Loading...
 

Volume 34, Issue 4, December 2023



Sign in to download the Issue in PDF format.

Mediterr J Rheumatol 2022;33(2):176-84
TGF-β1/Smad Signalling in Proliferative Glomerulonephritis Associated with Autoimmune Diseases
Authors Information

1Nephrology Department, Hippokration General Hospital, Athens, Greece

21st Department of Pathology, National and Kapodistrian University of Athens, School of Medicine, Athens, Greece

32nd Department of Pathology, National and Kapodistrian University of Athens, School of Medicine, Athens, Attikon University Hospital, Athens, Greece

42nd Department of Medicine and Laboratory, Clinical Immunology - Rheumatology Unit, National and Kapodistrian University of Athens, School of Medicine, Athens, Greece

Abstract

Glomerulonephritis is a common cause of chronic kidney disease, which has emerged as a major cause of end-stage renal disease. Autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) and ANCA-associated vasculitis (AAV) are often associated with proliferative glomerulonephritis. Transforming growth factor-β1 (TGF-β1) is a cytokine with pleiotropic effects in chronic renal diseases, based on in vivo and in vitro studies. The Smad-dependent signalling pathway plays an important role in the regulation of renal fibrosis (excessive production of extracellular matrix [ECM]) and inflammation. However, clinical trials targeting TGF-β1 have presented disappointing results, suggesting that the downstream signalling is quite complex. The diversity of the effects may associate with the interactions between TGF-β1 signalling and other downstream signalling, as well as the different cellular responses, which TGF-β1 promotes. Recently, macrophage chemoattract and epigenetic effects have also been identified as new mechanisms, wherefore TGF-β1/Smad signalling mediates renal injury. This review provides an overview of the role of TGF-β1/Smad signalling pathway from in vivo and in vitro studies in the pathogenesis of glomerulonephritis and particularly in proliferative glomerulonephritis, which is associated with autoimmune diseases.

Cite this article as: Chalkia A, Gakiopoulou H, Theochari I, Foukas PG, Vassilopoulos D, Petras D. TGF-β1/Smad Signalling in Proliferative Glomerulonephritis Associated with Autoimmune Diseases. Mediterr J Rheumatol 2022;33(2):176-84

Article Submitted: 31 May 2021; Revised Form: 4 Sep 2021; Article Accepted: 15 Sep 2021; Available Online: 30 Jun 2022

https://doi.org/10.31138/mjr.33.2.176

This work is licensed under a Creative Commons Attribution 4.0 International License (CC-BY).

©Chalkia A, Gakiopoulou H, Theochari I, Foukas PG, Vassilopoulos D, Petras D.

Full Text

INTRODUCTION

The proliferative glomerulonephritis (GN) is characterised by glomerular infiltration by inflammatory cells, such as neutrophils and macrophages, and/or proliferation of resident glomerular cells. These cells may induce thrombosis, necrosis, and crescent formation, resulting in rapidly progressive GN.1 The renal injury includes humoral (B cell activation, plasma cells) and/or cellular (T-helper cells, mononuclear inflammatory cells) immune response. ANCA-associated vasculitis (AAV) and Systemic Lupus Erythematosus (SLE), and more rarely other autoimmune diseases, such as primary Sjogren’s syndrome (pSS), Rheumatoid arthritis (RA), Scleroderma (SS), are associated with proliferative GN.

Transforming growth factor-beta 1 (TGF-β1) is a multifunctional cytokine that regulates cell proliferation, differentiation, apoptosis and adhesion. Recent studies have also shown new mechanisms, whereby TGF-β can mediate renal injury, such as macrophage chemoattractant and epigenetic effects. 2,3 Although, the role of TGF-β1 in the pathogenesis of glomerulosclerosis and renal fibrosisin patients with podocytopathies, such as focal and segmental glomerulosclerosis (FSGS) has been demonstrated, the signalling is also activated in proliferative GN, and correlates with the severity of inflammation. 4,5

