Novel role of 1,25(OH)(2)D(3) in induction of erythroid progenitor cell proliferation.
OBJECTIVE
Burst-forming unit erythroid and colony-forming unit erythroid growth in vitro is lower in studies of continuous ambulatory peritoneal dialysis patients than healthy controls. Burst-forming unit erythroid growth was potentiated by addition of 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and normalized by erythropoietin (Epo) therapy, suggesting an interaction between Epo and 1,25(OH)(2)D(3) at the stem cell level. The objective of this study was to determine the mechanism by which 1,25(OH)(2)D(3) enhances the stimulatory effect of Epo on the growth of erythroid precursor cells.


METHODS
We examined the effect of 1,25(OH)(2)D(3) and Epo on stem cell proliferation. Proliferation of TF1 cells of erythroid origin was measured by the XTT method, 3[H] thymidine incorporation, and cell counting by trypan blue exclusion; cord blood (CB) stem cells were counted. Epo receptor (EpoR) quantitation was evaluated by 125I-Epo binding and Scatchard analysis, immunoprecipitation, and Western blotting. Expression of EpoR mRNA was measured by reverse transcriptase polymerase chain reaction.


RESULTS
The stem cell factor-dependent CB stem cells and the TF1 cells responded to Epo and 1,25(OH)(2)D(3) by increased proliferation, while their simultaneous addition potentiated cell proliferation in a synergistic manner (25.67% +/- 4.8% of Epo proliferation at day 10 for CB cells; p < 0.005). 1,25(OH)(2)D(3) produced an up-regulation of EpoR number in TF1 cells and increased the expression of EpoR mRNA (p < 0.01).


CONCLUSIONS
The increase in EpoR expression induced by 1,25(OH)(2)D(3) might explain the synergistic interaction between Epo and 1,25(OH)(2)D(3) in stem cells.
Alon
Dora Ben
DB
Department of Clinical Biochemistry, Soroka University Medical Center and Ben-Gurion University of the Negev, Beer Sheva, Israel.
Chaimovitz
Cidio
C
Dvilansky
Alexander
A
Lugassy
Gilles
G
Douvdevani
Amos
A
Shany
Shraga
S
Nathan
Ilana
I
D000199:Actins / Q000235:genetics; D000954:Antigens, Surface / Q000378:metabolism; D002112:Calcifediol / Q000494:pharmacology*; D002117:Calcitriol / Q000494:pharmacology*; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D017931:DNA Primers; D004261:DNA Replication / Q000187:drug effects; D015672:Erythroid Precursor Cells / Q000166:cytology* / Q000187:drug effects; D004921:Erythropoietin / Q000235:genetics / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D010531:Peritoneal Dialysis, Continuous Ambulatory; D016133:Polymerase Chain Reaction; D012016:Reference Values; D013997:Time Factors; D014158:Transcription, Genetic
D000199:Actins; D000954:Antigens, Surface; D017931:DNA Primers; D004921:Erythropoietin; D002117:Calcitriol; D002112:Calcifediol