Assessing the role of hemodynamics in embryonic development

心血管系统是胚胎的第一个功能器官，早期心血管系统的正常功能对胚胎的健康和存活至关重要。胚胎的血管最初是通过一种称为血管生成的过程建立起来的，这种过程发生在没有血液流动的情况下。这些早期的血管然后通过二次过程重塑，这一过程已知依赖于血流的存在。近年来，关于早期血管形成的哪些方面是遗传决定的，哪些是由外部刺激(如机械和生化信号)控制的，一直存在争议。虽然最初的血管网络是在没有生理反馈的情况下形成的，但一旦血流开始，一套单独的物理和代谢信号就会出现。血压、血流和相关的物理力量，如周壁应力和壁切应力，以及代谢信息，如营养和氧气需求，都可以向遗传编码的信号机制提供反馈。从遗传机制到生理反馈机制的转换在什么时候发生，在很大程度上仍未被探索。

The cardiovascular system is the first functional organ in the embryo, and proper functioning of the early cardiovascular system is essential for embryonic health and survival. The blood vessels of the embryo are initially established by a process called vasculogenesis which occurs in the absence of blood flow. These early vessels are then remodeled through a secondary process that is known to be dependent on the presence of blood flow. In recent years, there has been a debate regarding which aspects of early vascular formation are genetically predetermined, and which are governed by external stimuli, such as mechanical and biochemical signaling. Though the initial vascular network is patterned without physiological feedback, once flow has begun, a separate set of physical and metabolic signals arise. Blood pressure, blood flow, and related physical forces such as circumferential wall stress and wall shear stress as well as metabolic information such as nutrient and oxygen requirements all can provide feedback to genetically encoded signaling mechanisms. The point at which the switch from genetic mechanisms to physiological feedback mechanisms occurs remains largely unexplored.