This Polymer Could Matter for Heart Valves

A new study from Rice University uses a natural polymer to serve as a template for the middle layer of synthetic heart valves--providing a potential novel solution in a field with limited options.

Kristopher Sturgis

When it comes to heart health, the functionality of heart valves can't be overvalued. The American Heart Association estimates that nearly 100,000 patients are hospitalized each year in need of heart valve repair or replacement. So far, replacement options have been limited to metal-based valve replacements--which require patients to be placed on anticoagulants--or biological valves made from pigs, which wear out over time.

Neither of these solutions are ideal for children in need of replacement valves, as they can't grow with the patient's heart over time. Which is why Jane Grande-Allen, a professor in bioengineering at Rice university, and her colleagues decided to design replacement heart valves made from natural materials. Her team set out to use a natural polymer called hyaluronan, one of the central components of skin and connective tissue, to serve as the template for spongiosa tissue--the middle tissue layer in valve leaflets.

"A tissue engineered heart valve, containing living cells, would be transformative for children, as well as adults who are not well suited to the options currently available," Grande-Allen says. "Hyaluronan is naturally present in heart valves and many other parts of the body, so it won't be rejected. Cells also have a number of receptors that can bind to hyaluronan, and it's also available in a range of molecular weights, so we can really tailor the characteristics of the hydrogel by working with different concentrations."

In a study that's nearly three years in the making, the group examined a variety of hydrogels based on hyaluronan, as the molecule attracts water and can serve as both a shock absorber and lubricant in heart valves. Through their study, the group found that naturally produced hyaluronan was just as effective as a synthetic hydrogel when used as a template for growing new spongiosa tissue. 

"The sponginess layer has been challenging to study because it is so soft," Grande-Allen said. "But it is essential to the proper mechanical behavior of heart valves, since it allows the stronger and stiffer outer layers to slide past each other as the valve opens and closes. Showing that valve cells will grow and behave normally in these soft spongiosa-mimicking scaffolds is a step towards incorporating these layers into more complicated scaffold structures for the tissue engineering of heart valves."

The industry certainly isn't short on investors, as companies seek innovative solutions for patients in need of heart valve repair and valve replacement surgeries.

This kind of demand next-gen valve technologies is why Grande-Allen and her colleagues have turned to hyaluronan as a potential solution that addresses the need for natural heart valve replacements that can regulate cell behavior. Grande-Allen says that these hydrogel components are the future of synthetic valve technologies, and could offer doctors the ability to customize valves for individual patients.

"Many scientists and bioengineers are already working with hyaluronan for various tissue engineering applications," she says. "These hydrogel models may be studied for the purpose of replacing diseased valves, or for studying aspects of valve disease in vitro by creating a simple valve model. I believe that the future of synthetic valve technology will include a hydrogel component--whether this is hyaluronan based or derived from another polymer -- because these materials offer so much potential in their ability to regulate cell behavior, as well as their ability to be extensively customized." 

Kristopher Sturgis is a contributor to Qmed.

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