RETINOIC ACID RECEPTORS AND ALVEOLAR FORMATION

肺泡是由肺隔分隔肺泡而形成的 包括间充质细胞和上皮细胞。据报 全反式维甲酸（RA）增加新生儿肺泡数量 以及在肺气肿的成年大鼠中。RA与三种视黄酸结合 受体（RAR，即，RAR-α，-β和-γ。初步 研究中，我们发现RAR的肺泡数量和表面积减少， β基因缺失的小鼠。肺泡隔的形成 肺的发育受血小板衍生生长因子-A（PDGF-）的调节。 A），由远端肺上皮细胞产生，其结合PDGF受体， 肺间充质细胞中表达的PDGF-Ra。所以我们 假设RA与肺上皮细胞中的RAR-β结合， 抑制肺泡化，可能通过下调PDGF-A表达。 我们进一步假设RA与肺间充质细胞中的RAR-γ结合， 细胞，并通过增加PDGF的表达促进肺泡化。 阿尔法为了解决这些假设，我们建议实现 具体目标。1.我们将进行形态测定分析， 从野生型和RAR-β和RAR-γ基因缺失的 小鼠在不同的发展阶段，以阐明这些作用， 肺泡化中的受体; 2.我们将研究RAR的影响 基因缺失对PDGF-A表达的影响以及对 肺泡上皮细胞的增殖和分化; 3. 我们 将评估PDGF-R α的表达以及细胞增殖， 和分化的肺泡肌成纤维细胞，一个关键的细胞类型， 在野生型和RAR基因缺失小鼠的肺泡隔中， 描述RA以及RAR特异性激动剂的直接作用 和拮抗剂对肺泡分化标志物的作用。我们将 随后用野生型和RAR基因处理新生小鼠， 删除，活性类维生素A在体外研究中确定。通过 进行这些研究，我们将测试的假设，肺泡 形成由RA信号通过特异性受体调节 受这个信号的影响。实现这些目标将提高 了解RA/RAR信号传导如何促进上皮细胞- 间充质相互作用参与肺泡形成。这些知识 将构成合理开发代理人的基础， 促进人类肺泡的生长和修复。

Lung alveoli are formed through the division of saccules by septae comprises of mesenchymal and epithelial cells. It has been reported that all-trans retinoic acid (RA) increases the number of alveoli in newborns and in emphysematous adult rats. RA binds to three retinoic acid receptors (RAR, i.e., RAR-alpha, -beta and -gamma. In preliminary studies, we found decreased numbers of alveoli and surface area in RAR- beta gene-deleted mice. The formation of alveolar septae in the developing lung is regulated by platelet derived growth factor-A (PDGF- A), produced by the distal lung epithelium, that binds to PDGF-receptor- alpha (PDGF-Ralpha) expressed in lung mesenchymal cells. Therefore, we hypothesize that RA binds to RAR-beta in lung epithelial cells and this inhibits alveolarization, perhaps by down-regulating PDGF-A expression. We further hypothesize that RA binds to RAR-gamma in lung mesenchymal cells and promotes alveolarization by increasing the expression of PDGF- Ralpha. To address these hypotheses, we propose to accomplish the following specific aims. 1. We will perform morphometric analyses in lungs obtained from wild-type and RAR-beta and RAR-gamma gene-deleted mice at different stages of development to elucidate the role of these receptors in alveolarization; 2. We will investigate the effects of RAR gene deletions on the expression of PDGF-A as well as on the proliferation and differentiation of alveolar epithelial cells; 3. We will assess the expression of PDGF-Ralpha as well as the proliferation and differentiation of alveolar myofibroblasts, a key cell type involved in alveolar septal from wild-type and RAR gene-deleted mice, to characterize the direct effects of RA, as well as RAR specific agonists and antagonists, on markers of alveolar differentiation. We will subsequently treat newborn mice in both, both wild type and RAR gene- deleted, with the active retinoids identified in vitro studies. By performing these studies, we will test the hypothesis that alveolar formation is regulated by RA signaling through specific receptors influenced by this signaling. Accomplishing these aims will enhance understanding of how RA/RAR signaling promotes the epithelial- mesenchymal interactions involved in alveolar formation. This knowledge will form the foundation for the rational development of agents that promote alveolar growth and repair in humans.