US bioengineers create heart-on-a-chip

Bioengineers at the University of California Berkeley have created an organ-on-a-chip that they claim could be used to radically reduce the expense of testing new heart drugs.

According to the authors of a study that appears in the journal Scientific Reports the device consists of a network of pulsating cardiac muscle cells housed in an inch-long silicone device that effectively works as a model heart.

Research leader Prof Kevin Healy claimed that it could ultimately help slash the cost of drug development.

’It takes about $5bn on average to develop a drug and 60 per cent of that figure comes from upfront costs in the research and development phase,’ Prof Healy said in a statement. ‘Using a well-designed model of a human organ could significantly cut the cost and time of bringing a new drug to market.’

The researchers designed the device so that its 3D structure would be comparable to the geometry and spacing of connective tissue fibre in a human heart. 

Differentiated human heart cells were then put into a loading area, and the system’s confined geometry helped align the cells in multiple layers and in a single direction.

The “heart-on-a-chip” developed at UC Berkeley houses human heart tissue derived from adult stem cells
The “heart-on-a-chip” developed at UC Berkeley houses human heart tissue derived from adult stem cells

Microfluidic channels on either side of the cell area serve as models for blood vessels, mimicking the exchange by diffusion of nutrients and drugs with human tissue.  

According to the researchers, within 24 hours of the heart cells being loaded into the chamber, they began beating on their own at a normal rate of 55 to 80 beats per minute.

The researchers put the system to the test by monitoring the reaction of the heart cells to four well-known cardiovascular drugs: isoproterenol, E-4031, verapamil and metoprolol. They used changes in the heart tissue’s beat rate to gauge the response to the compounds.

The baseline beat rate for the heart tissue consistently fell within 55 to 80 beats per minute, a range considered normal for adult humans. They found that the responses after exposure to the drugs were predictable. For example, after half an hour of exposure to isoproterenol, a drug used to treat bradycardia (slow heart rate), the beat rate of the heart tissue increased from 55 to 124 beats per minute.

The team claim the device could be adapted to model human genetic diseases or to screen for an individual’s reaction to drugs. They are also studying whether the system could be used to model multi-organ interactions. A standard tissue culture plate could potentially feature hundreds of cell culture systems.

‘Linking heart and liver tissue would allow us to determine whether a drug that initially works fine in the heart might later be metabolized by the liver in a way that would be toxic,’ said Prof Healy.