By virtue of their unlimited self-renewal potential, stem cells offer the promise of an inexhaustible source of genetically-defined cells that could dramatically change the study and treatment of human disease, including personalized therapies, regenerative medicine and circumvention of immune rejection for tissue replacements. The inability to direct stem cell differentiation into specified primary cell type(s) with high efficiency and at large scale has limited their widespread application. In the body, stem cell differentiation is guided by several developmental mechanisms including modifications in gene expression that is induced by cell-cell and cell-tissue component interactions and structure, and environmental factors including signalling factors and other proteins expressed by cells and communicated through the tissue. Researchers have attempted to improve the efficiency of directed stem cell differentiation in laboratory cultures through alteration of one or more of these factors. However, yields of specific differentiated cell types remain low, and the ability to select individual cell types from the differentiated population for use in specific patient therapies is limited by a lack selection markers for each cell type.
The goal of the proposed work is to enable efficient differentiation of embryonic stem cells (ESC) into desired cell types by mimicking in laboratory systems, the conditions in the body that drive stem cell differentiation. To achieve this, ESC will be grown in tissue cultures that have been proven to function as tissue replacements, repairing host tissue after transplantation into the body. These tissue cultures are formed on three-dimensional scaffolds and contain all of the cells of the native tissue, which like bees make a bee hive, the cells express all of the native tissue components to recreate tissue structure and function in the lab. All native tissues of the body contain progenitor cells that replenish cell types of the tissue as they are damaged or die. We have already proven that addition of these progenitor cells to the tissue cultures that are devoid of given cell types results in rapid differentiation of the progenitors to replenish these cell types. Using ESC results in the same differentiation, but at lower efficiency. The aims of proposed work are to increase this efficiency of differentiation of ESC into tissue-specific cell lineages by growing the ESC in the tissue replacements.
To assist in inducing differentiation of ESC in the tissues, genes that regulate ESC differentiation from embryos will be identified and inserted into the ESC to enhance differentiation down desired lineages. Because of its early development from embryos, liver will be chosen as the model tissue for these studies. The ability of liver tissue cultures and hepatic lineage genes identified by profiling liver versus other organs generated from embryos to drive ESC differentiation to hepatic lineage cells will be identified.
The goal of this proposal is to develop a stem cell-based human liver tissue model for use in the laboratory to study human disease, to facilitate the development of new drug therapies and to eventually directly treat human conditions such as organ failure. Lack of human predictive laboratory liver tissue models results in toxic and non-efficacious drugs reaching costly clinical trials. Liver toxicity alone is responsible for 2/3 of drug failures in clinical trials, 1/3 of drug withdrawals from the market, 1/2 of all black box warning labels on approved drugs, and 40% of liver failures are drug induced. Human predictive models in the lab would enable pharmaceutical companies to identify toxic drugs early in development when costs are low, enabling only those drugs that are safe to advance to clinical trials where costs are high, focusing time and money on effective drugs. The laboratory tissue models will also find utility in efficacy assessment of new drugs, in identification of biomarkers of disease, as antiviral screening platforms for liver-related diseases such as Hepatitis, and in studying the effects of other diseases with known impacts on the liver such as HIV, diabetes and obesity. They will also eventually serve as extracorporeal devices for treatment of liver failure, personalized and regenerative therapies and liver transplants. California has the greatest number of Hepatits C positive people of any state in the country. It also is among the top ten employers for the pharmaceutical and biotechnology industries. Hence, dramatic savings could be realized for the state upon commercialization of the human liver tissue products.
In addition to this direct benefit to the citizens of California, indirect benefits include development of novel core facilities and shared equipment resources, experienced collaborative research teams that can attract millions of dollars of additional funding to the state, spinout companies from new technology development, and employment opportunities resulting from this new technology as well as increased tax revenues.
The program would also build on a collaborative team spanning major liver research and clinical centers throughout California, facilitating researcher access to products, patient access to eventual treatments and the team's access to fetal and adult tissues and multiple clinical trial sites. The research teams involved have been successful largely because of the strong biotechnology community in California enabling partnership to expedite product commercialization. These partnerships have brought millions of dollars of government grants to California as well as the promise of a growing, profitable tissue engineering and stem cell industry that will deliver innovative cell and tissue technologies to revolutionize patient care. There are few cities in the US that have the biotechnology infrastructure and collaborative environment to foster multidisciplinary teams and expedite discovery.