title: Adhesion of synchronized human hematopoietic progenitor cells to fibronectin and vascular cell adhesion molecule-1 fluctuates reversibly during cell cycle transit in ex vivo culture.
abstract: Ex vivo expansion of hematopoietic stem/progenitor cells may result in defective engraftment. Human cord blood CD34(+) progenitor cells were synchronized and assayed for adhesion and migration onto fibronectin (Fn) and vascular cell adhesion molecule-1 (VCAM-1) at different stages of a first cell cycle executed ex vivo. During S phase transit, adhesion to Fn was transiently increased while binding to VCAM-1 was reversibly decreased, after which adhesion to both ligands returned to baseline levels with cell cycle completion. Transmigration across Fn and VCAM-1 decreased irreversibly during S phase progression. The function of alpha4 and alpha5 integrins was assessed with specific neutralizing antibodies. In uncultured CD34(+) cells and long-term culture-initiating cells (LTC-ICs), both adhesion and migration on Fn were inhibited by anti-alpha4 but not by anti-alpha5 antibodies. In mitotically activated CD34(+) cells and LTC-ICs, adhesion and migration on Fn were mainly dependent on alpha5 integrin and to a lesser extent on alpha4 integrin. Changes in integrin function were not dependent on parallel modulation of integrin expression. In conclusion, Fn and VCAM-1 binding of progenitor cells fluctuates reversibly during cell cycle transit ex vivo. In addition, our data show that mitogenic activation induces a shift from a dominant alpha4 to a preferential alpha5 integrin-dependent interaction with Fn.
mesh_terms: D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D002448:Cell Adhesion / Q000502:physiology*; D018929:Cell Culture Techniques / Q000379:methods; D002453:Cell Cycle / Q000502:physiology*; D002478:Cells, Cultured; D036861:Delivery, Obstetric; D005312:Fetal Blood / Q000166:cytology*; D005353:Fibronectins / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D013997:Time Factors; D019010:Vascular Cell Adhesion Molecule-1 / Q000502:physiology*
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34; D005353:Fibronectins; D019010:Vascular Cell Adhesion Molecule-1