Foster Jennifer J, Goss Kelli L, George Caroline L S, Bangsund Peter J, Snyder Jeanne M
Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA.
Am J Physiol Lung Cell Mol Physiol. 2006 Dec;291(6):L1142-9. doi: 10.1152/ajplung.00054.2006. Epub 2006 Aug 4.
In mice, alveolarization occurs during postnatal days 4 through 12, when secondary alveolar septae create thin-walled alveoli in the distal lung. We hypothesized that genes predominantly expressed in newly forming secondary alveolar septae influence the process of alveolarization. To address this hypothesis, tips of secondary alveolar septae were isolated from sections of postnatal day 6 mouse lung tissue using laser capture microdissection. Total RNA was isolated and amplified from the dissected alveolar septal tips and from intact postnatal day 6 lung tissue. Gene expression in the samples was characterized using Affymetrix mouse U74AN2 GeneChips. Galectin-1 was an abundantly expressed transcript that was enriched in the alveolar septal tips compared with levels in the whole lung tissue. Galectins are beta-galactoside-binding proteins involved in the regulation of cell proliferation, differentiation, and apoptosis in fibroblasts, muscle cells and endothelial cells, cell types that are present in the alveolar wall. Immunostaining in postnatal day 6 lung tissue confirmed that galectin-1 protein is concentrated in the tips of secondary alveolar septae, predominantly in myofibroblasts. Fibroblasts isolated from day 6 neonatal mouse lung tissue contained galectin-1 protein. Real-time PCR demonstrated that galectin-1 mRNA levels in mouse lung tissue peak at postnatal day 6. Immunoblot analysis confirmed that peak levels of lung galectin-1 protein are found at postnatal days 6 to 12. The increased expression of galectin-1 at the site and time of ongoing alveolarization in the newborn mouse is suggestive that galectin-1 may play an important role in this critical aspect of lung development.
在小鼠中，肺泡化发生在出生后第4天至第12天，此时次级肺泡隔在肺远端形成薄壁肺泡。我们假设在新形成的次级肺泡隔中主要表达的基因会影响肺泡化过程。为了验证这一假设，使用激光捕获显微切割技术从出生后第6天的小鼠肺组织切片中分离出次级肺泡隔的尖端。从解剖的肺泡隔尖端和完整的出生后第6天肺组织中分离并扩增总RNA。使用Affymetrix小鼠U74AN2基因芯片对样本中的基因表达进行表征。与全肺组织中的水平相比，半乳糖凝集素-1是一种在肺泡隔尖端大量表达的转录本。半乳糖凝集素是β-半乳糖苷结合蛋白，参与成纤维细胞、肌肉细胞和内皮细胞（这些细胞类型存在于肺泡壁中）的细胞增殖、分化和凋亡的调节。对出生后第6天肺组织的免疫染色证实，半乳糖凝集素-1蛋白集中在次级肺泡隔的尖端，主要存在于肌成纤维细胞中。从出生后第6天的新生小鼠肺组织中分离出的成纤维细胞含有半乳糖凝集素-1蛋白。实时PCR表明，小鼠肺组织中半乳糖凝集素-1 mRNA水平在出生后第6天达到峰值。免疫印迹分析证实，肺半乳糖凝集素-1蛋白的峰值水平出现在出生后第6天至第12天。新生小鼠在肺泡化进行的部位和时间半乳糖凝集素-1表达增加，提示半乳糖凝集素-1可能在肺发育的这一关键方面发挥重要作用。
