Mesenchymal Stem Cells from the Wharton's Jelly of Umbilical Cord Segments Support the Maintenance of Long Term Culture-Initiating Cells from Cord Blood.

Abstract

Hematopoietic Stem Cells (HSC) are routinely obtained from bone marrow, mobilized peripheral blood, and umbilical Cord Blood. Traditionally, adult bone marrow has been utilized as a source of Mesenchymal Stem Cells (MSC). Bone marrow derived MSC (BM-MSC) have previously been shown to maintain the growth of HSC obtained from cord blood and have been utilized for cord blood expansion purposes. However, the use of a mismatched BM-MSC feeder stromal layer to support the long term culture of cord blood HSC is not ideal for transplant purposes. The isolation of MSC from a novel source, the Wharton's Jelly of Umbilical Cord segments, was recently reported (Romanov Y, et al. Stem Cells. 2003; 21: 105–110) (Lee O, et al. Blood. 2004; 103: 1669–1675). We therefore hypothesized that Umbilical Cord derived MSC (UC-MSC) have the ability to support the long term growth of cord blood derived HSC similar to that previously reported for BM-MSC. To test this hypothesis, MSC were isolated from the Wharton's Jelly of Umbilical Cord segments and defined morphologically and by cell surface markers. UC-MSC were then tested for their ability to support the growth of pooled CD34+ cord blood cells in long term culture - initiating cell (LTC-IC) assays as compared to BM-MSC. We observed that like BM-MSC, CB-MSC express a defined set of cell surface markers. By flow cytometry we determined that that both UC-MSC and BM-MSC are positive for CD29, CD44, CD73, CD90, CD105, CD166, HLA-A and negative for CD45, CD34, CD38, CD117, HLA-DR expression. Utilizing Mitomycin C treated (200 μM, 15 min.) UC-MSC from multiple donors as a feeder layer we observed that UC-MSC have the ability to support the maintenance of long term hematopoiesis during the LTC-IC assay. Specifically, UC-MSC isolated from separate umbilical cord donors support the growth of 69.6±11.9 (1A), 31.7±3.9 (2B), 67.0±13.5 (3A), and 38.5±13.7 (3B) colony forming cells (CFC) per 1×104 CD34+ cord blood cells as compared to 64.0±4.2 CFC per 1×104 CD34+ cord blood cells supported by BM-MSC (Mean±SEM, N=4 separate segments from three different donors). Thus, Umbilical Cord derived Mesenchymal Stem Cells, a recently described novel source of MSC, have the ability to support long term maintenance of Hematopoietic Stem Cells, as defined by the LTC-IC assay. These results may have potential therapeutic application with respect to ex vivo stem cell expansion of Cord Blood Hematopoietic Stem Cells utilizing a Mesenchymal Stem Cell stromal layer. In addition, these data suggest the possibility of co-transplantation of matched Mesenchymal and Hematopoietic Stem Cells from the same umbilical cord and cord blood donor respectively. Lastly, these results describe a novel model system for the future study of the interaction between Cord Blood Hematopoietic Stem Cells and the appropriate supportive microenvironment represented by the Umbilical Cord - Mesenchymal Stem Cells.