Ten Have-Opbroek A A, De Vries E C
Department of Pulmonary, University of Leiden, The Netherlands.
Microsc Res Tech. 1993 Dec 1;26(5):400-11. doi: 10.1002/jemt.1070260508.
The morphologic and functional differentiation of the nonciliated columnar (Clara) cell, one of two secretory cell types in distalmost bronchioles in mammals, was studied in the mouse. Lungs from embryos (16-19 days of developmental age, dDA; birth on day 19), postnatal animals (5-20 days postnatally dPN), and adult animals were investigated by transmission electron microscopy, using standard staining procedures and immunogold (GAR-Au10) labeling for SP-A and Clara cell 10 kD antigen (CCA). At 16 dDa, all the columnar epithelial cells lining prospective distalmost bronchioles lacked distinctive features. By 17 dDa, some cells displayed a few cilia or apical dense granules. At 18 dDa, many nonciliated columnar cells had apical protrusions, as are seen in adult Clara cells. Apical concentrations of glycogen observed in nonciliated columnar cells perinatally were absent by 5 dPN, whereas apical dense granules became more abundant. Profiles of smooth and rough endoplasmic reticulum (ER), which had been randomly distributed, exhibited a selective, adult distribution at 20 dPN (apical vs. basal cytoplasmic domains). Labeling for SP-A and CCA, which was almost absent between 17 and 19 dDa, reached adult levels at the same time. The two proteins differed in distribution. SP-A predominated in adluminal cytoplasmic areas, where it was found over dense granules, vesicles, and multivesicular bodies; it was also present in bronchiolar lumens and intercellular spaces but not in rough ER or Golgi apparatus. In contrast, CCA showed a more uniform distribution; it was present over the same structures as SP-A and in the synthetic organelles. Ciliated columnar cells were virtually devoid of SP-A and CCA. We conclude that mouse Clara cells acquire a mature phenotype by 20 dPN. They are likely to be involved in recycling and/or degradation of SP-A that is internalized from airway lumens through their apical or lateral cell borders; furthermore, they synthesize the Clara cell 10 kD protein. These two Clara cell functions (first detectable late prenatally) reach mature levels by 20 dPN.
在小鼠中研究了哺乳动物最远端细支气管中两种分泌细胞类型之一的无纤毛柱状（克拉拉）细胞的形态和功能分化。通过透射电子显微镜，使用标准染色程序以及针对表面活性蛋白A（SP-A）和克拉拉细胞10 kD抗原（CCA）的免疫金（GAR-Au10）标记，对胚胎（发育年龄16 - 19天，dDA；第19天出生）、出生后动物（出生后5 - 20天，dPN）和成年动物的肺进行了研究。在16 dDA时，位于预期最远端细支气管的所有柱状上皮细胞均无明显特征。到17 dDA时，一些细胞出现了少量纤毛或顶端致密颗粒。在18 dDA时，许多无纤毛柱状细胞有顶端突起，这在成年克拉拉细胞中可见。围产期在无纤毛柱状细胞中观察到的糖原顶端聚集在出生后5天消失，而顶端致密颗粒变得更加丰富。原本随机分布的光滑和粗糙内质网（ER）轮廓在出生后20天呈现出选择性的、成年期的分布（顶端与基底细胞质区域）。在17至19 dDA之间几乎不存在的SP-A和CCA标记，在同一时间达到成年水平。这两种蛋白质分布不同。SP-A在管腔面细胞质区域占主导，在致密颗粒、囊泡和多泡体上可见；它也存在于细支气管腔和细胞间隙中，但不存在于粗糙内质网或高尔基体中。相比之下，CCA显示出更均匀的分布；它与SP-A存在于相同结构上，也存在于合成细胞器中。纤毛柱状细胞几乎没有SP-A和CCA。我们得出结论，小鼠克拉拉细胞在出生后20天获得成熟表型。它们可能参与从气道腔通过其顶端或侧面细胞边界内化的SP-A的再循环和/或降解；此外，它们合成克拉拉细胞10 kD蛋白。这两种克拉拉细胞功能（在产前晚期首次可检测到）在出生后20天达到成熟水平。
