Quantitative Magnetic Resonance Imaging (MRI) parameters, such as the apparent diffusion coefficient (ADC) derived from diffusion weighted MRI (DW-MRI), have been proven to be valuable biomarkers of tumor grade and aggressiveness. Although the ADC potentially informs on the microstructural properties of the tissue, the contribution of various components of the extracellular matrix (ECM) to the hindered water diffusion observed in tissues is not fully understood. As tumor ECM differs substantially in its microstructure from normal tissues, it is desirable to investigate which features of the ECM influence the ADC, in order to understand the changes in the ECM that relate to tumor behaviour. We therefore sought to establish the relationship between ECM microstructural properties and ADC.<br/><br/>The structural components of the ECM may be divided into fibrillar proteins, (collagens being the most abundant), and glycosaminoglycans (GAGs). We used collagen I based materials to model the ECM and investigate how changes in matrix microstructure relate to ADC, longitudinal (T1) and transverse (T2) relaxation times. This analysis was combined with torsional rheometry measurements of viscoelastic moduli, an established way to characterise properties of the ECM that is frequently used in cell culture studies.<br/><br/>Preliminary data demonstrate that whilst viscous and elastic moduli of collagen I gels increase with increasing collagen I concentration, there is little change in ADC. Changes in T1 and T2 were, however, observed, with a 70% decrease in T2 when the collagen concentration was increased from 1.6 to 16 mg/ml. This indicates that while collagen I fibres at these concentrations may not be a major contributor to the reduction of ADC seen in tumors, they do influence the relaxation properties of water. Adding a GAG component to the gel increases the complexity of the ECM model and allows us to further understand the differential effect of ECM components on the MRI parameters of water.

Investigating how physicochemical properties of extracellular matrix influence apparent diffusion coefficient in MRI

255th National Meeting (2018)

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