Lee Hyun-Tai, Hennig Grant W, Fleming Neal W, Keef Kathleen D, Spencer Nick J, Ward Sean M, Sanders Kenton M, Smith Terence K
Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89577, USA.
Gastroenterology. 2007 May;132(5):1852-65. doi: 10.1053/j.gastro.2007.02.049. Epub 2007 Feb 23.
BACKGROUND & AIMS: It has been generally assumed that interstitial cells of Cajal (ICC) in the human gastrointestinal tract have similar functions to those in rodents, but no direct experimental evidence exists to date for this assumption. This is an important question because pathologists have noted decreased numbers of ICC in patients with a variety of motility disorders, and some have speculated that loss of ICC could be responsible for motor dysfunction. Our aims were to determine whether myenteric ICC (ICC-MY) in human jejunum are pacemaker cells and whether these cells actively propagate pacemaker activity.
The mucosa and submucosa were removed, and strips of longitudinal muscle were peeled away to reveal the ICC-MY network. ICC networks were loaded with the Ca(2+) indicator fluo-4, and pacemaker activity was recorded via high-speed video imaging at 36.5 degrees C +/- 0.5 degrees C.
Rhythmic, biphasic Ca(2+) transients (6.03 +/- 0.33 cycles/min) occurred in Kit-positive ICC-MY. These consisted of a rapidly propagating upstroke phase that initiated a sustained plateau phase, which was associated with Ca(2+) spikes in neighboring smooth muscle. Pacemaker activity was dependent on inositol 1,4,5-triphosphate receptor-operated stores and mitochondrial function. The upstroke phase of Ca(2+) transients in ICC-MY appeared to result from Ca(2+) influx through dihydropyridine-resistant Ca(2+) channels, whereas the plateau phase was attributed to Ca(2+) release from inositol 1,4,5-triphosphate receptor-operated Ca(2+) stores.
Each ICC-MY in human jejunum generates spontaneous pacemaker activity that actively propagates through the ICC network. Loss of these cells could severely disrupt the normal function of the human small intestine.
人们普遍认为，人类胃肠道中的 Cajal 间质细胞（ICC）与啮齿动物中的具有相似功能，但迄今为止尚无直接实验证据支持这一假设。这是一个重要问题，因为病理学家已注意到多种运动障碍患者的 ICC 数量减少，一些人推测 ICC 的缺失可能是运动功能障碍的原因。我们的目的是确定人类空肠中的肌间 ICC（ICC-MY）是否为起搏细胞，以及这些细胞是否能主动传播起搏活动。
去除黏膜和黏膜下层，剥离纵行肌条以暴露 ICC-MY 网络。用 Ca(2+) 指示剂 fluo-4 加载 ICC 网络，并在 36.5℃±0.5℃下通过高速视频成像记录起搏活动。
在 Kit 阳性的 ICC-MY 中出现有节律的双相 Ca(2+) 瞬变（6.03±0.33 次/分钟）。这些瞬变由快速传播的上升相开始，该上升相引发持续的平台相，这与相邻平滑肌中的 Ca(2+) 尖峰相关。起搏活动依赖于肌醇 1,4,5-三磷酸受体操纵的储存库和线粒体功能。ICC-MY 中 Ca(2+) 瞬变的上升相似乎是由 Ca(2+) 通过抗二氢吡啶的 Ca(2+) 通道内流引起的，而平台相则归因于肌醇 1,4,5-三磷酸受体操纵的 Ca(2+) 储存库释放 Ca(2+)。
人类空肠中的每个 ICC-MY 都会产生自发的起搏活动，并通过 ICC 网络主动传播。这些细胞的缺失可能会严重破坏人类小肠的正常功能。
