Functional Analysis of Vascularized Collagen/Fibrin Templates by MRI In Vivo

Functional monitoring of the fate of implanted templates, which restore the function of lost tissues, is still a challenge. Whereas histology can give excellent insight into material and tissue remodeling, longitudinal studies are hampered by the invasive character. Noninvasive imaging techniques, which allow longitudinal studies in the same individual and provide functional information, might be beneficial. In this study, magnetic resonance imaging (MRI) was applied as a noninvasive tool to monitor the progress of vasculogenesis and inosculation in in vitro prevascularized collagen/fibrin templates implanted in mice during a period of 4 weeks. MRI results were compared with histological findings to evaluate whether the two technologies were complementary and to evaluate the added value of MRI. When in vitro prevascularized templates were implanted in mice, histological analysis showed the presence of mouse blood cells in the engineered vessels 2 weeks after implantation. The MR images showed that template perfusion, a measure of vascularity, became significant at 3 weeks. For tissue engineering purposes, contrast-enhanced MRI appears to be an attractive tool to evaluate the vascular outcome longitudinally without the need to sacrifice animals and the functional information can be superimposed on the static histological information.