Characterization of the effects and potential mechanisms leading to increased megakaryocytic differentiation under mild hyperthermia.
The physical culture parameters have important influences on the proliferation and differentiation fate of hematopoietic stem cells. Recently, we have demonstrated that CD34+ cord blood (CB) cells undergo accelerated and increased megakaryocyte (Mk) differentiation when incubated under mild hyperthermic conditions (i.e., 39 degrees C). In this study, we investigated in detail the impacts of mild hyperthermia on Mk differentiation and maturation, and explored potential mechanisms responsible for these phenomena. Our results demonstrate that the qualitative and quantitative effects on Mk differentiation at 39 degrees C appear rapidly within 7 days, and that early transient culture at 39 degrees C led to even greater Mk yields (p<0.03). Surprisingly, cell viability was only found to be significantly reduced in the early stages of culture, suggesting that CB cells are able with time to acclimatize themselves to 39 degrees C. Although mild hyperthermia accelerated differentiation and maturation of CB-derived Mks, it failed to promote their polyploidization further but rather led to a small reduction in the proportion of polyploid Mks (p=0.01). Conversely, gene arrays analysis demonstrated that Mks derived at 39 degrees C have a normal gene expression program consistent with an advanced maturation state. Finally, two independent mechanisms that could account for the accelerated Mk differentiation were investigated. Our results suggest that the accelerated and increased Mk differentiation induced by mild hyperthermia is not mediated by cell-secreted factors but could perhaps be mediated by the increased expression of Mk transcription factors.
Héma-Québec Research and Development Department, Québec City, PQ, Canada G1V 5C3. nicolas.pineaul@hema-quebec.qc.ca
Nicolas
N
Pineault
Jean-François
JF
Boucher
Marie-Pierre
MP
Cayer
Lars
L
Palmqvist
Lucie
L
Boyer
Réal
R
Lemieux
Chantal
C
Proulx
D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D005312:Fetal Blood / Q000166:cytology / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D018869:Heat-Shock Response / Q000187:drug effects; D006801:Humans; D008533:Megakaryocytes / Q000166:cytology* / Q000187:drug effects; D020411:Oligonucleotide Array Sequence Analysis; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011123:Polyploidy; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D016207:Cytokines; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D014157:Transcription Factors