Figure 9.

Western blot analysis of BM cells isolated from young and old mice. Cells were obtained either from whole BM (left) or a lineage-negative (center) or a CD34+ subpopulation (right). Expression levels of endothelial (vWF or CD31) and mesenchymal (SM22) markers were analyzed via Western blotting (A). Ratio of SM22 levels versus endothelial markers (vWF or CD31) was quantified as internal loading control in each lane (B). Whole old BM showed a significantly higher expression of SM22 when compared to young BM, while vWF did not change significantly between the different age group. To exclude contamination from mature cell populations (i.e., fibroblasts), precursor-enriched populations (lineage negative or CD34+ enriched) demonstrated similar pattern of increased SM22 expression in old compared to young mice compared to CD31. This result strongly suggests that the SM22+ cells were mesenchymal precursor cells.