title: Endogenous relaxin is a naturally occurring modulator of experimental renal tubulointerstitial fibrosis.
abstract: Relaxin is a naturally occurring regulator of collagen turnover. In this study, we determined the role of endogenous relaxin in the pathogenesis of primary tubulointerstitial fibrosis after unilateral ureteric obstruction (UUO). Four- to 6-wk-old relaxin (RLX) gene-knockout (RLX(-/-)) and age-matched wild-type (RLX(+/+)) mice, with equivalent baseline collagen levels, were subjected to UUO. Obstructed and contralateral kidneys were collected at d 0, 3, and 10 after surgery and analyzed for changes in inflammatory and fibrosis-related markers. UUO was associated with a progressive increase in fibrosis in all obstructed, but not contralateral kidneys. The increase in total collagen (hydroxyproline analysis) was associated with more alpha-smooth muscle actin (alpha-SMA) staining (myofibroblasts) and interstitial collagen sub-types (SDS-PAGE; types I, III, and V), whereas gelatin zymography demonstrated increased expression of matrix metalloproteinase-2 after surgery. By d 10 after UUO, there was a 5-fold decrease in RLX mRNA expression (quantitative RT-PCR) in RLX(+/+) animals. Total collagen and alpha-SMA expression were significantly greater in the obstructed kidneys of RLX(-/-) mice 3 d after UUO (both P < 0.05 vs. RLX(+/+) D3 after UUO), but comparable to that in RLX(+/+) animals 10 d after UUO. Administration of recombinant H2 relaxin to RLX(-/-) mice 4 d before UUO ameliorated the increase in collagen and alpha-SMA expression (both P < 0.05 vs. untreated RLX(-/-) mice) by d 3 after UUO. Expression of monocyte chemoattractant protein-1 and macrophage infiltration (inflammation) in addition to that of matrix metalloproteinases was unaffected by genotype after UUO. These combined data demonstrate that endogenous RLX acts as a modulating factor in tubulointerstitial fibrosis, a hallmark of progressive renal disease. This is likely to be via direct effects on renal myofibroblast function.
authors.affiliation: Howard Florey Institute, University of Melbourne, Parkville, Victoria 3010, Australia. c.samuel@hfi.unimelb.edu.au
authors.forename: Tim D
authors.initials: TD
authors.lastname: Hewitson
authors.forename: Ishanee
authors.initials: I
authors.lastname: Mookerjee
authors.forename: Rosemary
authors.initials: R
authors.lastname: Masterson
authors.forename: Chongxin
authors.initials: C
authors.lastname: Zhao
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Tregear
authors.forename: Gavin J
authors.initials: GJ
authors.lastname: Becker
authors.forename: Chrishan S
authors.initials: CS
authors.lastname: Samuel
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D003094:Collagen / Q000378:metabolism; D018450:Disease Progression; D005347:Fibroblasts / Q000473:pathology; D005355:Fibrosis; D006801:Humans; D007668:Kidney / Q000378:metabolism; D007674:Kidney Diseases / Q000209:etiology* / Q000378:metabolism / Q000473:pathology*; D007684:Kidney Tubules / Q000473:pathology*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000473:pathology; D009395:Nephritis, Interstitial / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D009994:Osmolar Concentration; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D012065:Relaxin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014517:Ureteral Obstruction / Q000150:complications* / Q000378:metabolism
chemical_list: D000199:Actins; C095068:RLN2 protein, human; D012333:RNA, Messenger; D011994:Recombinant Proteins; C492607:Rln1 protein, mouse; D012065:Relaxin; D003094:Collagen; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9