Division of Pulmonary and Critical Care, Department of Internal Medicine, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA.
Am J Respir Cell Mol Biol. 2010 Dec;43(6):731-9. doi: 10.1165/rcmb.2009-0328OC. Epub 2010 Jan 29.
Cilia are traditionally classified as motile or primary. Motile cilia are restricted to specific populations of well-differentiated epithelial cells, including those in the airway, brain ventricles, and oviducts. Primary cilia are nonmotile, solitary structures that are present in many cell types, and often have sensory functions such as in the retina and renal tubules. Primary cilia were also implicated in the regulation of fundamental processes in development. Rare depictions of primary cilia in embryonic airways led us to hypothesize that primary cilia in airway cells are temporally related to motile ciliogenesis. We identified primary cilia in undifferentiated, cultured airway epithelial cells from mice and humans and in developing lungs. The solitary cilia in the airways express proteins considered unique to primary cilia, including polycystin-1 and polycystin-2. A temporal analysis of airway epithelial cell differentiation showed that cells with primary cilia acquire markers of motile ciliogenesis, suggesting that motile ciliated cells originate from primary ciliated cells. Whereas motile ciliogenesis requires Foxj1, primary ciliogenesis does not, and the expression of Foxj1 was associated with a loss of primary cilia, just before the appearance of motile cilia. Primary cilia were not found in well-differentiated airway epithelial cells. However, after injury, they appear in the luminal layer of epithelium and in basal cells. The transient nature of primary cilia, together with the temporal and spatial patterns of expression in the development and repair of airway epithelium, suggests a critical role of primary cilia in determining outcomes during airway epithelial cell differentiation.
纤毛传统上分为运动性或原发性。运动性纤毛仅限于特定的分化良好的上皮细胞群体，包括气道、脑室和输卵管中的细胞。原发性纤毛是非运动性的、单一的结构，存在于许多细胞类型中，通常具有感觉功能，如视网膜和肾小管。原发性纤毛也参与了发育过程中基本过程的调节。胚胎气道中罕见的原发性纤毛描述导致我们假设气道细胞中的原发性纤毛与运动性纤毛发生有关。我们在未分化的、培养的人和小鼠气道上皮细胞以及发育中的肺中鉴定到了原发性纤毛。气道中的单一纤毛表达被认为是原发性纤毛特有的蛋白质，包括多囊蛋白-1 和多囊蛋白-2。气道上皮细胞分化的时间分析表明，具有原发性纤毛的细胞获得了运动性纤毛发生的标志物，这表明运动性纤毛细胞起源于原发性纤毛细胞。虽然运动性纤毛发生需要 Foxj1，但原发性纤毛发生不需要，Foxj1 的表达与原发性纤毛的丧失有关，就在运动性纤毛出现之前。在分化良好的气道上皮细胞中未发现运动性纤毛。然而，在损伤后，它们出现在上皮的腔层和基底细胞中。原发性纤毛的短暂性，以及在气道上皮细胞分化的发育和修复过程中的时空表达模式，表明原发性纤毛在决定气道上皮细胞分化的结果方面起着关键作用。
