Producing fully functional human organs using induced pluripotent stem cells (iPS cells) will, in the foreseeable future, cease to remain in the realm of science fiction. In a game-changing study published recently in Nature, a team of Japanese scientists led by Takanori Takebe from the Yokohama City University Graduate School of Medicine has taken a giant step by providing proof-of-concept demonstration of a “functional” miniature human liver that produced blood proteins and broke down drugs when transplanted into a mouse. This is the first time a rudimentary functional human organ has been produced using iPS cells. Though it might take about a decade for the technique to reach clinical application, it marks a “promising approach” for regenerative medicine. The same technique can be used to grow other organs like kidneys and pancreas. Even as others have had little success in growing liver and other organs, Mr. Takebe’s team adopted a novel approach to produce in lab three-dimensional liver buds with blood vessels. Unlike others who used only cell lines of the organ they wanted to grow, the Japanese team closely mimicked the conditions that exist during the very early stages of organ development. For this, cell lines from liver buds — a primitive, condensed liver mass that starts forming on the third or fourth week of gestation — were mixed with a few other essential cell lines. While reprogrammed adult stem cells are capable of becoming specialised cells, this study has highlighted that functional organs cannot be grown using the iPS cells alone. The presence of other cells that are normally found during the early stages of organ formation is essential.
But the need for liver stem cell therapy or even transplantation should never arise as, unlike other organs, the liver exhibits excellent regenerative capacity; it can heal when less than 70 per cent of the organ is damaged. While the liver’s failure due to moderate alcohol consumption can be prevented by providing it sufficient time every year to heal, liver failure due to hepatitis B infection can be easily avoided by getting vaccinated. Unfortunately, as the recent WHO figure indicates, a vast majority of Indians are not vaccinated against hepatitis B — over one million Indians are infected by hepatitis B, resulting in about 250,000 deaths annually. Hepatitis C kills about 100,000 Indians every year. While the hepatitis B vaccine is given to children as part of their immunisation programme since 2007, the vast majority of adults are not vaccinated. This is an irony, considering that the vaccine — three doses of which cost only a few hundred rupees — is one of the cheapest and most effective shields against a mass killer.