Expression of Vascular Endothelial Growth Factor Receptor 1 in Bone Marrow-derived Mesenchymal Cells Is Dependent on Hypoxia-inducible Factor 1

Balaji Krishnamachary,Gregg L Semenza,Yi Fu Zhou,Marta Bosch-Marce,Hiroaki Okuyama,Hideko Nagasawa

doi:10.1074/jbc.m602003200

Abstract

Bone marrow-derived cells are recruited to sites of ischemia, where they promote tissue vascularization. This response is dependent upon the expression of vascular endothelial growth factor (VEGF) receptor 1 (VEGFR1), which mediates cell migration in response to VEGF or placental growth factor (PLGF). In this study, we found that exposure of cultured mouse bone marrow-derived mesenchymal stromal cells (MSC) to hypoxia or an adenovirus encoding a constitutively active form of hypoxia-inducible factor 1 (HIF-1) induced VEGFR1 mRNA and protein expression and promoted ex vivo migration in response to VEGF or PLGF. MSC in which HIF-1 activity was inhibited by a dominant negative or RNA interference approach expressed markedly reduced levels of VEGFR1 and failed to migrate or activate AKT in response to VEGF or PLGF. Thus, loss-of-function and gain-of-function approaches demonstrated that HIF-1 activity is necessary and sufficient for basal and hypoxia-induced VEGFR1 expression in bone marrow-derived MSC.

Highlights

Bone marrow cells are mobilized into peripheral blood and recruited to sites of ischemia, where they participate in tissue repair and revascularization [1,2,3,4,5,6]
Characterization of mesenchymal stromal cells (MSC) Derived from Bone Marrow of C57BL/6 Mice—Mononuclear cells were isolated from bone marrow of C57BL/6 mice and cultured on uncoated dishes in DMEM with 10% FBS to isolate MSC
Because the antibody used in the immunoblot assay was raised against human HIF-2␣ protein, it was possible that the failure to detect HIF-2␣ protein in murine MSC was hypoxiainducible factor 1 (HIF-1) Is Required for VEGFR1 Expression in Bone Marrow-derived MSC—Given the important role of VEGFR1 in the recruitment of bone marrow-derived cells to sites of ischemia, we investigated whether HIF-1 played a role in the transcriptional regulation of VEGFR1 expression in mouse MSC

Summary

Introduction

Bone marrow cells are mobilized into peripheral blood and recruited to sites of ischemia, where they participate in tissue repair and revascularization [1,2,3,4,5,6]. Mobilization and recruitment of bone marrow cells to sites of ischemia is dependent upon vascular endothelial growth factor (VEGF) receptor 1 (VEGFR1) activity [15]. VEGFR1, which is encoded by the Flt gene in mice, binds VEGF and placental growth factor (PLGF), is expressed by multiple bone marrow-derived cell types, and plays a critical role in cell migration. VEGFR2, which is encoded by the Flk gene in mice, binds VEGF but not PLGF, is expressed by endothelial cells and their progenitors, and is required for their survival, proliferation, and differentiation [16, 17]. In human umbilical vein endothelial cells (HUVEC), transcription directed by the VEGFR1 gene promoter is induced by hypoxia, an effect that is dependent upon a cis-acting hypoxia response element, which contains a putative binding site for hypoxiainducible factor 1 (HIF-1) [18]. Using gain-of-function and loss-of-function approaches, we demonstrate that HIF-1 plays an essential role in the regulation of both basal and hypoxia-induced expression of VEGFR1 in bone marrow-derived MSC

Objectives

Results

Conclusion