In AAV, probably after exposure to infectious agent, TGF-β1 and interleukin (IL)-6 are released from dendritic cells and induce differentiation of naïve T cells into T helper 17 (Th17) cells. Th17 produce IL-17 and stimulate macrophages to produce tumour necrosis factor (TNF)-a and IL-1β, which act as major priming factors to neutrophils.6,7 Therefore, neutrophils are activated and present the MPO or PR3 target antigens. In lupus nephritis, the immune complex deposition in glomeruli can activate inflammatory response, which can recruit inflammatory cells and activate the glomerular cells. Increased levels of TGF-β1 have been detected in lupus renal tissue, and a positive correlation with histological activity has been reported. 8,9 Recently, in SLE new targets of autoantibodies have been confirmed to interact with TGF-β1 signalling, such as Smad2 and Smad5 protein.10

Interestingly, recent studies have demonstrated the involvement of TGF-β/Smad signalling in pSS salivary glands (SG) as a mediator of the epithelial-mesenchymal transition (EMT) activation. Furthermore, pSS SGs biopsy specimens were characterised by an elevated expression of TGF-β1 in the glandular epithelium, and TGF-β1, pSMAD2/3, and SMAD4 proteins were widely expressed in the pSS tissue in patients.11 In RA TGF-β/Smad3 signalling was markedly activated in synovial tissues, which was associated with the loss of Smad7, and enhanced Th17 and Th1 immune response.12 TGF-β signalling also participates in the progression of fibrosis in SS. High levels of TGF-β1 and its regulated genes have been detected in skin biopsies and were positively correlated with the severity of SS.13

In this review, we present an image of the role of TGF-β signalling in the pathogenesis of glomerular injury, especially in proliferative GN associated with autoimmune diseases.

 

TGF-β1 and Smad pathway

While in the normal human kidney TGF-β1 is negligibly expressed, under pathological circumstances it is synthesised by many renal cells and contributes to glomerular filtration barrier alteration, fibrosis, sclerosis, and tubule degeneration.11 Many factors, such as high level of glucose, oxidate stress, and cytokines can stimulate transcription of the TGF-β1 gene. Furthermore, activated T and B cells, macrophages, neutrophils, immature hematopoietic cells, and dendritic cells also produce TGF-β1 and/or are sensitive to its effects.14

There are three isoforms of TGF-β present in mammals. Among them, TGF-β1 has reported as an important and crucial mediator in the pathogenesis of progressive renal fibrosis. 15-17 TGF-β1 is synthesised as a part of a biologically inactive complex and after proteolytic cleavage becomes available to bind to receptor complexes (TGFβRI) (Figure 1). Then, the canonical Smad signalling is activated.18 The Smad2 and Smad3 are phosphorylated and their complex translocate into the nucleus to modulate the transcription levels of target genes.19-21 Therefore, TGF-β1 induces transcription of several miRNA species, with some miRNAs showing profibrotic and other antifibrotic effects.21-23 Smad7 can compete with Smad2 and Smad3 for binding to activated TGFβR1 and thus serves as negative feedback inhibitor of TGF-β1/Smad canonical signalling.

Clinical trials in diabetic nephropathy, septic acute kidney injury and focal segmental glomerulosclerosis have examined the direct targeting of TGF-β1 with disappointing results, highlighting the diversity and complexity of TGF-β1 signalling in renal fibrosis and inflammation. 24 However, targeting downstream signalling by specifically inhibiting or overexpressing Smad3-dependent non-coding RNAs or rebalancing Smad3/Smad7 may be a better approach.24



Figure 1. TGF-β1 binds TβRII and activated Smad2 and Smad3, resulting in formation of a complex with Smad4. The Smad2/3/4 complex then translates into the nucleus and binds to the target genes to induce fibrosis and inflammation. TGF-β, transforming growth factor β; TβRI, TGF-β receptor type I; TβRII, TGF-β receptor type II (modified24)
 



