IGF-1, smooth muscle plasticity, and pathogenesis of cerebral microhemorrhages in aging

项目摘要/摘要 脑微出血(CMH)由脑内小血管破裂引起，并逐渐损害 神经功能。CMH的发病率随着年龄和高血压的增加而急剧增加，这是一个主要原因。 与年龄相关的认知功能减退。CMH引起的认知衰退对生活质量有严重影响，但 仍然无法治愈。CMHS的发生是由于血管脆弱性增加，但其潜在机制尚不清楚。 因此，缓解CMHS的治疗干预措施是不可用的。血管的完整性需要血管的可塑性。 大血管平滑肌细胞(VSMCs)，表现出从高度收缩到保护性抗收缩的适应性转换。 应激反应的脆弱表型。老化从根本上改变了VSMC的表型转换，抑制了 采用这种保护性的VSMC表型。相反，胰岛素样生长因子(IGF)-1具有血管保护作用。 影响和促进保护性抗脆性表型的采用，但循环中的IGF-1水平显著 随年龄增长而减少。低IGF-1水平增加脑微血管疾病的风险，促进脑微血管疾病的发展。 CMH在我们的啮齿动物模型中的作用，支持IGF-1缺乏在年龄相关的血管脆性中的作用。我们的 假说认为，IGF-1缺乏所致的VSMC表型转换受损在血管紧张素转换障碍中起重要作用。 脑血管脆性和CMH的发生随年龄增长而增加。目标1将检验假设，在- 衰老中CMH的增加是由于VSMCs中IGF-1信号的减少引起的血管脆性。发展 将比较具有VSMC特异性的小鼠的CMH、相关的神经/步态缺陷和VSMC表型 IGF-1信号转导中断、IGF-1信号转导完全中断的小鼠和IGF-1偶联的衰老小鼠 补充/救援。AIM 2将使用培养的老年、年轻和IGF-1受体敲除的VSMCs来测试 假设IGF-1信号是VSMC细胞适应血流动力学应激所必需的，并将评估。 利用转录因子Tbx15/18介导的新机制进行这种调节。目标3将测试 VSMC表型异质性影响CMH发生的假说。VSMC存在于Heter- 多种表型共存的同源池，基于包括IGF-1和 细胞外间隙中的其他刺激，但这种脑动脉异质性的特征是不同的。 为人所知。VSMC系谱追踪衰老和IGF-1缺乏的遗传小鼠模型，结合单细胞 RNA测序将用于表征VSMC的异质性。新发现的亲脆弱和反脆弱 VSMC表型状态将与CMH出血的位置相关，以检验CMH发生的假设 主要是在VSMCs表现出不适应表型的地区，科学和技术创新 本文提出的研究将显著提高我们对IGF-1缺乏在糖尿病发病中的作用的理解。 并将提供对其背后的细胞机制的关键见解，这两个机制都是关键的 用于开发有效的治疗方法。

PROJECT SUMMARY/ABSTRACT Cerebral microhemorrhages (CMH) result from rupture of small intracerebral blood vessels and progressively impair neuronal function. The incidence of CMH dramatically increases with age and hypertension and is a major cause for age-related cognitive decline. Cognitive decline caused by CMH has severe impacts on quality-of-life, yet remains untreatable. CMHs occur due to increased vascular fragility but underlying mechanisms are unknown, and thus therapeutic interventions to mitigate CMHs are not available. Blood vessel integrity requires plasticity of vascu- lar smooth muscle cells (VSMCs), which exhibit an adaptive switch from a highly contractile to a protective anti- fragility phenotype in response to stress. Aging fundamentally alters VSMC phenotypic switching, suppressing the adoption of this protective VSMC phenotype. In contrast, insulin-like growth factor (IGF)-1 has vasoprotective ef- fects and promotes adoption of the protective anti-fragility phenotype, but circulating IGF-1 levels are dramatically decreased with age. Low IGF-1 levels increase the risk for cerebromicrovascular disease and promote the devel- opment of CMH in our rodent models, supporting a role for IGF-1 deficiency in age-related vascular fragility. Our hypothesis is that impaired VSMC phenotypic switching due to IGF-1 deficiency has a fundamental role in in- creased cerebrovascular fragility and development of CMH with age. Aim 1 will test the hypothesis that in- creased CMH in aging is due to vascular fragility arising from decreased IGF-1 signaling in VSMCs. Development of CMH, associated neurological/gait defects, and VSMC phenotype will be compared in mice with VSMC-specific disruption of IGF-1 signaling, mice with overall disruption of IGF-1 signaling, and aged mice coupled with IGF-1 supplementation/rescue. Aim 2 will use cultured aged, young, and IGF-1 receptor knockdown VSMCs to test the hypothesis that IGF-1 signaling is required for VSMC cellular adaptation to hemodynamic stress and will eval- uate novel mechanisms mediated by the transcription factors Tbx15/18 for this regulation. Aim 3 will test the hypothesis that VSMC phenotypic heterogeneity influences the development of CMH. VSMCs exist in a heter- ogeneous pool in which multiple phenotypes co-exist, determined based on growth factors including IGF-1 and other stimuli in the extracellular space, but the characteristics of this heterogeneity in cerebral arteries is un- known. VSMC lineage tracing genetic mouse models of aging and IGF-1 deficiency, coupled with single-cell RNA-sequencing will be used to characterize VSMC heterogeneity. Newly discovered pro- and anti-fragility VSMC phenotypic states will be correlated with location of CMH bleeds to test the hypothesis that CMHs occur primarily in regions where VSMCs show a maladaptive phenotype The scientifically and technically innovative studies proposed here will significantly enhance our understanding of the role of IGF-1 deficiency in the devel- opment of CMH and will provide critical insight into cellular mechanisms underlying it, both of which are critical for the development of effective therapies.