Injectable Tissue Patch - Revolutionary Concept In Repair Of Damaged Tissue

Damaged or diseased heart or other organs could be fixed by injectable lab engineered tissue, overcoming the need for painful, invasive open surgery, according to a biomedical engineering research team at the University of Toronto Faculty of Applied Science & Engineering. Injectable Lab Grown Tissue Patch – Game Changer In Tissue Repair Technology

The last couple of decades have seen a huge expansion in stem cell and tissue engineering research and development.

Generally lab generated tissue used for repair and regeneration of injured or damaged organs (eg: heart attack ) has involved implantation of the tissue at the site of injury through an invasive surgical procedure such as open heart surgery and required general anesthesia.

The authors of the study however felt that given the patient’s serious illness and delicate state of health following a heart attack, surgery under general anesthesia might actually be dangerous. The team therefore, wanted to develop an injectable biomaterial that could be delivered via catheter directly into the infarcted area, avoiding invasive surgery and general anesthesia.

Biomedical engineering Professor Milica Radisic at the University of Toronto Faculty of Applied Science & Engineering and her colleagues are experts in developing polymer scaffolds on which realistic 3D tissue resembling native tissue can be grown in the lab setting. AngioChip, one of their innovations, is a tiny patch of heart tissue having its own blood supply. These heart cells are able to beat with a regular rhythm. Yet another of their novel creation snaps together like sheets of Velcro™.

The team hoped to translate their expertise in the field of polymer science to create an injectable biocompatible material that could be used to repair injured tissues and organs.

Developing An Injectable Biocompatible Material – A Herculean Task

• Miles Montgomery, a PhD candidate in Radisic's lab, spent nearly three years just experimenting in order to produce a tissue patch that could be injected, rather than implanted.

"At the beginning it was a real challenge; there was no template to base my design on and nothing I tried was working," says Montgomery. "But I took these failures as an indication that I was working on a problem worth solving."

• After several gut wrenching failures, Montgomery finally managed to produce what he was looking for – a scaffold material that matched the mechanical properties of the target tissue and possessed the necessary shape-memory behaviour. Thus, the patch would unfold itself into a bandage-like shape as it is delivered into the target area in vivo.

Shape-memory polymers refer to a type of active polymers becoming increasingly popular due to their dual-shape capability. They can alter their shape in a pre-programmed manner from shape A to shape B when given an appropriate stimulus.

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According to Radisic, the shape-memory effect depends on physical properties, not chemical ones. This essentially means that the unfolding process does not further injections, and local tissue reactions or conditions will not affect the process.

Testing The Lab Grown Injectable Tissue Patch

• The next step was growing (seeding) heart cells on the above scaffold, and the created tissue was injected into rats and pigs.

• The injected tissue unfolded into a postage stamp sized patch (nearly the same size as implanted tissue) as it emerged from the needle. The heart thankfully withstood the procedure very well

"When we saw that the lab-grown cardiac tissue was functional and not affected by the injection process, that was very exciting," says Montgomery. "Heart cells are extremely sensitive, so if we can do it with them, we can likely do it with other tissues as well."

• The scaffold made of biodegradable material would disintegrate over time leaving behind only the heart tissue

• It was found that following the procedure, the heart function also improved and the ventricles were able to pump better than before injection of the patch.

Plans For Future Research

• Whether the improved cardiac function is sustained over a long period of time.
• The team has also applied for patents on the invention and are planning to test the use of the patch in other organs, such as the liver.
• Prof Radisic opines that this platform could be customized as per requirements by, for instance the addition of growth factors to encourage tissue regeneration.

In conclusion, though this innovation still has to undergo further testing and modifications before it is ready for clinical trials, it nevertheless opens up exciting possibilities in the realm of tissue regeneration and repair.

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References:

1. Materials Science and Tissue Engineering: Repairing the Heart - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3786696/)

Source-Medindia