Liver Regeneration

Liver Regeneration

Liver Regeneration

Human livers have a remarkable capacity to grow to a larger size after part of it is removed. Liver is the only major human organ that regenerates after removing part of it. This happens at an astonishing pace. By about 2 weeks after removal of part of the liver, most of the regenerative response is complete. The mechanisms involved in liver regeneration are very complex and have not been completely understood. Understanding the mechanisms of liver regeneration is likely to have a major impact on management of certain liver diseases and living donor liver transplantation.

Let us consider the situation of living donor liver transplantation as an example of why research on liver regeneration is important. Live liver donors donate the right lobe of their liver if they are donating for another adult. If a son is donating for his father or mother, the donor undergoes removal of right lobe of liver commonly. This procedure will remove about 60% of the donor’s liver mass. Idea is to get a liver that is at least 0.8% of body weight of the recipient. If we do the liver transplant operation without this amount of liver, the new liver gets injured by its own blood flow (called portal hyperperfusion), fails to function well, is less likely to regenerate and ultimately likely to result either in loss of the new liver or death of the liver transplant recipient.

Liver Donors

It is interesting to note that live liver donors can recover completely with only 40% remnant liver volume after their operation whereas liver recipients (who have preexisting liver disease) need a larger volume of liver to survive the operation. Understanding liver regeneration by high quality research is likely to result in understanding why a larger size of liver is required by the liver transplant recipient and mechanisms behind injury to new liver if a smaller sized liver is used for transplantation. Currently, though there is some understanding on why these could be happening, the information available is incomplete and does not have wide clinical application.

Further research in this area may allow transplantation of small sized livers successfully into patients who undergo living donor liver transplantation. This will result in increased donor safety as liver donors can donate smaller portions of their liver (say, their left lobe or part of left lobe) and would not run the risk of postoperative liver failure.

Acute Liver Failure

Another liver disease that would greatly benefit by research on liver regeneration is acute liver failure. Here, there is sudden, massive loss of liver cells due to an acute insult. Common causes for acute liver failure include viral hepatitis and paracetamol poisoning. Even though most of the functioning liver cells die in acute liver failure, the basic architecture (framework) of liver is well preserved in this situation (unlike chronic liver disease where the framework is lost completely). Liver transplantation is life saving in acute liver failure as it immediately provides a functioning mass of liver cells. If mechanisms of liver regeneration are better understood, we may be able to induce proliferation of the remaining undamaged liver cells in patients with acute liver failure quickly. If this is achieved, it may be possible to avoid liver transplantation in the management of acute liver failure.