The liver is likely to be one of the earliest human organs grown to order from a patient's stem cells: liver tissue is already far more capable of regeneration than the tissues of other organs, and researchers have been making good progress in recent years in coaxing stem cells to form live tissue. As of today, a press report is doing the rounds to claim that a Japanese group have managed to grow a small functional mass of liver tissue - calling it a liver is no doubt considerably overstating the case, given the small size. Details are somewhat light on the ground, but we'll no doubt hear more soon.
Japanese researchers have created a functioning human liver from stem cells, a report says. ... A team of scientists transplanted induced pluripotent stem (iPS) cells into the body of a mouse, where it grew into a small, but working, human liver, the Yomiuri Shimbun said.
A team led by professor Hideki Taniguchi at Yokohama City University developed human iPS cells into "precursor cells", which they then transplanted into a mouse's head to take advantage of increased blood flow. The cells grew into a human liver 5 millimetres (0.2 inches) in size that was capable of generating human proteins and breaking down drugs, the Yomiuri reported.
An abstract of Taniguchi's research was delivered to regenerative medicine researchers ahead of an academic conference next week, but Taniguchi declined to comment to AFP before the meeting.
The liver is a good example of an organ where the real challenges will lie in generating suitable blood vessels throughout the liver tissue and then integrating it with a patient's vascular system - being able to reliably build a mass of liver tissue from stem cells is but the first step on the path. Not that this is unknown; you might take a look at one of the more recent publications from Hideki Taniguchi's team, for example:
One of the major obstacles in regenerating thick, complex tissues such as the liver is their need for vascularization, which is essential to maintain cell viability during tissue growth and to induce structural organization. Herein, we have described a method to engineer a functional human vascular network.
Vascularization is the key challenge to organ generation. We successfully generated human vascular networks inside a matrix. Integration of parenchymal cells using our engineering technique should facilitate future efforts to reconstitute vascularized human organ systems in vitro.