Abstract A65: Topographical guidance of angiogenesis at an interface of collagen densities
Authors: Zanotelli Matthew R. , Bordeleau Francois , Reinhart-King Cynthia A. 
Published: March 2017

Abstract
Tumor vasculature is characterized by leaky, tortuous, and dilated blood vessels that create heterogeneous blood flow and diminish the transport of oxygen. Pioneered by Jain, an emerging cancer treatment strategy seeks to normalize tumor vasculature in order to increase the delivery and efficacy of therapeutics. Overexpression of vascular endothelial growth factor (VEGF) and other pro-angiogenic factors within the tumor microenvironment have been considerably investigated as the major contributing factor to abnormal tumor vasculature, but less is understood about the influence of the physical environment and the underlying molecular mechanisms. During tumor progression, increased extracellular matrix (ECM) deposition occurs resulting in mechanically heterogeneous tissue defined by local alterations in density. Such changes to ECM density and composition can significantly disrupt cell behaviors. Our previous work has demonstrated that the presence of an interface produces directional migration and net cell migration is a function of collagen matrix density. Here, we utilize a similar sequential polymerization technique to create a distinct low-to-high collagen density interface, in order to replicate the heterogeneity found in tumor tissue and investigate the role of tumor matrix mechanics in promoting abnormal tumor vasculature. Specifically, Human Umbilical Vein Endothelial Cells (HUVECs) were encapsulated in a low-density collagen matrix, cultured for three days until capillary-like networks were formed, and a second, high-density collagen matrix supplemented with VEGF and basic fibroblast growth factor (bFGF) was added to create a 3D interface. Angiogenesis across and capillary-like network organization at the collagen density interface was then evaluated by time-lapse microscopy and immunofluorescence. Preliminary data indicates that the presence of a low-to-high density interface increased HUVEC capillary-like network branching and length. We demonstrate that the number of branches per network, total number of branches, and total network length all increased as a function of the density interface, where the larger difference in density between the two regions produced more branching points and increased network length. Together, our data demonstrate how ECM heterogeneities, in the form of interfacial boundaries, affect capillary-like network architecture and promote abnormal branching. This work provides further insight into cellular sensing during tumor angiogenesis, as well as helps to identify novel methods for tumor vasculature normalization, as a means to improve the efficacy of many chemotherapeutic and radiation treatments.
Citation Format: Matthew R. Zanotelli, Francois Bordeleau, Cynthia A. Reinhart-King. Topographical guidance of angiogenesis at an interface of collagen densities. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A65.