Mechanisms of Airway Smooth Muscle Hypertrophy

描述（由申请人提供）：极早产儿生存率的增加伴随着支气管肺发育不良（BPD）发病率的增加。在“新型BPD”中，肺泡间隔增厚，胶原蛋白和1-平滑肌动蛋白阳性、转化生长因子(TGF)-阳性的肌成纤维细胞。我们从早产儿气管吸入物中分离出间充质间质细胞。这些细胞产生TGF-¿1并经历TGF-¿1诱导的肌成纤维细胞分化，这表明，在缺乏其他信号的情况下，肌成纤维细胞分化代表了间充质基质细胞特化的“默认程序”。间充质间质细胞似乎也是BPD发展的有效生物标志物；考虑到性别、出生体重和胎龄的潜在影响，间充质间质细胞的分离使BPD的调整优势比增加了31倍以上。最后，我们的微阵列数据显示基质细胞表达高水平的mrna编码基质蛋白，这是一个调节细胞-基质相互作用和纤维沉积的非结构性细胞外基质蛋白亚家族。总之，这些数据支持我们的一般假设，即间充质间质细胞肌成纤维细胞分化和基质细胞蛋白表达在BPD发病中起关键作用。为了验证这一假设，我们提出以下具体目标：新生儿肺间充质基质细胞蛋白表达与临床预后的关系我们假设：i)间充质间质细胞维持稳定的促纤维化表型，基质细胞蛋白表达与肌成纤维细胞分化相结合；基质细胞蛋白结缔组织生长因子（CTGF）、SPARC和骨膜蛋白的表达预测BPD的发展。2. 研究基质细胞蛋白表达对新生儿肺间充质间质细胞增殖和分化的影响，以及糖原合成酶激酶(GSK)-3和-catenin在体外肌成纤维细胞分化中的作用。我们假设(i)基质细胞蛋白诱导间充质间质细胞增殖，并且是TGF-¿-诱导的最大肌成纤维细胞分化所必需的；（ii）肌成纤维细胞分化依赖于Nox4/GSK-3¿/¿-catenin信号传导。3. 检测体内BPD表型中基质细胞蛋白及其下游信号中间体的表达、定位、需求和充分性。我们假设：i)成纤维细胞特异性表达CTGF足以导致BPD表型；（ii）高氧诱导的低肺泡化和间质纤维化需要SPARC和骨膜素；iii)间充质特异性抑制GSK-3¿足以抑制BPD表型；iv) BPD患儿肺部基质细胞蛋白表达升高。这项工作的完成将为BPD的发病机制提供新的见解，导致更准确的生物标志物的开发，并为基质细胞蛋白在肺纤维化中的作用提供新的信息。

DESCRIPTION (provided by applicant): Increased survival of very premature infants has been accompanied by an increased incidence of bronchopulmonary dysplasia (BPD). In the "new BPD," alveolar septa are thickened with collagen and 1-smooth muscle actin-positive, transforming growth factor (TGF)-¿-positive myofibroblasts. We have isolated mesenchymal stromal cells from the tracheal aspirates of premature infants. These cells produce TGF-¿1 and undergo TGF-¿-induced myofibroblastic differentiation, suggesting that, in the absence of other signals, myofibroblastic differentiation represents the "default program" for mesenchymal stromal cell specialization. Mesenchymal stromal cells also appear to be potent biomarkers for the development of BPD; accounting for the potential influences of gender, birth weight and gestational age, isolation of mesenchymal stromal cells increased the adjusted odds ratio of BPD over 31-fold. Finally, our microarray data show that stromal cells express high levels of mRNAs encoding matricellular proteins, a subfamily of non-structural extracellular matrix proteins that regulate cell-matrix interactions and fiber deposition. Together, these data support our general hypothesis that mesenchymal stromal cell myofibroblastic differentiation and matricellular protein expression play critical roles in BPD pathogenesis. To test this hypothesis, we propose the following Specific Aims: 1. Correlate neonatal lung mesenchymal stromal cell matricellular protein expression with clinical outcomes. We hypothesize that: i) mesenchymal stromal cells maintain a stable pro-fibrotic phenotype of matricellular protein expression that is coupled with myofibroblastic differentiation; and (ii) expression of the matricellular proteins connective tissue growth factor (CTGF), SPARC and periostin predicts BPD development. 2. Examine the effects of matricellular protein expression on neonatal lung mesenchymal stromal cell proliferation and differentiation, as well as the roles of glycogen synthase kinase (GSK)-3¿ and ¿-catenin in myofibroblastic differentiation in vitro. We hypothesize that (i) matricellular proteins induce mesenchymal stromal cell proliferation and are required for maximal TGF-¿-induced myofibroblastic differentiation; and (ii) myofibroblastic differentiation is dependent on Nox4/GSK-3¿/¿-catenin signaling. 3. Examine the expression, localization, requirement and sufficiency of matricellular proteins and their downstream signaling intermediates for the BPD phenotype in vivo. We hypothesize that: i) fibroblast-specific expression of CTGF is sufficient for the BPD phenotype; (ii) SPARC and periostin are required for hyperoxia-induced hypoalveolarization and interstitial fibrosis; iii) mesenchyme-specific inhibition of GSK-3¿ is sufficient for the BPD phenotype; and iv) matricellular protein expression in increased in the lungs of infants with BPD. Completion of this work will provide insight into the pathogenesis of BPD, lead to the development of more accurate biomarkers, and provide new information on the role of matricellular proteins in lung fibrosis.