Layers of interstitial fluid flow along a

Hongyi LI; You Lyu; Xiaoliang Chen; Bei LI; Qi Hua; Fusui JI; Yajun Yin; Hua LI

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Layers of interstitial fluid flow along a "slit-shaped" vascular adventitia.

Author: Hongyi LI ¹ ; You LYU ² ; Xiaoliang CHEN ³ ; Bei LI ² ; Qi HUA ⁴ ; Fusui JI ² ; Yajun YIN ⁵ ; Hua LI ⁶
Author Information

1. Cardiology Department, Xuanwu Hospital, Capital Medical University, Beijing 100053, China. leehongyi@bjhmoh.cn.
2. Cardiology Department, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, China.
3. Radiology Department, China-Japan Friendship Hospital, Beijing 100029, China.
4. Cardiology Department, Xuanwu Hospital, Capital Medical University, Beijing 100053, China. leehongyi@bjhmoh.cn, huaqi5371@sina.com.
5. Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
6. Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100190, China.
Publication Type:Journal Article
Keywords: Connective tissue; Interfacial zone; Interstitial fluid; Vascular adventitia
From: Journal of Zhejiang University. Science. B 2021;22(8):647-663
CountryChina
Language:English
Abstract: Interstitial fluid (ISF) flow through vascular adventitia has been discovered recently. However, its kinetic pattern was unclear. We used histological and topographical identification to observe ISF flow along venous vessels in rabbits. By magnetic resonance imaging (MRI) in live subjects, the inherent pathways of ISF flow from the ankle dermis through the legs, abdomen, and thorax were enhanced by paramagnetic contrast. By fluorescence stereomicroscopy and layer-by-layer dissection after the rabbits were sacrificed, the perivascular and adventitial connective tissues (PACTs) along the saphenous veins and inferior vena cava were found to be stained by sodium fluorescein from the ankle dermis, which coincided with the findings by MRI. The direction of ISF transport in a venous PACT pathway was the same as that of venous blood flow. By confocal microscopy and histological analysis, the stained PACT pathways were verified to be the fibrous connective tissues, consisting of longitudinally assembled fibers. Real-time observations by fluorescence stereomicroscopy revealed at least two types of spaces for ISF flow: one along adventitial fibers and another one between the vascular adventitia and its covering fascia. Using nanoparticles and surfactants, a PACT pathway was found to be accessible by a nanoparticle of <100 nm and contained two parts: a transport channel and an absorptive part. The calculated velocity of continuous ISF flow along fibers of the PACT pathway was 3.6‒15.6 mm/s. These data revealed that a PACT pathway was a "slit-shaped" porous biomaterial, comprising a longitudinal transport channel and an absorptive part for imbibition. The use of surfactants suggested that interfacial tension might play an essential role in layers of continuous ISF flow along vascular vessels. A hypothetical "gel pump" is proposed based on interfacial tension and interactions to regulate ISF flow. These experimental findings may inspire future studies to explore the physiological and pathophysiological functions of vascular ISF or interfacial fluid flow among interstitial connective tissues throughout the body.