Collagen-Polymer Guidance of Vessel Network Formation and Stabilization by Endothelial Colony Forming Cells In Vitro

摘要

The dynamic process of vessel formation and remodeling is essential to embryonic development, post-natal tissue homeostasis and function, wound healing, and next-generation therapeutic vascularization and tissue engineering strategies. Here, uncommon collagen polymer building blocks, specified by their intermolecular cross-link composition, were used to tune the fibril microstructure and physical properties of collagen matrices for purposes of guiding three-dimensional (3D) lumenized vessel network formation by endothelial colony forming cells (ECFC) in vitro. A new and comprehensive 3D vessel morphometric analysis approach was also used to quantify vessel network morphology and architecture parameters. Results show that independent variation of collagen concentration (fibril density) and oligomer:monomer ratio (interfibril branching), two independent determinants of matrix stiffness, yield vessel networks with different architectures and persistence. Increases in fibril density decreased the overall number of vessel networks formed, while an increase in interfibril branching led to formation of highly branched vessel networks with increased vessel volume density. In general, increasing matrix stiffness, whether by modulation of fibril density or interfibril branching, contributed to increased lumen expansion and vessel segment elongation. Finally, oligomer, but not monomer, matrices induced maturation and stabilization (>14 days) of ECFC vessel networks, marked by changes in the temporal and spatial deposition of collagen type IV. Collectively, this work highlights that ECFC vessel morphogenesis is not dependent upon matrix stiffness alone, but rather the interplay of collagen fibril microstructure and matrix physical properties. Furthermore, it identifies oligomers and their associated intermolecular cross-links as new and important design parameters for vascular-inductive matrices for use in cell culture, regenerative medicine, and engineered tissue applications.