Simulated glomerular hypertension promotes mesangial cell apoptosis and expression of cathepsin-B and SGP-2.
BACKGROUND
Focal glomerulosclerosis (FGS) is characterized by the accumulation of mesangial matrix and lack of mesangial cells (MC). We studied the role of glomerular hypertension (GH) in the development of MC hypoplasia.


METHODS
We used an in vitro model of GH to study the effect of GH on MC apoptosis. Cultured rat endothelial cells were grown in the intracapillary space and MCs were grown in the extracapillary space. MC proliferation as well as apoptosis was evaluated under simulated normal glomerular pressure (SNGP) as well as simulated glomerular hypertension (SGH). Apoptosis was determined morphologically by DNA fragmentation using Hoechst staining as well as with the use of DNA gel electrophoresis. MCs grown under SNGP and SGH were also evaluated for the expression of genes associated with active cell death. In addition, we evaluated the effect of direct applied pressure on MC apoptosis.


RESULTS
MCs grown under SGH were less elliptical and had a tendency to develop a dome in the center. Direct applied pressure promoted MC apoptosis in a dose and time dependent manner. DNA gel electrophoresis from MCs grown under SGH also showed integer multiples of 180 base pairs (ladder pattern); whereas cells grown under SNGP showed no DNA fragmentation. SGH increased mRNA expression of cathepsin-B (SNGP, 0.31 +/- 0.04 vs SGH, 0.57 +/- 0.03, P < 0.01, n = 3) and SGP-2 (SNGP, 0.55 +/- 0.05 vs SHG, 1.08 +/- 0.12, P < 0.01, n = 3) in MCs when compared to cells grown under SNGP.


CONCLUSIONS
The present in vitro study suggests that GH has the potential to convert a hypercellular mesangium into a hypocellular one. This effect of GH is associated with expression of genes associated with active cell death.
Singhal
P C
PC
Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, NY 11040, USA.
Gibbons
N
N
Franki
N
N
Reddy
K
K
Sharma
P
P
Mattana
J
J
Wagner
J D
JD
Bansal
V
V
D000818:Animals; D017209:Apoptosis; D002401:Cathepsin B / Q000235:genetics; D002478:Cells, Cultured; D051152:Clusterin; D015870:Gene Expression; D005920:Glomerular Mesangium / Q000378:metabolism / Q000473:pathology*; D006023:Glycoproteins / Q000235:genetics; D006977:Hypertension, Renal / Q000235:genetics / Q000473:pathology*; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D018832:Molecular Chaperones; D011312:Pressure; D051381:Rats
D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D002401:Cathepsin B