Thursday, 17 March 2016

The Future of Skin Replacement: Xenografts

Science and technology are advancing at a groundbreaking pace, yet many with people with serious medical ailments continue to be plagued by inefficient, ineffective treatment options. For instance, individuals who need skin grafts, such as those who have suffered severe burns, diabetic foot ulcers, or require reconstructive operations after major surgery may have limited or no options. Delayed treatment of such ailments can lead to disfigurement, prolonged healing times, and even death in severe cases. Autografts derived from unaffected areas of a patient's own body are the ideal treatment, but are often not advisable or possible due to likely negative effects on patient stability.  The current preferred alternative treatment method  of most clinicians when autografts aren't possible is human cadaver allograft. However, this material is in limited supply and cannot be manufactured. Additionally, it poses serious risks of disease transmission.

For many years, alternatives to cadaver allografts have been explored, but a material that performs at its level has yet to emerge. Scientists continue to pursue the development of xenografts, which rely on xenotransplantation, the science of transplanting organs and tissues from one species into a dissimilar species. In this case, scientists have been especially interested in the possibility of using porcine or bovine skin tissue as a treatment option for those who require grafts. A few have made it to market, but they are terminally sterilized. This means that they cannot vascularize or integrate with the patient's internal systems; they can only act as a simple cover. Without the ability to vascularize in a manner similar to allograft, such options are considered inferior, as they can only provide temporary coverage for a few days, versus the few weeks that allograft can last before it sloughs off.

Thus, scientists continue to pursue the development of viable xenografts, ones that can utilize live cells instead of sterilized, inactive ones. Porcine options have been especially attractive, as pigs and humans share many physiological similarities, and swine are easy and inexpensive to raise. However, a critical hurdle is an enzyme, Gal, which is present on all pig cells. Humans have a natural antibody to this enzyme, so they reject tissues and organs that contain it. However, scientists are currently working on breeding lines of pigs that lack this enzyme so that live cell xenografts can become a viable possibility.

There is another major obstacle that must be considered as well: the potential of swine to human disease transmission. Of particular concern is PERV, a retrovirus that for many years was feared to share characteristics with HIV, the virus that causes AIDS. Research over the last few decades has shown that PERV is not a major risk; in fact, there have not been any documented cases of pig to human transmission. With the concern of PERV addressed, scientists excitedly observe that there are very few diseases that pigs and human share. Thus, the risks of disease transmission involved with using xenografts are likely much lower than the risks associated with using the current preferred treatment option, human cadaver allograft.

Undoubtedly, xenografts represent an attractive alternative treatment option for patients requiring skin grafts; continued pursuit of their development could end a great deal of unnecessary suffering.