title: Collagen type I modulates the platelet-derived growth factor (PDGF) regulation of the growth and expression of beta1 integrins by rat mesangial cells.
abstract: Mesangial cell (MC) proliferation and the deposition of collagen type I (collagen I) are the major pathological features in many types of glomerulonephritis (GN). Recent work suggested that beta-integrins play a critical role in the cell proliferation and extracellular matrix (ECM) remodeling observed in tissue repair after injury. To examine the involvement of beta-integrins in MC proliferation in association with the interaction of MCs with pathological collagen I, we investigated the effect of a prominent mitogen, platelet-derived growth factor-BB (PDGF-BB) on the growth and expression of beta-integrins by MCs cultured on plastic or in a three-dimensional collagen I gel. Immunoprecipitation using 35S-metabolic labeling, flow cytometry and a 3H-thymidine-uptake analysis demonstrated that PDGF-BB stimulated the cell mitogenicity and the expression of alpha5beta1 integrin (a fibronectin receptor), but not alpha1beta1 integrin (a collagen and laminin receptor) of MCs on plastic, in a dose-dependent manner. In contrast, MCs in the collagen I gels showed no significant changes in mitogenicity or alpha1beta1 and alpha5beta1 integrin expression, but increased alpha1beta1 integrin-mediated gel contraction was observed after PDGF-BB stimulation. Thus, the parallel up-regulation of MC-mitogenicity and alpha5beta1 integrin expression by PDGF-BB suggested that alpha5beta1 integrin is an important ECM receptor involved in the proliferative phenotype of MC. A spatial interaction between MCs and pathological collagen I in GN may influence the PDGF regulation of the MC phenotype regarding the cell growth and the expression of beta1 integrins.
authors.affiliation: School of Medicine, University of Tokushima, Tokushima, 770-0042, Japan. kagami@medclin.clin.med.tokushima-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Kagami
authors.forename: S
authors.initials: S
authors.lastname: Kondo
authors.forename: K
authors.initials: K
authors.lastname: Löster
authors.forename: W
authors.initials: W
authors.lastname: Reutter
authors.forename: M
authors.initials: M
authors.lastname: Urushihara
authors.forename: A
authors.initials: A
authors.lastname: Kitamura
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Kuroda
mesh_terms: D000818:Animals; D000077214:Becaplermin; D002455:Cell Division; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D005920:Glomerular Mesangium / Q000166:cytology*; D019012:Integrin beta1 / Q000096:biosynthesis*; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D019012:Integrin beta1; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D000077214:Becaplermin; D003094:Collagen