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Magnetic Isolation And Attachment Of Endothelial Precursors On Synthetic Vascular Grafts

Adriana Harbuzariu, Gautam Agarwal, Barry Boilson, Manju Kalra, Robert Simari, Gurpreet Sandhu ∙ Mayo Clinic College of Medicine, Rochester, MN

Objective: The facilitated endothelialization of synthetic vascular grafts may improve long-term patency and could allow for placement of small diameter conduits in peripheral and coronary locations. Magnetized Dacron grafts can be rapidly coated with paramagnetically labeled autologous endothelial cells cultured from blood. These captured cells remain attached during blood flow and proliferate normally after graft implantation. The three-week cell culture time is a barrier to clinical translation. We attempted to reduce this time to one day by magnetically purifying circulating CD133+ progenitor cells from blood, followed by direct paramagnetic labeling and delivery to a magnetized graft. Methods: CD133+ cells were magnetically isolated from blood using the Miltenyi process to a purity of 97 %. These were allowed to endocytose 0.9 micron Bangs Labs superparamagnetic particles for 12 hours at a 500 particle/cell incubation ratio. CM-DiI staining was used a cell surface marker (red fluorescence). A flexible magnetic layer was annealed to the outer surface of a 6 mm Dacron graft. The cells (1x106/ml) were placed within magnetic and control grafts for 10 minutes. Segments of pig carotid arteries were excised and replaced with these grafts. The grafts were harvested after 24 hours of blood flow and analyzed. Results: FACS analysis and immunostaining confirmed that the isolated cells expressed progenitor cells markers (CD34, CD133). The delivered cells successfully attached to and seeded the inner surface of the magnetized graft (Fig.1, top panel), while few cells were found attached to a control graft. Conclusions: Circulating endothelial precursor cells can be magnetically isolated to a high level of purity and rapidly targeted to a magnetized graft. This shortens the processing time from 3 weeks to 1 day. The elimination of ex vivo culture may facilitate clinical translation of small diameter magnetically endothelialized conduits.