Liver disease is one of the leading causes of death in the US. Liver transplantation is the only treatment for patients with acute or end-stage liver failure. However, donor shortage places a substantial number of patients on the waiting list for liver transplantation (around17,000 in the US and 3500 in California by December, 2010) and only a small proportion of patients actually received liver transplantation (6320 in the US and 551 in California in 2010). Many patients die from their disease unnecessarily while waiting for liver transplant. Recent advances in derivation of hepatocytes from human embryonic cells (hESCs) make cell therapy for liver patients a promising possibility in the future. However, one of the major obstacles for clinical applications of these hESC derived hepatocytes is that these hepatocytes are not fully matured to fulfill all functions of adult liver cells and still express the fetal hepatocyte protein, AFP, which is absent in the normal adult liver, but present in malignant liver cells. Therefore, these immature hepatocytes may impose a potential danger for tumorigenesis in patients. Another major obstacle for hepatocyte transplantation is the lack of an ideal transplantable scaffold for cell attachment, survival and function. Very few studies have addressed the role of cell microenvironment on hepatic lineage specification from hESCs. Even less is known about the mechanism regulating hepatocyte differentiation from hESCs by cell microenvironment. We propose to use natural liver extracellular microenvironment for further maturation of ESC-derived hepatocytes and maintenance of hepatic function. We will seek to provide fundamental understanding of the possible mechanism responsible for the expected enhanced maturation of ESC-derived hepatocytes induced by the liver extracellular microenvironment with focusing on integrin and growth factor signaling pathways. With the novel approach we propose here, we expect that successful completion of the proposed research will not only significantly advance our understanding of hepatocyte maturation but also provide a platform for future organ engineering, ultimately leading to human embryonic stem cell-based clinical application to treat patients suffering from liver disease.
Statement of Benefit to California:
Patients with acute or end-stage liver failure need liver transplantation to save their lives. However, donor shortage is a serious problem the US and even more serious in California. Only 16% of California patients (3500 in the year 2010) with liver diseases actually received liver transplantation in contrast to 37% of patients national wide (17,000 in the year 2010) received liver transplantation. Human embryonic cells provide an alterative promising cell source for treatment of liver patients. However, hESC-derived hepatocytes are immature, and therefore may not fulfill all functions of adult liver cells and impose a potential danger for tumorigenesis in patients. We will use a novel approach for further maturation of ESC-derived hepatocytes and maintenance of hepatic function using natural liver extracellular matrix. We will identify fundamental molecular mechanisms responsible for the expected enhanced maturation of ESC-derived hepatocytes. We expect that successful completion of the proposed research will ultimately lead to human embryonic stem cell-based clinical application to treat patients suffering from liver disease. Since the immaturity is a general problem in ESC differentiation toward targeted cell types in vitro, our approach can be applied to cell types other than hepatocytes and therefore also benefits patients with diseases other than liver failure in the long run. The benefits will first come to the California patients and their families. We also expect to obtain intellectual property for the state of California and continuously maintain the leading role in California in embryonic stem cell research toward clinical applications.