ALVEOLAR TYPE II CELL GROWTH IN INJURY

二氧化硅会导致肺损伤和最终的肺纤维化。肺泡I型上皮细胞损伤和II型上皮细胞增殖是损伤的显著特征。我们的初步研究表明，在二氧化硅损伤后，II型细胞也会发生凋亡。人们普遍认为，II型细胞的增殖是一个重要的修复过程。然而，II型细胞生长对二氧化硅损伤恢复的功能和结构的影响从未被明确，调节二氧化硅暴露后II型细胞生长和死亡的因素也是未知的。我们的研究表明，甲状旁腺的氨基末端和中分子部分在二氧化硅诱导的肺损伤后对这些细胞起调节作用。PTHrP是一种激素前体，在翻译后被加工成不同的具有不同生物学活性的子肽。我们发现大鼠二氧化硅损伤后肺组织中PTHrP的表达下降，这与肺II型细胞增殖和凋亡的开始相一致。外源性PTHrP1-34氨基末端片段可减少肺细胞分裂(通过BrdU摄取)，而外源性PTHrP67-86(一种中分子片段)可减少II型细胞凋亡(TUNEL染色)。我们假设氨基末端和中期增殖和凋亡的减少。此外，我们认为，II型细胞数量的增加有利于修复上皮细胞，恢复肺结构和功能，减少肺纤维化。我们的具体目标如下：1)我们将明确PTHrP多肽对二氧化硅损伤后肺泡II型细胞和成纤维细胞数量的影响的结构-功能关系。3)探讨矽肺损伤后肺组织中II型细胞数量的变化对上皮修复、肺纤维化进展及肺组织结构的影响。该项目将导致对二氧化硅诱导的肺损伤后第二类细胞生长对上皮修复的重要性的理解，并将评估一类新的生长因子家族在调节肺泡细胞生长和死亡中的作用。该项目将评估甲状旁腺素相关治疗干预措施的潜在用途，这些干预措施可能会加速或改善二氧化硅诱导的肺损伤后的恢复。

Silica causes lung injury and eventual pulmonary fibrosis. Alveolar type I epithelial cell damage and type II epithelial cell proliferation are prominent features of the injury. Our pilot studies show that type II cells undergo apoptosis afer silica injury also. It is widely believed that type II cell proliferation is an important repair process. However, the functional and structural impact of type II cell growth on recovery from silica induced injury has never been defined and the factors that regulate type II cell growth and death after silica exposure are unknown. Our studies suggest that amino terminal and mid-molecule portions of parathyroid regulate these cell after silica-induced lung injury. PTHrP is a pro- hormone that is processed after translation into different daughter peptides with distinct biologic activities. We have found that lung PTHrP expression falls after silica injury in rats, coincident with the onset of type II cell proliferation and apoptosis. Treating rats with exogenous PTHrP 1- 34, the amino-terminal fragment, reduces pneumocyte division (measured by BrdU uptake), while exogenous PTHrP 67-86, a mid-molecule fragment, decreases type II cell apoptosis (measured by TUNEL staining). We hypothesis that the decrease in amino-terminal and mid-proliferation and apoptosis. Furthermore, we believe that an increase in the type II cell population is beneficial in repairing the epithelium, restoring lung architecture and function, and reducing pulmonary fibrosis. Our specific aims are as follows: 1) We will define the structure-function relationships for the effects of PTHrP peptides on the number of type II cells and fibroblasts in the alveoli after silica injury. 3) We will examine the effect of changes in type II cell number on epithelial repair, progression of pulmonary fibrosis and pulmonary structure after silica-induced lung injury. This project will lead to an understanding of the importance of type II cell growth for epithelial repair after silica-induced lung injury and will assess the role of a novel family of growth factors in regulating pneumocyte growth and death. The project will evaluate the potential use of PTHrP-related therapeutic interventions that might speed or improve recovery following silica-induced lung injury.