Epidermal growth factor suppresses renal tubular apoptosis following ureteral obstruction.
OBJECTIVE
Acute unilateral ureteral obstruction (UUO) results in ipsilateral hydronephrosis characterized by a decrease in epidermal growth factor (EGF) mRNA expression and EGF protein levels in the distal renal tubules. UUO results in programmed cell death with increases in the characteristic markers of apoptosis. To suppress the apoptotic response during UUO, recombinant EGF was administered during renal obstruction and the ensuing molecular and histologic changes were studied.


METHODS
Mature Sprague-Dawley rats underwent left ureteral obstruction and the kidneys were harvested at 24, 48, and 72 hours. Markers of apoptosis included DNA laddering pattern on agarose gel electrophoresis, in situ gap labeling of fragmented DNA for quantitative apoptotic body determination, polyadenylated mRNA expression of SGP-2, and in situ hybridization for sulfated glycoprotein-2 (SGP-2) mRNA. Studies were repeated in rats following administration of 10, 20, and 40 micrograms of subcutaneous recombinant EGF on a daily basis after UUO.


RESULTS
Subcutaneous injection of EGF into unilaterally obstructed rats promotes renal tubular epithelial cell regeneration, as demonstrated by increased cortical mitotic activity. Systemic EGF supplementation in these unilaterally obstructed rats also resulted in a decrease in the intensity of the DNA laddering pattern associated with renal tubular apoptosis. An in situ labeling procedure to identify apoptotic nuclei in the ureterally obstructed kidneys revealed a 50% reduction in apoptosis after EGF administration. Northern blot analysis and in situ hybridization for SGP-2 mRNA or clustering gene product also revealed a decreased expression in the obstructed and EGF-treated renal parenchyma.


CONCLUSIONS
These data suggest that EGF, apart from its known role as a mitogenic substance for renal tubular epithelial cells, is also a critical in vivo renal cell survival factor for the developmentally mature kidney.
Kennedy
W A
WA
Department of Urology, College of Physicians and Surgeons, Columbia University, New York, New York, USA.
Buttyan
R
R
Garcia-Montes
E
E
D'Agati
V
V
Olsson
C A
CA
Sawczuk
I S
IS
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051152:Clusterin; D053938:DNA Fragmentation; D004815:Epidermal Growth Factor / Q000494:pharmacology / Q000502:physiology*; D006023:Glycoproteins / Q000096:biosynthesis; D007684:Kidney Tubules / Q000166:cytology* / Q000187:drug effects; D018832:Molecular Chaperones; D051381:Rats; D017207:Rats, Sprague-Dawley; D014517:Ureteral Obstruction / Q000378:metabolism* / Q000473:pathology
D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D004815:Epidermal Growth Factor