Brody A R, Hook G E, Cameron G S, Jetten A M, Butterick C J, Nettesheim P
Lab Invest. 1987 Aug;57(2):219-29.
The purpose of our studies was to determine the growth and differentiation potential of Clara cells isolated from rabbit lungs. The Clara cell preparations were enriched (80 to 85%) by density gradient-elutriation procedures and then were inoculated into rat tracheas denuded of their own epithelium. These tracheas then were transplanted subcutaneously on the backs of nude mice. For purposes of comparison, other denuded tracheas were inoculated with mixed epithelial cells obtained from rabbit tracheas by enzymatic procedures. Control tracheas were inoculated with cell-free media. At 2, 4, and 14 weeks after transplantation, the tracheal grafts were removed from the recipient nude mice and examined by light and electron microscopy. Tracheal grafts not receiving cell inocula contained no epithelial lining, and the tracheal lumens were filled with loose connective tissue. Tracheas inoculated with 2 X 10(4) mixed tracheal cells showed a columnar, pseudostratified epithelium composed of five cell types: (a) poorly-differentiated cells, (b) ciliated cells, (c) mucous cells, (d) Clara-like cells, and (e) typical basal cells. A very different epithelium was established in tracheas repopulated with Clara cell isolates. This epithelium, at all time points examined, was cuboidal, single layered (never pseudostratified), and lacked basal cells. The tracheal lumens were lined with ciliated and nonciliated cells. The latter showed typical features of mature Clara cells (i.e., electron dense granules and smooth endoplasmic reticulum). At 14 weeks, the same two cell types were present, and often they were located on ridges and furrows of the tracheal walls. Mixed tracheal cells inoculated into denuded tracheas gave rise to a normal-appearing pseudostratified mucociliary epithelium, whereas the Clara cells inoculated under identical conditions gave rise to a low cuboidal epithelium resembling that seen in normal bronchioles. Establishment of these two types of epithelial linings occurred in the presence of the same mesenchymal components. Thus, we conclude that Clara cells have considerable self-renewal capacity, and their differentiation potential appears to be quite narrow.
我们研究的目的是确定从兔肺中分离出的克拉拉细胞的生长和分化潜能。通过密度梯度淘析法富集克拉拉细胞制剂（80%至85%），然后将其接种到去除自身上皮的大鼠气管中。然后将这些气管皮下移植到裸鼠背部。为了进行比较，用酶法从兔气管获得的混合上皮细胞接种到其他去除上皮的气管中。对照气管接种无细胞培养基。移植后2周、4周和14周，从受体裸鼠中取出气管移植物，进行光镜和电镜检查。未接种细胞的气管移植物没有上皮内衬，气管腔内充满疏松结缔组织。接种2×10⁴混合气管细胞的气管显示出由五种细胞类型组成的柱状假复层上皮：（a）低分化细胞，（b）纤毛细胞，（c）黏液细胞，（d）类克拉拉细胞，和（e）典型的基底细胞。在用克拉拉细胞分离物重新填充的气管中建立了非常不同的上皮。在所有检查的时间点，这种上皮都是立方状的，单层的（从不假复层），并且没有基底细胞。气管腔内衬有纤毛细胞和非纤毛细胞。后者显示出成熟克拉拉细胞的典型特征（即电子致密颗粒和平滑内质网）。在14周时，存在相同的两种细胞类型，并且它们通常位于气管壁的嵴和沟上。接种到去除上皮的气管中的混合气管细胞产生外观正常的假复层黏液纤毛上皮，而在相同条件下接种的克拉拉细胞产生类似于正常细支气管中所见的低立方上皮。在相同的间充质成分存在的情况下建立了这两种类型的上皮内衬。因此，我们得出结论，克拉拉细胞具有相当大的自我更新能力，并且它们的分化潜能似乎相当有限。
