Three-Dimensional Characterization of Mechanical Interactions between Endothelial Cells and Extracellular Matrix during Angiogenic Sprouting.

Yue Du,Dong-An Wang,Sahan C B Herath,Qing-Guo Wang,Peter C Y Chen,H Harry Asada

doi:10.1038/srep21362

Abstract

We studied the three-dimensional cell-extracellular matrix interactions of endothelial cells that form multicellular structures called sprouts. We analyzed the data collected in-situ from angiogenic sprouting experiments and identified the differentiated interaction behavior exhibited by the tip and stalk cells. Moreover, our analysis of the tip cell lamellipodia revealed the diversity in their interaction behavior under certain conditions (e.g., when the heading of a sprout is switched approximately between the long-axis direction of two different lamellipodia). This study marks the first time that new characteristics of such interactions have been identified with shape changes in the sprouts and the associated rearrangements of collagen fibers. Clear illustrations of such changes are depicted in three-dimensional views.

Highlights

The mechanical interactions between a cell and the ECM generally refer to the cell-mediated assembly of ECM proteins and the subsequent cellular responses to the ECM’s resistance to deformation, such as the reshaping of lamellipodia and the changing of cellular attachment to certain ECM regions
In13, immunofluorescent staining for membrane type 1-matrix metalloproteinases (MMPs), which may co-localize with the proteolytic forms of MMP2 and MMP9, showed that it appeared alongside a certain portion of the ECs’ membrane that had formed apparent filopodia
Using beads as a tool to probe cell-ECM interactions allows the analysis of the deformation field throughout the entire ECM while minimally interfering with cell activities. This is based on (i) the average gap between two adjacent beads was sufficient to allow filopodia to freely protrude and swerve within the bead-containing ECM and (ii) the change in ECM stiffness produced by the beads at the concentration used (i.e., 0.075 mg/ml) was negligible

Summary

Introduction

The mechanical interactions between a cell and the ECM generally refer to the cell-mediated assembly of ECM proteins and the subsequent cellular responses to the ECM’s resistance to deformation, such as the reshaping of lamellipodia and the changing of cellular attachment to certain ECM regions. The work reported here partially revealed how the tip and stalk cells mechanically interacted with the 3D ECM during angiogenesis The study of these cells belonging to multicellular structures marks a point of departure from most existing studies that focused on a single cell migrating over a substrate. We were the first, to our knowledge, to establish the spatiotemporal interaction behavior of the tip cells in the context of reshaping (or remodeling) the surrounding ECM combined with the evolution of the lamellipodia (and filopodia) over time. This behavior was described in detail based on the associated movement of a mass of beads bound to collagen fibers.

Objectives

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Conclusion