It is interesting that heart and bladder tissue engineering have been consistently ahead of work on liver tissue these past years, because the liver is the vital organ most capable of regeneration in humans - as much as three quarters of a lost liver can grow back. In theory, then, the additional effort needed to spur full liver regrowth is less than for other internal organs. From a position of knowledge a decade ago, one might have wagered money on progress in liver tissue engineering leading the pack - but that was not to be.
The advent of induced pluripotency is in the process of leveling the tissue engineering playing field, however. In the past year research groups have demonstrated the creation of all sorts of tissue through genetic reprogramming of commonly available cells. The latest in line are liver cells, and the natural regenerative capacity of the liver means that a low-cost source of unlimited numbers of liver cells might be put to good clinical use more rapidly than other types of engineered tissue:
The Medical College research team generated patient-specific liver cells by first repeating the work of James Thomson and colleagues at University of Wisconsin-Madison who showed that skin cells can be reprogrammed to become cells that resemble embryonic stem cells. They then tricked the skin-derived pluripotent stem cells into forming liver cells by mimicking the normal processes through which liver cells are made during embryonic development. Pluripotent stem cells are so named because of their capacity to develop into any one of more than 200 cell types in the human body.
At the end of this process, the researchers found that they were able to very easily produce large numbers of relatively pure liver cells in laboratory culture dishes. "We were excited to discover that the liver cells produced from human skin cells were able to perform many of the activities associated with healthy adult liver function and that the cells could be injected into mouse livers where they integrated and were capable of making human liver proteins," says Dr. Duncan.
The liver may be particularly suitable for stem-cell based therapies because it has a remarkable capacity to regenerate. ... It is possible that in the future a small piece of skin from a patient with loss of liver function could be used to produce healthy liver cells, replacing the diseased liver with normal tissue.
Onwards and upwards, cell type by cell type. The sooner that a general biotech repair-and-replacement kit for human organs is established, the sooner we will all benefit from that technology.