Human hepatocyte isolation for clinical transplantation

Hello. I'm Stephen Strom. I'm a Torsten och Ragnar Soderberg Professor of Cell Transplantation Regenerative Medicine at the Department of Laboratory and Medicine, Karolinska Institute in the Division of Pathology. I'm going to talk today about the Human Hepatocyte Isolation for Clinical Transplants. Our group is the first to transplant human hepatocytes into patients with liver disease in America, and my laboratory was the first one to be approved by the FDA for isolation of hepatocytes for clinical transplants so we'd like to share this experience with you. We've collected about 2,000 livers for hepatocyte isolation, so we have some considerable experience in this area.

Although I don't believe there's any conflict of interest, I put this slide in there. I am a stockholder in Stemnion, which is a stem cell company interested in placental stem cells and Yecuris, which is a company interested in making mice with humanized livers for drug discovery and drug metabolism research. But none of the products from Yecuris or Stemnion are used in any of these slides I'm going to present today. So what we're interested in is really this field called hepatocyte transplantation, and this is a cellular therapy for liver disease.

So what we try to do with hepatocyte transplantation is shown on this slide, which is to "bridge" patients to whole organ transplant, or possibly repopulate their liver if they're dying of acute liver failure, or to correct metabolic defects. So in the bridge technique, what we try to do is to keep a person alive long enough to receive an organ. So about 10% to 15% of the patients who are waiting for liver transplant in America can die on the waiting list. So what we can do in some of these cases is to actually transplant hepatocytes, isolated liver cells into their liver to give them enough liver support to keep them alive for several days, in which time you hope to get a whole organ for transplant. We call that the "bridge" technique. The second use of a hepatocyte transplantation is really for repopulation of the liver of acute liver failure patients. So in this slide, it says FHA. F, which is fulminant hepatic failure. And this is a person who's dying of acute liver failure. And this is an urgent case for liver transplant of course, when they present in the hospital. And oftentimes, liver is not available for these people in sufficient time to keep them alive. In these cases, we can transplant isolated hepatocytes into their liver or sometimes into their spleen, and provide temporary liver support. What has happened in at least two of our patients is that they have recovered after the cell therapy without the whole organ transplant. So there are two reports from our group, and now there's five total reports in the world of recovery of patients from acute liver failure without the need of a whole organ transplant. So that's really the second use of hepatocyte transplant, to try to keep a person alive, and repopulate their liver during this acute liver failure phase. It's important with these acute liver patients is that we really can't transplant enough hepatocytes into their liver to support the entire function. But what we can do is keep then alive long enough for their native liver to regenerate. So without native liver regeneration, this cellular therapy really would not work. But it is sufficient to keep a personal alive long enough to allow their native liver to regenerate. And the third and most useful case for use of hepatocyte transplants is really for the correction of metabolic defects. These are mostly pediatric patients. These are young children obviously that are born with a metabolic defect. The defects that we're talking about are single gene mutations in certain enzymes that are mainly affecting the liver. The two types of diseases, or the two most frequently diseases that are transplanted with hepatocytes would be ornithine transcarbamylase deficiency, or OTC deficiency. This is a problem with ammonia metabolism. The second most common disease that is transplanted with hepatocytes would be Criglar-Najjar. This is a problem with metabolism of bilirubin. And the native liver cannot metabolize these compounds, and then the patients will end up dying of CNS problems from the buildup of the toxins, either the ammonia or the bilirubin. So what we can do in these cases is transplant isolated liver cells into the patient's liver, and then give them metabolic activity that's missing. So the livers that we use are from an organ donor, and they are proficient in the enzyme that's missing in the child. So therefore, we can try to repopulate their liver up to about 10% of their recipient liver can be repopulated with donor hepatocytes. And if we can get to that level of repopulation, we can get basically a complete metabolic correction of the disease. The patient still has the disease, but they would show no symptoms of the disease because we've provided enough metabolic activity in the transplanted cells to accommodate all of the ammonia, metabolism, or the bilirubin metabolism for instance, that these patients would require. So these are the main reasons for doing hepatocyte transplants. And on the next slide we will tell you basically, how do you do this?