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New 'Tissue Velcro' Could Help Repair Damaged Hearts

Scientists create sheets of beating cells

Engineers at the University of Toronto have created a biocompatible scaffold that allows sheets of beating heart cells to snap together like Velcro, according to a report published in Science Advances.

“One of the main advantages is the ease of use,” said project leader Professor Milica Radisic. “We can build larger tissue structures immediately before they are needed, and disassemble them just as easily.”

Growing heart muscle cells in the lab is nothing new. The problem is that too often these cells don’t resemble those found in the body. Real heart cells grow in an environment replete with protein scaffolds and support cells that help shape them into long, lean beating machines. In contrast, lab-grown cells often lack these supports, and tend to be amorphous and weak. Radisic and her colleagues have focused on engineering artificial environments that more closely imitate what cells experience in the body, resulting in tougher, more robust cells.

Two years ago, Radisic and her team invented the Biowire, in which heart cells grew around a silk suture, imitating the way real muscle fibers grow in the heart.

In the new research, the investigators used a special polymer called POMaC to create a 2D mesh for the cells to grow around. The mesh resembles a honeycomb, except that the holes are not symmetrical but wider in one direction than in another. This provides a template that causes the heart muscle cells to line up together. When stimulated with an electrical current, the cells contract together, causing the flexible polymer to bend.

Next, the team bonded T-shaped posts on top of the honeycomb. When a second sheet is placed above, the posts act like tiny hooks, poking through the holes of the honeycomb and clicking into place. The concept is the same as the plastic hooks and loops of Velcro, which itself is based on the burrs that plants use to hitch their seeds to passing animals.

The assembled sheets start to function almost immediately. “As soon as you click them together, they start beating, and when we apply electrical field stimulation, we see that they beat in synchrony,” Radisic said. The team has created layered tissues up to three sheets thick in a variety of configurations, including tiny checkerboards.

The project’s ultimate goal is to create artificial tissue that could be used to repair damaged hearts. The modular nature of the technology should make it easier to customize the graft to each patient, according to Radisic. “If you had these little building blocks, you could build the tissue right at the surgery time to be whatever size that you require,” she said.

The polymer scaffold is biodegradable; within a few months it will gradually break down and be absorbed by the body.

Best of all, the technique is not limited to heart cells. “We use three different cell types in this paper: cardiomyocytes, fibroblasts, and endothelial cells, but conceptually there is really no limitation,” Radisic said. That means that other researchers could use the scaffold to build layered structures that imitate a variety of tissues, from livers to lungs. These artificial tissues could then be used to test new drugs in a realistic environment.

The next step is to determine how well the system functions in vivo. Radisic and her team are collaborating with medical researchers to design implantation experiments that will take the project one step closer to the clinic.

Sources: Medical Xpress; August 28, 2015; and Science Advances; August 28, 2015.


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