EXECUTIVE SUMMARY

Alginate Poly-L-Lysine Encapsulation as a Technology for

Controlled Differentiation of Embryonic Stem Cells

SUMMARY:  Drs. Martin Yarmush and Tim Maguire in the Department of Biomedical Engineering at Rutgers University have developed a murine embryonic stem cell alginate poly-L-lysine microencapsulation hepatocyte differentiation system that maintains cell viability, is conducive to embryonic stem cell differentiation and maintains differentiated cellular function.  This system may help to provide a renewable hepatocyte cell source needed for a variety of clinical and pharmaceutical applications.

BACKGROUND:  The development of effective extracorporeal bioartificial liver devices, in vitro systems for pharmaceutical toxicology studies and biosensors for environmental toxins is currently limited by the absence of large numbers of mature, functional hepatocytes.  To address this cell source issue, research into alternate hepatocyte precursor populations has been conducted.  One potential population that has been identified contains hepatic stem cells (hepatoblasts), which are not only capable of expressing differentiated hepatic function, but are also self-renewing. 

A few hepatoblasts have been identified that can differentiate into mature hepatocytes, including bipotential precursors for hepatocytes and biliary cells (oval cells), and hematopoietic stem cells.  Despite the fact that hepatoblasts potentially represent a renewable hepatocyte cell source, these cells are hard to isolate and exist in very low numbers.  In addition, the efficacy of utilizing these precursor cells is questionable, since the long-term functional stability of hepatocytes obtained from these systems has yet to be assessed. 

As an alternative approach to hepatoblasts, many investigators have incorporated embryonic stem cell differentiation strategies into the generation of a renewable hepatocyte cell source.  However, while hepatocyte function has been described, these strategies are limited in a number of ways, including the absence of large scale processing considerations, incomplete downstream enrichment techniques, and ineffective long-term functional maintenance.  Thus, a culture environment that not only promotes hepatocyte function, but is also controllable, and scalable may alleviate the practical limitations of stem cell biotechnology.

TECHNOLOGY:  Drs. Yarmush and Maguire have developed an alginate-poly-L-lysine microencapsulation system for stem cell cultivation.  Studies verify that the alginate microenvironment supports embryonic stem cell proliferation and differentiation toward the hepatocyte lineage as indicated by significant increases in albumin and urea production.  Additionally they have determined that the encapsulation system yields a relatively homogenous population, whose output function can be modulated through changes in key encapsulation parameters.  In summary, the end product is a tissue culture microenvironment that maximizes embryonic stem cell differentiation as well as scales to increase differentiated cell yield.

Experimental data demonstrates that alginate-PLL encapsulation provides a scalable system to control embryonic stem cell differentiation into hepatocytes.  The results indicate that the encapsulated embryonic stem cell population displays at least two hepatocyte specific functions, urea and albumin synthesis.

PATENT STATUS:  PCT Patent Application Number 2006122147 entitled “Alginate Poly-L-Lysine Encapsulation as a Technology for Controlled Differentiation of Embryonic Stem Cells” was published on November 16, 2006 and claims priority to May 10, 2005.

PUBLICATIONS:  T. Maguire, E. Novik, R. Schloss and M. Yarmush, Alginate-PLL Microencapsulation: Effect on the Differentiation of Embryonic Stem Cells into Hepatocytes, Biotechnology and Bioengineering, 93 (3), 581-591 (2006).