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

1.肺泡II型细胞生长因子在肺损伤中的作用：我们已证实角质形成细胞生长因子(KGF)是促进肺泡II型细胞增殖和分化的重要因子。我们研究了KGF是否可以预防博莱霉素所致的肺损伤和纤维化。分别于给药前48h和给药后48h气管内注射重组人KGF(RhKGF)。KGF治疗可防止(1)体重减轻，(2)减少肺总容量，(3)I型和III型胶原及其mRNAs的积聚，以及(4)减少肺表面活性蛋白A(SP-A)、SP-B和SP-CmRNAs的放射自显影银粒。KGF在酸(0.1NHCl)滴注前72小时预处理也可预防酸滴注所致的肺损伤，但不能预防后处理。2.通过检测转录因子C/EBP家族成员和肺表面活性物质蛋白在C/EBP缺陷小鼠急性肺损伤及肺组织中的表达，探讨其预防作用的机制。C/EBP家族成员在急性肺损伤中的表达存在差异。尤其是C/EBPDδ在部分肺泡II型细胞中表达，提示该细胞存在某种亚型。此外，C/EBPα缺陷小鼠有类似于肺泡蛋白沉积症的肺异常。分子生物学研究表明，C/eBPα缺陷小鼠肺组织中存在SP-C基因的高表达，提示C/eBPα可能对SP-C基因具有抑制调节作用。3.为探讨KGF预防肺损伤的机制，我们观察了KGF对沙土鼠另一器官损伤--脑缺血所致海马区神经元死亡的保护作用。组织学和TUNEL研究显示其对神经元死亡有抑制作用。4.下一步工作：通过气管内腺病毒转导KGF基因预防肺损伤和纤维化的研究。

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.