Matrix anisotropy promotes angiogenesis in a density-dependent manner

Abstract

Angiogenesis is necessary for wound healing, tumorigenesis, implant inosculation, and homeostasis. In each situation, matrix structure and mechanics play a role in determining whether new vasculatures are able to establish transport to new or hypoxic tissues. Neovessel growth and directional guidance are sensitive to 3D matrix anisotropy and density, although the individual and integrated roles of these matrix features have not been fully recapitulated in vitro. We developed a tension-based method to align 3D collagen constructs seeded with microvessel fragments in matrices of three levels of collagen fibril anisotropy and two levels of collagen density. The extent and direction of neovessel growth from the parent microvessel fragments increased with matrix anisotropy and decreased with density. The proangiogenic effects of anisotropy were attenuated at higher matrix densities. We also examined the impact of matrix anisotropy in an experimental model of neovessel invasion across a tissue interface. Matrix density was found to dictate the success of interface crossing while interface curvature and fibril alignment were found to control directional guidance. Our findings indicate that complex configurations of matrix density and alignment can facilitate or complicate the establishment or maintenance of vascular networks in pathological and homeostatic angiogenesis. Further, we demonstrate a novel approach for tuning collagen anisotropy in thick constructs. This approach addresses gaps in tissue engineering and cell culture by supporting the inclusion of large multicellular structures in aligned constructs.

Spatial Configurations of 3D Extracellular Matrix Collagen Density and Anisotropy Simultaneously Guide Angiogenesis

“…To highlight the crucial role that the degree of anisotropy plays during cell guidance, we simulated microvessel growth using either vector fields or EFD fields. Simulations were generated to correspond to experiments from our recent in vitro study on the roles of matrix density and anisotropy during angiogenesis [ 1 ]. Microvessel culture was performed or simulated in low, medium, or high degrees of collagen alignment as well as low or high collagen density (Figs 2 , 3A , and S3A ).…”

“…This anisotropy contributes to durotaxis via guidance of cells along variously-tensed fibrils, as well as contact guidance and haptotaxis–the guidance of cells by matrix binding site gradients (e.g., integrins) [ 11 , 12 ]. In a recent study, we demonstrated that both microvessel rate of extension and guidance (reorientation and taxis) increased with matrix anisotropy during in vitro microvascular angiogenesis [ 1 ]. Interestingly, collagen density attenuated the effects of anisotropy so that stronger alignment was required for significant proangiogenic effects to occur in dense scaffolds.…”

“…Unlike vector field models, ODF-based models typically model cell populations as continuous concentrations whose migration (modeled as anisotropic diffusion) is influenced by the ODF shape and orientation. Such models, however, have generally neglected the degree of anisotropy as a model input, despite evidence that anisotropy significantly affects neovessel extension rate, proliferation, guidance, and persistence [ 1 , 8 , 29 ]. Furthermore, the assumption that cell populations move as a continuum is ill-suited for phenomena characterized by stochastic behaviors of individual migrating cells (e.g., neovessel recruitment by solid tumors, circulating tumor cell extrusion/extravasation) [ 30 , 31 ].…”

“…The objectives of this study were 1) to develop an enhanced simulation framework to predict microvascular growth and guidance based on 3D EFD representations of matrix collagen anisotropy and density, and 2) to apply the framework to predict experimental observations of microvascular growth in the contexts of wound healing and tumorigenesis. To do this, we extended our AngioFE simulation framework to integrate prior experimental findings that the degree of matrix anisotropy and density simultaneously affect microvascular growth [ 1 ]. First, we simulated anisotropic fibril guidance during sprouting angiogenesis where matrix anisotropy was described using a field of either vectors or EFDs.…”

Optimization of 3D printing and in vitro characterization of alginate/gelatin lattice and angular scaffolds for potential cardiac tissue engineering

“…The primary challenges in CTE are 1) vasculogenesis -for efficient exchange of oxygen between the cells and blood- and 2) mimicking the complex structure of the myocardium ( Vunjak-Novakovic et al, 2011 ; Izadifar et al, 2014 ; Kitsara et al, 2017 ). The orientation of the extracellular matrix fibrils can change vascularization by affecting the migration and polarization of endothelial cells, their branching, formation of basement membrane, and cellular traction ( Labelle et al, 2022 ). Thus, to replicate the complex structure of the human heart tissue, many parameters including alignment of the cells within the fibrils should be appropriately designed and controlled ( Zhang et al, 2015 ; Qasim et al, 2019 ).…”