Device Harvests Adult Stem Cells, Kills Cancer Cells
By Dr. Matt Wilkinson, DrugResearcher.com, January 10, 2007
Sidestepping the contentious use of stem cells derived from embryos, researchers at the University of Rochester have unveiled a new device technology that makes it feasible to harvest stem cells from the blood.
Potentially improving the prognosis for many cancer sufferers, the technology is also being developed into an anti-cancer implant that programs cancer cells to die. The technique may even produce implants that direct the body’s own stem cells to differentiate into the required cells to repair damaged organs, as long as the stem cells researchers are able to develop the expertise.
In order to slow down the flow of specific cells along the length of the device relative to the majority of the blood, the new technology employs selectin molecules which have an elevated affinity for stem and cancer cells as opposed to other cells.
Since embryonic stem cells have so many legislative restrictions, the advances could facilitate more efficient access to adult stem cells, thus negating the ethical issue. Research into this potentially crucial therapeutic source of cells is often hindered by the lack of a pure source of stem cells.
Michael, who is an associate professor at the University of Rochester, has been developing these new medical devices since 2002. He was working for Daniel at the University of Pennsylvania on the biological adhesion of cells and that is where this new technology originated.
During inflammatory responses selectin molecules are mobilized to the surface of cells on the blood vessel wall and bind to the sialyl lewis X (SleX) carbohydrate groups on the cell surface proteins exhibited on the surface of stem cells, cancer cells, and white blood cells.
Affecting how strongly the SleX groups can bind to the selectin molecules, different cells present different proteins at their surfaces that influence the reaction.
Allowing them to be separated from the mass of blood cells, both cancer cells and stem cells bind to selectins making them absolutely instrumental in the process.
Two devices, one to kill the cancer cells and another to enrich the stem cells, have been developed by Michael thanks to the findings.
Michael has produced an apparatus that allows the enrichment of stem cells from the blood since bone marrow stem cells bind strongly to selectin molecules. A plastic tube coated with selectin molecules has a blood sample passed thorough it, causing the blood cells to stick to the tube walls with 40 percent being stem cells. It is currently in use as an ex vivo device.
It has been designed to function like a real blood vessel.
See the device at work.
See an animal vessel with white blood cells rolling along the vessel wall.
With the majority of the collected cells being blood cells, typical centrifugation stem cells separation techniques yield stem cells in about one percent purity.
The reliability of stem cell research often depends on the relative abundance of stem cells compared to the number of contaminating cells that may interfere with the results. This non-controversial method of gathering stem cells should permit more efficient stem cells research and benefit the science greatly.
The technique can collect adult stem cells that can still differentiate appropriately after collection, as studies by group coworkers Srinivas and Joel have concluded.
Due to the reasonably short regulatory process for medical devices, a stem cell enrichment device could be quickly licensed.
In the future, King predicts an in vivo device will allow stem cells to be enriched in a vascular shunt device close to a problem organ. Then the stem cells would transform into the cell types needed to mend the organ using differentiation factors that are still un-clear at this point in time.
King says that, “one of the problems with stem cell therapies is that only about five per cent go where they are supposed to, which is a problem as there is a fine line between stem cells and cancer cells,” when discussing the benefits of programming stem cells in the vicinity of a problem area.
Currently being tested in a preclinical trial using rats, a comparable mechanism has been applied to construct a cancer-killing implant. The device consists of a plastic tube coated with an anticancer agent, TNF-related apoptosis ligand (TRAIL), and selectins.
TRAIL is presently being utilized in various clinical trials. It is a naturally occurring protein that, with a high degree of specificity, induces cell suicide or apoptosis in cancer cells.
The cancer cells come into contact with the anchored TRAIL molecules thanks to the selectin surface. The cancer cells are programmed to die as they stream through the shunt by the TRAIL molecules. Scaling the device up to human size should be rather simple believes Michael. An example for a human model would be an arterial venular shunt in the arm.
Michael says that, “the cancer cells don’t need to stick to the surface before apoptosis, but if they do the bodies own white blood cells clean them out – meaning this can be a more long-term implant. We are now on preclinical trials and are optimistic that we can initiate human trials in two years from now.”