Nonexpanded primary lung and bone marrow-derived mesenchymal cells promote the engraftment of umbilical cord blood-derived CD34(+) cells in NOD/SCID mice

Objective Previously, we have found that human culture-expanded fetal lung–derived mesenchymal stem cells (MSC) promote the engraftment of umbilical cord blood (UCB)-derived CD34 + cells. The high frequency of MSC in fetal lung allowed us to study whether this represented a biological feature of these cells or a property that was acquired during expansion in culture. Materials and methods Irradiated NOD/SCID mice (n=80) were transplanted with 0.1×10 6 UCB CD34 + cells in the presence or absence of 10 6 primary nonexpanded or culture-expanded fetal lung, liver, or BM CD45 − cells, or with nonexpanded fetal lung liver or BM CD45 − cells only. Results In comparison with transplantation of UCB CD34 + cells only, cotransplantation of UCB CD34 + cells and primary fetal lung or BM CD45 − cells resulted in a significantly higher level of engraftment (% hCD45 + cells) in BM, PB, and spleen. In addition, primary mesenchymal cells derived from adult BM had a similar promoting effect. The engraftment-enhancing effect was similar to that of culture-expanded fetal lung and BM MSC. Primary mesenchymal cells, but not culture-expanded MSC, were detected in recipient mice, suggesting that the primary cells were able to home and that this capacity was lost after expansion. Conclusion These results show that primary mesenchymal cells from fetal lung and BM promote the engraftment of UCB-derived CD34 + cells to a similar degree as culture-expanded MSC, indicating that it reflects a biological property of primary MSC that is preserved during expansion in culture.