Hypoxia regulates PDGF-B interactions between glomerular capillary endothelial and mesangial cells.
BACKGROUND
Platelet-derived growth factor (PDGF)-B regulates mesangial cell and vessel development during embryogenesis, and contributes to the pathogenesis of adult renal and vascular diseases. Endothelial cell PDGF-B exerts paracrine effects on mesangial cells, but its regulation is not well defined. We examined the impact of hypoxia on PDGF-B-mediated interactions between glomerular endothelial and mesangial cells, a condition of potential relevance in developing, and diseased adult, kidneys.


METHODS
Glomerular endothelial or mesangial cells were subjected to hypoxia and responses compared to normoxic cells. Endothelial PDGF-B was studied by Northern and Western analysis. Mesangial proliferative responses to PDGF-B were assessed by (3)H-thymidine incorporation, and migration by a modified Boyden chamber assay. Hypoxia-induced changes in receptor specific binding capacity were studied by saturation binding assays.


RESULTS
Hypoxia stimulated increases in endothelial PDGF-B mRNA and protein. In normoxic mesangial cells, PDGF-B stimulated dose-dependent proliferation, but the proliferative response of hypoxic cells was two to three times greater. Exogenous PDGF-B also caused prompter migration in hypoxic mesangial cells. Mesangial cells were treated with endothelial cell-conditioned medium. More cells migrated when hypoxic cells were stimulated with hypoxic conditioned medium, than when normoxic cells were stimulated with normoxic conditioned medium. Preincubating conditioned medium with PDGF-B neutralizing antibody greatly decreased the chemoattractant activity. Binding studies demonstrated increased specific binding capacity in hypoxic cells.


CONCLUSIONS
Hypoxia enhances PDGF-B paracrine interactions between glomerular endothelial and mesangial cells. These hypoxia-regulated interactions may be important during glomerulogenesis in fetal life and during the pathogenesis of adult glomerular disease.
Eng
Eudora
E
Division of Nephrology and Hypertension, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA. e-eng@northwestern.edu
Holgren
Cory
C
Hubchak
Susan
S
Naaz
Parveen
P
Schnaper
H William
HW
D000818:Animals; D002417:Cattle; D002450:Cell Communication / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007678:Kidney Glomerulus / Q000098:blood supply / Q000166:cytology* / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D020574:Proto-Oncogene Proteins c-sis / Q000235:genetics / Q000378:metabolism*; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020574:Proto-Oncogene Proteins c-sis; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D020797:Receptor, Platelet-Derived Growth Factor beta