Renal Fibrosis and TGF-β1

It is well accepted that TGF-β1/Smad signalling is a major pathway for renal fibrosis, synthetizing extracellular matrix (ECM) protein in both the glomerulus (glomerulosclerosis) and the tubulointerstitial tissue (interstitial fibrosis). Initials studies focused on this growth factor’s effects on fibroblasts via promoting activation of myofibroblasts.25 However, its role also includes proliferation, differentiation, hypertrophy, apoptosis, angiogenesis, cell cycle control, chemotaxis, and haematopoiesis.In experimental and human kidney diseases with renal fibrosis, regardless the initial cause of chronic kidney disease (CKD), TGF-β1 signalling is activated, such as diabetic nephropathy,26-28 obstructive kidney disease,29 ⅚ nephrectomy,30 hypertensive nephropathy,31 and glomerular diseases (IgA nephropathy, FSGS, lupus nephritis, crescentic GN). Transgenic mice with increased circulating levels of TGF-β1 developed glomerulosclerosis and those with increased tubular production of TGF-β1 developed tubulointerstitial fibrosis in the absence of any additional injury.32 Furthermore, the role of Smad3 in renal fibrosis is supported, because genetic inhibition of Smad3 reduced ECM in unilateral ureteral obstruction (UUO).33

 

Renal Inflammation and TGF-β1

The role of TGF-β1 in inflammation after renal injury is more complex.  It is generally accepted that renal inflammation serves as the initial event of renal fibrosis in CKD, and the persistent activation of inflammatory processes promotes fibrogenous responses. Despite this pro-inflammatory role, TGF-β1 also possesses anti-inflammatory responses. Firstly, this was demonstrated, because mice that lack TGF-β1 develop uncontrollable systemic inflammation and die 3 weeks after birth.34 Furthermore, the protective role of TGF-β1 was reported in immune-mediated kidney disease in transgenic mice by administering the sheep anti-mouse glomerular basement membrane (GBM) antibody. Interestingly, mice with experimental crescentic GN, which had increased levels of latent, but not active, TGF-β1 in plasma and kidney tissue, and upregulation of renal Smad7 in keratinocytes, preserved renal function and were protected against renal fibrosis.35 Likewise, a recent study showed that it is possible to dissociate the fibrotic effect of TGF-β1 from its anti-inflammatory effect, by preventing the cross-talk interaction with the Wnt/β-catenin pathway.36

 

TGF-β1 signalling and inflammatory cells (Figure 2)

T cells

There is increasing evidence supporting the role of TGF-β1 in inflammation, both pro- and anti-inflammatory effect. On one hand, TGF-β1 can induce activation of Foxp3+, regulatory T cell subset (Treg), which suppresses renal injury and on the other hand can induce T cell differentiation to T17 subtype (Th17), which plays a significant role in inflammation in some forms of GN.37 These cells are called Th17 cells because they produce the interleukin (IL)-17 cytokine. Th17 cells also promote autoimmune anti-MPO-mediated GN through the secretion of IL-17a.



Figure 2. TGF-β1 signalling and inflammatory cells.
 


 

Macrophages

Recent investigations have also explored the role of TGF-β signalling in macrophage differentiation during inflammationMacrophage-myofibroblast transition (MMT) is a newly identified phenomenon driven by TGF-β1 signalling as a direct mechanism of macrophage for promoting myofibroblast generation under unresolved renal inflammation.38 The macrophage infiltration has been shown to correlate with the severity of renal injury.39 Macrophages are divided into two types: the proinflammatory M1-type (classically activated)and the anti-inflammatory M2-type (alternatively activated). In acute kidney injury, in the early phase, there is recruitment of macrophage, which polarized into M1-type by various inflammatory mediators, including Th17 cells. This differentiation is induced from TGF-β1, indicating the role as a macrophage chemoattractant. Subsequently, in the repair phase of acute kidney injury TGF-β1 signalling can induce a M2 macrophage polarization, which may suppress inflammation, but the uncontrolled activation can promote fibrosis. However, selective deletion of TGF-β1 from macrophages did not alter fibrosis in animal model.40,41

 

Platelets

Platelets secrete vasoactive, chemotactic, and mitogenic substances that interact with mediators generated by renal resident or inflammatory cells and could contribute to glomerular injury.  It is believed that growth factors, such as TGF-β1, are released from platelets and play an important role in this process.

