Pyruvate dehydrogenase kinase 1 is essential for transplantable mouse bone marrow hematopoietic stem cell and progenitor function.
BACKGROUND
Accumulating evidence suggests that hypoxic areas in the bone marrow are crucial for maintenance of hematopoietic stem cells (HSCs) by supporting a quiescent state of cell cycle and regulating the transplantation capacity of long-term (LT)-HSCs. In addition, HSCs seem to express a metabolic profile of energy production away from mitochondrial oxidative phosphorylation in favor of glycolysis. At oxygen deprivation, hypoxia inducible factor 1α (HIF-1α) is known to induce glycolytic enzymes as well as suppressing mitochondrial energy production by inducing pyruvate dehydrogenase kinase 1 (Pdk1) in most cell types. It has not been established whether PDK1 is essential for HSC function and mediates hypoxia-adapting functions in HSCs. While the Pdk gene family contains four members (Pdk1-4), it was recently shown that Pdk2 and Pdk4 have an important role in regulating LT-HSCs.


RESULTS
Here we demonstrate that PDK1 activity is crucial for transplantable HSC function. Whereas Pdkl, Pdk2, and Pdk3 transcripts were expressed at higher levels in different subtypes of HSCs compared to differentiated cells, we could not detect any major differences in expression between LT-HSCs and more short-term HSCs and multipotent progenitors. When studying HIF-1α-mediated regulation of Pdk activity in vitro, Pdk1 was the most robust target regulated by hypoxia, whereas Pdk2, Pdk3, and Pdk4 were not affected. Contrary, genetic ablation in a cre-inducible Hif-1α knockout mouse did not support a link between HIF-1α and Pdk1. Silencing of Pdk1 by shRNA lentiviral gene transfer partially impaired progenitor colony formation in vitro and had a strong negative effect on both long-term and short-term engraftment in mice.


CONCLUSIONS
Our study demonstrates that PDK1 has broad effects in hematopoiesis and is a critical factor for engraftment of both HSCs and multipotent progenitors upon transplantation to recipient mice. While Pdk1 was a robust hypoxia-inducible gene mediated by HIF-1α in vitro, we could not find evidence of any in vivo links between Pdk1 and HIF-1α.
Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.|Linköping Integrative Regenerative Medicine Centre, Linköping University, Linköping, Sweden.
Camilla
C
Halvarsson
Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
Pernilla
P
Eliasson
Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.|Linköping Integrative Regenerative Medicine Centre, Linköping University, Linköping, Sweden.
Jan-Ingvar
http://orcid.org/0000-0003-4814-978X
JI
Jönsson
D000818:Animals; D001853:Bone Marrow / Q000378:metabolism / Q000502:physiology; D001854:Bone Marrow Cells / Q000502:physiology*; D016026:Bone Marrow Transplantation; D015687:Cell Hypoxia / Q000235:genetics; D002478:Cells, Cultured; D006019:Glycolysis / Q000235:genetics; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010085:Oxidative Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase
C000631433:Pdk1 protein, mouse; C000631435:Pdk2 protein, mouse; C000631437:Pdk3 protein, mouse; C000631439:Pdk4 protein, mouse; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D017346:Protein Serine-Threonine Kinases