The conditional GPR30 knockout mouse: a model of female-specific cardiac aging

描述(由申请人提供)：绝经后女性中舒张期功能障碍的患病率急剧增加，并可能导致心力衰竭，目前还没有得到证实的治疗方法。虽然有证据表明雌激素可以保护绝经前的心脏免受高血压和心室重塑的影响，但其中涉及的机制尚不清楚。新发现的G蛋白偶联雌激素受体GPR30可能会保护绝经后女性免受心血管疾病的侵袭。然而，需要建立和改进合适的动物模型，以更好地了解心脏GPR30的激活如何降低老年女性舒张期功能障碍及其进展为舒张性心力衰竭的可能性。这项先导性研究的主要目标有两个： 首先，建立和鉴定心肌细胞特异性的、多西环素诱导的GPR30基因敲除小鼠，其次，确定GPR30在成年雌性小鼠心脏中的分子、组织学和功能作用。为了达到这一目标，我们将检验一个工作假设，即在缺乏心脏GPR30的情况下，与年龄匹配的未受GPR30影响的小鼠相比，心肌松弛、左室腔顺应性、运动耐量和左心室重构的损害都会加速。我们将利用一种新的啮齿动物模型来验证我们的假设，该模型涉及Cre/loxP基因敲除方法，以及对女性心肌细胞特异性、多西环素诱导的GPR30基因敲除小鼠的心功能、结构和血流动力学的无创和有创体内评估。在建立模拟老年妇女动态卵巢激素环境的实验模型时，空间(仅心脏组织)和时间调节GPR30基因表达的能力是至关重要的。这项拟议研究的成功完成将为我们现有的知识贡献一个缺失的基本元素，如果没有这些元素，我们就无法理解GPR30失活在绝经后妇女加速心脏老化中的心脏特异性作用。这一知识将对测试GPR30相关的分子机制在性别特有的舒张期功能障碍的发生和进展背后，以及测试新的治疗策略方面将是重要的。当拟议的研究完成后，我们预计1)我们将全面鉴定心肌细胞特异性的、多西环素诱导的GPR30基因敲除小鼠的分子、组织学和功能表型；2)我们将在我们独特的模型中确定是否由实验诱导的压力超负荷启动和/或加剧了雌性小鼠缺失GPR30的不利结构和功能特征(尤其是舒张期功能障碍、运动能力降低和左心室重构)。这一发现将使开发急需的治疗方法，如GPR30激活，可以暂时启动，以防止绝经后或收缩期高血压发作后心脏加速老化或舒张期功能障碍的进展。

DESCRIPTION (provided by applicant): The prevalence of diastolic dysfunction sharply increases in women after menopause and may lead to heart failure, for which there are no proven treatments. While evidence suggests that estrogen may protect the premenopausal heart from hypertension and ventricular remodeling, the mechanisms involved are not understood. The newly recognized G protein-coupled estrogen receptor, GPR30, may protect postmenopausal women from cardiovascular disease. However, appropriate animal models need to be established and refined to better understand how activation of cardiac GPR30 might reduce the likelihood of diastolic dysfunction and its progression to diastolic heart failure in oler women. The primary objective of this pilot research study is two-fold: first, to generate and characterize the cardiomyocyte-specific, doxycycline-inducible GPR30 knockout mouse and second, to determine the molecular, histological, and functional roles of GPR30 in hearts from adult female mice exposed to chronic hemodynamic overload induced by transverse aortic constriction. To attain this objective, we will test the working hypothesis thatin the absence of cardiac GPR30, impairments in myocardial relaxation, left ventricular chamber compliance, exercise tolerance and left ventricular remodeling are accelerated compared to age-matched GPR30-intact littermates exposed to the same perturbation. We will test our hypothesis utilizing a new rodent model that involves the Cre/loxP gene knockout methodology, coupled with non-invasive and invasive in vivo assessments of cardiac function, structure and hemodynamics in the female cardiomyocyte-specific, doxycycline-inducible GPR30 knockout mouse. The ability to spatially (cardiac tissue only) and temporally regulate GPR30 gene expression is critical when establishing experimental models that mimic the dynamic ovarian hormone milieu of aging women. Successful completion of the proposed research will contribute a missing, fundamental element to our existing knowledge, without which we cannot understand the cardio-specific role of GPR30 inactivation in accelerated cardiac aging of postmenopausal women. This knowledge will be important in testing GPR30-related molecular mechanisms behind the development and progression of sex-specific diastolic dysfunction, and to test new therapeutic strategies. When the proposed studies have been completed, it is our expectation that 1) we will fully characterize the molecular, histological, ad functional cardiac phenotype of the cardiomyocyte-specific, doxycycline-inducible GPR30 knockout mouse, and 2) we will identify, in our unique model, whether the unfavorable structural and functional features (specifically, diastolic dysfunction, reduced exercise capacity, and left ventricular remodeling) of deleting GPR30 in female mice are initiated and/or exacerbated by experimentally-induced pressure overload. Such a finding would allow development of much-needed therapeutic approaches, such as GPR30 activation, to be temporally initiated to prevent the progression of accelerated cardiac aging, or diastolic dysfunction, after menopause or the onset of systolic hypertension.