Investigation of molecular mechanism in the development of pulmonary emphysema and susceptibility to cigarette smoke-induced lung injury using transgenic animal models

纯合子突变Klotho小鼠表现出血管钙化和肺泡壁钙化。我们分析了骨相关蛋白和成骨转录因子CBFA-1在来自纯合子突变Klotho小鼠的主动脉钙化病变中的表达。免疫组织化学染色显示中膜有CBFA-1阳性细胞增殖。RT-PCR显示编码骨桥蛋白、骨连蛋白和CBFA-1的成骨细胞标志基因表达上调。这些结果表明，在Klotho纯合子突变小鼠体内观察到的血管钙化不是被动的过程，Klotho基因的表达对出生后维持肺的完整性是必不可少的。我们着重于Notch信号通路在肺成熟和肺损伤发展中的作用，Notch信号通路具有诱导细胞分化和增殖的潜力。Notch信号的转录靶点Herp-2在1周龄的毛细血管和肺泡上皮细胞中表达上调。在博莱霉素性肺损伤模型中，我们发现在博莱霉素性肺损伤模型中，HERP-2的表达在博莱霉素性肺损伤后的第1天到第14天呈下降趋势。这些发现表明，Notch信号与维持肺的完整性有关，特别是通过毛细血管和肺泡上皮细胞的增殖。

Homozygous mutant klotho mice show vascular calcification as well as alveolar wall calcification. We analyzed expression of bone-associated proteins and osteogenic transcription factor Cbfa-1 in calcified lesions of aorta obtained from homozygous mutant klotho mice. Immunohistochemical staining disclosed proliferation of Cbfa-1 positive cells in tunica media. RT-PCR showed upregulation of the osteoblast-marker genes coding osteopontin, osteonectin as well as Cbfa-1. These results indicate that vascular calcification observed in homozygous mutant klotho mice is not to be passive process.The klotho gene expression is essential to maintaining pulmonary integrity during postnatal life. We focused on the role of the Notch signaling pathway, which has the potential to induce cell differentiation and proliferation, in maturation of lung and in the development of lung injury. The expression of HERP-2, transcriptional targets of Notch-signaling, was up-regulated in capillary and alveolar epithelial cells at 1 week of age. In bleomycin-induced lung injury model, we found the expression of HERP-2 decreased from day 1 through day 14 after bleomycin administration. These findings suggest that Notch signaling is related to maintaining pulmonary integrity, especially through proliferation of capillary and alveolar epithelial cells.