Credit: ©PPL Therapeutics

PPL Therapeutics (Edinburgh, UK), the company that, along with the Roslin Institute, cloned Dolly the sheep, announced on March 14 that it had created the first pigs cloned from adult cells. Independent DNA testing of blood from the five female piglets–Millie, Christa, Alexis, Carrel, and Dotcom–confirmed that their DNA was identical to that of the cells used to produce them and different from that of the surrogate mother. PPL says the successful cloning of the pigs opens the door to producing modified pigs whose organs and cells can be transplanted into humans. The method used to produce the piglets differs from that used to create Dolly, and the company has applied for a patent for “additional inventive steps”. PPL says the next stage is to create “knock-out” pigs, in which the gene for α-1-3 gal transferase is inactivated. That gene is responsible for the sugar group in pig cells that is recognized by the human immune system as foreign, thus causing transplant rejection. PPL says it hopes to begin clinical trials for xenotransplantation of pig organs in as little as four years.