Mexican Pig-to-Human Islet Transplant Draws Interest, and Skepticism

A Mexican researcher's report of successfully transplanting islet cells taken from the pancreas of pigs into 12 adolescent diabetics, which then survived and produced insulin with no need for use of immunosuppressive drugs, drew attention -- and skepticism -- at the 19th International Congress of The Transplantation Society.

Dr. Rafael Valdes, professor of surgery at the Universidad Nacional Autonoma de Mexico, said that one of the children who received the pig islets remained insulin free after a year, while half of the remaining adolescents in the trial now require up to 75 percent less insulin than before the transplant.

The islet cells and testicular Sertoli cells were taken from neonatal pigs in New Zealand, and were implanted into tubular areas that had been created beneath the surface of the skin of children with type 1 diabetes ranging in age from 11 to 17.

Valdes reported that absolutely no immunosuppressive methods were used either in preparation for or following the transplant, and that the immune systems of the children did not reject the pig cells as would have been expected.

Dr. David White, a professor of xenotransplantation at the Robards Research Institute in London, Ontario, offered the theory that the Sertoli cells transplanted with the islets "probably turned off the immune response to pigs" in the transplant recipients.

Valdes also emphased that the children were being closely monitored for any sign that porcine retrovirus -- a virus found in pigs but not in humans -- may have been transmitted along with the cells, and "none has shown any sign of it."

Valdes said his group was now beginning a larger trial with 24 children using islets and Sertoli cells cultivated from pigs in Mexico instead of New Zealand.

Several leading diabetic researchers attending the conference greeted Valdes' report with interest, but considerable skepticism.

"We hear these kind of reports all the time," one said off the record. "I think there is about a one percent chance that there is something to this."

Dr. Camillo Riccordi, head of the Diabetes Research Institute at the University of Miami School of Medicine, and Dr. Bernhard J. Hering, director of islet transplantation at the University of Minnesota, and pressed Valdes to have his results verified through trials conducted at centers in other countries.

Both Riccordi and Hering also expressed concern over the safety of the Mexican approach, and urged Valdes to quickly agree to a test at a U.S. institution of the Mexican approach using monkeys instead of humans as the recipients of the pig cells.

"A monkey protocol is much easier," said Riccordi. "I cannot see why Dr. Valdes wouldn't agree to that," Hering added.

Other sources: 19th International Congress of The Transplantation Society