Timing xenotransplants

Israeli researchers report in PNAS this week that embryonic pig tissues used for liver, pancreas, and lung transplants need to come from very specific windows of time in embryonic development.

The findings offer new insights into organogenesis and may help explain past failures in xenotransplantation, coauthor Yair Reisner of the Weizmann Institute of Science in Rehovot, Israel, told The Scientist.

Reisner explained that although research into using embryonic pig tissues as a source of transplantable organs has gone on for more than two decades, timing of the transplant is a challenge. Too early, and undifferentiated embryonic tissue may develop into a teratoma, he said. Transplant too late, and embryonic tissues may have been marked with identifiers that trigger rejection by the new host.

"Studying these windows provides a great assay system for basic research regarding the timing of developmental events at the molecular level," Reisner said.

In 2003,...