In vitro development of microvascular networks with a cylindrical fibrin scaffold

Abstract

The importance of generating a microvessel network in vitro lies in the ability to engineer vital tissue of considerable size or working as a platform for biomedical or cardiovascular studies. However, most of the current methods for generating microvessel networks in vitro based on encapsulating the channel structure inside an extracellular matrix like gel, which requires a circulation pumps at the beginning of the culture and increases the difficulties in observing cell situation due to the thickness of the gel. Thus, we propose a biomimetic scaffold-wrapping method which enables fabrication of customized microvascular network in an easier and controllable way. In our previous studies, we had successfully fabricated the cylindrical scaffold with PLGA and confirmed the human umbilical vein endothelial cells (HUVECs) could grow and cover our cylindrical scaffold after seeding on it. However, a relative long-term degradation of PLGA scaffold restricts the scaffold's widely applications. Fibrin, which is a natural fibrous protein and can be degraded with plasmin enzyme at any time, is a more feasible material for fabricating cylindrical scaffolds with controllable degradation. HUVECs were seeded on fibrin scaffolds and cultured without any additional circulation pump. The expression of vascular endothelial marker CD31 and VE-cadherin on scaffold-covering HUVECs indicated that the cultured cells have high possibility to form a functional microvascular network after the treatment of plasmin degradation. Our method allows cells to be cultured on a scaffold using a conventional culture approach and monitors cell conditions continuously. We hope our cell-covered scaffold can serve as a framework for building large tissues or can be used as the core of a vascular chip for in vitro circulation studies.