0659 GMT December 07, 2019
The liver is the largest internal organ in the human body, serving as the main site of metabolism. Human hepatocytes — cells that comprise 85 percent of the liver — are routinely used by the pharmaceutical industry for study of hepatotoxicity, drug clearance and drug-drug interactions. They also have clinical applications in cell therapy to correct genetic defects, reverse cirrhosis, or support patients with a liver-assist device, business-standard.com reported.
Regrettably, while the human liver can rapidly regenerate in vivo, recognized by the ancient Greeks in the myth of Prometheus, this capability to proliferate is rapidly lost when human cells are removed from the body. Thus far, attempts to expand human hepatocytes in the laboratory resulted in immortalized cancer cells with little metabolic function. The scarce supply of human hepatocytes and this inability to expand them without losing function is a major bottleneck for scientific, clinical and pharmaceutical development.
To address this problem, the researchers began to develop a new approach to rapidly expand the number of human liver cells in the laboratory without losing their unique metabolic function.
Based on early work emerging from the German Cancer Research Center (DKFZ) on the Human Papilloma Virus (HPV), the research team demonstrated that weak expression of HPV E6 and E7 proteins released hepatocytes from cell-cycle arrest and allowed them to proliferate in response to Oncostatin M (OSM), a member of the interleukin 6 (IL-6) superfamily that is involved in liver regeneration. Whereas previous studies caused hepatocytes to proliferate without control, turning hepatocytes into tumor cells with little metabolic function, the researchers carefully selected colonies of human hepatocytes that only proliferate in response to OSM. Stimulation with OSM caused cell proliferation, with doubling time of 33 to 49 hours.
Removal of OSM caused growth arrest and hepatic differentiation within four days, generating highly functional cells. The method allows expanding human hepatocytes for 35 population doubling, resulting in 1015 cells (quadrillion) from each liver isolation. By comparison, only 109 cells (billion) can be isolated from a healthy organ.