They create a left ventricle of the heart with living cells

The bioartificial ventricle, smaller than the natural version, is made of living heart cells and beats hard enough to pump fluid into a tube.

The achievement is the work of the team of Sargol Okhovatian, Milica Radisic and Mohammad Hossein Mohammadi, from the University of Toronto in Canada, both the first two and the third.

In the human heart, the left ventricle is what pumps newly oxygenated blood to the aorta, and from there to the rest of the body. The new lab-grown model could offer researchers a new way to study a wide range of heart diseases and abnormalities, as well as test potential therapies.

Many of the challenges facing living tissue engineers are related to geometry: although it is easy to grow human cells in two dimensions (that is, by forming structures one cell thick, for example a layer in the soil of a petri dish), the result will never closely resemble real tissues or organs as they appear in the human body.

To go three-dimensional, Radisic and his team use tiny scaffolds made of biocompatible polymers. The scaffolds, which often have a pattern of grooves or mesh-like structures, are seeded with heart muscle cells and allowed to grow in a liquid medium.

Over time, living cells occupy the desired spaces, and not others, and thus end up forming a tissue with the exact desired shape. The underlying pattern of the scaffold encourages the growing cells to line up or stretch in a certain direction. In addition, it is feasible to use electrical pulses to control the speed of the heartbeat.

Cultured from real, live heart cells, this model heart ventricle beats powerfully enough to pump fluid through a tube. (Photo: Sargol Okhovatian)

For the bioartificial left ventricle, the team created a three-panel, mesh-like, flat-sheet scaffold. After seeding the scaffold with cells and letting them grow for a week, the researchers wound the sheet around the axis.

The result: a tube made up of three overlapping layers of heart cells beating in unison, pumping fluid out the hole at the end. The inner diameter of the tube is 0.5 millimeters and its height is approximately 1 millimeter. This size is the size of the ventricle in a human fetus around the 19th week of gestation.

Although this preliminary version of the left ventricle represents a significant advance, there is still a long way to go before fully functional artificial living organs are possible. “The dream of every tissue engineer is to grow organs that are totally ready to be transplanted into the human body,” admits Okhovatian. “We are still many years away from that, but I think this bioartificial ventricle is an important step.”

Okhovatian and his colleagues present the technical details of their achievement in the academic journal Advanced Biology, under the title “Toward Hierarchical Assembly of Aligned Cell Sheets into a Conical Cardiac Ventricle Using Microfabricated Elastomers.” (Font: NCYT by Amazings)