Homing and clonogenic outgrowth of CD34+ peripheral blood stem cells: A role for L-selectin?

: ObjectiveAfter transplantation of hematopoietic stem cells, adhesion molecules play a major role in the multistep process of engraftment in which L-selectin is suggested to be of relevance. A positive correlation previously was found between the number of reinfused L-selectin+ stem cells and platelet recovery. In the present study, we determined the role of L-selectin in different engraftment steps, i.e., adhesion to endothelial cells, migration, and clonogenic outgrowth by in vitro assays that closely mimic the in vivo situation.: Materials and MethodsFlow adhesion and migration experiments were performed using the human bone marrow endothelial cell line 4LHBMEC and isolated peripheral CD34+ cells with or without blocking of L-selectin–ligand interaction. Various clonogenic assays, including serum-free colony-forming unit-megakaryocytes (CFU-MK) and burst-forming unit-megakaryocytes (BFU-MK), were performed with sorted L-selectin+L-selectin− cells or in the presence of antibodies.: ResultsBlocking of L-selectin on CD34+ cells did not significantly affect rolling over and firm adhesion to 4LHBMEC. In addition, no role for L-selectin was found in transendothelial migration experiments. Finally, in clonogenic outgrowth of sorted or anti–L-selectin monoclonal antibody-incubated CD34+ cells, no key role for L-selectin expression could be defined in BFU-MK and CFU-MK assays.: ConclusionUsing in vitro assays for CD34+ stem cell adhesion, migration, and clonogenic capacity, we were not able to define a major role for L-selectin. [Copyright &y& Elsevier]