3D Printed Vascular Networks Enhance Viability in High-Volume Perfusion Bioreactor

Abstract

There is a significant clinical need for engineered bone graft substitutes that can quickly, effectively, and safely repair large segmental bone defects. One emerging field of interest involves the growth of engineered bone tissue in vitro within bioreactors, the most promising of which are perfusion bioreactors. Using bioreactor systems, tissue engineered bone constructs can be fabricated in vitro. However, these engineered constructs lack inherent vasculature and once implanted, quickly develop a necrotic core, where no nutrient exchange occurs. Here, we utilized COMSOL modeling to predict oxygen diffusion gradients throughout aggregated alginate constructs, which allowed for the computer-aided design of printable vascular networks, compatible with any large tissue engineered construct cultured in a perfusion bioreactor. We investigated the effect of 3D printed macroscale vascular networks with various porosities on the viability of human mesenchymal stem cells in vitro, using both gas-permeable, and non-gas permeable bioreactor growth chamber walls. Through the use of 3D printed vascular structures in conjunction with a tubular perfusion system bioreactor, cell viability was found to increase by as much as 50% in the core of these constructs, with in silico modeling predicting construct viability at steady state.

Recent advances in bioreactors for cell-based therapies

“…Cutting-edge research in this field continues to focus on the improved application of biophysical stimuli to optimize functional tissue assembly 30 – 35 and computational modeling to improve predictability of the outcomes 19 , 36 , 37 – 40 . Additionally, notable efforts to enhance the clinical applicability of these grafts have focused on engineering grafts that are similar in size to critical-sized bone defects in humans and are tailored to the patient 20 , 41 – 42 . Nguyen et al .…”

“…Nguyen et al . recently demonstrated the ability to culture a 200 cm 3 cell-based construct in vitro without the development of necrotic centers 20 , 42 . In this approach, bone marrow-derived mesenchymal stem cells were encapsulated in hydrogel beads and placed in a tubular perfusion bioreactor.…”

The Evolution of Polystyrene as a Cell Culture Material

“…The potential exists to revolutionize cell culture: 3D models have been shown to improve disease and pharmaceutical modeling 94–97 and capitalize on dynamic culture methods, generating clinically relevant geometries and numbers of cells. 98–100 Transitioning culture from a 2D to a predictable 3D model standard would drastically increase the biomimicry of in vitro culture methods. These do come with additional challenges: ensuring sufficient nutrient exchange through the bulk of the object (overcome with bioreactor expansion methods 101 ), visualizing growing cells (overcome with utilizing a clear material, such as PS, or with a microfluidic approach 16 , 102 , 103 ), and efficient capture of the cells after culture and expansion (overcome with highly permeable, porous, and interconnected scaffolds 104 , 105 ).…”

Computational fluid dynamic analysis of bioprinted self‐supporting perfused tissue models

“…Tissue vasculature is further integrated with the cardiovascular system, which drives nutrient perfusion. Generating biofabricated tissues exhibiting similar distributed vasculature‐like structures integrated with a system capable of driving perfusion, however, has proved to be an engineering, biological, and practical challenge (Ball, Nguyen, Placone, & Fisher, ; Egger et al, ; Goldstein, Juarez, Helmke, Gustin, & Mikos, ; Stiehler et al, ; Wang, Wu, Wang, Lin, & Sun, ; Warren et al, ; Wu & Ringeisen, ), which must be overcome to generate in vivo‐like tissue structures (Carrier et al, ; Dennis, Smith, Philp, Donnelly, & Baar, ; Guller, Grebenyuk, Shekhter, Zvyagin, & Deyev, ; Maidhof et al, ).…”

“…Tissue vasculature is further integrated with the cardiovascular system, which drives nutrient perfusion. Generating biofabricated tissues exhibiting similar distributed vasculature-like structures integrated with a system capable of driving perfusion, however, has proved to be an engineering, biological, and practical challenge (Ball, Nguyen, Placone, & Fisher, 2016;Egger et al, 2017;Goldstein, Juarez, Helmke, Gustin, & Mikos, 2001;Stiehler et al, 2009;Wang, Wu, Wang, Lin, & Sun, 2009;Warren et al, 2009;Wu & Ringeisen, 2010), which must be overcome to generate in vivo-like tissue structures (Carrier et al, 2002;Dennis, Smith, Philp, Donnelly, & Baar, 2009;Guller, Grebenyuk, Shekhter, Zvyagin, & Deyev, 2016;Maidhof et al, 2012). Impeller-driven spinner flask bioreactors provide perfusion by flowing media over the tissue construct, which results in poorly controlled and poorly defined perfusion to tissues within the bulk of tissues or result in no perfusion within the bulk of solid tissues (Radisic et al, 2004;Sikavitsas, Bancroft, & Mikos, 2002).…”