 

C5b-9 (membrane attack complex)

The sublytic effects of C5b-9 on podocytes not only lead to proteinuria (mainly in membranous glomerulopathy) and produce hydrogen peroxide, but also increase the expression of TGF-β1 and its receptors, leading to overproduction of extracellular matrix resulting in GBM thickening.42

 

TGF-β1 mediated renal pathology  

It has been demonstrated that TGF-β1 affects various renal cells, including mesangial, endothelial cells, epithelial cells (podocytes), and tubular epithelial cells.  (Figure 3)



Figure 3. TGF-β1 mediated renal pathology.
 

 

Mesangial cells

TGF-β1 stimulates the mesangial cells to synthetizing type I, III and IV collagen, laminin, fibronectin and heparan sulphate proteoglycans, as well as plays a role in mesangial hypertrophy. Therefore, TGF-β1 is a major contributor to glomerular ECM accumulation by stimulating mesangial cells.43

 

Epithelial cells (podocytes)

The podocytes play a critical role in maintaining the glomerular integrity and function. They also synthesise most components of the GBM. It has been shown that podocytes with highly expression of TGF-β1 lead to apoptosis. In addition, in these damaged podocytes Smad7 expression is strongly expressed.44,45 Furthermore, in vitro experiments have shown that TGF-β1 induces epithelial-to-mesenchymal transition (EMT) after podocyte injury.46

 

Endothelial cells

It has also been demonstrated that TGF-β1 is a central inducer of endothelial-to-mesenchymal transition (EntMT) of these cells, cell proliferation and apoptosis. These changes contribute to proteinuria, inflammation, and glomerulosclerosis. A recent study reported that endothelial cells react differently in Smad3 deletion compared with podocytes. Hence, changes to glomerular endothelial cells, such as swelling, fenestrations and basement membrane reduplication were Smad3 dependent.47

 

Tubular epithelial cells

The expression of TGF-β1 has also been associated with tubular apoptosis.48 However, recently it has been shown a beneficial effect of TGF-β1 in proximal tubule. One study in animal CKD model reported that selective deletion of proximal tubular TβRII deteriorated tubular apoptosis. This may be reported in part through reduced β-catenin activity or through beneficial effect of TGF-β1 on autophagy. Likewise, recent evidence showed that TGF-β1 signalling reduced expression of Klotho, which is produced in proximal renal tubule.49

Fibroblast-type cells

TGF-β1 signalling can also induce proliferation and myofibroblast transition to intrinsic renal fibroblast-type cells, including interstitial fibroblasts and pericytes. It has also been demonstrated that damaged tubular epithelial cells secrete TGF-β1, which induce myofibroblast transition to the adjacent pericytes. 50

 

Expression of TGF-β1/Smad signalling in Proliferative glomerulonephritis

TGF-β1/Smad signalling is activated and highly expressed in progressive forms of human kidney disease (Figure 4).51-53 TGF-β1 has been reported to serve as a critical mediator in the pathogenesis of glomerulosclerosis in glomerular diseases, including lupus nephritis and crescentic GN.52-54 Although the upregulation of TGF-β1 has been proved its role in the pathogenesis of renal fibrosis, glomerular immunoreactivity for TGF-β1 isoforms is also correlated with the severity of proliferative lesions, especially in lupus nephritis.54 Significant upregulation of the three TGF-β1 isoforms as well as TGFβRI and TGFβRII have been demonstrated in the glomerular, tubular, and interstitial area in kidney diseases. Furthermore, the urinary TGF-β1 level is increased and correlated with the severity of tubular-interstitial fibrosis.55 In TGF-β1 transgenic mice, an acute and massive increase in plasma levels of TGF-β1 results in severe GN with crescents.48-49 TGF-β1 expression is also strong in the cellular crescents.56 In disorders with abnormal glomerular and tubulointerstitial matrix accumulation, including crescentic GN and diffuse proliferative lupus nephritis, were noted significant increases in the immunoreactivity of all three TGF-β isoforms in glomeruli (p<0.025) and tubulointerstitium (p < 0.025).57



