Abstract
Adequate vascularization in biomaterials is essential for tissue regeneration and repair. Current models do not allow easy analysis of vascularization of implants in vivo, leaving it a highly desirable goal. A tool that allows to monitor the perfusion capacity of such biomaterials non-invasively in a cheap, efficient and reliable in vivo model would hence add great benefit to the research in this field. We established, for the first time, an in vivo Magnetic Resonance Imaging (MRI) method to quantify the perfusion capacity of a model biomaterial, DegraPol® foam scaffold, placed on the embryonic avian chorioallantoic membrane (CAM) in ovo. Perfusion capacity was assessed through changes in the longitudinal relaxation rate before and after injection of a paramagnetic MRI contrast agent, Gd-DOTA (®Dotarem, Guerbet S.A.). Relaxation rate changes were compared in three different regions of the scaffold, i.e. at the interface to the CAM, in the middle and on the surface of the scaffold (p < 0.05). The highest relaxation rate changes, and hence perfusion capacities, were measured in the interface region where the scaffold was attached to the CAM, whereas the surface of the scaffold showed the lowest relaxation rate changes. A strong positive correlation was obtained between relaxation rate changes and histologically determined vessel density (R2 = 0.983), which corroborates our MRI findings. As a proof-of-principle, we measured the perfusion capacity in different scaffold materials, silk fibroin either with or without human dental pulp stem cells. For these, 3 - 4 times larger perfusion capacities were obtained compared to DegraPol®; demonstrating that our method is sensitive to reveal such differences. In summary, we present a novel in vivo method for analyzing the perfusion capacity in 3D- biomaterials grown on the CAM, enabling the determination of the perfusion capacity of a large variety of bioengineered materials.
Kivrak-Pfiffner, Fatma