Optical Tools to Assess the Role of Hemodynamics in the Development of Congenital Heart Defects

 先天性心脏缺陷（CHD）是最常见和最具破坏性的出生缺陷之一，每年在美国出生的32，000名婴儿和超过100万的美国人今天活着。在发育过程中改变的血液动力学已被证明是CHD的一个促成因素，无论最初的触发因素是环境还是遗传。然而，目前缺乏适当的工具来研究临床相关血流动力学扰动对后期缺陷发展的影响。该项目的目标是设计，构建和应用必要的工具来测量和精确地扰动早期胚胎发育中的血流动力学，然后检测和量化所产生的CHD。我们建议使用光学技术的测量和微扰。我们以前已经证明，光学相干断层扫描（OCT）可以测量许多血液动力学参数，包括心率，心输出量，每搏输出量，剪切应力和反流。在这个项目中，我们将构建一个超高速OCT系统，使用新的硬件和软件算法来实时采集血液动力学参数。我们将建立一个能够并行对多个胚胎进行纵向成像研究的系统。新的光学控制（OC）技术已经开发用于刺激和抑制神经和神经元，使用脉冲红外光诱导热效应。我们最近采用了这种技术来刺激体内和体外的胚胎心脏，并对抑制心脏活动进行了概念验证。OC能够精确控制心率，先进的OC协议的开发将能够复杂地改变心脏的跳动模式（例如，改变房室延迟）。我们将进一步优化OC参数，并将OC集成到超高速OCT系统中。这将使得能够开发利用实时OCT参数作为反馈的闭环控制系统，以将血液动力学参数长时间保持在期望值，即使在胚胎生长和发育时。我们还将构建一个双面贝塞尔光束OCT系统，以获得与光学清除技术相结合，足够的深度穿透，以获取后期4室胚胎心脏的结构图像。最后，在验证这些系统后，我们将应用该技术来检验以下假设：发育中的心脏垫（瓣膜前体）上的反流和剪切应力改变将导致瓣膜缺陷。我们还将探讨受损的心脏垫是否也会导致大血管错位（例如右心室双出口）。完成后，我们将开发工具并收集更多关于发育中的心血管系统何时、如何以及在何种程度上最容易受到异常血流动力学影响的信息。有了这些知识，我们将能够更好地确定哪些分子途径最受血流动力学改变的影响，开发早期检测策略，并可能更有效地治疗CHD。

 DESCRIPTION (provided by applicant): Congenital heart defects (CHDs) are one of the most common and devastating birth defects, afflicting 32,000 babies born in the United States each year, and over 1 million Americans alive today. Altered hemodynamics during development has been shown to be a contributing factor to CHDs, regardless of whether the initial trigger is environmental or genetic. However, there is currently a lack of appropriate tools for studying the effects of clinically relevant hemodynamic perturbations on the development of later defects. The objective of this project is to design, construct, and apply the tools necessary to measure and precisely perturb hemodynamics in early embryonic development and then detect and quantify the resultant CHDs that develop. We propose to use optical techniques for both measurement and perturbation. We have previously demonstrated that optical coherence tomography (OCT) can measure many hemodynamic parameters, including heart rate, cardiac output, stroke volume, shear stress, and regurgitation. For this project, we will construct an ultrahigh-speed OCT system using new hardware and software algorithms to acquire hemodynamic parameters in real-time. We will build the system to be able to conduct longitudinal imaging studies of multiple embryos in parallel. New optical control (OC) technology has been developed for stimulating and inhibiting nerves and neurons, using pulsed infrared light to induce thermal effects. We have recently adapted this technology to stimulate embryonic hearts both in vivo and ex vivo and have a proof-of-concept demonstration for inhibiting cardiac activity. OC enables precise control of heart rate and development of advanced OC protocols will enable complex alteration of the heart's beat patterns (e.g. altered atrioventricular delay). We will perform further optimization of OC parameters and integrate OC into our ultrahigh-speed OCT system. This will enable the development of a closed-loop control system utilizing real-time OCT parameters as feedback to maintain hemodynamic parameters at desired values for long periods of time, even as the embryo grows and develops. We will also construct a double-sided Bessel-beam OCT system to obtain, in conjunction with optical clearing techniques, sufficient depth penetration to acquire structural images of later stage 4-chambered embryonic hearts. Finally, after validating these systems, we will apply this technology to test the hypothesis that altered regurgitation and shear stress on the developing cardiac cushions (valve precursors) will lead to valve defects. We will also explore whether compromised cardiac cushions also lead to misalignment of the great vessels (e.g. double outlet right ventricle). Upon completion, we will have developed tools and gathered significantly more information on when, how, and to what degree the developing cardiovascular system is most vulnerable to abnormal hemodynamics. With this knowledge, we will be better equipped to determine which molecular pathways are most influenced by altered hemodynamics, to develop earlier detection strategies, and potentially to treat CHDs more effectively.