Figure 4. A, B, C Lupus nephritis (arrows indicating the positive immunostaining). Immunohistochemical evaluation of pSmad3 (A), Smad7 (B), TGF-β1 (C). D, E, F ANCA-associated glomerulonephritis (arrows indicating the positive immunostaining). Immunohistochemical evaluation of pSmad3 (D), Smad7 (E), TGF-β1 (F).51-53
 




The effect of Smad pathway in proliferative (including pauci-immune GN and lupus nephritis III, IV) and non-proliferative GN was examined and demonstrated that pSmad 2/3 was increased in all glomerular cells and was positively correlated with serum creatinine level and interstitial inflammation in both GN.58   A recent study evaluated the role of Smad3 as an important mediator of glomerulosclerosis and interstitial fibrosis in a model of proliferative crescentic GN. SMAD3-/- mice had only transient proteinuria, and the glomerular endothelium demonstrated transient injury, which was temporally correlated with proteinuria.47 Interestingly, the effect of Smad3 deletion was different between the glomerular cells.

Further evidence indicated that blocking TGF-β1 signalling by overexpression of Smad7 may have a therapeutic effect in a mouse model of autoimmune crescentic GN. Results showed that overexpression of Smad7 blocked both renal fibrosis and inflammatory pathways in terms of Smad2/3 and NF-B activation, respectively (p<0.01). Severe histologic damage (glomerular crescents and tubulointerstitial injury) and functional parameters, including proteinuria, were significantly improved (all p<0.05). 59

Although this research field in human tissue is limited, a recent study from our research group demonstrated that TGF-β1/pSmad3/Smad7 was upregulated in human GN, including AAV and lupus nephritis.51 TGF-β1 was correlated with glomerulosclerosis and interestingly indicated as independent risk factor for progression to chronic kidney disease. Another noteworthy point was that the concomitant glomerular expression of high Smad7 and medium pSmad3 was associated more with renal inflammation, such as cellular crescent and interstitial inflammation, than fibrosis.51

Comparing the miR expressions in renal biopsies of lupus nephritis, it was identified that miR-150 was related to higher chronicity level (chronicity index [CI] ≥4), suggesting as biomarker of specific histologic manifestations of lupus nephritis.60 Furthermore, miR-183 could mediate the TGF-β1/Smad pathway, in mice with lupus nephritis (LN) and in human renal glomerular endothelial cells (HRGECs).61 


Table 1. Selected studies demonstrating expression of TGF-β1/Smad signalling in autoimmune disease- associated glomerulonephritis.
 

 

CONCLUSION

TGF-β1 plays a central role in renal fibrosis and inflammation via its downstream Smad signalling. Most cell types, including immature hematopoietic cells, activated T and B cells, macrophages, neutrophils, and dendritic cells, produce TGF-β1 and/or are sensitive to its effects. Overexpression of this pathway has been closely linked to the pathogenesis of GN, including the proliferative one, which is associated with autoimmune diseases. However, the role of TGF-β1 signalling is demonstrated from few studies, in vivo and in vitro. The current evidence from human renal tissue is limited and concerns only to GN, which is associated with lupus nephritis or AAV from the autoimmune diseases. While the TGF-β1 signalling could be a potential target of treatment, direct inhibition of TGF-β1 has provided negative results. Recently, new mechanisms and new interactions of TGF-β signalling have been demonstrated to mediate renal injury. Therefore, a better understanding of the specific role of the downstream signalling in pathogenesis of GN, preferably in human tissue, is appropriate for conducting potent results for renal prognosis and novel therapeutic strategies.

