RETINOIC ACID RECEPTORS AND ALVEOLAR FORMATION

肺泡是通过隔膜分裂球囊而形成的。 由间充质细胞和上皮细胞组成。据报道， 全反式维甲酸(RA)增加新生儿肺泡数 在肺气肿的成年大鼠身上也有。RA与三种维甲酸结合 受体(RAR，即RAR-α、-β和-γ)。在预赛中 研究发现，RAR的肺泡数和表面积减少。 β基因缺失的小鼠。大鼠肺泡间隔的形成 发育中的肺受血小板衍生生长因子-A(PDGF-A)的调节 A)，由远端肺上皮产生，与PDGF受体结合- α(PDGF-Rpha)在肺间充质细胞中表达。因此，我们 假设RA与肺上皮细胞中的RAR-β结合，这 抑制牙槽骨形成，可能是通过下调PDGF-A的表达。 我们进一步假设在肺间充质中RA与RAR-γ结合。 并通过增加PDGF-1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 遵循特定的目标。1.我们将在 从野生型和RAR-β和RAR-伽马基因缺失获得的肺 以阐明小鼠在不同发育阶段的作用 肺泡化中的受体；2.我们将研究RAR的作用 血小板衍生生长因子-A的基因缺失及其在血管内皮细胞中的表达 肺泡上皮细胞的增殖和分化； 将评估PDGF-Rpha的表达以及细胞的增殖 和肺泡肌成纤维细胞的分化，这是一种关键的细胞类型 在野生型和RAR基因缺失小鼠的肺泡间隔中， 描述RA的直接作用，以及RAR特异性激动剂 和拮抗剂，对肺泡分化的标记物。我们会 随后在新生小鼠中同时处理野生型和RAR基因- 删除，并在体外研究中确定了活性维甲酸。通过 在进行这些研究时，我们将检验肺泡的假说 RA信号通过特定的受体调节形成 受这一信号的影响。实现这些目标将增强 了解RA/RAR信号如何促进上皮细胞- 间充质相互作用参与了肺泡的形成。这一知识 将形成合理发展的代理的基础， 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.