Initial bFGF Distribution Affects the Depth of Three-dimensional Microvessel Networks in Vitro

Abstract

Control of three-dimensional (3D) microvessel formation is critical for regenerative medicine and tissue engineering because vessels are essential for the formation and maintenance of organ function. In order to function, tissues need an internal network of vessels. To introduce a 3D vessel network deep into the tissue, it is necessary to introduce 3D microvessel control which makes it a critical factor in regenerative medicine and tissue engineering. This study focuses on the effect of the concentration gradient of growth factors used in seeding the endothelial cells (ECs) on the morphology of the network. First, ECs were seeded using two model environments: collagen gel containing bFGF and incubated without bFGF medium (gel-bFGF model), and collagen gel containing no bFGF and incubated with bFGF medium (medium-bFGF model). The networks were observed in 3D with confocal laser scanning microscopy. The migration of ECs on the collagen gel was analyzed to study the effect of the concentration gradient on the network formation process. We found that the ECs of the gel-bFGF model showed significantly longer migration distance and more sprouting points compared with those of the medium-bFGF model. The networks of the gel-bFGF model, expanded mainly in a depth of 20-30 µm, and many reached a depth of 50-60 µm, whereas many networks in the medium-bFGF model expanded in a depth of only 10-20 µm. These results revealed that the initial growth factor distribution affects (a) both EC migration of the network formation process and the number of sprouting points, and (b) network morphology.

Progress and challenges in vascular tissue engineering using self-organization/pre-designed approaches

“…For example, this model demonstrated that fibronectin incorporated in the matrix promoted elongation of the newly formed microvessels when aortic explants were embedded in a collagen matrix (Nicosia et al, 1993). Moreover, several studies using an in vitro angiogenesis model reported that ECs invaded into 3D matrices and underwent lumen formation in response to exogenous factors such as sphingosine-1phosphate (S1P), stromal cell-derived factor-1α, or basic fibroblast growth factor (bFGF) (Davis et al, 2000;Bayless and Davis, 2003;Saunders et al, 2006;Ueda et al, 2006) (Fig. 2A, upper panel).…”