In vivo osteoprogenitor potency of human stromal cells from different tissues does not correlate with expression of POU5F1 or its pseudogenes.

Expression of "stemness" markers is widely used as a predictor of stem cell properties of mesenchymal stem cells (MSC). Here, we show that bone marrow-derived (BM)-MSC show stem cell-like behavior in vivo; that is, they form ossicles with formation of bone, formation of adipocytes, and establishment of the murine hematopoietic microenvironment. Multipotent umbilical vein-derived stromal cells (UVSC), on the other hand, do not form bone, nor do they give rise to adipocytes in vivo. Despite these differences in stem-cell-like behavior, BM-MSC and UVSC express the two transcripts variants of POU5F1 at a similar level. Also, we found that in BM-MSC and UVSC, POU5F1 is detectable. However, more than 89% of the POU5F1 transcripts correspond to the POU5F1P1, -P3, or -P4 pseudogene. Despite low-level expression of POU5F1, we were unable to precipitate POU5F1 protein in either BM-MSC or UVSC. These results demonstrate that MSC stemness does not correlate to expression of POU5F1 transcripts or its pseudogenes.