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Renal fibrosis is not reduced by blocking transforming growth factor-β signaling in matrix-producing interstitial cells.

Neelisetty S, Alford C, Reynolds K, Woodbury L, Nlandu-Khodo S, Yang H, Fogo AB, Hao CM, Harris RC, Zent R, Gewin L - Kidney Int. (2015)

Bottom Line: To address this, we deleted the TGF-β type II receptor in matrix-producing interstitial cells using two different inducible Cre models: COL1A2-Cre with a mesenchymal enhancer element and tenascin-Cre that targets medullary interstitial cells, and either the mouse unilateral ureteral obstruction or the aristolochic acid renal injury model.Renal interstitial cells lacking the TGF-β receptor had significantly impaired collagen I production, but, unexpectedly, overall tissue fibrosis was unchanged in the conditional knockouts after renal injury.Thus, abrogating TGF-β signaling in matrix-producing interstitial cells is not sufficient to reduce fibrosis after renal injury.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology, Department of Medicine, Vanderbilt Medical Center, Nashville, Tennessee, USA.

ABSTRACT
Transforming growth factor-β (TGF-β) strongly promotes renal tubulointerstitial fibrosis, but the cellular target that mediates its profibrotic actions has not been clearly identified. While in vitro data suggest that TGF-β-induced matrix production is mediated by renal fibroblasts, the role of these cells in TGF-β-dependent tubulointerstitial fibrosis following renal injury is not well defined. To address this, we deleted the TGF-β type II receptor in matrix-producing interstitial cells using two different inducible Cre models: COL1A2-Cre with a mesenchymal enhancer element and tenascin-Cre that targets medullary interstitial cells, and either the mouse unilateral ureteral obstruction or the aristolochic acid renal injury model. Renal interstitial cells lacking the TGF-β receptor had significantly impaired collagen I production, but, unexpectedly, overall tissue fibrosis was unchanged in the conditional knockouts after renal injury. Thus, abrogating TGF-β signaling in matrix-producing interstitial cells is not sufficient to reduce fibrosis after renal injury.

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COL-Cre;Tgfbr2fl/fl mice are not protected from fibrosis 5 weeks after aristolochic acid. (A) Frozen sections of COL-Cre+ cells (green fluorescence) in COL-Cre;Tgfbr2fl/fl mice with mT/mG reporter. (B) H&E staining and (C) collagen I and F4/80 staining were performed on COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl kidneys after aristolochic acid injury. (D) Immunoblots of collagen I and FAK (loading control) of renal cortical lysates after aristolochic acid administration and quantified by densitometry (E). F4/80+ area was quantified using Image J on 10 high powered fields per mouse, n=4 per genotype (F).
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Figure 7: COL-Cre;Tgfbr2fl/fl mice are not protected from fibrosis 5 weeks after aristolochic acid. (A) Frozen sections of COL-Cre+ cells (green fluorescence) in COL-Cre;Tgfbr2fl/fl mice with mT/mG reporter. (B) H&E staining and (C) collagen I and F4/80 staining were performed on COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl kidneys after aristolochic acid injury. (D) Immunoblots of collagen I and FAK (loading control) of renal cortical lysates after aristolochic acid administration and quantified by densitometry (E). F4/80+ area was quantified using Image J on 10 high powered fields per mouse, n=4 per genotype (F).

Mentions: Medullary and cortical fibroblasts are distinct populations,(16, 29) and UUO targets the collecting system with a predominance of medullary interstitial cells (Figure 1B, 2A). We then assessed the role of TGF-β signaling in MPIC after a cortical injury as heterogeneous responses to TGF-β1 have been noted by subpopulations of renal interstitial cells.(30) We injured COL-Cre;Tgfbr2fl/fl mice with aristolochic acid which targets the proximal tubule acutely, produces a delayed TGF-β-dependent fibrotic response, and causes end-stage renal disease in humans.(31, 32) Five weeks after aristolochic acid injections, there was an increased number of COL-Cre cells which was particularly robust in the cortico-medullary and medullary regions (Figure 7A). Both the COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl mice had dilated cortical tubules with casts, an inflammatory infiltrate, and expansion of interstitial matrix (Figure 7B). Collagen I expression by immunoblots and macrophage infiltration by immunohistochemistry were similarly increased in injured COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl mice (Figure 7C–F). Therefore, abrogating TGF-β signaling in COL-Cre+ cells did not alter the fibrotic response to either a medullary or cortical renal injury.


Renal fibrosis is not reduced by blocking transforming growth factor-β signaling in matrix-producing interstitial cells.

