Researchers working at Harvard and Massachusetts General Hospital have done something really remarkable. They have engineered functional blood vessels from pluripotent stem cells, meaning these oft-divisive wonder cells could be used in regenerative therapies for vascular tissue. The study, published in the July 30th issue of the PNAS, used a collection of stem cells primed to become endothelial cells, and then implanted them in mice to construct the new vessels.
Now stem cells have been a hot button topic for quite a while, even achieving the pop culture honor of inspiring a South Park episode (amid such other scientific greats as Al Gore’s Inconvenient Truth and a giant robotic Barbara Streisand). The controversy arose around the cells’ source, which at the time was human fetuses. The debate was heated and passionate and rife with ethical dilemmas that there are no easy answers for. Well actually there was one easy answer. And Shinya Yamanaka of Kyoto University found it in 2007.
The answer was human induced pluripotent stem cells. These are not embryonic stem cells, nor are they even the more acceptable but harder to procure umbilical cord stem cells. These were stem cells engineered from fully functional adult cells. Yamanaka found that by inducing certain genes to be expressed, mature cells could be transformed into pluripotent stem cells (the pluripotent means they can differentiate into a variety of cell types, but not all cell types, those being totipotent or omnipotent). Yamanaka and fellow induced stem cell pioneer John Gurdon from the University of Wisconsin-Madison won the Nobel Prize in Physiology and Medicine in 2012 for their work with engineering these stem cells.
This study out of the northeast was using these human induced pluripotent stem cells when they managed to assemble new vascular tissue. By sorting out those stem cells already primed to become endothelial cells (identified by a series of surface proteins unique to the endothelial lineage), the group could grow brand new and fully functional vascular tissue by simply culturing it with what are called mesenchymal precursor cells, which act as the context necessary to trigger the stem cells to become endothelial cells and subsequently form stable blood vessels.
This new vascular tissue remained functional and stable in the mice for 280 days after implantation. The study also tested whether or not stem cells derived from patients with type-1 diabetes could be used in this type of therapy, since type-1 diabetes is often associated with weakened vascular tissue. As it turns out, cells from type-1 diabetes patients can, in fact, be used, meaning that stem cell therapy used to treat both vascular and pancreatic dysfunction could come from the patient’s own cells. This would remove the threat of an immune response to foreign cells, and thus greatly decrease the danger of this type of experimental therapy. Hopefully other diseases characterized by impaired tissue function can be similarly circumvented with stem cell therapies.
Now this study does hold a lot of potential for future medical advances. That being said, these results are most likely still far away from clinical applications as there are a number of possible issues to be addressed before we could see everyday benefits in our local doctor’s office. But results like these show how big of an impact a finding like induced stem cells can have. With the questions of ethics safely addressed, stem cells can now begin to be explored as the incredibly exciting frontier they are rightly considered to be, with applications in countless fields of medicine and research. Well maybe not countless, but it’s most likely a really big number.
Original article: http://www.pnas.org/content/110/31/12774.full