Fibrinogen, acting as a mitogen for tubulointerstitial fibroblasts, promotes renal fibrosis

Abstract

Fibrinogen plays an important role in blood coagulation but its function extends far beyond blood clotting being involved in inflammation and repair. Besides these crucial functions it can also promote tissue fibrosis. To determine whether fibrinogen is involved in the development of renal tubulointerstitial fibrosis we utilized the profibrotic model of unilateral ureteral obstruction in fibrinogen-deficient mice. In the heterozygotes, obstruction was associated with a massive deposition of intrarenal fibrinogen. Fibrinogen deficiency provided significant protection from interstitial damage and tubular disruption, attenuated collagen accumulation, and greatly reduced de novo expression of α-smooth muscle actin in the obstructed kidney. While no differences were found in renal inflammatory cell infiltration, fibrinogen deficiency was associated with a significant reduction in interstitial cell proliferation, a hallmark of renal fibrosis. In vitro, fibrinogen directly stimulated renal fibroblast proliferation in a dose-dependent manner. This mitogenic effect of fibrinogen was mediated by at least three different cell surface receptors on renal fibroblasts: TLR2, TLR4, and ICAM-1. Thus, our study suggests that fibrinogen promotes renal fibrosis by triggering resident fibroblast proliferation.

Inflammation and Progression of CKD: The CRIC Study

“…Plasma fibrinogen may influence kidney function through its effect on the coagulation cascade, blood viscosity, and blood flow in the microcirculation (37). Fibrinogen is a receptor-mediated mitogen for renal fibroblasts and a possible facilitator of tubulointerstitial fibrosis (38). Association between low SAlb and progression of CKD has been reported (39).…”

Role of fibrinogen in acute ischemic kidney injury

“…Heterozygous mice have no overt phenotypic differences, but their levels of circulating fibrinogen are reduced to 70% (39). Genotyping was done by PCR of tail biopsy genomic DNA, as previously described (39). All experimental procedures were in agreement with institutional and legislational regulations and were approved by the local authorities.…”

“…For cell adhesion assays, mPT cells were trypsinized and washed with DMEM containing 10% FCS (GIBCO-Invitrogen). After two washes with non-FCS-containing DMEM, equal numbers of cells were plated on uncoated or collagen type I-coated 24-well plates in the presence of the indicated concentrations of fibrinogen or albumin as a control protein diluted in DMEM for 2 h [protein concentrations were chosen according to our previous study (39)]. Cells were washed three times with PBS, and the total number of adherent cells was counted.…”

“…Mice used in this study were either wild-type male C57BL/6J mice (10-16 wk, Janvier, France) or previously described C57BL/6J mice with a genetic deletion of the fibrinogen A␣-chain lacking all components of fibrinogen in the circulation (39,40). Heterozygous mice have no overt phenotypic differences, but their levels of circulating fibrinogen are reduced to 70% (39). Genotyping was done by PCR of tail biopsy genomic DNA, as previously described (39).…”

“…Western blot analysis was performed as previously described (39). In brief, a representative part of each kidney was frozen in liquid nitrogen immediately after being harvested.…”