Early proliferation of umbilical cord blood cells from premature neonates.
OBJECTIVE
Human umbilical cord blood (UCB) is an important source of haematopoietic stem cells; however, the behaviour of progenitor cells obtained from premature and full-term neonates is still a controversy subject. Thus, the aim of this study was to evaluate cell cycle parameters and the proliferative capacity of UCB progenitor cells from premature and full-term neonates.


METHODS
Clonogenic assays were performed with methylcellulose, medium supplemented with recombinant stimulating growth factors and the colonies were scored on the seventh day and the 14th day of culture. A cell cycle study was carried out by DNA analysis using flow cytometry and 30 000 events were acquired; p107 and p130 expressions were analysed by Western blotting.


RESULTS
Cultures obtained from UCB of premature neonates showed an early growth of colony-forming unit (CFU)-burst forming unit erythroid/CFU-granulocyte, erythrocyte, macrophage and megakaryocyte (BFU-E/GEMM), and CFU-granulocyte, macrophage (GM) by the seventh day of culture (P < 0.001). Therefore, the number and morphological characteristics of these colonies were comparable with those obtained from full-term neonates, on the 14th day of culture. At the 14th day, a large amount of CFU-GM was detected in the premature group (P < 0.0032). The premature culture on the 14th day showed fibroblasts and was comparable to those of full-term neonates on the 21st day in terms of number and morphology of the colonies. DNA analysis showed that the number of cells in S-phase was also higher in premature samples when compared to full-term neonates, P < 0.0021 (0 h = 12.8 vs. 2.5%; 16 h = 10.5 vs. 5.9%; 20 h = 13.5 vs. 10.3%; 24 h = 13.8 vs. 9.1%; 48 h = 14.0 vs. 5.4%; 72 h = 20.5 vs. 8.9%; 96 h = 13.8 vs. 7.7%). The Western blotting results demonstrated that p107 and p130 cell cycle protein expressions were higher in premature cells than in full-term cells.


CONCLUSIONS
These results suggest that the higher capacity of proliferation and early differentiation of premature UCB might not be related only to the amount of stem/progenitor cells but also to a different timing of cell cycle entry.
Hemocentro and Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), CEP 13083-970 Campinas, São Paulo, Brazil.
A C M
AC
Luzo
A S S
AS
Duarte
T S I
TS
Salles
M L S
ML
Queiroz
I
I
Lorand-Metze
F F
FF
Costa
S T O
ST
Saad
D002453:Cell Cycle; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004247:DNA / Q000032:analysis; D005312:Fetal Blood / Q000166:cytology*; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood*
D004247:DNA