A Self-Assembled Vascular Network on a Chip for Ex Vivo Organoid Perfusion

• Shriya Bagdi, Neuroscience, University of Delaware

• Jason Gleghorn, Biomedical Engineering, University of Delaware

Organoids are a 3D in-vitro model that allow for multiple primary cell types to be studied within an organotypic structure. While organoid models are more complex than 2D cellular models, the challenge of ex vivo organoid vascularization persists, preventing these models from recapitulating organ functionality¹. Microfluidic devices can be used to generate microvasculature models to perfuse tissues. However, endothelial networks and organoids are traditionally grown in different extracellular matrix (ECM) hydrogels based on distinct needs of each system, frequently collagen and matrigel, respectively. It is imperative to develop an ECM hydrogel that supports coculture of endothelial cells and organoids². Therefore, the goal of this project was to determine a hydrogel that supports a self-assembled vascular network that can be applied to ex vivo organoid perfusion. The microfluidic device was fabricated with polydimethylsiloxane (PDMS) and plasma bonded to a glass coverslip. Various collagen-matrigel hydrogel combinations encapsulated with varying seeding densities of primary human umbilical vein endothelial cells (HUVECs) were incorporated in the device . This formed the structure of two endothelialized microchannels connected via a self-assembled vascular plexus as the HUVECs were cultured in growth media supplemented to induce vasculogenesis. As a result, we developed a self-assembled vascular network on a chip testing 10%, 20%, 33%, and 50% v/v matrigel in 4mg/mL collagen hydrogels. The 10% matrigel v/v in 4 mg/mL collagen networks had greater total vasculature length, number of branches, and vessel volume fraction compared to the other conditions. Moreover, we were able to successfully perfuse the 10% matrigel v/v in 4 mg/mL collagen vascular networks with fluorescent microbeads, confirming connectivity between the microchannels and self-assembled plexus. Because the ECM hydrogels contained matrigel, organoids could be incorporated into the established vascular network and be perfused along the continuous vascular network to better model cellular functions. 

1. Schulla LS, Alupoaie ED, De Silva L, Gawlitta D, Middendorp S, Coffer PJ, Roukens MG. Development of a Novel Microfluidic Co-culture model to study Organoid Vascularization. bioRxiv. 2022 Mar 27:2022-03.
2. Homan KA, Gupta N, Kroll KT, Kolesky DB, Skylar-Scott M, Miyoshi T, Mau D, Valerius MT, Ferrante T, Bonventre JV, Lewis JA. Flow-enhanced vascularization and maturation of kidney organoids in vitro. Nature methods. 2019 Mar;16(3):255-62.