 

CONFLICT OF INTEREST

The authors declare no conflict of interest.

References
  1. Sethi S, Haas M, Markowitz GS, D’Agati VD, Rennke HG, Jennette JC, et al. Mayo Clinic/Renal Pathology Society Consensus Report on Pathologic Classification, Diagnosis, and Reporting of GN. J Am Soc Nephrol 2016;27(5):1278-87.
  2. Tampe, B., Zeisberg, M. Evidence for the involvement of epigenetics in the progression of renal fibrogenesis. Nephrol Dial Transplant 2014;29(Suppl. 1):i1–i8.
  3. Nikolic-Paterson DJ, Wang S, Lan HY. Macrophages promote renal fibrosis through direct and indirect mechanisms. Kidney Int Suppl 2014; Nov;4(1):34-8.
  4. Yamamoto T, Noble NA, Cohen AH, Nast CC, Hishida A, Gold LI, et al. Expression of transforming growth factor-beta isoforms in human glomerular diseases. Kidney Int 1996; Feb;49(2):461-9.
  5. Ito Y, Goldschmeding R, Kasuga H, Claessen N, Nakayama M, Yuzawa Y, et al. Expression patterns of connective tissue growth factor and of TGF-β isoforms during glomerular injury recapitulate glomerulogenesis. Am J Physiol Renal Physiol 2010 Sep;299(3):F545-58.
  6. Jennette JC, Falk RJ. Pathogenesis of antineutrophil cytoplasmic autoantibody-mediated disease. Nat Rev Rheumatol 2014;10:463-73.
  7. Jennette JC, Xiao H, Falk R, Gasim AM. Experimental models of vasculitis and glomerulonephritis induced by antineutrophil cytoplasmic autoantibodies. Contrib Nephrol 2011;169:211-20.
  8. Savage CO, Gaskin G, Pusey CD, Pearson JD. Myeloperoxidase binds to vascular endothelial cells, is recognized by ANCA and can enhance complement dependent cytotoxicity. Adv Exp Med Biol 1993;336:121-3.
  9. Flint SM, McKinney EF, Smith KG. Emerging concepts in the pathogenesis of antineutrophil cytoplasmic antibody-associated vasculitis. Curr Opin Rheumatol 2015;27(2):197-203.
  10. Becker-Merok A, Eilertsen GØ, Nossent JC. Levels of transforming growth factor-beta are low in systemic lupus erythematosus patients with active disease. J Rheumatol 2010;37:2039-45.
  11. Yang CW, Hsueh S, Wu MS, Lai PC, Huang JY, Wu CH, et al. Glomerular transforming growth factor-beta1 mRNA as a marker of glomerulosclerosis-application in renal biopsies. Nephron 1997;77:290-7.
  12. Lewis MJ, McAndrew MB, Wheeler C, Workman N, Agashe P, Koopmann J, et al. Autoantibodies targeting TLR and SMAD pathways define new subgroups in systemic lupus erythematosus. J Autoimmun 2018 Jul;91:1-12.
  13. Sisto M, Ribatti D, Lisi S. SMADS-Mediate Molecular Mechanisms in Sjögren’s Syndrome. Int J Mol Sci 2021; 22(6):3203.
  14. Zhu D, Zhao J, Lou A, Huang Q, Yang Q, Zhu J, et al. Transforming growth factor _1 promotes fibroblast-like synoviocytes migration and invasion via TGF-_1/Smad signalling in rheumatoid arthritis. Mol Cell Biochem 2019;459:141-50.
  15. Long Y, Chen W, Du Q, Zuo X, Zhu H. Ubiquitination in Scleroderma Fibrosis and Its Treatment. Front Immunol 2018 Oct 17;9:2383.
  16. Dennler S, Goumans MJ, ten Dijke P. Transforming growth factor beta signal transduction. J Leukoc Biol 2002;71:731-40.
