Cord blood stem cell expansion is permissive to epigenetic regulation and environmental cues.
OBJECTIVE
Augmentation of the number of cord blood (CB) hematopoietic stem cells (HSC) present in a unit is required before it can be considered as an alternative graft for hematopoietic reconstitution for adult patients. In order to further optimize strategies to augment HSC numbers, we examined whether expansion of HSC mediated by epigenetic mechanisms remains permissive to external environmental cues.


METHODS
The chromatin-modifying agents 5-aza-2'-deoxycytidine (5azaD) and trichostatin A (TSA) were used to ameliorate epigenetic alteration of CB cells during ex vivo culture by adding various cytokines. After culture, CD34(+)CD90(+) cell numbers, their division history, in vitro clonogenic potential, and in vivo hematopoietic reconstitution potential and frequency were determined.


RESULTS
5azaD/TSA-treated, CD34(+)CD90(+) cells were greatly influenced in terms of their degree of expansion, clonogenic potential, cell-division rate, and transplantability by the combination of cytokines used in culture. Furthermore, our current results verify that the sequential addition of 5azaD followed by TSA is crucial for expansion of HSC. We demonstrate that following 5azaD/TSA treatment, the rate of CD34(+)CD90(+) cell division is also dependent on the cytokine cocktail and that this is associated with functional changes, including alteration of in vitro clonogenic potential and in vivo reconstitution potential.


CONCLUSIONS
Our studies indicate there are interactions between intrinsic factors influenced by epigenetic mechanisms and external environmental signals in the regulation of HSC expansion. Epigenetic influences on HSC can be accentuated by environmental factors. Regulation of the rate of divisions may be a critical determinant for the maintenance of HSC functional potency during ex vivo expansion.
Araki
Hiroto
H
Section of Hematology/Oncology, Department of Medicine, University of Illinois at Chicago, Chicago IL 60607, USA.
Baluchamy
Sudhakar
S
Yoshinaga
Kazumi
K
Petro
Benjamin
B
Petiwala
Sakina
S
Parajuli
Ritesh
R
Milhem
Mohammed
M
Lavelle
Donald
D
DeSimone
Joseph
J
Mahmud
Nadim
N
D000328:Adult; D000818:Animals; D018952:Antigens, CD34; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D018929:Cell Culture Techniques; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D036101:Cord Blood Stem Cell Transplantation / Q000379:methods; D016207:Cytokines / Q000378:metabolism; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects / Q000502:physiology*; D005312:Fetal Blood / Q000166:cytology*; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D018800:Thy-1 Antigens; D014183:Transplantation, Heterologous; D014184:Transplantation, Homologous
D018952:Antigens, CD34; D016207:Cytokines; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; D018800:Thy-1 Antigens; C012589:trichostatin A; D000077209:Decitabine; D001374:Azacitidine