One of FDA's primary missions is to make sure that the products we approve are safe and effective. There is tremendous interest in the development of regenerative medicine, including numerous proposed products that rely on stem cells. Stem cells have the ability to generate more stem cells or to turn into more mature cell types such as nerve- or bone-producing cells. These properties make stem cells potentially well suited for use in regenerative medicine. They might be used in repairing heart, nerve, and brain damage or in treating diabetes and other diseases by repairing or replacing cells and tissues.

Steve Bauer, Ph.D., chief of the Cellular and Tissues Therapy Branch, Division of Cellular and Gene Therapies, in the Office of Cellular, Tissue and Gene Therapy at CBER.Because stem cells can change based on their surroundings, whether during growth outside of the body or following injection into the body, ensuring the safety of effective regenerative medicine products can be challenging. One type of adult stem cell, the multipotent marrow stromal cell (MSC) — more popularly called the mesenchymal stem cell — is the subject of a great deal of research in regenerative medicine. These cells can divide repeatedly, making additional cells, and under the right conditions can be turned into a variety of more specialized and mature types of cells. Depending upon the culture conditions, these more specialized cells have the potential to produce cartilage, bone, and fat, and help with control of inflammation and immunity.

MSCs can be obtained from bone marrow and adipose tissue (fat) and can be grown outside of the body to produce the large numbers needed for many proposed clinical trials. Donated MSCs can also suppress the immune system in individuals who receive them, preventing their rejection and allowing cells from one donor to potentially treat many different people, unlike most other cells or tissues.

But there are still scientific questions to answer about MSCs. A particularly important set of questions is how the manufacturing of these cells outside of the body could affect their potential healing properties and their safety. FDA scientists believe that answering these questions will improve the way MSCs are characterized and thereby facilitate the development of products made from MSCs. For this reason, the FDA's Center for Biologics Evaluation and Research assembled seven of its laboratories into a consortium to develop tests and techniques that will help answer these types of questions as these products move through the development process.

Using bone-marrow-derived MSCs from eight different human donors, the consortium has published scientific articles on the following topics:

• Evaluation of the ability of human MSCs to suppress activation of certain types of mouse immune cells in order to reduce variation in MSC immune suppression assays that use T-cells from human donors who might have many different T-cells. The mouse cells come from a genetically modified strain in which all of the mouse immune T-cells are identical.
• Creation of a large database of MSC proteins (a total of 7753) that enabled us to demonstrate the large variability among proteins from different MSC samples. This database will enhance our understanding of MSC biology and help define the variability among various MSC samples.
• Identification of 84 proteins (14 identified for the first time) on the surface of MSCs that may be useful for tracking these cells as they grow, divide, and differentiate to produce specific tissues.
• Development of techniques that enable scientists to quantify the ability of MSCs to multiply and to differentiate into specific cell types.
• Identification of specific genes that distinguish aging MSCs grown in cell culture, which could facilitate development of tests that evaluate the quality of MSCs before they are used to treat patients

These contributions are part of the overall effort of FDA to bring safe and effective stem cell-based therapies to the many patients who could potentially benefit from this type of regenerative medicine.

Steve Bauer, Ph.D., is the chief of the Cellular and Tissues Therapy Branch, Division of Cellular and Gene Therapies, in the Office of Cellular, Tissue and Gene Therapy at FDA's Center for Biologics Evaluation and Research.