Role of gap junction communication in hepatocyte/fibroblast co-cultures: Implications for hepatic tissue engineering

Controlled Apoptosis of Stromal Cells to Engineer Human Microlivers

Engineered tissue models comprise a variety of multiplexed ensembles in which combinations of epithelial, stromal, and immune cells give rise to physiologic function. Engineering spatiotemporal control of cell-cell and cell-matrix interactions within these 3D multicellular tissues would represent a significant advance for tissue engineering. In this work, a new method, entitled CAMEO (Controlled Apoptosis in Multicellular tissues for Engineered Organogenesis) enables the non-invasive triggering of controlled apoptosis to eliminate genetically-engineered cells from a pre-established culture. Using this approach, the contribution of stromal cells to the phenotypic stability of primary human hepatocytes is examined. 3D hepatic microtissues, in which fibroblasts can enhance phenotypic stability and accelerate aggregation into spheroids, were found to rely only transiently on fibroblast interaction to support multiple axes of liver function, such as protein secretion and drug detoxification. Due to its modularity, CAMEO has the promise to be readily extendable to other applications that are tied to the complexity of 3D tissue biology, from understanding in vitro organoid models to building artificial tissue grafts.

A hybrid co-culture model with endothelial cells designed for the hepatic tissue engineering

The cultured hepatic cells in vitro are prone to losing their characteristic morphologies and biological functions. To avoid this problem, a hybrid co-culture system was proposed to elucidate the effect of cellular communication on the phenotype of hepatic cells. A monolayer of endothelial cells (ECs) was co-cultured on the surface of a three-dimensional (3D) scaffold embedded with HepG2 cells. In this hybrid co-culture system, the growth of encapsulated hepatic cells is barely influenced by the co-cultured ECs. However, the liver-special functions of hepatic cells, including the albumin secretion and the expression levels of hepatocyte-specific genes, are significantly improved. It is deduced that the improved liver-special functions is likely related to the paracrine mechanisms. Hence, this hybrid co-culture model may open a window for the co-cultivation of the multi-type of cells as well as the study of cell-cell signaling interaction.

Design of biomimetic cellular scaffolds for co-culture system and their application

The extracellular matrix of most natural tissues comprises various types of cells, including fibroblasts, stem cells, and endothelial cells, which communicate with each other directly or indirectly to regulate matrix production and cell functionality. To engineer multicellular interactions in vitro, co-culture systems have achieved tremendous success achieving a more realistic microenvironment of in vivo metabolism than monoculture system in the past several decades. Recently, the fields of tissue engineering and regenerative medicine have primarily focused on three-dimensional co-culture systems using cellular scaffolds, because of their physical and biological relevance to the extracellular matrix of actual tissues. This review discusses several materials and methods to create co-culture systems, including hydrogels, electrospun fibers, microfluidic devices, and patterning for biomimetic co-culture system and their applications for specific tissue regeneration. Consequently, we believe that culture systems with appropriate physical and biochemical properties should be developed, and direct or indirect cell-cell interactions in the remodeled tissue must be considered to obtain an optimal tissue-specific microenvironment.