tissues heart valves, who often work for decades without pause, are some of the strongest and most durable in nature and to repair or replace options they are limited.
A step closer to synthetic heart valves that mimics the original
The search for a synthetic heart valve that mimics closely the original is a step closer to its goal with Rice University found that a natural polymer called hyaluronic acid, one of the main components of the skin and connective tissue, can serve as a versatile template for farming fluffy, middle layer tissue valve leaflets.
“In many diseases of the heart valves, there is greater expression of hyaluronan synthase, therefore the cells produce more hyaluronic acid, a major component of skin and connective tissue.”
Rice bioengineer Jane Grande-Allen and his colleagues are working towards the construction of heart valve replacement materials that respond to those produced by nature as accurately as possible. “It is worth pursuing more scaffolding gel based on tissue engineering, as these can be easily adjusted to match the stiffness of the natural tissue and researchers can encapsulate cells during crosslinking to study in full 3-D” , He said.
In a three-year study, researchers took a close look at the hydrogels based on hyaluronic acid, a glycosaminoglycan molecule long known that attracts water and serves as a shock absorber and lubricant in the heart valves look. Their work appears in the journal American Chemical Society Biomacromolecules .
hyaluronic acid constitutes 60 percent of the foam layer carbohydrate a valve. The soft and flexible spongy tissue joins the hard fibrous ventricularis leaflets on each side of each of four heart valves’. Spongy have to combine remarkable strength and flexibility to withstand the pushing and pulling of the tissue surrounding the heart for life.
The study led by Grande-Allen and graduate student Dan Puperi determined that the hyaluronan produced naturally carried out, as well as a synthetic hydrogel, polyethylene glycol diacrylate (PEGDA) as a template for the growth of new spongy tissue. It was reported stiffness of any hydrogel and the presence of peptide known as RGDS could be even more influential in controlling behavior of a cell culture.
The scaffolds are designed to degrade as the cells grow in the natural tissue, the researchers noted that the use of any type of scaffold can be better than the polymers based mesh used in valves most common heart tissue engineering because meshes have been widely reported to shrink over time after implantation in the body.
In the laboratory, researchers at Rice construct matrices bioscaffold natural or synthetic hyaluronic acid PEGDA. Each type of scaffold was tuned to match the mechanical properties of cancellous tissue, and the two types were used to compare the behavior of colony growth interstitial cell valve, which help the three layers of the valve maintain their structural integrity .
“Many people are interested in hyaluronan because it is known to be a bioactive material found naturally in the heart valves,” Grande-Allen said. “We were surprised that after the process of what is crosslinkable, hyaluronic acid became a generic material support was not as bioactive more.” Scaffolds must maintain the bioactivity to nourish the cells and direct their growth, he said.
“It helps to have another material candidate support, but our study showed that if you really want to imitate the carbohydrate component of the spongy region, may have to add that instead of just using a carbohydrate crosslinked as the scaffold itself” , Grande-Allen said. hyaluronic acid scaffolds can be effective natural platforms to test how cell cultures react to various additives carbohydrate, he said.
Although both natural and synthetic scaffolds were found to be biologically inert, researchers observed differences in the way they were broken. “The PEGDA was precisely degradable with collagenase and not at all susceptible to hyaluronidase, and vice versa,” Puperi said. “The cells may use different enzymes to degrade different materials, although having the same stiffness. This gives control over the way of degrading scaffold.”
Despite its mechanical properties were almost identical, Puperi said hyaluronic acid hydrogel displayed more energy dissipation PEGDA. “We also saw some regulation of hyaluronic acid synthase enzyme (which produces natural hyaluronic acid), and which may or may not be good,” he said.
This could provide a new vision of the roots of heart valve disease, Grande-Allen said. “In many diseases of the heart valves, there is a greater expression of hyaluronan synthase, making the cells produce more hyaluronic acid,” he said. “If they keep doing more, it will accumulate, so that cells usually react simultaneously on enzymes to break down as well. That action may actually cause problems because these fragments not just go away. Small fragments of acid hyaluronic are very bioactive and can make cells behave in problematic way. ”
While studying hyaluronan, the team found a protein expressed by cells of valves that can play a role in consolidating and degradation. The protein, known as KIAA1199, previously studied in relation to hearing loss, cancer and skin repair, but their presence was unexpected in the tissues of the valve and will be studied in the future, Puperi said .
“It’s a great symphony of molecules that work together, and it is difficult to analyze that if you do not know all the players,” Grande-Allen said. “So when a new player is shown, one wonders, how is this involved?” Showing that cells have more tools for creating hyaluronan gives us a little more power to understand what is happening and helps us to paint a better picture of how cells manage this large molecule hyaluronic acid in normal valves and sick and tissue engineered valves, “he said
Source :. Newswise
This article was originally published on medindia.net
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