CELL THERAPY: How to Grow a New Heart Valve - Tepha Inc - Brief Article

Applied Genetics News, Dec 19, 1999

First make a heart valve-shaped scaffold out of biodegradable polymers. Then seed it with endothelial cells scavenged from an artery. Place the construct in an incubator and supply it liberally with culture medium. After about two weeks, the cells have completely covered the scaffold and are beginning to replace the scaffold with extracellular matrix. Voila! You have a heart valve ready to be implanted.

At the American Heart Association meeting, Simon Hoerstrup, a research fellow in John Mayer's laboratory at Children's Hospital, Boston, described how a heart valve incubator (bioreactor) had been developed to produce the new valves. By seeding cells onto a porous valve-like scaffold and subjecting the seeded scaffold construct to conditions in the incubator similar to those inside the heart, the researchers were able to produce functional tissue engineered heart valves.

The valves showed a close resemblance to native ones, and continued to grow and function after being transplanted into sheep. After 8 to 12 weeks the entire bioabsorbable scaffold was reported to have been resorbed and replaced with healthy cardiovascular tissue.

Patients receiving mechanical valve replacements must currently be placed on anticoagulant drugs and monitored for the rest of their lives to prevent blood clotting, and those receiving animal valves face the prospect of repeat surgeries as the performance of these valves begins to deteriorate. The new tissue engineered valves, however, are expected to be free from these problems. It is also hoped that the new technology will provide young children requiring heart valve replacement with a valve that can grow, removing the need for multiple surgeries to replace artificial implant valves as the child grows.

Previous attempts to engineer new tissue heart valves had been hindered by the lack of suitable bioabsorbable materials that could endure the repetitive bi-directional flexing of the heart valve leaflets. Simon Williams, president of Tepha, Inc. (303 Third St., Cambridge, MA 02142-1126; Tel: 617/492-0505 x216, Fax: 617/492-1996, Website: www. tepha.com), noted that the dual requirements of bioabsorption rate and mechanical properties were overcome using Tepha's proprietary technology. The company produced a flexible bioabsorbable material, known as PHA4400, to address these requirements and permit the fabrication of the heart valve scaffold.

Tepha is a recently formed spinout of Metabolix that is engaged in the development of a new range of bioabsorbable medical devices for therapeutic applications. The company is applying a core technology that allows it to engineer bioabsorbable polymers with properties suitable for use in a wide range of implantable products.