In Vivo Generation of Thick, Vascularized Hepatic Tissue from Collagen Hydrogel-Based Hepatic Units

Abstract

In vivo engineering of hepatic tissue based on primary hepatocytes offers new perspectives for the treatment of liver diseases. However, generation of thick, three-dimensional liver tissue has been limited by the lack of vasculature in the tissue-engineered constructs. Here, we used collagen hydrogel as a matrix to generate engineered hepatic units to reconstitute three-dimensional, vascularized hepatic tissue in vivo. Hepatocytes harvested from Sprague-Dawley rats were mixed with liquid type I collagen, concentrated Dulbecco's modified Eagle's medium (2 x), and hepatocyte maintenance medium to create hepatocyte/collagen hydrogel constructs. The constructs were then dissociated into cylindrical hepatic units (diameter/height: 2000-4000 microm/500-1000 microm). Stacking of hepatic units under the subcutaneous space resulted in significant cell engraftment, with the formation of large fused hepatic system (more than 0.5 cm thickness) containing blood vessels. In contrast, only less cell engraftment could be achieved when hepatocytes were transplanted in a manner of whole constructs. Functional maintenance of the engineered hepatic tissue was confirmed by the expression of liver-specific mRNA and proteins. The engineered hepatic tissue has the ability to respond to the regenerative stimulus. In conclusion, large hepatic tissue containing blood vessels could be engineered in vivo by merging small hepatic units. This approach for tissue engineering is simple and represents an efficient way to engineer hepatic tissue in vivo.

Bone Graft Prefabrication Following the In Vivo Bioreactor Principle

“…This task becomes more complicated when the target tissue is vascularized and composed of a hierarchical organization of heterogeneous tissues. Successful proof of the IVB principle has been shown for complex tissues such as the trachea (Tsao et al, 2014), full-thickness skin (Eriksson and Vranckx, 2004), bladder (Baumert et al, 2007b), esophagus (Badylak et al, 2011), and skeletal muscle (Bitto et al, 2013); and for organs such as the liver (Zhao et al, 2010), heart (Ott et al, 2008), and lung (Wu et al, 2013). However, the unmet clinical demands in these areas and the barriers to clinical translation in existing demonstrations are well known.…”

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME

“…Although collagen has arginine-glycine-aspartic acid (RGD) sequence as the recognition site instead of galactose, collagen gels were used in hepatocyte culture for the application of bioartificial liver (Zhao et al 2010b). The results indicated that the collagen gels reconstituted a 3D vascularized hepatic tissue in vivo although they have weak mechanical property.…”

Freestanding 3-D microvascular networks made of alginate hydrogel as a universal tool to create microchannels inside hydrogels

“…The first is to use a scaffold that mimics the extracellular matrix (ECM) to immobilize cells and to construct the 3-D cell stacks. 12 Many porous scaffolds have been developed for this purpose such as those made of poly(d,l-lactide-co-glycolide) (PLGA), 13 hyaluronic acid, 14 collagen, 15,16 polyacrylic acid (PAA), 17 poly(ethylene glycol), 10 chitosan, 18 alginate, 19,20 and others. [21][22][23] These scaffolds can immobilize cells and support cell growth.…”