Preparation of gelled substrates

Generation of 3D Collagen Gels with Controlled Diverse Architectures

Rat tail collagen solutions have been used as polymerizable in vitro three dimensional (3D) extracellular matrix (ECM) gels for single and collective cell migration assays as well as spheroid formation. Factors such as ECM concentration, pH, ionic concentration, and temperature can alter collagen polymerization and ECM architecture. This unit describes how to generate 3D collagen gels that have distinct architectures ranging from a highly reticular meshwork of short thin fibrils with small pores to a loose matrix consisting of stiff, parallel-bundled long fibrils by changing collagen polymerization temperature. This permits analysis of 3D cell migration in different ECM architectures found in vivo while maintaining a similar ECM concentration. Also included are collagen labeling techniques helpful for ECM visualization during live fluorescence imaging. © 2016 by John Wiley & Sons, Inc.

Direct comparisons of the morphology, migration, cell adhesions, and actin cytoskeleton of fibroblasts in four different three-dimensional extracellular matrices

Interactions between cells and the extracellular matrix are at the core of tissue engineering and biology. However, most studies of these interactions have used traditional two-dimensional (2D) tissue culture, which is less physiological than three-dimensional (3D) tissue culture. In this study, we compared cell behavior in four types of commonly used extracellular matrix under 2D and 3D conditions. Specifically, we quantified parameters of cell adhesion and migration by human foreskin fibroblasts in cell-derived matrix or hydrogels of collagen type I, fibrin, or basement membrane extract (BME). Fibroblasts in 3D were more spindle shaped with fewer lateral protrusions and substantially reduced actin stress fibers than on 2D matrices; cells failed to spread in 3D BME. Cell-matrix adhesion structures were detected in all matrices. Although the shapes of these cell adhesions differed, the total area per cell occupied by cell-matrix adhesions in 2D and 3D was nearly identical. Fibroblasts migrated most rapidly in cell-derived 3D matrix and collagen and migrated minimally in BME, with highest migration directionality in cell-derived matrix. This identification of quantitative differences in cellular responses to different matrix composition and dimensionality should help guide the development of customized 3D tissue culture and matrix scaffolds for tissue engineering.

Spheroid-based human endothelial cell microvessel formation in vivo

The study of angiogenic endothelial cells (ECs) has in recent years greatly stimulated multiple fields of vascular biology research. A number of cellular models and numerous complex developmental, manipulatory and tumor animal models have been developed to study angiogenesis in vitro and in vivo. To connect the versatility of cellular assays with the complexity of readouts of in vivo experimentation, we have developed an endothelial transplantation assay. This assay is based on grafting ex vivo generated EC spheroids (2 d) in a suitable matrix in immunocompromised mice, to give rise to a 3D network of capillaries (20 d). This vasculature connects to the mouse vasculature, is perfused and matures by recruiting mouse mural cells. Here we describe the detailed protocol for this assay, including generation of spheroids, injection into mice, excision and processing of resulting plugs, and quantification by immunohistochemical analysis of the resulting vasculature.