Duke researchers use gene therapy to direct stem cells into becoming new cartilage on a synthetic scaffold even after implantation into a living body

By Ken Kingery

By combining a synthetic scaffolding material with gene delivery techniques, researchers at Duke University are getting closer to being able to generate replacement cartilage where it's needed in the body.

Performing tissue repair with stem cells typically requires applying copious amounts of growth factor proteinsa task that is very expensive and becomes challenging once the developing material is implanted within a body. In a new study, however, Duke researchers found a way around this limitation by genetically altering the stem cells to make the necessary growth factors all on their own.

They incorporated viruses used to deliver gene therapy to the stem cells into a synthetic material that serves as a template for tissue growth. The resulting material is like a computer; the scaffold provides the hardware and the virus provides the software that programs the stem cells to produce the desired tissue.

The study appears online the week of Feb. 17 in the Proceedings of the National Academy of Sciences.

An artistic rendering of human stem cells on the polymer scaffolds. Photo courtesy of Charles Gersbach and Farshid Guilak, Duke University

The traditional approach has been to introduce growth factor proteins, which signal the stem cells to differentiate into cartilage. Once the process is under way, the growing cartilage can be implanted where needed.

But a major limitation in engineering tissue replacements has been the difficulty in delivering growth factors to the stem cells once they are implanted in the body, said Guilak, who is also a professor in Dukes Department of Biomedical Engineering. Theres a limited amount of growth factor that you can put into the scaffolding, and once its released, its all gone. We need a method for long-term delivery of growth factors, and thats where the gene therapy comes in.

A microscopic view using electron microscopy of human stem cells and viral gene carriers adhering to the fibers of a polymer scaffold. Photo courtesy of Charles Gersbach and Farshid Guilak, Duke University

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