Engineered heart tissue has been made to beat in the lab and in animals, a major step towards creating an artificial heart from scratch.

 

Enormous progress has been made in producing individual cells that replicate those of different parts of the body. Unfortunately, most organs have complex structures that means they cannot be manufactured purely out of the appropriate cells, although the trachea is a rare exception.

 

In the words of Dr Ali Khademhosseini of the Harvard Medical School. “Our hearts are more than just a pile of cells. They’re very organized in their architecture.” 

 

The problem parallels that of making new lungs, where only last month it was announced that collagen and elastin scaffolding had been used to support cells to make lung-like tissue that responds to pumped air for the first time.

 

Making an entire new heart is probably a long way off, but millions of lives could be saved if we could repair damaged tissue resulting from clogged arteries to parts of the heart. This is what Khademhosseini and colleagues have done for animals, according to a presentation to the 247th National Meeting of the American Chemical Society. 

 

Khademhosseini has been working on constructing heart tissue using hydrogels, proteins with the consistency of gelatin. “The reason we like these materials is because in many ways they mimic aspects of our own body’s matrix,” Khademhosseini says, particularly in their capacity to hold water.

 

However, while hydrogels fit the chemical, biological and electrical attributes the team were seeking, they also fall apart like gelatin. Khademhosseini created a new type of gel using tropoelastin, the protein that, combined together to form elastin, allows stretching and contracting of connective tissue in vertebrates.

 

As with the lungs, the elastin forms a scaffold on which heart cells can be grown. By using the patient's own cells it will be possible to avoid rejection by the immune system. To form the tissue into the shape required to be serviced by blood vessels Khademhosseini used 3-D printing to create patterns where the cells need to grow. 

 

The tissues produced in this way are small, but they beat together and work as cardiac patches in small animals.  Khademhosseini's next step is to move onto larger species. Meanwhile the elastin based hydrogels have potential for replicating other body parts, including blood vessels and skeletal muscle.