13 Sep 2017

Scientist combines medicine and engineering to repair a damaged heart

Regenerating heart muscle tissue using a 3D printer – once the stuff of Star Trek science fiction – now appears to be firmly in the realm of the possible.

The combination of the Canadian Light Source synchrotron’s unique biomedical imaging and therapy (BMIT) beamline and the vision of a multi-discipline researcher from the University of Saskatchewan in confirming fiction as fact was published in the September issue of Tissue Engineering, one of the leading journals in this emerging global research field of tissue regeneration.

U of S researcher Mohammad Izadifar says he is combining medicine and engineering to develop ways to repair a damaged heart.

“The problem is the heart cannot repair itself once it is damaged due to a heart attack.” he explained.

Izadifar has conducted his research out of three places on campus – the College of Engineering, the CLS and the College of Medicine where he has been certified in doing open heart surgery on rats, having trained in all the ethical protocols related to these research animals.

And thanks to the confirmation photo images he has from his collaboration with the CLS, Izadifar has already proven the 3D printed human cells, which he has dubbed the “heart patch,” can start to grow as intended in theory.

Once implanted in the laboratory mice, the heart patch is invisible to regular medical imaging. Izadifar has developed an X-ray imaging technique at the CLS to monitor the 3D-printed heart patch after implanting them in the laboratory mice. The CLS-derived pictures submitted to the journal show a 3D-printed heart patch with human cells arranged in 200 micron-wide strands with the distance between each strand being 400 microns. One micron is one-thousandth of a millimeter.

Izadifar says the key in printing live human tissue is finding the right gel medium to become the “ink” for the printer.

Heart with 3D printed patch.
Image courtesy of Mohammad Izadifar

His chosen “ink” or hydrogel is a natural, algae-based gel that is proven to be biocompatible with the human body and also non-immunogenic, meaning the human body shouldn’t reject the gel. It is also biodegradable because, at some point, the body should just absorb the gel and get rid of it.

“My goal is to take stem cells from the patient and then, in-vitro, I expand and instruct them to become heart cells,” he explains. 

When the heart starts absorbing the patch, those cells grow and slowly turn the 3D printed patch from soft tissue into dense, heart muscle.  In the meantime, if everything is working as it should, the rat’s heart starts shooting out blood vessels into the heart patch so the new tissue gets a healthy supply of oxygen.

The key, says Izadifar, is getting the cells to align in the 3D printed heart patch, ensure they are tightly joined and that they are capable of conducting electricity, just like natural heart muscle.

“If it is to become heart tissue, the patch needs to be robust and conductive.

“With different 3D printing patterns, we can control the toughness, conductivity and cell alignment of the patch,” he said. “With the medical imaging technique that I developed at the CLS, we would be able to monitor the 3D-printed heart patch during the healing process.”

Now that this work has been published, Izadifar is looking forward to continuing his research and his collaboration with the CLS.

Dean Chapman, science director of the CLS, says he has been thrilled to work with an enthusiastic and talented researcher in Izadifar at a facility well suited to the new field of tissue engineering using 3D printing.

“Our biomedical beamline (BMIT) is in a very unique environment on a university campus with a college of medicine and a veterinary college where animal models of research must be used,” said Chapman, a co-author of Izadifar’s paper.

What really makes the BMIT so unique is something radiologists call phase contrast imaging. The CLS beamline station refracts the high intensity x-ray beams ever so slightly.

Chapman says the concept is familiar to every grade school student: Put a pencil in water and it makes a unique photograph as the pencil seems to bend below the waterline.

It turns out refracting or bending the light shows images of material at the molecular level one thousand times bigger than looking at it directly, Chapman explains. As a result, researchers can see the framework the 3D printer has left behind and see the tissue turn into muscle.

“Phase contrast imaging as we do on this beamline is the future of radiology,” Chapman said.

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Story by Murray Lyons

Izadifar, Mohammad, Paul Babyn, Michael E. Kelly, Dean Chapman, and Xiongbiao Chen. "Bioprinting Pattern-Dependent Electrical/Mechanical Behavior of Cardiac Alginate Implants: Characterization and Ex Vivo Phase-Contrast Microtomography Assessment." Tissue Engineering Part C: Methods (2017). DOI: 10.1089/ten.TEC.2017.0222

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