"Clinical trials and animal studies show that there is a significant loss of islets following transplantation due to many factors, not just rejection," says Anna Moore, PhD, of the Massachusetts General Hospital (MGH), who led the study. "Currently there is no direct way to follow the causes behind this loss and how it proceeds over time. Monitoring islet survival by noninvasive imaging could give us the ability to detect and measure rates of islet loss under a variety of conditions, which could help develop procedures leading to better therapeutic outcomes."

In a previously published animal study, the MGH group showed that Magnetic resonance imaging (MRI) could detect transplanted islets that had been marked with experimental iron-containing nanoparticles. The current study utilised islets labeled with an Food and Drug Administration-approved contrast agent and procedures virtually identical to the Edmonton protocol, in which islets are infused into the recipient's liver. Labeled islets were transplanted into mice with a normal immune system and into mice with a severe genetic immune deficiency that would practically eliminate the rejection process. MR images of the animals' livers were taken seven times over the 14 days after the transplant procedure.

The results verified that MRI could track the labeled islets over time and reveal how many were surviving. For both groups of mice, the number of islets began to drop immediately after transplantation and reached a plateau at ten to 14 days. The researchers note that much of the early islet death probably was caused by factors other than rejection, such as damage during the transplant procedure. However, by day ten the mice with normal immune systems showed a 20 percent greater loss of islets than did the immune-deficient animals and close examination verified significant immune cell activity in the normal mice.

MEDICA.de; Source: Massachusetts General Hospital (MGH)