Engineered blood and lymphatic capillaries in 3‐D VEGF‐fibrin‐collagen matrices with interstitial flow

Abstract

In vitro endothelial cell organization into capillaries is a long standing challenge of tissue engineering. We recently showed the utility of low level interstitial flow in guiding the organization of endothelial cells through a 3-D fibrin matrix-containing covalently bound vascular endothelial growth factor (VEGF). Here this synergistic phenomenon was extended to explore the effects of matrix composition on in vitro capillary morphogenesis of human blood versus lymphatic endothelial cells (BECs and LECs). Different mixtures of fibrin and collagen were used in conjunction with constant concentrations of matrix-bound VEGF and slow interstitial flow over 10 days. Interestingly, the BECs and LECs each showed a distinct preference in terms of organization for matrix composition: LECs organized the most extensively in a fibrin-only matrix, while BEC organization was optimized in the compliant collagen-containing matrices. Furthermore, the BECs and LECs produced architecturally different structures; while BECs organized in thick, branched networks containing wide lumen, the LECs were elongated into slender, overlapping networks with fine lumen. These data demonstrate the importance of the 3-D matrix composition in facilitating and coordinating BEC and LEC capillary morphogenesis, which is important for in vitro vascularization of engineered tissues.

Role of Lymphatic Vessels in Tumor Immunity: Passive Conduits or Active Participants?

“…In addition to regulating function, fluid flow is also an important regulator of lymphatic morphogenesis or lymphangiogenesis, and has been shown to drive lymphatic capillary organization in dermal wound healing models [45,46] as well as in vitro culture models [47][48][49]. Without flow, as in the case of lymphedema, lymphatic endothelium becomes hyperplastic (i.e.…”

Cells in 3D matrices under interstitial flow: Effects of extracellular matrix alignment on cell shear stress and drag forces

“…While normal IF can be in the range of 0.1-1 mm/s (Chary and Jain, 1989;Dafni et al, 2002), increased IF in such inflammatory environments are evidenced by drastically increased lymph flow rates (Mullins and Hudgens, 1987;Matsumoto et al, 1990;He et al, 2002;Modi et al, 2007) because lymph drains the interstitial space. In addition to its role in wound healing, IF is important for tissue homeostasis via transport of metabolites and cell-signaling molecules; it is also an important morphoregulator both in vivo (Boardman and Swartz, 2003;Hirokawa et al, 2006;Schweickert et al, 2007) and in vitro, where it has been used to engineer functional blood and lymphatic capillaries (Ng et al, 2004;Helm et al, 2005;Semino et al, 2006;Helm et al, 2007).…”

The New Era of the Lymphatic System: No Longer Secondary to the Blood Vascular System

“…These studies indicate that lymphatic vessels are not mere passive conduits for immune cells but actively participate in modulating the immune responses. Interestingly, while lymphatic vessels transport lymph fluids, both interstitial pressure and fluid flow can also activate LECs, thus increasing fluid/solute permeability and uptake (Swartz et al 2008;Miteva et al 2010), and regulate lymphatic morphogenesis in vitro and in vivo (Boardman and Swartz 2003;Goldman et al 2007;Helm et al 2007;Lund and Swartz 2010).…”