Improved characterization of bone marrow stromal stem cells could support their use as safe and effective therapies

Scientists at the U.S. Food and Drug Administration (FDA) have used a mass spectrometry-based proteomics technique for characterizing human bone marrow multipotent stromal cells (hBM-MSC) that may lead to improved ways to characterize different batches of these cells. hBM-MSC hold great potential for stem cell therapy because they are thought to play key roles in repairing or regenerating organs and helping the body grow blood vessels; they also play important roles in preventing cell death and supporting immune system functions.

In this study, the FDA scientists focused on the analysis of the proteins on the membrane surrounding hBM-MSC that had been multiplied in a culture dish but had not yet differentiated (changed into a more specialized cells) or matured. Some of these membrane proteins are called “cell surface markers,” and combinations of these cell surface markers may be used to characterize hBM-MSC. The OCTGT researchers used a combination of existing techniques to extract and identify membrane proteins from hBM-MSC that had been cultured in the laboratory to produce a large cell population—similar to what would have to be done to produce cells for actual therapy. Using these techniques they analyzed potential markers on hBM-MSC obtained from four human donors aged 22-24 years old. Compared to previous protein analysis of hBM-MSC, use of a technique involving cycling of cells between low and high pressure improved the extraction of the proteins markers from the cell surface of the hBM-MSCs.

The researchers identified twice as many membrane proteins than had been reported previously in the scientific literature. The team identified 84 markers (also called CD proteins), including 14 that have not been reported and may represent markers for hBM-MSC. The team is from the Office of Cell, Tissue, and Gene Therapies (OCTGT) of the Center for Biologics Evaluation and Research (CBER).

The OCTGT work is important because the source of hBM-MSC is bone marrow (although they can also be obtained from other sites, e.g., adipose and placental tissue). It is impractical to repeatedly remove samples of hBM-MSCs from individuals in order to accumulate enough cells for therapy. Instead, scientists must grow in the laboratory large numbers of hBM-MSC using an initial population of cells harvested from a particular individual. Since markers may play critical roles as entry and exit points to chemical signals going into and out of the hBM-MSC, knowing which markers are present may enable scientists to determine if they are able to differentiate and mature into cells with specific functions. This would help scientists predict which batches of these cells are able to differentiate and mature; it would also help scientists better understand the biology of hBM-MSC and the processes that guide their differentiation into other types of cells that could be used as safe and effective therapies.

Currently, the limited amount of knowledge about hBM-MSC proteins makes it difficult to use cell surface markers to determine if a particular batch of cells growing in the laboratory is capable of correct differentiation and maturation, which would enable their use as a particular type of cell therapy.

Title

Improved proteomic profiling of the cell surface of culture-expanded human bone marrow multipotent stromal cells

Journal of Proteomics 78 (2013) 1-14

Authors

Samuel T. Mindaye^a, Moonjin Ra^a, Jessica Lo Surdo^b, Steven R. Bauer^b, Michail A. Alterman^a,*

^aTumor Vaccines and Biotechnology Branch, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, US Food and Drug Administration, Bethesda, MD

^bCellular and Tissue Therapies Branch, Division of Cellular and Gene Therapies, Center for Biologics Evaluation and Research, US Food and Drug Administration, Bethesda, MD

^*Corresponding author