现单次加载后 3 小时，有 150 多个基因的表达上调或下调。我们推测，这些变化之前存在少数调节基因，因此在单次短时间加载后 15 分钟进行了微阵列分析，以捕捉对加载的初始反应。我们切断了 54 只大鼠的跟腱，并让它们自行愈合。在整个实验过程中，除了在加载期间外，所有后肢都通过尾部悬吊进行卸载。通过机械测试、微阵列和定量实时聚合酶链反应（qRT-PCR）分析愈合的肌腱组织。机械测试表明，每天加载 5 分钟，连续 4 天可使组织更结实。单次加载后进行的微阵列分析确定了 15 个受调控的基因。用新大鼠在重复实验中对其中的 10 个基因进行 qRT-PCR 分析。这证实了 4 个基因的表达增加：早期生长反应 2（Egr2）、c-Fos、FosB 和 G 蛋白信号调节因子 1（Rgs1）。其他基因没有变化。我们还分析了早期生长反应 1（Egr1）的表达，它通常与 c-Fos 或 Egr2 共同调节，发现加载后其表达也增加了。Egr1、Egr2、c-Fos 和 FosB 是可以被多种刺激触发的转录因子。然而，Egr1 和 Egr2 是正常肌腱发育所必需的，并且可以诱导肌腱标记物的异位表达。这 5 个受调控的基因似乎构成了一个通用的激活机制。基因调控的进一步发展可能取决于组织背景。
