Miracle Grow

Above: Synthetic scaffold of an ear (photo credit: Rebecca Hale, NGM Staff)

Bioartificial organs, or organs grown from a patient's own cells, are seeing advances in an effort to overcome the problems of transplant rejection and the shortage of organs. Recently, Anthony Atala worked with a team of researchers at the Wake Forest Institute for Regenerative Medicine have developed a technique for a lab-grown bladder. A balloon-shaped scaffold is created from collagen and seeded with healthy bladder cells from a patient's diseased bladder, then incubated at body temperature for six to eight weeks. At least two different types of cells are used: urothelial and muscle. They are seeded in the appropriate locations, urothelial on the inside and muscle on the outside. At least 30 people to date have received lab-grown bladders.

This technique, however, has limitations: the bladder's vasculature is far less extensive than that of solid organs such as kidneys or livers. Angiogenesis is a complex process, and the direction of growth is less predictable than layers of cells surrounding hollow organs. Despite this hurdle, Atala's team produced a piece of liver using a technique analogous to a jet printer, which "prints" a layer of cells on the scaffold one at a time.

Additionally, using a patient's cells may not be an option if the organ is too diseased, as may be the case with advanced cancers. The usage of embryonic stem cells has long been a controversy, primarily because the embryo is damaged or destroyed in the process - but Atala's team has proven a way that leaves the embryo unharmed by using amniotic fluid in the womb. They subsequently have grown a variety of cell types, although not necessarily complete organs. In a bank of stem cell types, it could be possible to have a "library" from which to order organs from in the future.

Other bioartificial organs of notable mention in this article include a jawbone at Columbia University, a lung at Yale, and a non-implantable kidney at the University of Michigan.

After the SNBAL on a regenerated lung, I was curious about the progress of other bioartificial organs. Apparently, the idea of using a decellurized bioscaffold is not exactly new, with Taylor's heart being grown on its scaffold in 2008. Additionally, I found the author's view on embryonic stem cell usage to be thought-provoking: if we aren't harming the embryo while extracting the cells, will the number of ethical objections be just as high? I could see a potential "God-complex" argument. Finally, growing organs has been of interest to me since I discovered the field of biomedical engineering, and it's interesting to know that so many successful techniques are based off of using bioscaffolds. Perhaps I should consider a different track if the idea of working with stem cells is unappealing.

National Geographic, March 2011
"Miracle Grow", Josie Glausiusz
http://ngm.nationalgeographic.com/2011/03/big-idea/organ-regeneration-text

When does life belong to the living?

Years ago, physiological failure was a simple matter: a person was either dead or alive. Now, medical technology has blurred the line and raised important ethical questions about death and its relation to organ donation. According to the "dead-donor rule", organs can only be taken from donors declared dead. However, because early removal raises the chances of a successful transplant, transplant surgeons must act quickly yet without ethical violations.

In some cases, death is an obvious condition. The concept of brain death finds its origins in a 1968 panel from Harvard Medical School, who definied it as the destruction of the cerebral cortex and brain stem. The cerebral cortex controls consciousness and emotion; the brain stem regulates breathing and homeostasis. Despite biotechnology that can maintain basic functions enough to keep the body oxygenated, brain death is a legally accepted standard in the United States. With these types of patients, removal of organs is easy to time with the disconnection from life support, and they account for 85% or more of vital organ donors.

However, the real issue is determining the moment that organs can be removed from the other 15% of donors. Without the definition of "brain death", we are left only with our very first concepts of life: breaths and heartbeats. Organs cannot be harvested from these patients until they are removed from all life support. Yet, the process of death may irreversibly damage organs that could save another person if removed early enough. The heart must cease beating within an hour of removal to remain eligible for transplant. Furthermore, the Pittsburgh protocol dictates that transplant surgeons wait a further two minutes before removing the organ to ensure that the heart does not resume beating spontaneously. Only then can organs be removed.

Some ethicists oppose the dead-donor rule in cases in which the donor's family has agreed to organ donation and the patient is beyond recovery. They argue that death due to removal of organs and natural death are ethically synonymous, and healthy, vital organs can be transplanted to recipients who desperately need them. However, unconditional supporters of the dead-donor rule anticipate the possibility of fewer people registering for organ donation due to fears that they will be killed before they are truly past the point of recovery.

This article engaged my interest due to its relevance in both the classroom and the real world. In a recent lecture, we discussed the properties of living organisms and the significance to ethicists. Additionally, my family and I are all registered donors.

Article by Robin Marantz Henig
"When does life belong to the living?"
Scientific American, Sept. 2010: 50-55

Accessible online at http://www.scientificamerican.com/article.cfm?id=when-does-life-belong