  17. Kingsley DM. The TGF-beta superfamily: new members, new receptors, and new genetic tests of function in different organisms. Genes Dev 1994;8:133-46.
  18. Shi Y, Massagué J. Mechanisms of TGF-beta signalling from cell membrane to the nucleus. Cell 2003;113:685-700.
  19. Romeo DS, Park K, Roberts AB, Sporn MB, Kim SJ. An element of the transforming growth factor-beta 1 5’-untranslated region represses translation and specifically binds a cytosolic factor. Mol Endocrinol 1993;7:759-66.
  20. Meng XM, Nikolic-Paterson DJ, Lan HY. TGF-β: the master regulator of fibrosis, Nat Rev Nephrol 2016;12:325-38.
  21. Budi EH, Duan D, Derynck R. Transforming growth factor-β receptors and Smads: regulatory complexity and functional versatility. Trends Cell Biol 2017;27:658-72.
  22. Macias MJ, Martin-Malpartida P, Massague J. Structural determinants of Smad function in TGF-β signalling. Trends Biochem Sci 2015;40:296-308.
  23. Lucarelli P, Schilling M, Kreutz C, Vlasov A, Boehm ME, Iwamoto N, et al. Resolving the combinatorial complexity of Smad protein complex formation and its link to gene expression, Cell Syst 2017;6:75-89.
  24. Wang B, Koh P, Winbanks C, Coughlan MT, McClelland A, Watson A, et al. miR-200a Prevents renal fibrogenesis through repression of TGF-beta2 expression. Diabetes 2011;60:280-7.
  25. Chung AC, Huang XR, Meng X, Lan HY. miR-192 mediates TGF-beta/Smad3-driven renal fibrosis. J Am Soc Nephrol 2010;21:1317-25.
  26. Gu YY, Liu XS, Huang XR, Yu XQ, Lan HY. Diverse Role of TGF-β in Kidney Disease. Front Cell Dev Biol  2020;8:123.
  27. Desmoulière A, Geinoz A, Gabbiani F, Gabbiani G. Transforming growth factor-beta 1 induces alpha-smooth muscle actin expression in granulation tissue myofibroblasts and in quiescent and growing cultured fibroblasts. J Cell Biol 1993 Jul;122(1):103-11.
  28. Chung AC, Zhang H, Kong YZ, Tan JJ, Huang XR, Kopp JB, et al. Advanced glycation end-products induce tubular CTGF via TGF-β-independent Smad3 signalling. J Am Soc Nephrol 2010;21:249-26.
  29. Chen HY, Huang XR, Wang W, Li JH, Heuchel RL, Chung AC, et al. The protective role of Smad7 in diabetic kidney disease: mechanism and therapeutic potential. Diabetes 2011;60: 590-601.
  30. Al-Rasheed NM, Al-Rasheed NM, Al-Amin MA, Hasan IH, Al-Ajmi HN, Mohammad RA, et al. Fenofibrate attenuates diabetic nephropathy in experimental diabetic rat’s model via suppression of augmented TGF-β1/Smad3 signalling pathway, Arch Physiol Biochem 2016;122:186-94.
  31. Zhou B, Mu J, Gong Y, Lu C, Zhao Y, He T, et al. Brd4 inhibition attenuates unilateral ureteral obstruction-induced fibrosis by blocking TGF-β-mediated Nox4 expression. Redox Biol 2017;11:390-402.
  32. Wang W, Koka V, Lan HY. Transforming growth factor-beta and Smad signalling in kidney diseases. Nephrology (Carlton) 2005;10:48-56.
  33. Liu Z, Huang XR, Chen HY, Fung E, Liu J, Lan HY. Deletion of angiotensin- converting enzyme-2 promotes hypertensive nephropathy by targeting Smad7 for ubiquitin degradation. Hypertension 2017;70:822-30.
  34. Kopp JB, Factor VM, Mozes M, Nagy P, Sanderson N, Böttinger EP, et al. Transgenic mice with increased plasma levels of TGF-beta 1 develop progressive renal disease. Lab Invest 1996 Jun;74(6):991-1003.
