Molecular mechanism of alveolar epithelial healing process in acute lung injury : roles of KGF and transcription factor on lung repair

1. 肺泡II型细胞生长因子对肺损伤的影响：我们已经证明角化细胞生长因子（KGF）是肺泡II型细胞增殖和分化的有效因子。我们研究了KGF是否能预防博莱霉素引起的肺损伤和纤维化。重组人KGF（rhKGF）分别于博莱霉素使用前48小时和使用后24小时气管内注射。KGF治疗可防止(1)减轻体重，(2)降低肺活量，(3)I型和III型胶原及其mrna的积累，(4)减少博来霉素诱导的大鼠肺部表面活性剂蛋白A（SP-A）、SP-B和SP-C mrna的放射自显影银粒。酸（0.1N HCl）注射前72h预处理KGF也能预防酸致肺损伤，但后处理不能。2. 为了阐明预防机制，我们检测了转录因子、C/EBP家族成员和表面活性剂蛋白在急性肺损伤和C/EBP缺陷小鼠肺中的表达。C/EBP家族成员在急性肺损伤中有差异表达。特别是，C/EBPdδ在一些肺泡II型细胞中表达，这表明存在一种亚型细胞。此外，C/ ebp α-缺陷小鼠出现类似肺泡蛋白沉积症的肺部异常。分子研究表明，SP-C mRNA在C/EBPα-缺陷小鼠肺中过表达，提示C/EBPα可能对SP-C基因有抑制调控作用。3. 为了探讨KGF预防肺损伤的机制，我们研究了KGF是否能预防沙鼠海马区另一器官损伤——脑缺血引起的神经元死亡。组织学和TUNEL研究显示其对神经元死亡有抑制作用。4. 未来项目：研究利用腺病毒气管内转移KGF基因，预防肺损伤和纤维化。

1. Effect of growth factor for alveolar type II cells on lung injury: We have demonstrated that keratinocyte growth factor (KGF) is a potent factor for proliferation and differentiation of alveolar type II cells. We have examined whether KGF would prevent bleomycin-induced lung injury and fibrosis. Recombinant human KGF(rhKGF) was injected intratracheally at 48h before and 24h after bleomycin. KGF treatment prevents (1)loss of body weight, (2)reduced total lung capacity, (3)accumulation of collagen type I & III and their mRNAs, and (4)decreased autoradiographic silver grains for surfactant protein A(SP-A), SP-B and SP-C mRNAs in the rat lungs induced by bleomycin. Lung injury due to acid instillation was also prevented by KGF pretreatment at 72h before acid (0.1N HCl) instillation, but not by posttreatment. 2. To clarify the mechanisms of prevention, we were examining the expression of the transcription factor, C/EBP family members, and the surfactant proteins in acute lung injury and in lungs of C/EBP deficient mice. C/EBP family members are differentially expressed in the lung with acute injury. Especially, C/EBPdδ is expressed in some of alveolar type II cells, which suggests the presence of a subtype of the cell. Further C/EBPα-deficient mice had a pulmonary abnormality resembling pulmonary alveolar proteinosis. Molecular study demonstrated overexpression of SP-C mRNA in the lungs of C/EBPα-deficient mice, which suggests C/EBPα may have an inhibitory regulation on SP-C gene. 3. To investigate the mechanism of preventing lung injury by KGF, we have examined whether KGF prevents another organ injury, brain ischemia-induced neuronal death in hippocampal region in gerbils. Histological and TUNEL studies showed its inhibition on neuronal death. 4. Future project: We are going to study gene transfer of KGF using adeno-virus intratracheally for preventing lung injury and fibrosis.