Vaccaro C, Brody J S
Anat Rec. 1978 Dec;192(4):467-79. doi: 10.1002/ar.1091920402.
We examined the ultrastructural features of postnatal alveolar septal formation in rats from birth to 28 days of age. At birth, the rat lung consists of large saccules with thick walls and cellular interstitium. Interstitial cells have large oval nuclei with scant cytoplasm containing few organelles and scattered lipid droplets. These cells appear to be poorly differentiated mesenchymal cells not engaged in active protein synthesis or secretion. Between 5 and 15 days of age, saccule walls thin and many new alveolar septa form. Two types of interstitial fibroblasts are present: one which appears at the tips of newly formed septa has the characteristics of a myofibroblast and appears to be engaged in synthesis and secretion of elastin; the other fibroblast appears at the base of new septa, is filled with lipid and contains few other cytoplasmic organelles. After 15 days of age, alveolar walls become thinner, few new septa form and interstitial fibroblasts begin to resemble the dormant type of fibroblasts seen at birth. Thus, the process of postnatal alveolarization of lung parenchyma involves differentiation of the interstitial fibroblast and elastogenesis. The factors which control this process, the precise role of elastogenesis in alveolar septal formation, the origin and fate of the lipid filled fibroblast and the ultimate fate of the myofibroblast remain to be determined.
我们研究了出生至28日龄大鼠出生后肺泡间隔形成的超微结构特征。出生时，大鼠肺由壁厚且细胞间质丰富的大囊泡组成。间质细胞有大的椭圆形细胞核，细胞质稀少，含少量细胞器和散在的脂滴。这些细胞似乎是未充分分化的间充质细胞，不参与活跃的蛋白质合成或分泌。在5至15日龄之间，囊泡壁变薄，许多新的肺泡间隔形成。存在两种类型的间质成纤维细胞：一种出现在新形成间隔的顶端，具有肌成纤维细胞的特征，似乎参与弹性蛋白的合成和分泌；另一种成纤维细胞出现在新间隔的基部，充满脂质，几乎不含其他细胞质细胞器。15日龄后，肺泡壁变薄，很少有新的间隔形成，间质成纤维细胞开始类似于出生时所见的静止型成纤维细胞。因此，肺实质出生后肺泡化过程涉及间质成纤维细胞的分化和弹性蛋白生成。控制这一过程的因素、弹性蛋白生成在肺泡间隔形成中的精确作用、充满脂质的成纤维细胞的起源和命运以及肌成纤维细胞的最终命运仍有待确定。
