Hedgehog Signaling in Kidney Homeostasis and Repair

描述（由申请人提供）：急性和慢性肾损伤对美国人的健康造成了深刻的和不断增长的损失。肾脏在许多形式的急性损伤后具有令人印象深刻的自我修复能力，对这一过程的细胞和分子机制的更深入理解将确定新的治疗方法来治疗人类肾衰竭。Hedgehog（Hh）家族的分泌信号分子调节细胞增殖、分化和组织模式。它们在肾发生过程中起着重要作用，并且在其他器官中作为组织再生的调节剂越来越受到重视。这个提议将研究刺猬配体在肾脏稳态和修复中的作用。两种Hh配体在肾脏中表达，Indian hedgehog（Ihh）和Sonic hedgehog（Shh），并且这些由肾小管上皮细胞表达。Hedgehog反应细胞位于肾间质上皮细胞附近。我们假设，Hh-生产上皮细胞和Hh-反应性间质细胞之间的串扰维持细胞分化过程中的稳态，而肾损伤上调Hh信号触发组织修复，或如果损伤正在进行中，导致适应不良的间质纤维化。在目标1中，我们将在细胞水平上表征Hh通路组分的表达，并检查急性损伤期间Hh信号传导的药理学抑制是否导致肾上皮细胞再分化的延迟。在目标2中，我们使用药理学和遗传获得或功能丧失方法来激活或抑制急性和慢性肾损伤期间的Hh信号传导，以评估Hh通路的调节是否可能代表新的治疗靶点。在目标3中，我们将使用周细胞培养模型具体解决Hh信号在肾脏中发挥其作用的机制，并且我们采用体内周细胞命运作图来测试Hh应答细胞是否在慢性损伤期间扩增并分化成瘢痕形成肌成纤维细胞。

DESCRIPTION (provided by applicant): Acute and chronic kidney injury exacts a profound and growing toll on the health of Americans. The kidney possesses an impressive capacity to repair itself after many forms of acute injury, and a deeper understanding of the cellular and molecular mechanisms of this process will identify new therapeutic approaches to treat human suffereing from kidney failure. Members of the Hedgehog (Hh) family of secreted signaling molecules regulate cell proliferation, differentiation and tissue patterning. They play important roles during nephrogenesis and in other organs are increasingly appreciated as regulators of tissue regeneration. This proposal will investigate the role of hedgehog ligands in kidney homeostasis and repair. Two Hh ligands are expressed in kidney, Indian hedgehog (Ihh) and Sonic hedgehog (Shh), and these are expressed by tubular epithelial cells. Hedgehog responsive cells are located adjacent to epithelia, in the renal interstitium. We hypothesize that crosstalk between Hh-producing epithelia and Hh-responsive interstitial cells maintains cellular differentiation during homeostasis, whereas kidney injury upregulates Hh signaling triggering tissue repair, or if the injury is ongoing, resulting in maladaptive interstitial fibrosis. In Aim 1, we will characterize at the cellular level the expression of Hh pathway components, and examine whether pharmacologic inhibition of Hh signaling during acute injury results in a delay in the re-differentiation of renal epithelia. In Aim 2, we use pharmacologic and genetic gain or loss-of-function approaches to activate or inhibit Hh signaling during acute and chronic renal injury to assess whether modulation of the Hh pathway might represent a novel therapeutic target. In Aim 3, we will specifically address the mechanism by which Hh signals exert their effects in kidney using pericyte cell culture models and we employ in vivo pericyte fate mapping to test whether Hh-responsive cells expand and differente into scar forming myofibroblasts during chronic injury.