Tissue engineered vascular graft (TEVG) are used when native vessels are not available to repair vascular damage. At the time of implantation in human body, these constructs present poor cellularity. To understand the cellularization kinetics under physiological conditions in a setting suitable for experimentation, bioreactors are often used in laboratory setting because of its controllable culture parameters including seeding conditions, flow type, pressure and temperature. Therefore, a non-destructive, label-free imaging modality that is capable of evaluating cell migration on luminal surfaces of TEVGs inside bioreactors is valuable for studying cellularization kinetics and providing a potential quality control method for manufacturing mature TEVGs. A multispectral Fluorescence Lifetime Imaging (ms-FLIm) using 355 nm excitation was configured to accommodate a rotating side-firing scanning probe for intraluminal imaging of tubular-shaped bovine pericardium (BP) scaffolds. The scanning was realized by reciprocal rotation and pullback of the fiber probe. Mesenchymal stem cells were seeded on BP-based TEVGs and cultured in the prototype bioreactor for up to one week. Distinct experimental conditions including the seeding side (i.e. BP serious and fibrous side) and media flow (i.e. static and dynamic pulsatile flow) were evaluated. Using ms-FLIm, the migration of cells on antigen removed BP TEVGs was periodically examined over a week; and the migration rates under different conditions were analyzed. Current results suggest helical ms-FLIm has potential to monitor in situ tissue recellularization process in bioreactors.
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