Scientists cultivate substitute hearts

 

SCIENTISTS have turned old hearts into new, rebuilding rat hearts from the ground up in a startling advance that could one day be used to repair damaged human hearts or even grow new ones for transplantation.

The technique developed by biomedical engineers in the US was so successful that the rebuilt organs started beating within days, the team reported in the journal Nature Medicine.

"It looks like a ghost heart, and it feels a little like jello," said team leader Doris Taylor, a bioengineer at the University of Minnesota in Minneapolis.

Dr Taylor said the technology offered hope to about 22 million people worldwide living with heart failure. The team is optimistic the technique could increase the pool of donor organs.

The supply of donor organs is limited and once a heart is transplanted, patients must take drugs to prevent rejection of their new heart. The medication may cause high blood pressure, diabetes and kidney failure.

Dr Taylor's group hopes to overcome such problems by using patients' own cells to seed the bioengineered heart.

Melbourne-based stem cell scientist Graham Jenkin yesterday said the procedure also had potential for treating other ailing organs. "Although they haven't reported it yet, (the team) has already had results with lung, liver, kidney and muscle," said Professor Jenkin, of the Monash Immunology and Stem Cell Laboratories at Monash University.

Using a process called organ decellularisation, Dr Taylor and her colleagues at UM and Boston's Harvard Medical School stripped the cells out of rat hearts and reseeded them with a mixture of live cells from fetal hearts.

Dr Taylor and her colleagues maintained the ghost heart in a special bioreactor, and then injected it with heart cells from newborn mice. Within four days, the hearts began to beat slightly, and within eight days the rebuilt organs were pumping at 2 per cent of their normal function.

"We just took nature's own building blocks to build a new organ," Harvard's Harald Ott said.

"When we saw the first contractions, we were speechless."

Surgeon and tissue engineer Joseph Vacanti of Boston's Massachusetts General Hospital said while the efficiency of the beating cells may seem low, it was still a "significant achievement".

"The fact that there is any contractile function after going through what (these hearts) went through is pretty amazing." Dr Vacanti said that an increase in function of as little as 10 per cent would be an improvement for some heart patients.

The new experiments add to previous work in which other researchers have engineered small sheets of tissue to patch damaged hearts or injected cardiac stem cells directly into organs. Professor Jenkin said that research had limited results in part because the patches were too small and the stem cells did not seem to grow into the right kinds of heart cells.

But he said the shortcomings could be bypassed by using the decellularisation procedure.

However, he cautioned that clinical applications were still a long way off.

Dr Taylor agreed. "We wanted to see if this was just some crazy idea," she said.

"It sounds like science fiction, but then in retrospect you think, 'Duh, it's kind of simple'."