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RESEARCH ARTICLE

Bioprinting-Associated Shear Stress and Hydrostatic

Pressure Affect the Angiogenic Potential of Human

Umbilical Vein Endothelial Cells

Marius Köpf , Ramin Nasehi , Franziska Kreimendahl , Stefan Jockenhoevel , Horst Fischer *
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1 Department of Dental Materials and Biomaterials Research (ZWBF), RWTH Aachen University Hospital, Aachen, Germany
2 Department of Biohybrid and Medical Textiles (BioTex), Institute of Applied Medical Engineering, Helmholtz Institute
Aachen, RWTH Aachen University, Aachen, Germany
Abstract: Bioprinting-associated shear stress and hydrostatic pressure can negatively affect the functionality of dispensed
cells. We hypothesized that these mechanical stimuli can potentially affect the angiogenic potential of human umbilical vein
endothelial cells (HUVECs). A numerical simulation model was used to calculate the shear stress during microvalve-based
droplet ejection. The impact of different levels of applied pressure and the resulting shear stress levels on the angiogenic
potential of HUVECs was investigated after up to 14 days of cultivation. In vitro results showed that bioprinting-associated
stress not only has short-term but also long-term effects. The short-term viability results indicate a 20% loss in post-printing
cell viability in samples printed under the harshest conditions compared to those with the lowest shear stress level. Further,
it was revealed that even in two-dimensional culture, HUVECs were able to form a capillary-like network organization
regardless of bioprinting pressure. In three-dimensional culture experiments; however, the HUVECs printed at 3 bar were not
able to form tubular structures due to their exposure to high shear stress levels. In conclusion, this study provides new insights
into how the bioprinting process should be conducted to control printing-associated shear stress and hydrostatic pressure to
preserve the functionality and angiogenetic potential of HUVEC.
Keywords: Bioprinting; Shear stress; Hydrostatic pressure; Fluid-dynamic finite element analysis; Angiogenesis

*Correspondence to: Horst Fischer, Department of Dental Materials and Biomaterials Research, RWTH Aachen University Hospital, Aachen,
Germany; hfischer@ukaachen.de
Received: April 12, 2022; Accepted: June 12, 2022; Published Online: August 18, 2022

Citation: Köpf M, Nasehi R, Kreimendahl F, et al., 2022. Bioprinting-Associated Shear Stress and Hydrostatic Pressure Affect the Angiogenic
Potential of Human Umbilical Vein Endothelial Cells. Int J Bioprint, 8(4):606. http://doi.org/10.18063/ijb.v8i4.606

1. Introduction human umbilical vein endothelial cells (HUVECs) and
a supporting cell type such as human mesenchymal
The application of additive manufacturing techniques stromal cells (hMSCs) or human dermal fibroblasts [6,7] .
in the field of tissue engineering enables the build-up
of geometrically complex, three-dimensional (3D) cell- High concentrations of viable and functional cells are
laden structures that can be matured into functional among the main prerequisites for successful formation of
tissues [1,2] . However, due to the limited diffusion range such tubular structures, which represent the first step in
within the hydrogel used in this process, it is essential the formation of a biofunctional vasculature in vitro. It
to ensure nutrient and oxygen supply within such printed is, therefore, essential to determine the set of bioprinting
structures. The ability of some cell types to self-assemble parameters that will avoid a critical drop in post-printing
into capillary-like network structures before implantation cell viability, as well as long-term negative effects on
holds great promise as an essential step toward a fully functionality and angiogenic potential.
bioprinted and pre-vascularized tissue replacement [3-5] . Various bioprinting techniques have previously
As previously reported, the formation of capillary- been described, such as micro-extrusion and drop-on-
like cell structures can be achieved in a co-culture of demand (DoD), that differ in various aspects such as
© 2022 Author(s). This is an Open-Access article distributed under the terms of the Creative Commons Attribution License, permitting distribution and
reproduction in any medium, provided the original work is properly cited.
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