Effects of platelet-derived growth factor on the ex vivo expansion of cord blood CD34+ cells

Platelet-derived growth factor (PDGF) is a major mitogen for connective tissues. It also regulates the red cell and megakaryocytic lineages. In this study, we investigated the role of PDGF on the expansion of enriched human cord blood CD34+ cells (MACS, purity 95.1 ± 0.71%, N=7) in liquid culture. These cells were cultured at 4–5 x104/ml with various cytokine combinations, composing of TPO (50ng/ml), IL-1β (20ng/ml), IL-3 (20ng/ml), IL-6 (20ng/ml), Flt-3L (20ng/ml) in the presence or absence of PDGF (50ng/ml). Our results showed that PDGF in combination with TPO, IL-6 and Flt-3L induced the maximal CD34+ and CD34+CD38- cell expansion (Table, ± PDGF, # = p < 0.05). TPO+IL-1β+IL-3+IL-6+Flt-3L produced the maximal expansion of megakaryocytic progenitors (CD61+CD41+ cells and CFU-MK) which were again significantly increased in the presence of PDGF (CFU-MK: 32.3 ± 5.42 fold vs 51.2 ±10.9 fold, p<0.05 at day 7 and 346 ± 122 fold vs 483 ± 175 fold p = 0.063 at day 14). Our data demonstrated that PDGF is a novel growth factor supporting the expansion of cord blood CD34+ cells. PDGF may affect hematopoietic cells directly or via the release of growth factors by contaminating cells of the connective origin.