Neelisetty S, Alford C, Reynolds K, Woodbury L, Nlandu-Khodo S, Yang H, Fogo AB, Hao CM, Harris RC, Zent R, Gewin L - Kidney Int. (2015)

COL-Cre;Tgfbr2fl/fl mice are not protected from fibrosis 5 weeks after aristolochic acid. (A) Frozen sections of COL-Cre+ cells (green fluorescence) in COL-Cre;Tgfbr2fl/fl mice with mT/mG reporter. (B) H&E staining and (C) collagen I and F4/80 staining were performed on COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl kidneys after aristolochic acid injury. (D) Immunoblots of collagen I and FAK (loading control) of renal cortical lysates after aristolochic acid administration and quantified by densitometry (E). F4/80+ area was quantified using Image J on 10 high powered fields per mouse, n=4 per genotype (F).
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Related In: Results  -  Collection

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Figure 7: COL-Cre;Tgfbr2fl/fl mice are not protected from fibrosis 5 weeks after aristolochic acid. (A) Frozen sections of COL-Cre+ cells (green fluorescence) in COL-Cre;Tgfbr2fl/fl mice with mT/mG reporter. (B) H&E staining and (C) collagen I and F4/80 staining were performed on COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl kidneys after aristolochic acid injury. (D) Immunoblots of collagen I and FAK (loading control) of renal cortical lysates after aristolochic acid administration and quantified by densitometry (E). F4/80+ area was quantified using Image J on 10 high powered fields per mouse, n=4 per genotype (F).
Mentions: Medullary and cortical fibroblasts are distinct populations,(16, 29) and UUO targets the collecting system with a predominance of medullary interstitial cells (Figure 1B, 2A). We then assessed the role of TGF-β signaling in MPIC after a cortical injury as heterogeneous responses to TGF-β1 have been noted by subpopulations of renal interstitial cells.(30) We injured COL-Cre;Tgfbr2fl/fl mice with aristolochic acid which targets the proximal tubule acutely, produces a delayed TGF-β-dependent fibrotic response, and causes end-stage renal disease in humans.(31, 32) Five weeks after aristolochic acid injections, there was an increased number of COL-Cre cells which was particularly robust in the cortico-medullary and medullary regions (Figure 7A). Both the COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl mice had dilated cortical tubules with casts, an inflammatory infiltrate, and expansion of interstitial matrix (Figure 7B). Collagen I expression by immunoblots and macrophage infiltration by immunohistochemistry were similarly increased in injured COL-Cre;Tgfbr2fl/fl and Tgfbr2fl/fl mice (Figure 7C–F). Therefore, abrogating TGF-β signaling in COL-Cre+ cells did not alter the fibrotic response to either a medullary or cortical renal injury.

Bottom Line: To address this, we deleted the TGF-β type II receptor in matrix-producing interstitial cells using two different inducible Cre models: COL1A2-Cre with a mesenchymal enhancer element and tenascin-Cre that targets medullary interstitial cells, and either the mouse unilateral ureteral obstruction or the aristolochic acid renal injury model.Renal interstitial cells lacking the TGF-β receptor had significantly impaired collagen I production, but, unexpectedly, overall tissue fibrosis was unchanged in the conditional knockouts after renal injury.Thus, abrogating TGF-β signaling in matrix-producing interstitial cells is not sufficient to reduce fibrosis after renal injury.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology, Department of Medicine, Vanderbilt Medical Center, Nashville, Tennessee, USA.

ABSTRACT
Transforming growth factor-β (TGF-β) strongly promotes renal tubulointerstitial fibrosis, but the cellular target that mediates its profibrotic actions has not been clearly identified. While in vitro data suggest that TGF-β-induced matrix production is mediated by renal fibroblasts, the role of these cells in TGF-β-dependent tubulointerstitial fibrosis following renal injury is not well defined. To address this, we deleted the TGF-β type II receptor in matrix-producing interstitial cells using two different inducible Cre models: COL1A2-Cre with a mesenchymal enhancer element and tenascin-Cre that targets medullary interstitial cells, and either the mouse unilateral ureteral obstruction or the aristolochic acid renal injury model. Renal interstitial cells lacking the TGF-β receptor had significantly impaired collagen I production, but, unexpectedly, overall tissue fibrosis was unchanged in the conditional knockouts after renal injury. Thus, abrogating TGF-β signaling in matrix-producing interstitial cells is not sufficient to reduce fibrosis after renal injury.

Show MeSH
Related in: MedlinePlus