How to mend a broken heart - Scientists make dead hearts beat again

Scientists in America have been able to revive the hearts of dead rats and start them beating again.

The researchers at the Center for Cardiovascular Repair at the University of Minnesota believe their research could lead to customized organ transplants for people.

The team led by Dr. Doris Taylor coaxed the hearts from dead rats to beat again in the laboratory and suggest the research goes some way to fulfilling the promise of using stem cells to grow tailor-made organs for transplant.

Dr. Taylor and her colleagues conducted a study using a process called decellularisation which involves washing away existing cells from the dead hearts by using a powerful detergent, while retaining the basic collagen structure intact.

They then injected this basic connective tissue with the heart cells from newborn rats, fed them a nutrient-rich solution and left them in the lab to grow; within four days the hearts started to contract.

In order to coordinate the contractions the researchers used a pacemaker and connected the hearts to a pump so they were being filled with fluids; a small amount of pressure helped to simulate blood pressure.

The hearts started to pump blood eight days later at 2 per cent of the normal rate.

Many researchers are currently working on stem cell therapies which aim to repair the damage done to hearts by heart attacks and a British team recently created mature, beating heart cells from embryonic stem cells that could be used to make a heart patch.

Other research has involved injecting heart stem cells directly into the scarred heart in the hopes of regenerating damaged tissue but the Minnesota team used a different approach.

The researchers say as nature had provided the perfect scaffold they were curious to see what would happen in the laboratory if nature was given the appropriate tools.

The team already knew that decellularization had been used in making tissue heart valves and blood vessels and decided to try the process out on whole organs such as rat and pig hearts.

The scaffold which is made up of collagen, fibronectin and laminin, apparently resembles 'ghost tissue'; immature heart cells were chosen because they were considered to have the best chance of success.

The study focused on the regeneration of rat hearts and Dr. Taylor suggests the process could be used on other organs, and possibly offer a potential new source of donor organs such as livers, lungs or kidneys.

In theory too such organs would be less likely to be rejected by the body.

Experts believe as many as 50,000 people in the United States die each year waiting for a donor heart and they say the research could be a step towards resolving a huge problem.

The study is published in the journal Nature Medicine.