Umbilical cord blood (CB) contains a large number of early hematopoietic progenitors with high proliferating capacity and has been used alternatively to bone marrow (BM) for related and unrelated allogeneic transplants. As cell adhesion molecules (CAM) have a crucial role in homing and microevironnment regulation, we compared CAM expression in CB and BM progenitors in order to investigate a possible advantage of CB.

We studied by three colour cytofluorimetric analysis the expression of CD49d, CD49e, CD44, CD11 and CD62L in the subsets of CB and BM CD34+/CD38+ and CD34+/CD38- cells to identify the phenotypic pattern or more immature progenitors. CAM expression was evaluated after exposure of CD34+ cells to different combinations of cytokines (SCF, IL-3, FLT3 ligand) for 4-24 hours.

CAM were highly expressed in both CB and BM CD34+ cells, mainly on more mature progenitors CD34+/CD38+. Among the pool of earlier progenitors, CD49e, CD44, CD11a and CD62L were more expressed in CB CD34+38- subset than in BM CD34-CD38- cells (see table).

Table 1
Full size table

The exposure to cytokines increased the number of CD34+ cell expressing CD38 and CAM both in CB and BM cells. For all the CAM the mean fluorescence intensity was significantly enhanced. Since the expression of CD62L, CD44 and CD49e has been related to the repopulating capacity, our results suggest a possible advantage in homing and engraftment of CB more indifferentiated progenitors compared to BM progenitors. A short exposure to cytokines could probably improve the hematopoietic progenitors homing in transplant setting.