Immunophenotypic characterization of bone marrow-derived stem cells versus their side population cells

Several studies have demonstrated that bone marrow-derived stem cells are plastic, thus capable of being differentiated or transdifferentiated into specialized cells, each with new specialized cell function. It is hypothesized that bone marrow, in addition to hematopoietic stem cells (HSC), also houses heterogeneous population of cells used in regenerative medicine At present, bone marrow-derived stem cells are used for treating a wide spectrum of diseases (Pittenger et al., 1999; Deda et al., 2008; Kumar et al., 2009). Hence, in this study, heterogenous population of cells was isolated from the mononuclear cells of bone marrow source and they were characterized based on their cell surface markers expression using flowcytometry. Also, the cell enumeration and viability testing were done to determine the total number of viable cells isolated from the bone marrow. It was found that hematopoietic stem cells, mesenchymal stem cells, and endothelial progenitor cells were present in bone marrow. Furthermore, it was observed that side population cells also reside in bone marrow and they were characterized based on their immunocytochemistry. Further studies need to be carried out to understand the role of side population in the potential of bone marrow derived stem cells, which could provide new insight in to the regeneration process of bone marrow stem cells that are used in therapeutics.