Mesangial cell proliferation mediated by PDGF and bFGF is determined by levels of the cyclin kinase inhibitor p27Kip1.
Mesangial cell proliferation in vitro is regulated by many cytokines. Platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) are potent mesangial cell mitogens, whereas transforming growth factor-beta1 (TGF-beta1) reduces their effects. We examined how these cytokines regulate rat mesangial cell proliferation at the level of the cell-cycle. Quiescent mesangial cells in vitro express the cyclin kinase inhibitor, p27Kip1 (p27), and PDGF- and bFGF-induced mesangial cell proliferation is associated with a substantial decrease in p27 levels. Consequently there is a marked increase in expression (Western blot analysis, immunostaining) of cyclin A and CDK2. The decline in p27 levels was prevented by TGF-beta1 during inhibition of PDGF- and bFGF-induced mesangial cell proliferation. To determine the functional role of p27 during cytokine-mediated mesangial cell proliferation, the expression of p27 was reduced with specific p27Kip1 antisense oligodeoxynucleotides. Reducing the levels of p27 resulted in an increased magnitude of mesangial cell proliferation (BrdU and 3H-thymidine incorporation) induced by PDGF and bFGF compared to non-transfected mesangial cells and mesangial cells transfected with control mismatch oligodeoxynucleotides. Furthermore, the onset of maximal proliferation occurred earlier in mesangial cells transfected with antisense compared to control. The reduction in proliferation by TGF-beta1 were not altered by decreased p27 expression. Reducing p27 expression in the absence of mitogens was not associated with entry into the cell-cycle. These results suggest cytokine mediated mesangial cell proliferation is associated with specific cell-cycle proteins, and that the levels of p27 may be important in determining the mesangial cell's proliferative response to PDGF and bFGF in vitro.
Shankland
S J
SJ
Department of Nephrology, University of Washington, Seattle 98195, USA. stuartjs@u.washington.edu
Pippin
J
J
Flanagan
M
M
Coats
S R
SR
Nangaku
M
M
Gordon
K L
KL
Roberts
J M
JM
Couser
W G
WG
Johnson
R J
RJ
D000818:Animals; D001483:Base Sequence; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D025521:Tumor Suppressor Proteins
C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D016213:Cyclins; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D016376:Oligonucleotides, Antisense; D010982:Platelet-Derived Growth Factor; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D016222:Fibroblast Growth Factor 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases