The mechanism of beta-cell regeneration

描述(申请人提供)：本申请着眼于刺激细胞再生作为治疗糖尿病的长期目标。控制细胞周期进程的机制使它们保持在极低的增殖状态，这种状态随着年龄的增长而进一步下降。利用我们之前展示的增强细胞再生的模型，我们计划检验p16和细胞周期蛋白D是导致观察到的缓慢再生表型的假设。PTEN(第10号染色体上缺失的磷酸酶和张力蛋白同源物)是一种特殊的细胞有丝分裂信号PI3K/AKT的负调节因子。我们已经证明，PTEN在细胞中的缺失会导致胰岛质量和有丝分裂活性的增加。为了评估这种表型的分子机制，我们探索了各种细胞周期调节因子，发现细胞周期蛋白D和p16在胰岛中发生了显著的变化。我们跟踪了这一初步观察，并证实PTEN可以通过胶质瘤细胞系直接调节p16和细胞周期蛋白D。由于p16上调与衰老细胞再生丧失的相关性，我们推测PTEN缺失可能能够诱导甚至老年小鼠的再生细胞。我们的初步数据显示，在没有发育缺失Pten的成年小鼠中，这是可能的。为了证明这一结果，我们采用了一个可以在成年小鼠中诱导Pten缺失的模型。综上所述，这些数据导致了目前的假设，即PTEN通过p16和Cyclin D调节b-细胞的再生。为了验证这一假设，我们计划了三个具体的目标：首先，我们将调查PTEN缺失诱导的β-细胞有丝分裂活性是否依赖于p16和Cyclin D。第二，我们将确定PTEN缺失是否能够诱导超过生理刺激不再能促进β-细胞再生的年龄(1岁)的小鼠β-细胞再生。第三，我们将确定PTEN是否通过PI3K/AKT信号调节p16。这项分析的结果将极大地提高对细胞如何再生的理解，并阐明需要操纵哪些分子来促进它们的再生。

DESCRIPTION (provided by applicant): This application focuses on the long term goal of stimulating ¿-cell regeneration as a cure for diabetes. The mechanism controlling the cell cycle progression of ¿-cells keeps them at an extremely low proliferating state that decreases further with age. Using a model that we have previously shown to exhibit enhanced ¿-cell regeneration, we plan to test the hypothesis that p16 and cyclin D are responsible for the observed slow regeneration phenotype. PTEN (phosphatase and tensin homologue deleted on chromosome 10) is a negative regulator of a particular ¿-cell mitogenic signal, PI3K/AKT. We have shown that loss of PTEN in ¿- cells leads to increased islet mass and mitotic activity. To evaluate the molecular mechanisms responsible for this phenotype, we explored various cell cycle regulators and discovered that cyclin D and p16 are significantly altered in the islets. We followed this initial observation and confirmed that PTEN can directly regulate p16 and cyclin D using a glioma cell line. Because of the correlation of p16 upregulation with loss of regeneration in aged ¿-cells, we hypothesized that PTEN loss may be capable of inducing regeneration of ¿- cells in even older mice. Our preliminary data showed that this is possible in adult mice without the contribution of developmental deletion of Pten. To demonstrate this result, we employed a model that can induce the deletion of Pten in adult mice. Together, these data led to the current hypothesis that PTEN regulates regeneration of b-cells through p16 and cyclin D. To test this hypothesis, we have planned three specific aims: First, we will investigate whether the mitotic activity in ¿-cells induced by PTEN loss depends on p16 and cyclin D. Second, we will determine if loss of PTEN is capable of inducing regeneration of ¿-cells in mice beyond the age (1 year) at which physiological stimuli can no longer enhance ¿-cell regeneration. Third, we will determine whether PTEN regulates p16 through PI3K/AKT signaling. The results from this analysis will substantially improve the understanding of how ¿-cells regenerate and shed light on what molecules need to be manipulated to promote their regeneration.