Non-invasive tracking of human haemopoietic CD34(+) stem cells in vivo in immunodeficient mice by using magnetic resonance imaging.

OBJECTIVE: To assess migration of CD34(+) human stem cells to the bone marrow of athymic mice by using magnetic resonance (MR) imaging and Resovist, a contrast agent containing superparamagnetic iron oxide (SPIO) particles. METHODS: All animal and human procedures were approved by our institution's ethics committee, and women had given consent to donate umbilical cord blood (UCB). Balb/c-AnN Foxn1(nu)/Crl mice received intravenous injection of 1 x 10(6) (n=3), 5 x 10(6) (n=3) or 1 x 10(7) (n=3) human Resovist-labelled CD34(+) cells; control mice received Resovist (n=3). MR imaging was performed before, 2 and 24 h after transplantation. Signal intensities of liver, muscle and bone marrow were measured and analysed by ANOVA and post hoc Student's t tests. MR imaging data were verified by histological and immunological detection of both human cell surface markers and carboxydextrancoating of the contrast agent. RESULTS: CD34(+) cells were efficiently labelled by Resovist without impairment of functionality. Twenty-four hours after administration of labelled cells, MR imaging revealed a significant signal decline in the bone marrow, and histological and immunological analyses confirmed the presence of transplanted human CD34(+) cells. CONCLUSION: Intravenously administered Resovist-labelled CD34(+) cells home to bone marrow of mice. Homing can be tracked in vivo by using clinical 1.5-T MR imaging technology.

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.