The effect of hypoxia and stem cell source on haemoglobin switching.
This study investigated whether relative changes that accompany the naturally occurring shifts in haematopoietic sites during human development play a role in haemoglobin (Hb) switching or whether Hb switching is innately programmed into cells. CD34(+)/Lineage(-) haematopoietic stem/progenitor cells (HSCs) were isolated from human fetal liver (F-LVR), cord blood (CB), and adult bone marrow (ABM), and the Hb was characterized by flow cytometry on cultures that generated enucleated red cells. All feeder layers (stroma from F-LVR, ABM, and human fetal aorta) enhanced cell proliferation and erythropoiesis but did not affect Hb type. HSCs from CB and F-LVR generated the same Hb profile under normoxia and hypoxia. HSCs from ABM had single-positive HbA and double-positive HbA and HbF cells at normoxia and almost entirely double-positive cells at hypoxia. Further characterization of these ABM cultures was determined by following mRNA expression for the transcription factors erythroid Kruppel-like factor (EKLF) and fetal Kruppel-like factor (FKLF) as a function of time in cultures under hypoxia and normoxia. The erythroid-specific isoform of 5-amino-levulinate synthase (ALAS2) was also expressed under hypoxic conditions. We conclude that Hb switching is affected by the environment but not all HSCs are preprogrammed to respond.
Narayan
A Daisy
AD
Department of Animal Biotechnology, University of Nevada, Reno, NV 89557, USA. daisy@med.unr.edu
Ersek
Adel
A
Campbell
Thomas A
TA
Colón
Donna M
DM
Pixley
John S
JS
Zanjani
Esmail D
ED
D000328:Adult; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D019070:Cell Lineage / Q000502:physiology; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004920:Erythropoiesis / Q000502:physiology*; D005312:Fetal Blood / Q000166:cytology; D005319:Fetal Hemoglobin / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006441:Hemoglobin A / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000166:cytology / Q000196:embryology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016895:Culture Media, Serum-Free; D006441:Hemoglobin A; D005319:Fetal Hemoglobin