I recently blogged about a scientific endeavor to grow new organs by applying stem cells to the scaffolding of de-cellularized (dead) organs (the result of this was to produce rudimentary, minimally-functional organs, but this is still an amazing first step). On Wednesday July 3, the journal “Nature” published a different and equally amazing approach at growing new organs – in this case new livers (or, more correctly, new miniature buds of functioning liver tissue).
Dr. Takanori Takebe, based at Japan’s Yokohama City University Graduate School of Medicine, led the research team. They started by taking human skin cells and coaxing them to transform back into stem cells. Next, the scientists added two other cell types (endothelial cells and mesynchymal stem cells). The scientists anticipated they would need to manipulate the mixture of cells to get them to align properly. However, they observed that, when combined together, these three cell lines spontaneously organized themselves correctly. This yielded tiny (4 mm) buds of liver tissue that appeared to have normal activity and function.
As an organ, the liver is somewhat unique in the body. Many organs such as the heart, kidneys, etc require a complete and complex structure to function. The liver on the other hand serves to wash/detoxify the blood and also to secrete necessary proteins for the rest of the body. Accordingly, small pieces of liver tissue can exist in a somewhat unstructured framework and still function as needed.
With functional liver tissue growing in their petri dishes, the team then transplanted these liver buds into mice and observed that they were healthy and functional. These buds of tissue detoxified blood and produced the proper proteins. Indeed, after they were implanted, they attached themselves to nearby blood vessels and continued to grow (in a testament to how clever these scientists were, they removed a piece of skull bone in several mice and implanted a single liver buds adjacent to the brain. They then covered the hole in the skull with clear plastic and watched visually as the liver tissue recruited new blood vessels and grew).
The hope is that one day liver buds could be injected into a patient with a diseased liver who would otherwise need a liver transplant to survive. Given the nature of these newly-generated buds, it is conceivable that new liver tissue could be implanted via an injection through the skin or intravenously (these would be minimally invasive procedures, avoiding the need for surgery). The liver buds hopefully would grow and assume the necessary liver function. This is truly futuristic, amazing science. While much more work needs to be done before this is ready for human trials, this is a huge leap forward in discovering what looks to be a viable pathway to growing new organs.