Rabbit skeletal muscle tissue was successfully transplanted into rats, as part of a study to use animal parts to overcome human organ shortages.

The xenotransplanted muscle tissue, transplanted by a team lead by the UCL Institute of Child Health, London, retained its biochemical properties and also triggered anti-inflammatory and immunosuppressive response, preventing the typical immune system ‘attack’ that can lead to organ rejection.

The transplant was a part of a study, published in the journal PNAS and funded principally by the Medical Research Council (MRC) and Sparks Charity. The skeletal muscle tissue was removed from rabbits, washed with detergents to strip it of cells – in a process known as decellularisation – and then transplanted into rats with and without stem cells.

The critical shortage of human organs available for transplantation has stimulated researchers to explore synthetic and animal-derived body parts, but the latter brings with it the risk of organ rejection and the necessity for lifelong medications in order to prevent such rejection, said a study.

The team examined the immune response of the rats to the rabbit tissue. They found a significantly lowered immune response, with less T-cell activity (a type of immune cell instrumental in rejection) and evidence of delayed biodegradation; a process by which the immune system normally erodes transplanted organs.

Two weeks following the operation, new blood vessels had grown between the host and transplanted tissues, with the donated muscle stem cells still intact after a month.

The study pointed out a further problem of replacing functional tissue, which remains a major challenge in medicine.

Animal-derived tissue is already used in some surgical procedures. Bovine (from cows) heart valves are sometimes used to repair children’s hearts at Great Ormond Street Hospital.

However, animal-derived materials do not have a long lifespan in the human body – researchers believe that the human body slowly rejects them, which may explain why these heart valves only last about ten years. The advantage of the new approach developed in the study is that it may prevent implanted tissues from being rejected in the future.

Dr Jonathan Fishman, MRC-Sparks clinical research training fellow, UCL Institute of Child Health and first author of the study, said: “Our study used a regenerative medicine approach to explore ways of overcoming both the current lack of available organs for transplantation and organ rejection. Given the long waiting lists for organs, we need to explore the option of using animal organs and tissues to meet the gap between supply and demand. While some patients might not like the idea of having an animal part inside them, animal tissue is already used to repair some heart defects.”

Dr Paolo De Coppi, consultant paediatric surgeon at Great Ormond Street Hospital who coordinated the study, says: “The anti-rejection drugs currently taken by transplant patients are toxic to the kidneys and can increase the risk of children developing infections or cancer, so we need to find ways to develop organs that don’t trigger rejection. The goal for surgeons is to one day have off-the-shelf organs ready to transplant within a matter of days.

“However, although we have successfully transplanted a tissue-engineered trachea, it remains very difficult to find matched human donors for neonates or infants who are born with a severe malformation. Animal-derived tissue may offer a solution, but we are not there yet. The next stage of our research is to assess whether the effects observed in our study can be reproduced in larger animals and ultimately humans,” he said. - TradeArabia News Service