According to the Organ Procurement and Transplantation Network, the agency that oversees the allocation of this scarce resource in the United States, the number of waitlist candidates for organs is 118,634 as of 2:47 PM on the 11th of July, 2013. The top three organs on the list: kidneys, livers, and hearts.
Efforts to remedy the shortage of organs have approached the problem on numerous fronts: increasing the supply of cadaveric organs by switching to an opt-out policy, increasing living donor opportunitiesand trying to identify entirely new sources for transplantable organs. On this third front, two recent reports highlight the promise (and perils) of using regenerative medicine as a strategy to grow organs and bypass the limits created by relying on cadaveric and/or living donors.
Researchers at the Texas Heart Institute in Houston, Texas, are working on engineering completely new organs using induced pluripotent stem cells (iPS) —adult cells that are coaxed into regaining a more flexible state that appears to be similar to embryonic stem cells. With a complex approach of scaffolding, stem cells, and a bioreactor, they are well on the path to creating a heart seemingly from thin air.
Using a slightly different approach, a team based at the Yokohama City University Graduate School of Medicine in Japan reported on their successful efforts to create a functional (but mouse-scaled) human liver, also using iPS cells. The team differentiated these iPS cells into hepatic endoderm cells, endothelial cells, and hepatic endoderm cells. These three types of cells combine naturally in a developing embryo to form a human liver. The result of combining these three cell types were three-dimensional structures, liver buds, which have the potential of forming the complete liver. After transplanting the liver buds into mice, the liver buds matured and began to function as human liver cells would.
These laboratory successes suggest the promise of a future in which we no longer have to ration transplantable organs. There remain significant technical and ethical challenges. And, ultimately, this promise may never be fully realized. Still, it is essential to take the time now to identify and address the related ethical challenges in the same way that scientists are confronting the technical hurdles.
It will add a host of daunting safety-related concerns, particularly in designing and completing early clinical trials – but also including things like long term follow-up. And, with the costs related to researching, developing and implementing the use of this technology and the potentially huge market value that desperate patients might assign to an organ, financial considerations will inevitably lead to concerns about access. Considerations of justice will demand attention.
In general, organ transplantation is already fraught with ethical peril and growing organs in a lab promises to make things more complicated still. This is not to say that we should abandon this science, just a call to be mindful that the ethics work proceeds apace.
