A New Way to Make Cartilage from Stem Cells

Cell Transplantation, October 29, 2009

One of the major practical successes of stem cell therapy has been treatment of race horses and companion animals who have suffered joint injuries using stem cells from the fat. The company Vet-Stem has developed a procedure in which a small amount of fat is extracted from the injured animal, the fat is shipped to a processing plant where a stem cell-enrichment process occurs, and then the animal's own cells are shipped back to the veterinarian who implants them into the injured tissue. This procedure, which can be seen on this representative video http://www.youtube.com/watch?v=hEkSJo3CmPc .

While the process of injecting stem cells into joints has demonstrated beneficial effects, one of the main goals of current regenerative research is to be able to develop brand new joint tissue (cartilage) in the laboratory in mass quantities that can subsequently be implanted surgically. This process has traditionally been difficult because the cartilage cells grow under highly specific conditions. A paper (Markway et al. Cell Transplant. Enhanced Chondrogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells in Low Oxygen Environment Micropellet Cultures. 2009 Oct 29) that appeared today in the journal Cell Transplantation addresses this issue.

The investigators used mesenchymal stem cells from the bone marrow together with micropellets, which are small biodegradable beads that the stem cells attach in order to mimic what occurs in the body when new cartilage is made. Two sizes of micropellets where compared, as well, different concentrations of oxygen were compared. In order to detect which approach made cartilage that resembled the cartilage found in the body, the scientists assessed levels of proteins called sulfated glycosaminoglycans, proteoglycans and collagen II. These are proteins that allow cartilage to perform its normal function in the body, such as maintaining a smooth surface, and having ability to carrier water.

It was found that the micropellets that were larger in size could produce cartilage that resembled the natural form, and additionally, production was enhanced under conditions of lower oxygen.

These finds are important because they demonstrate that stem cells are guided not only by growth factors but also that they can detect other stem cells around them. Additionally, several other studies have demonstrated that oxygen levels contribute to the activity of stem cells. In general stem cells seem to prefer conditions of low oxygen. This may be because high oxygen content is associated with mutations and mutations in stem cells could have disastrous consequences in the body.