Measuring vascular graft cellularity non-destructively: merging magnetic resonance imaging and tissue engineering

Despite significant growth in the field of tissue engineering over the past decades, non-invasive, non-destructive methods to characterize the cellularisation of grafts are lacking. Here, in a proof-of-concept study, a non-invasive magnetic resonance imaging method, diffusion tensor imaging (DTI), within acellular and cellularised vascular grafts is investigated. Using decellularised porcine carotid grafts, smooth muscle cells are cultured dynamically for two weeks with terminal time points at day 3, 7, and 14. Grafts are fixed at each time point and investigated by DTI in an ex vivo set up. Semi-quantitative histology is used as a ground truth for collagen, elastin, and cell density changes over time. DTI-derived metrics, namely the fractional anisotropy, mean diffusivity, and tractography, are significantly different between day 3 and day 7 grafts and distinguish between acellular and cellularised grafts. Specifically, increasing fractional anisotropy is correlated to increasing cell density. The results from this study show the potential of MR-DTI in the field of tissue engineering, offering non-invasive, non-destructive insight into graft cellularisation.