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Human erythrocyte ghosts: Exploring the origins of multiexponential water diffusion in a model biological tissue with magnetic resonance
Author(s) -
Thelwall Peter E.,
Grant Samuel C.,
Stanisz Greg J.,
Blackband Stephen J.
Publication year - 2002
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.10270
Subject(s) - permeability (electromagnetism) , chemistry , extracellular , diffusion , biophysics , compartment (ship) , cellular compartment , membrane , membrane permeability , cell membrane , nuclear magnetic resonance , biological system , cell , thermodynamics , biochemistry , physics , oceanography , biology , geology
A tissue model composed of erythrocyte ghosts was developed to study the effects of compartmentation on the MR signal acquired from biological tissues. This simple and flexible model offers control over the biophysical parameters that contribute to multicomponent signals arising from cellular systems. Cell density, size, intra‐ and extracellular composition, and membrane permeability can be independently altered. The effects of cell density and cell size on water diffusion properties were assessed. The data demonstrate non‐monoexponential water diffusion in ghost cell suspensions of 17–67% cell density. Data were analysed with the widely employed two‐compartment (biexponential) model, and with a two‐compartment model that accounted for exchange between compartments. Water exchange between the intra‐ and extracellular compartments appeared to be significant over the range of diffusion times studied (7–35 ms). The biexponential fit to the ghost data appeared to be underparameterised as the ADCs and relative fractions of the fast and slow components were dependent on the experimental acquisition parameters, specifically the diffusion time. However, both analysis methods proved effective at tracking changes in the ghost model when it was perturbed. This was demonstrated with cell density variation, cell swelling and shrinkage experiments, and reduction of membrane water permeability using a water channel blocker (pCMBS). We anticipate that this model system could be used to investigate compartmental diffusion effects to simulate a range of pathologies, especially ischemic stroke. Magn Reson Med 48:649–657, 2002. © 2002 Wiley‐Liss, Inc.