Making life sweeter
diabetes makes the life of a patient sour. Sugar-rich preparations are struck off the menu of the patient because the body fails to regulate the blood-sugar level. The insulin-making capacity of the body wanes, or just stops, and requires either daily injections of the hormone or extremely careful control over diet and exercise.
Insulin is the hormone produced by the pancreas to allow the body to use sugar in the blood for energy and tissue building and to regulate its level. The good news is that a novel tissue transplant technique has been devised that promises to improve treatment for millions of diabetics.
In diabetics, the insulin-making pancreatic 'islet' cells are either destroyed by the person's immune system, for reasons still incompletely known, or the insulin receptors, responsible to sense its presence, are turned off.Researchers have been investigating several procedures to implant functioning pancreatic cells into the diabetic patients. But all such efforts failed in the past as the body's immune system recognises implanted pancreatic cells as foreign and promptly attacks them.
An alternative available to the physicians could be to administer drugs that suppress the entire immune system, as is a common practice in most of the major organ transplants. But that would make the recipient vulnerable to complications that might be worse than diabetes itself, feel scientists. Therefore, many research teams set out to circumvent these obstacles by trying various methods. Researchers are testing all the possible alternatives, encasing transplants in special membranes to keep attacking t cells out, transplanting in a few sites (like the eye, thymus and testes) where t cells do not attack, searching for biochemicals that knock out the specific kind of t cells that attack pancreatic implants.
A breakthrough in this direction came recently when a group of researchers at the Children's Hospital of Philadelphia in the us successfully transplanted pancreatic cells in mice. Under the leadership of Henry T Lau, the team discovered an ingenious means to defeat the vigilant immune system. They found that the particular kind of t cells that kill pancreatic implants could be eliminated by a protein called Fas ligand (fasl). fasl can deliver a death signal to encroaching t cells by turning on their internal suicide machinery. A self-destruction process called apoptosis takes place in the t cells before they can attack transplanted tissue, thereby letting the transplanted tissue strike roots inside the host's body.
Scientists genetically manipulated some muscle cells to express the fasl protein. These were later transplanted along with healthy pancreatic cells next to the kidneys of mice who had been chemically induced to develop diabetes. To the surprise of the scientists, transplanted cells survived for more than three months in contrast to the usual eight or ten days, before being slaughtered by the immune system of the mice.
While the ultimate aim is to make the transplant acceptable to the humans, scientists are currently working to 'optimise the expression of the protein', meaning that the implants produce fasl for a longer period. But the researchers feel that while it is extremely important to treat diabetes by this technique, the final goal would be to "develop a prototype system that would be generally applicable to many types of transplants".