Department of Bioengineering, University of Pittsburgh, 15261 Pittsburgh, PA, USA.
Department of Surgery, University of Pittsburgh, 15261 Pittsburgh, PA, USA.
Morphologie. 2024 Dec;108(363):100902. doi: 10.1016/j.morpho.2024.100902. Epub 2024 Aug 23.
In elastic and resistance arteries, an elastin-rich membrane, the Internal Elastic Lamina (IEL), separates the tunica intima from the underlying tunica media. The IEL often appears wrinkled or corrugated in histological images. These corrugations are sometimes ascribed to vessel contraction ex vivo, and to fixation artifacts, and therefore regarded as not physiologically relevant. We examine whether the IEL remains corrugated even under physiological conditions.
The diameters of carotid arteries of anesthetized pigs were measured by ultrasound. The arteries were then excised, inflated within a conical sleeve, fixed, and imaged by confocal microscopy. The conical sleeve allows fixing each artery across a wide range of diameters, which bracket its ultrasound diameter. Thus the study was designed to quantify how corrugations change with diameter for a single artery, and test whether corrugations exist when the fixed artery matches the ultrasound diameter.
At diameters below the ultrasound diameter (i.e. when the artery was constricted as compared to ultrasound conditions), the IEL corrugations were found to decrease significantly with increasing diameter, but not fully flatten at the ultrasound diameter. The contour length of the IEL was found to be roughly 10% larger than the circumference of the artery measured by ultrasound. Since ultrasound was conducted with the animal under general anesthesia which induces vasodilation, the physiological diameter is likely to be smaller than the ultrasound diameter, and hence the arteries are likely to have a higher level of corrugation under physiological conditions. For arterial cross sections constricted below the ultrasound diameter, the IEL contour length decreased roughly with the square root of the diameter.
The primary conclusions of this study are: a) the IEL is corrugated when the artery is constricted and flattens as the artery diameter increases; b) the IEL is corrugated under physiological conditions and has a contour length at least 10% more than the physiological arterial diameter; and c) the IEL despite being relatively stiffer than the surrounding arterial layers, does not behave like an inextensible membrane.
在弹性和阻力动脉中，富含弹性蛋白的膜——内弹性膜（IEL）——将内膜与下方的中膜分隔开来。在组织学图像中，IEL 通常呈现出褶皱或波纹状。这些波纹有时归因于血管在体外收缩，以及固定过程中的人为因素，因此被认为与生理无关。我们研究了 IEL 在生理条件下是否仍然保持波纹状。
通过超声测量麻醉猪颈动脉的直径。然后将动脉取出，在锥形套管内充气固定，并用共聚焦显微镜成像。锥形套管允许将每根动脉固定在一个较宽的直径范围内，该范围涵盖了其超声直径。因此，该研究旨在定量研究单个动脉的直径变化与波纹变化的关系，并测试固定后的动脉与超声直径相匹配时是否存在波纹。
在低于超声直径的直径（即与超声条件相比，动脉收缩时）下，发现 IEL 波纹随着直径的增加而显著减小，但在超声直径处并未完全变平。IEL 的轮廓长度比超声测量的动脉周长大约大 10%。由于超声是在动物全身麻醉下进行的，全身麻醉会引起血管扩张，因此生理直径可能小于超声直径，因此在生理条件下，动脉的波纹程度可能更高。对于低于超声直径的动脉横截面，IEL 轮廓长度大致随直径的平方根减小。
本研究的主要结论是：a）当动脉收缩时，IEL 呈波纹状，随着动脉直径的增加而变平；b）IEL 在生理条件下呈波纹状，其轮廓长度至少比生理动脉直径长 10%；c）尽管 IEL 比周围的动脉层更硬，但它的行为并不像不可伸展的膜。
