EGF-related growth factors in the pathogenesis of murine ARPKD

• Published in: Kidney international Vol. 65; no. 6; pp. 2018 - 2029
• Main Authors: DELL, Katherine Macrae, NEMO, Raghad, SWEENEY, William E, AVNER, Ellis D
• Format: Journal Article
• Language: English
• Published: New York, NY Nature Publishing 01-06-2004
• Subjects: Amphiregulin; Animals; Biological and medical sciences; Cell Division; Cyst Fluid - metabolism; Disease Models, Animal; EGF Family of Proteins; Epidermal Growth Factor - physiology; Glycoproteins - physiology; Heparin-binding EGF-like Growth Factor; Intercellular Signaling Peptides and Proteins - physiology; Kidney Tubules, Collecting - metabolism; Kidney Tubules, Collecting - pathology; Kidneys; Malformations of the urinary system; Medical sciences; Mice; Mice, Inbred BALB C; Mice, Mutant Strains; Mitogens - metabolism; Nephrology. Urinary tract diseases; Polycystic Kidney, Autosomal Recessive - etiology; Polycystic Kidney, Autosomal Recessive - genetics; Polycystic Kidney, Autosomal Recessive - pathology; Polycystic Kidney, Autosomal Recessive - physiopathology; Receptor, Epidermal Growth Factor - physiology; Transforming Growth Factor alpha - physiology; Binding; Kidney disease; Nephrology; Urinary system disease; amphiregulin; mouse models; immortalized cells; Pathogenesis; Polycystic kidney; Rodentia; Urology; Genetic disease; Vertebrata; Mammalia; Mouse; Animal; Cyst; polycystic kidney disease; heparin-binding EGF; Models; Benign neoplasm; Heparin; Cell; Growth factor
• ISSN: 0085-2538; 1523-1755
• DOI: 10.1111/j.1523-1755.2004.00623.x

Epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha) and their receptor, EGFR, play key roles in polycystic kidney disease (PKD) pathogenesis. Renal expression of two related growth factors, amphiregulin and heparin-binding EGF, has not been examined previously in PKD. The aims of this study of murine autosomal-recessive polycystic kidney disease (ARPKD) were (1) to characterize amphiregulin and heparin-binding EGF expression in cystic versus normal kidneys and cells; and (2) to identify the functional effects of abnormal EGF-related growth factor expression.
Amphiregulin and heparin-binding-EGF expression were examined by immunohistology and Western blot of kidneys and conditionally-immortalized collecting tubule cells obtained from cystic bpk mice (a murine model of ARPKD) and normal littermates. EGF, TGF-alpha, amphiregulin, and heparin-binding EGF in vitro effects on cystic and control collecting tubule cells were assessed by cell proliferation, cyst fluid mitogenicity, and EGFR activation.
By immunohistology, amphiregulin and heparin-binding EGF localized to apical and basolateral surfaces of proximal tubule cysts > normal proximal tubules. In cystic collecting tubules, heparin-binding EGF (but not amphiregulin) localized to both apical and basolateral surfaces; whereas in normal collecting tubules, amphiregulin and heparin-binding EGF localized to the basolateral surface only. Increased amphiregulin and heparin-binding EGF expression by Western blot was seen in cystic vs. normal kidneys and increased heparin-binding EGF (but not amphiregulin) expression was present in cystic collecting tubule cell lines vs. controls. EGF, TGF-alpha, amphiregulin, and heparin-binding EGF were all mitogenic to cystic > control collecting tubule cells. Immunoprecipitation of EGF and TGF-alpha reduced cyst fluid mitogenicity by almost 80%, whereas heparin-binding EGF and amphiregulin immunoprecipitations had minimal effects. Differential receptor activation was also seen: Heparin-binding EGF markedly activated EGFR (>EGF = TGF-alpha > amphiregulin), with a greater effect seen in cystic vs. control collecting tubule cells.
Multiple EGF-related growth factors are abnormally expressed in murine ARPKD and may have differential roles in disease pathogenesis. In particular, newly identified abnormalities in heparin-binding EGF expression in cystic kidneys and cells may have important implications for disease pathogenesis.