The team was able to replicate this twisting arrangement by patterning each of their three panels with grooves at different angles to each other. This enables the heart to pump more blood than it otherwise would.” When the heart beats, these layers not only contract, they also twist, a bit like how you twist a towel to wring water out of it. But a real heart has many layers, and the cells in each layer are oriented at different angles. “Virtually all of those have been made with a single layer of cells. “Until now, there have only been a handful of attempts to create a truly 3-D model of a ventricle, as opposed to flat sheets of heart tissue,” says Radisic. The inner diameter of the tube is 0.5 millimetres and its height is about 1 millimetre, making it the size of the ventricle in a human fetus at about the 19 th week of gestation. The result: a tube composed of three overlapping layers of heart cells that beat in unison, pumping fluid out of the hole at the end. After seeding the scaffold with cells and allowing them to grow for about a week, the researchers rolled the sheet around a hollow polymer shaft, which they call a mandrel. Electrical pulses can even be used to control how fast they beat – a kind of training gym for the heart tissue.įor the bioartificial left ventricle, Okhovatian and Mohammadi created a scaffold shaped like a flat sheet of three mesh-like panels. The underlying shape or pattern of the scaffold encourages the growing cells to align or stretch in a particular direction. Over time, the living cells grow together, forming a tissue. The scaffolds, which are often patterned with grooves or mesh-like structures, are seeded with heart muscle cells and left to grow in a liquid medium. To move into three dimensions, Radisic and her team use tiny scaffolds made from biocompatible polymers. Many of the challenges facing tissue engineers relate to geometry: while it’s easy to grow human cells in two dimensions – for example, in a flat petri dish – the results don’t look much like real tissue or organs as they would appear in the human body. We can also use them to screen large libraries of drug candidate molecules for positive or negative effects.” “With these models, we can study not only cell function, but tissue function and organ function, all without the need for invasive surgery or animal experimentation. “The unique facilities we have at CRAFT enable us to create sophisticated organ-on-a-chip models like this one,” Radisic says. A unique partnership between Canada’s National Research Council and U of T, CRAFT is home to world-leading experts who design, build and test miniaturized devices to control fluid flow at the micron scale, a field known as microfluidics. Their multidisciplinary team was led by Milica Radisic, a professor in the department of chemical engineering and applied chemistry and senior author of the paper.Īll three researchers are members of the Centre for Research and Applications in Fluidic Technologies (CRAFT). Okhovatian and Mohammad Hossein Mohammadi, who graduated from U of T with a master’s in chemical and biomedical engineering, are co-lead authors on a new paper in Advanced Biology that describes the model they designed.
“Both of these were nearly impossible to get with previous models.”
“With our model, we can measure ejection volume – how much fluid gets pushed out each time the ventricle contracts – as well as the pressure of that fluid,” says Sargol Okhovatian, a PhD candidate in the Institute of Biomedical Engineering. The new lab-grown model could offer researchers a new way to study a wide range of heart diseases and conditions, as well as test potential therapies. In the human heart, the left ventricle is the one that pumps freshly oxygenated blood into the aorta, and from there into the rest of the body. The bioartificial tissue construct is made with living heart cells and beats strongly enough to pump fluid inside a bioreactor. University of Toronto researchers in the Faculty of Applied Science & Engineering have grown a small-scale model of a human left heart ventricle in the lab.
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