Quest for Cartilage Growth Continues

The search for a method to grow cartilage—the shock-absorbing lining of hip and knee joints—goes on. Tissue engineers at Johns Hopkins University School of Medicine, in Baltimore, Maryland, have used tiny artificial fiber scaffolds thousands of times smaller than a human hair to coax stem cells into developing into cartilage. Has it worked? To a degree, yes. 

Jennifer Elisseeff, Ph.D., Jules Stein Professor of Ophthalmology and director of the Translational Tissue Engineering Center, said, "Joint pain affects the quality of life of millions of people. Rather than just patching the problem with short-term fixes, like surgical procedures such as microfracture, we're building a temporary template that mimics the cartilage cell's natural environment, and taking advantage of nature's signals to biologically repair cartilage damage."

According to the June 17 press release, Elisseeff's team is trying to build scaffolding that mimics the cartilage cell environment and generates new cartilage tissue. This environment is a 3-dimensional mix of protein fibers and gel that provide support to connective tissue throughout the body, as well as physical and biological cues for cells to grow and differentiate.

In the laboratory, the researchers created a nanofiber-based network using a process called electrospinning, which entails shooting a polymer stream onto a charged platform, and added chondroitin sulfate to serve as a growth trigger. They then seeded goat bone marrow-derived stem cells in various scaffolds to see how the stem cells responded to the material.

The cells developed into voluminous, cartilage-like tissue. "The nanofibers provided a platform where a larger volume of tissue could be produced, " Elisseeff said. They implanted the nanofiber scaffolds into damaged cartilage in the knees of rats, and compared the results to damaged cartilage in knees left alone.

They found that the limbs with damaged cartilage treated with nanofiber scaffolds generated a higher percentage of the more durable collagen (type 2) than those damaged areas that were left untreated. "Whereas scaffolds are generally pretty good at regenerating cartilage protein components in cartilage repair, there is often a lot of scar tissue-related type 1 collagen produced, which isn't as strong, " says Elisseeff. "We found that our system generated more type 2 collagen, which ensures that cartilage lasts longer."