Via EurekAlert!: "tissue engineers have used tiny, artificial fiber scaffolds thousands of times smaller than a human hair to help coax stem cells into developing into cartilage, the shock-absorbing lining of elbows and knees that often wears thin from injury or age. ... 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. ... Unlike skin, cartilage can't repair itself when damaged. For the last decade, [researchers have] been trying to better understand the development and growth of cartilage cells called chondrocytes, while also 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 provides 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. After characterizing the fibers, they made a number of different scaffolds from either spun polymer or spun polymer plus chondroitin. They then used goat bone marrow-derived stem cells (a widely used model) and seeded them in various scaffolds to see how stem cells responded to the material. ... compared to cells growing without scaffold, these cells developed into more voluminous, cartilage-like tissue. ... The investigators then tested their system in an animal model. 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 use of the nanofiber scaffolds improved tissue development and repair as measured by the production of collagen, a component of cartilage. The nanofiber scaffolds resulted in greater production of a more durable type of collagen, which is usually lacking in surgically repaired cartilage tissue."