A novel method for measuring hydraulic conductivity at the human blood-nerve barrier in vitro

• Published in: Microvascular research 2017-01, Vol.109, p.1-6
• Main Authors: Helton, E. Scott, Palladino, Steven, Ubogu, Eroboghene E.
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Polyomavirus Transforming - immunology; Axons - metabolism; Blood-brain barrier; Blood-Nerve Barrier; Bubble tracker; Capillary Permeability; Cattle; Cell Line; Cell Membrane Permeability; Cytokines - metabolism; Cytological Techniques; Diffusion chamber; Endoneurial endothelial cells; Endothelial Cells - cytology; Fibroblasts - metabolism; Homeostasis; Humans; Hydraulic conductivity; Inflammation; Mice; Peripheral Nerves; Permeability; Rats; Sheep; Signal Transduction; Swine; Tight Junctions - metabolism; Transendothelial water flux; Water - chemistry
• ISSN: 0026-2862; 1095-9319
• DOI: 10.1016/j.mvr.2016.08.005

Microvascular barrier permeability to water is an essential biophysical property required for the homeostatic maintenance of unique tissue microenvironments. This is of particular importance in peripheral nerves where strict control of ionic concentrations is needed for axonal signal transduction. Previous studies have associated inflammation, trauma, toxin exposure and metabolic disease with increases in water influx and hydrostatic pressure in peripheral nerves with resultant endoneurial edema that may impair axonal function. The regulation of water permeability across endoneurial microvessels that form the blood-nerve barrier (BNB) is poorly understood. Variations exist in apparatus and methods used to measure hydraulic conductivity. The objective of the study was to develop a simplified hydraulic conductivity system using commercially available components to evaluate the BNB. We determined the mean hydraulic conductivity of cultured confluent primary and immortalized human endoneurial endothelial cell layers as 2.00×10−7 and 2.17×10−7cm/s/cm H₂O respectively, consistent with restrictive microvascular endothelial cells in vitro. We also determined the mean hydraulic conductivity of immortalized human brain microvascular endothelial cell layers, a commonly used blood-brain barrier (BBB) cell line, as 0.20×10−7cm/s/cm H₂O, implying a mean 10-fold higher resistance to transendothelial water flux in the brain compared to peripheral nerves. To our knowledge, this is the first reported measurement of human BNB and BBB hydraulic conductivities. This model represents an important tool to further characterize the human BNB and deduce the molecular determinants and signaling mechanisms responsible for BNB hydraulic conductivity in normal and disease states in vitro. •Experimental apparatus and methods to measure hydraulic conductivity are described.•An adaptable diffusion chamber and digital camera-based bubble tracker were used.•The human blood-nerve and blood-brain barrier hydraulic conductivities were obtained.•Cellular immortalization does not affect blood-nerve barrier water flux in vitro.•Reliable mechanistic studies of blood-nerve barrier water flux can be performed.