Tuning of Collagen Scaffold Properties Modulates Embedded Endothelial Cell Regulatory Phenotype in Repair of Vascular Injuries In Vivo

Abstract

Perivascularly implantated matrix embedded endothelial cells (MEECs) are potent regulators of inflammation and intimal hyperplasia following vascular injuries. ECs in porous collagen scaffolds adopt a reparative phenotype with significant therapeutic potential. Although the biological effects of MEECs are increasingly understood, less work has studied the tuning of scaffold properties to control cell-substrate interactions and subsequent biological outcomes. We hypothesized that modulating scaffold degradation would change EC phenotype. Scaffolds with differential degradation rates were prepared by crosslinking and pre-degradation. Vascular injury increased degradation and the presence of MEECs retarded injury-mediated degradation. MEECs responded to differential scaffold properties with altered cell viability in vivo, suppression of smooth muscle cell (SMC) proliferation in vitro, and changes in IL-6 and MMP-9 expression. When implanted perivascularly to a murine carotid wire injury model, tuned scaffolds changed MEEC effects on vascular repair and inflammation. Live animal imaging allowed for real-time tracking of cell viability, inflammation, and scaffold degradation in vivo, affording an unprecedented understanding of interactions between cells, substrate, and tissue. MEEC-treated injuries exhibited improved endothelialization and reduced SMC hyperplasia over 14 days. These data demonstrate the potent role material design plays in tuning MEEC efficacy in vivo, with implications for the design of clinical therapies.

Tumor-Associated Tertiary Lymphoid Structures: Gene-Expression Profiling and Their Bioengineering

“…Based on the origin of materials, scaffolds can be classified into synthetic or natural polymeric systems ( 32 ). We have developed optical means by which to track the fate of implanted materials ( 33 ) and embedded cells fate ( 34 ) non-invasively over time. This enables us to study cell:material interactions in vivo and to rationally modify the materials, as needed, to attain the desired preclinical outcomes.…”

Mimicking the physical cues of the ECM in angiogenic biomaterials

“…collagen, fibrin, hyaluronic acid) that were modified via a novel crosslinking strategy. For example, it was determined that tuning the degradability of collagen hydrogels by introducing EDC/NHS-mediated crosslinks affected matrix-embedded EC gene expression and SMC proliferation in vitro as well as the re-reendothelialization of a murine carotid wire injury model in vivo [82]. In a pioneering study, Trappmann et al .…”

New artery of knowledge: 3D models of angiogenesis

“…High results variability depending on background and age of the animal or donor (79,80,81) Retinal explant assay Studying microvessel formation and its remodelling (82,83) In vivo In-ovo chorioallantoic membrane assay Assessing the vascularisation of allografts or xenografts. Testing the effect of pro-angiogenic and anti-angiogenic treatments EC sprouting compared to more-degradable ones (53,54). Finally, stiffness of the substrate can also influence EC proliferation, signalling and differentiation (55), Therefore, ECM protein composition and concentration must be carefully optimised to ensure that hydrogels promote vascularisation while maintaining their structural integrity.…”

“…At the same time, the concentration cannot be too low, as low-density hydrogels do not provide enough support for EC migration ( 52 ). Moreover, matrix biodegradability was shown to profoundly alter EC migration speed and efficiency, with less-biodegradable hydrogels encouraging EC sprouting compared to more-degradable ones ( 53 , 54 ). Finally, stiffness of the substrate can also influence EC proliferation, signalling and differentiation ( 55 ), Therefore, ECM protein composition and concentration must be carefully optimised to ensure that hydrogels promote vascularisation while maintaining their structural integrity.…”