Yamada Mie, Kurihara Hidetake, Kinoshita Katsuyuki, Sakai Tatsuo
Department of Anatomy, Juntendo University School of Medicine, Bunkyo-ku, Tokyo 113-8421, Japan.
J Histochem Cytochem. 2005 Jun;53(6):735-44. doi: 10.1369/jhc.4A6483.2005.
In rat lung, the definitive alveoli are established during development by the outgrowth of secondary septa from the primary septa present in newborn; however, the mechanism of alveolar formation has not yet been fully clarified. In this study, we characterize the septal interstitial cells in developing alveoli. During the perinatal period, alpha-SMA-containing slender cells were found in the primitive alveolar septa. Alpha-SMA-containing cells were detected at the tips of the septa until postnatal day 21, when the alveolar formation was almost completed, but disappeared in adult. Immunoelectron microscopy demonstrated that alpha-SMA is localized mainly in the cellular protrusions, which are connected with the elastic fibers around the interstitial cells. Developmentally regulated brain protein (drebrin) is also located in the cell extensions containing alpha-SMA in immature alveolar interstitial cells. In adult lung, alpha-SMA-positive cells are located only at the alveolar ducts but are not found in the secondary septa. Desmin is expressed only in alpha-SMA-containing cells at the alveolar ducts but not in those at the tip of alveolar septa. These results suggest that a part of the septal interstitial cells are temporarily alpha-SMA- and drebrin-positive during maturation. Alpha-SMA- and drebrin-containing septal interstitial cells (termed septal myofibroblast-like cells) may play an important role in alveolar formation.
在大鼠肺中，终末肺泡在发育过程中由新生儿期存在的初级隔的次级隔长出而形成；然而，肺泡形成的机制尚未完全阐明。在本研究中，我们对发育中的肺泡中的隔间质细胞进行了特征描述。在围产期，在原始肺泡隔中发现了含α -平滑肌肌动蛋白（α - SMA）的细长细胞。在出生后第21天之前，含α - SMA的细胞在隔的尖端被检测到，此时肺泡形成几乎完成，但在成年后消失。免疫电子显微镜显示，α - SMA主要定位于细胞突起中，这些突起与间质细胞周围的弹性纤维相连。发育调控脑蛋白（drebrin）也位于未成熟肺泡间质细胞中含α - SMA的细胞延伸部分。在成年肺中，α - SMA阳性细胞仅位于肺泡导管，而在次级隔中未发现。结蛋白仅在肺泡导管中含α - SMA的细胞中表达，而在肺泡隔尖端的细胞中不表达。这些结果表明，一部分隔间质细胞在成熟过程中暂时呈α - SMA和drebrin阳性。含α - SMA和drebrin的隔间质细胞（称为隔肌成纤维细胞样细胞）可能在肺泡形成中起重要作用。
