Engineering tissues with a perfusable vessel-like network using endothelialized alginate hydrogel fiber and spheroid-enclosing microcapsules.

Yang Liu,Masahito Taya,Shinji Sakai

doi:10.1016/j.heliyon.2016.e00067

Abstract

Development of the technique for constructing an internal perfusable vascular network is a challenging issue in fabrication of dense three-dimensional tissues in vitro. Here, we report a method for realizing it. We assembled small tissue (about 200 μm in diameter)-enclosing hydrogel microcapsules and a single hydrogel fiber, both covered with human vascular endothelial cells in a collagen gel. The microcapsules and fiber were made from alginate and gelatin derivatives, and had cell adhesive surfaces. The endothelial cells on the hydrogel constructs sprouted and spontaneously formed a network connecting the hydrogel constructs with each other in the collagen gel. Perfusable vascular network-like structure formation after degrading the alginate-based hydrogel constructs by alginate lyase was confirmed by introducing solution containing tracer particles of about 3 μm in diameter into the lumen templated by the alginate hydrogel fiber. The introduced solution flowed into the spontaneously formed capillary branches and passed around the individual spherical tissues.

Highlights

The purpose of tissue engineering is the creation of three-dimensional (3D) tissue constructs that will benefit human health [1,2]
We examined the effect of the density of spherical vehicles covered with Green fluorescent protein (GFP)-human umbilical vein endothelial cells (HUVEC) in the collagen gel on the vessel-like network formation
We used empty gelatin microbeads covered with GFP-HUVECs

Summary

Introduction

The purpose of tissue engineering is the creation of three-dimensional (3D) tissue constructs that will benefit human health [1,2]. The fabrication of dense tissues faces problems in developing methods for constructing perfusable vascular-like network inside them [11]. Among varieties of reported approaches for solving the problem, a feasible approach is based on the combination of following two approaches: 1) Development of tubular structure (several hundred micrometer to several millimeter in diameter) large enough to flow medium directly from medium reservoirs in hydrogels using appropriate templates [12, 13, 14, 15, 16, 17], and 2) spontaneous formation of capillary (less than dozens micrometers in diameter) network in hydrogels by the original ability of vascular endothelial cells [13, 14, 15, 17, 18, 19, 20]. For more effective oxygenation and nutrition of the parenchymal cells, the capillary branches should be induced closer to the parenchymal cells

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Conclusion