Assessment of hepatocellular function within PEG hydrogels

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWB-4KXDWJ4-3&_coverDate=01%2F31%2F2007&_alid=508921244&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5558&_sort=d&view=c&_acct=C000059607&_version=1&_urlVersion=0&_userid=4420&md5=0a6bb7dc1ed695e1446012bbc052fe98


Tissue engineered liver has the potential to replace organ transplantation; however, due to the complexity of liver structure and function, fabricating the hepatic tissue is very challenging. This paper illustrate the utility of photopolymerizable poly (ethylene glycol) hydrogels for 3D encapsulation of heptic cells.
In this paper, they studied the survival and function of hepatic cells within the PEG hydrogel platform. They seeded bipotential mouse embryonic liver (BMEL) and Fibroblasts making Hepatocytes and Fibroblasts co-cultures (were seeded at a density of 5.0X105 cells/well, absorbed with 0.13mg/mL Collagen-1 extract from rat tail tendons) in PEG hydrogel platform, then, performed encapsulation of BMEL cells and primary hepatocytes. The cell viability was examined using calcein AM and ethidium homodimer fluorescent stains; also, performed RT-PCR to analysis gene expression and short interfering RNA transfection. To assess hepatocellular function and albumin release, used ELISA method, an enzyme linked immunosorbent assay. Found that the encapsulated BMEL aggregates and displayed a substantial induction of both albumin and alcohol dehydrogenase, which are both important markers of hepatocyte differentiation. So, this exhibited that BMEL cells can differentiate within PEG hydrogel plateform. Survival of PEG hydrogel encapsulated BMEL cells, for monodispersed cell culture, after one hour the viability was high of a 95%. However, after 3 days of post-encapsulation, the viability dropped down to 25%. As for pre-aggregated BMEL cells showed a significant increase in viability. This demonstrated the cell-cell interactions in maintenance of BMEL viability.
Also, to demonstrate the efficiency of siRNA-mediated gene knockdown for the hydrogel encapsulated BMEL cells, they examined slicing efficiency for a representative gene, lamin A. Found that the hydrogel encapsulation does not directly affect the maintenance of gene knockdown. This shows the compatibility of BMEL cell differentiation with hydrogel culture and the capacity to regulate gene expression through RNA interference.

I choose this paper because my final project is testing the hepatocyte’s ability to survive in agarose gel culture, which is similar with what this paper described. We tested the expression of albumin by RT-PCR, which is similar with what the paper did. Also, we measured the cell viability and the albumin production rate each time frame per cell. In our project, we used partially collagen I mixture with agarose to make the 3D culture. We observed that the culture with collagen I tend to have cells clumping together, and have better survival rate than the agarose only culture. This is also observed in this paper where they demonstrated the cell-cell interactions in maintenance of BMEL viability.