Bioprinting of Multiscaled Hepatic Lobules within a Highly Vascularized Construct

Abstract

Highly vascularized complex liver tissue is generally divided into lobes, lobules, hepatocytes, and sinusoids, which can be viewed under different types of lens from the micro‐ to macro‐scale. To engineer multiscaled heterogeneous tissues, a sophisticated and rapid tissue engineering approach is required, such as advanced 3D bioprinting. In this study, a preset extrusion bioprinting technique, which can create heterogeneous, multicellular, and multimaterial structures simultaneously, is utilized for creating a hepatic lobule (≈1 mm) array. The fabricated hepatic lobules include hepatic cells, endothelial cells, and a lumen. The endothelial cells surround the hepatic cells, the exterior of the lobules, the lumen, and finally, become interconnected with each other. Compared to hepatic cell/endothelial cell mixtures, the fabricated hepatic lobule shows higher albumin secretion, urea production, and albumin, MRP2, and CD31 protein levels, as well as, cytochrome P450 enzyme activity. It is found that each cell type with spatial cell patterning in bioink accelerates cellular organization, which could preserve structural integrity and improve cellular functions. In conclusion, preset extruded hepatic lobules within a highly vascularized construct are successfully constructed, enabling both micro‐ and macro‐scale tissue fabrication, which can support the creation of large 3D tissue constructs for multiscale tissue engineering.

Current Advances on 3D‐Bioprinted Liver Tissue Models

“…Hepatocytes, responsible for major liver functions, such as bile synthesis, metabolism of glucose, and toxic substance are the main parenchymal cells in the liver which account for 60% of total cells and 80% of the total volume in the liver. [ 32 ] Primary hepatocytes, the cells directly isolated from the liver, are the most desirable cell sources for bioprinting to construct liver tissues in vitro [ 23,32,33 ] for their high metabolic activities. However, due to the lack of human‐sourced primary hepatocytes, the cultivation of primary hepatocytes is still difficult and these cells are easy to lose their phenotype; [ 34 ] some hepatoma sourced cell lines such as HepG2 [ 13a,22,28a,35 ] and HUH7 [ 24 ] which can represent a large number of functions of the primary hepatocytes such as albumin secretion, urea synthesis, and cytochrome 450 (CYP) related enzyme activities were widely used for bioprinting of liver microenvironment instead.…”

“…Reproduced with permission. [ 32 ] Copyright 2020, Wiley‐VCH GmbH. e) Liver‐like tissue constructed with 3D bioprinting and needle array technology.…”

“…However, with the development of coaxial printing, sacrificial printing, and preset extrusion, it is now possible to embed the vascular system into 3D‐bioprinted tissues and organs. A recent study adopted preset extrusion and 3D‐bioprinted hepatic lobules with HCs and endothelial cells surrounding the HCs, with a lumen in the center of the hepatic lobules, which represented the portal vein structure in vivo [ 32 ] (Figure 3d). Preset extrusion can construct heterogeneous, multicellar, and multimaterial structures simultaneously.…”

Microfluidic Encapsulation of Single Cells by Alginate Microgels Using a Trigger-Gellified Strategy

“…Constructing cell carriers has become a powerful way to address biomedical questions, such as screening and delivery of drugs ( Holloway et al, 2014 ; Yeung et al, 2016 ; Kang et al, 2020 ), cell therapy ( Lim and Sun, 1980 ; Burdick et al, 2016 ), and tissue regeneration ( Caiazzo et al, 2016 ; An et al, 2020 ). Hydrogels containing hydrophilic polymeric networks are widely used as matrix materials to construct cell carriers because it resembles a natural extracellular matrix (ECM) and can be further functionalized to offer physiologically relevant environmental cues ( Borenstein et al, 2007 ; Mao et al, 2017 ).…”

Printing of vessels for small functional tissues – a preliminary study

“…Since the human vascular system extends over several size scales, ranging from small capillaries up to larger vessels like the aorta or portal vein, unique demands are placed on the manufacturing technologies. In particular, smaller vessels for the supply of small structural subunits of organs, such as nephrons or liver lobules, or in vitro tumor models are difficult to fabricate due to the special demands on the material and the accuracy of the manufacturing process [4][5][6]. In this preliminary study we present first results for the production of small hollow structures on the basis of extrusion-based bioprinting into a gelatine support bath using freeform reversible embedding of suspended hydrogels (FRESH) [7].…”