REGULATION OF ATROPHY-INDUCED PROGENITOR CELLS IN THE GASTRIC CORPUS

描述（由申请人提供）：尽管最近在鉴定预期的干细胞标志物方面取得了突破（例如，LGR 5）在肠和胃窦，相对较少的是知道胃（体）体上皮干细胞。我们的总体目标是更好地描述正常条件下和对损伤的反应中的体干细胞。初步数据显示，选择性雌激素受体调节剂他莫昔芬导致几乎所有的壁细胞，酸分泌谱系，在小鼠胃消融3天内。在6小时内，壁细胞开始死亡（萎缩），并且胃体单位的峡部干细胞龛中的祖细胞开始作为响应而扩增。我们进一步发现：1）细胞表面蛋白CD 44是正常干细胞稳态所需的，因为相对于野生型小鼠，Cd 44-/-小鼠的增殖减半; 2）CD 44标志着扩大的峡部祖细胞群。CD 44激活STAT 3并由ERK信号转导诱导。我们发现ERK和STAT 3在早期扩增的祖细胞中被激活，ERK诱导的转录因子EGR 1的水平在第3天达到峰值，与最大的祖细胞扩增一致。 我们假设壁细胞死亡导致信号激活峡部干/祖细胞中的ERK通路，这导致CD 44表达增加和增殖增加。在目的1中，我们将确定ERK信号传导是否需要正常的干细胞稳态和萎缩诱导的扩张使用ERK药理学抑制和小鼠家系与缺陷（Egr 1-/-）和过度活跃（Nab 2-/-）ERK。在目标2中，我们将确定CD 44是否是萎缩诱导的祖细胞扩增所需的或足够的。我们将研究干细胞在Cd 44-/-小鼠中扩增的动力学，并且我们将通过注射CD 44配体Hybrononan来激活野生型小鼠中的CD 44，或者用抑制剂PEP-1阻断CD 44-Hybrononan相互作用。我们将确定CD 44是否诱导STAT 3和/或它是否是祖细胞扩增所需的。在目标3中，我们将通过FACS和激光捕获显微切割分离载体和他莫昔芬处理的表达CD 44的上皮祖细胞，然后使用RNA-Seq生成正常和萎缩扩展祖细胞的基因表达谱，然后将其与我们现有的干细胞和祖细胞全球基因表达数据库进行生物信息学整合。我们还将进行有限稀释试验，以确定上皮CD 44群体中的干细胞频率。 在人类中，慢性炎症可导致壁细胞萎缩，这反过来又改变干细胞增殖和分化。萎缩使患者易患胃癌，但继发于炎症/损伤的干细胞变化也是多种其他组织（例如，关节炎中造血干细胞分化的变化）。因此，提出的实验可能有助于我们开始了解干细胞对多种组织和疾病损伤的反应。最后，我们的新发现，关键药物他莫昔芬导致胃毒性，值得进一步研究人类。

DESCRIPTION (provided by applicant): Despite recent breakthroughs in identifying prospective stem cell markers (e.g., LGR5) in the intestines and the gastric antrum, relatively little is known about the stem cells of the gastric (body) corpus epithelium. Our overall goal is t better characterize the corpus stem cell under normal conditions and in response to injury. Preliminary data show that the selective estrogen receptor modulator tamoxifen causes ablation of nearly all parietal cells, the acid-secreting lineage, in the mouse stomach within 3 days. Within 6 hours, parietal cells begin to die (atrophy), and progenitor cells in the isthmal stem cel niche of corpus gastric units begin to expand in response. We further find that: 1) the cell surface protein CD44 is required for normal stem cell homeostasis, because proliferation is halved in Cd44-/- relative to wildtype mice; and 2) CD44 marks the expanding isthmal progenitor population. CD44 activates STAT3 and is induced by ERK signaling. We show here that ERK and STAT3 are activated in early expanding progenitors, and levels of the ERK-induced transcription factor EGR1 peak at 3 days, in concert with maximal progenitor expansion. We hypothesize that parietal cell death leads to signals that activate the ERK pathway in isthmal stem/progenitor cells, which causes increased CD44 expression and increased proliferation. In Aim 1, we will determine whether ERK signaling is required for normal stem cell homeostasis and atrophy-induced expansion using both ERK pharmacological inhibition and pedigrees of mice with deficient (Egr1-/-) and overactive (Nab2-/-) ERK. In Aim 2, we will determine whether CD44 is required or sufficient for atrophy-induced progenitor expansion. We will examine kinetics of stem cell expansion in Cd44-/- mice, and we will either activate CD44 in wildtype mice ¿tamoxifen by injection of the CD44 ligand Hyaluronan or block CD44- Hyaluronan interactions with the inhibitor PEP-1. We will determine if CD44 induces STAT3 and/or if it is required for progenitor expansion. In Aim 3, we will isolate vehicle- and tamoxifen-treated CD44-expressing epithelial progenitor cells by FACS and laser-capture microdissection and then use RNA-Seq to generate gene expression profiles of the normal and atrophy-expanded progenitor cells that will then be integrated bioinformatically with our existing database of global gene expression in stem and progenitor cells. We will also perform limiting dilution assays to determine the stem cell frequency within the epithelial CD44 population. In humans, chronic inflammation can cause parietal cell atrophy, which in turn changes stem cell proliferation and differentiation. Atrophy predispose patients to gastric cancer, but changes in stem cells secondary to inflammation/injury are also an important and understudied aspect of adult diseases in multiple other tissues (e.g., hematopoietic stem cell differentiation changes in arthritis). Thus, the experiments proposed may help us begin to understand stem cell response to injury in multiple tissues and diseases. Finally, our new finding that the key drug tamoxifen causes gastric toxicity warrants further study in humans.