Animal studies suggest that applying a cardiac patch made of a regenerative polymer scaffold onto the surface of the heart could be an effective way to preserve heart function after a heart attack. However, such a procedure would most likely require open-chest surgery, which is traumatic and presents a major barrier to it being used in human patients. Now, new research on mice suggests that "spray painting" biomaterials onto the heart using a minimally invasive procedure could be less risky, less costly, but just as effective.
The new study - led by the University of North Carolina at Chapel Hill - is published in the journal Tissue Engineering Part C: Methods.
Heart attack, or myocardial infarction, is a major cause of death worldwide. It occurs when heart muscle does not receive enough oxygen-rich blood. The longer the heart muscle is starved of the blood it needs, the greater the damage.
Heart attack results in loss of heart muscle cells (cardiomyocytes) accompanied by changes to the structure and shape of the heart, as well as impaired function. These can eventually result in heart failure.
In their study paper, the researchers say that current treatments - including medications and heart pumps (ventricular assist devices) - only delay progression of disease.
This limitation, together with a shortage of heart donors, means that there is an urgent need for new therapies that focus on regenerating damaged hearts to improve outcomes for patients.
'Inspired by spray painting in the construction industry'
In recent years, biomaterials have been showing some promising results in tissue engineering studies to repair cardiac tissue.
- Every year in the United States,
around 735,000 peoplehave a heart attack
- One out of 5 heart attacks is silent - people are not aware of it, but the damage is done
- Coronary artery disease is the main cause of heart attack.
For example, cardiac patches - regenerative polymer scaffolds that are layered onto the surface of the heart - have proven effective in preserving heart function after heart attack in rodents.
However, applying a cardiac patch by layering onto the heart would probably require open-chest surgery - a risky and traumatic procedure for patients who have had heart attacks.
The researchers therefore looked for a way in which regenerative biomaterials might be applied in a less invasive manner, as they note:
"Inspired by the practice of spray painting used by [the] construction industry, we hypothesize that in situ polymerizable biomaterials can be spray painted onto the surface of the heart to form a uniform layer of cardiac patch."
The team decided to base their "spray paint" on platelet fibrin gel, as this biomaterial is known to help clot formation and has already been tested in various animal studies.
Spray painting platelet fibrin gel onto the heart
The gel has two ingredients that are carried in a "double-barreled" syringe. The two ingredients come together at the syringe tip - together with a tube carrying carbon dioxide under pressure - to form the gel as it is sprayed onto the target.
In the case of this study, the researchers tested the effectiveness of the gel on cultured cells and on the hearts of live mice via a small incision in the side of the chest.
The results showed that the sprayed-on biomaterial was nontoxic to heart muscle, stuck to the surface of the heart, and degraded over time.
Also, because the gel contains "interconnected pores," it could also be used to release substances such as growth factors to promote the repair of heart muscle.
The researchers conclude that spray painting biomaterials is feasible as a way to place a cardiac patch without the need for invasive surgery and sutures, and offers a promising strategy for cardiac repair after heart attack.
"The spray painting method, as described in this manuscript, is an excellent example of how tissue engineering has evolved since the 1990s. The described delivery method is easy to apply in clinics and shows significant potential for patient treatment."
Methods co-editor-in-chief Prof. John A. Jansen, Radboud University Medical Center, the Netherlands