Objective: To study the effects on adherence of hematopoietic stem/progenitor cells, PF4 was assessed alone or in combination with IL-3 for effects on the total adherence and various kinds of adhesion molecules of KG1a cells as well as actin polymerization in KG1a cells.
Methods: The total adherence was assayed by crystal violet dye staining. The adhesion molecule expression was determined by FACS analysis. These adhesion molecule monoclonal antibodies individually blocked total adherence by MTT. F-actin content was monitored by fluorospectrophotometry.
Results: 100 ng/ml PF4 could increase the total adherence of KG1a cells by 80%. 20 ng/ml IL-3 could increase the total adherence of KG1a cells by 96%. When PF4 and IL-3 were combined, the total adherence could be promoted by 97%. Exposure of 1 x 10(6) cells/ml of KG1a cells to 100 ng/ml PF4 the increased total adherence of KG1a cells was mediated by PECAM-1 (CD31), CD44, LFA-1 (CD11a) and Mac-1 (CD11b) but not by P-selectin (CD62P) and E-selectin (CD62E). These adhesion molecule monoclonal antibodies could individually block total adherence for 34%-43%. Similar phenomenon was observed when IL-3 was added onto KG1a cells. Further study found that PF4 induced actin polymerization of KG1a cells.
Conclusions: Our study indicated that PF4 promoted total adherence, as well as several adhesion molecule expression and actin polymerization of KG1a cells. The results suggest that PF4 may have therapeutic utility along with other cytokines by enhancing the total adhesion of hematopoietic stem/progenitor cells to promote the homing.