  35. Sato M, Muragaki Y, Saika S, Roberts AB, Ooshima A. Targeted disruption of TGF-beta1/Smad3 signalling protects against renal tubulointerstitial fibrosis induced by unilateral ureteral obstruction. J Clin Invest 2003 Nov;112(10):1486-94.
  36. Letterio JJ, Roberts AB. Transforming growth factor-beta1- deficient mice: Identification of isoform-specific activities in vivo. J Leukoc Biol 1996;59:769-74.
  37. Huang ΧR, Chung ACK, Zhou L, Wang XJ, Lan HY. Latent TGF-β1 Protects Against Crescentic Glomerulonephritis. J Am Soc Nephrol 2008;19:233-42.
  38. Qiao X, Rao P, Zhang Y, Liu L, Pang M, Wang H, et al. Redirecting TGF-β Signalling through the β-Catenin/Foxo Complex Prevents Kidney Fibrosis. J Am Soc Nephrol 2018 Feb;29(2):557-70.
  39. Kitching AR, Holdsworth SR. The emergence of TH17 cells as effectors of renal injury. J Am Soc Nephrol 2011;22(2):235.
  40. Meng XM, Wang S, Huang XR, Yang C, Xiao J, Zhang Y, et al. Inflammatory macrophages can transdifferentiate into myofibroblasts during renal fibrosis. Cell Death Dis 2016 Dec 1;7(12):e2495.
  41. Eardley KS, Kubal C, Zehnder D, Quinkler M, Lepenies J, Savage CO, et al. The role of capillary density, macrophage infiltration and interstitial scarring in the pathogenesis of human chronic kidney disease. Kidney Int 2008 Aug;74(4):495-504.
  42. Zhang F, Wang H, Wang X, Jiang G, Liu H, Zhang G, et al. TGF-β induces M2-like macrophage polarization via SNAIL-mediated suppression of a pro-inflammatory phenotype. Oncotarget 2016 Aug 9;7(32):52294-306.
  43. Murray PJ, Wynn TA. Protective and pathogenic functions of macrophage subsets. Nat Rev Immunol 2011;11(11):723-37.
  44. Nangaku M, Shankland SJ, Couser WG. Cellular response to injury in membranous nephropathy. J Am Soc Nephrol 2005;16(5):1195.
  45. López-Hernández FJ, López-Novoa JM. Role of TGF-β in chronic kidney disease: an integration of tubular, glomerular and vascular effects. Cell Tissue Res 2012;347:141-54.
  46. Wolf G, Ziyadeh FN. Cellular and molecular mechanisms of proteinuria in diabetic nephropathy. Nephron Physiol 2007;106:p26-p31.
  47. Schiffer M, Bitzer M, Roberts IS, Kopp JB, Dijke P, Mundel P, et al. Apoptosis in podocytes induced by TGF-beta and Smad7. J Clin Invest 2001;108:807-16.
  48. Li Y, Kang YS, Dai C, Kiss LP, Wen X, Liu Y. Epithelial-to-mesenchymal transition is a potential pathway leading to podocyte dysfunction and proteinuria. Am J Pathol 2008;171:299-308.
  49. Ghayur A, Padwal MK, Liu L, Zhang J, Margetts PJ. SMAD3-dependent and -independent pathways in glomerular injury associated with experimental glomerulonephritis. Am J Physiol Renal Physiol 2019;317:152-62.
  50. Böttinger EP, Bitzer M. TGF-beta signalling in renal disease. J Am Soc Nephrol 2002;13:2600-10.
  51. Yin S, Zhang Q, Yang J, Lin W, Li Y, Chen F, et al.  TGFβ-incurred epigenetic aberrations of miRNA and DNA methyltransferase suppress Klotho and potentiate renal fibrosis. Biochim Biophys Acta Mol Cell Res 2017 Jul;1864(7):1207-16.
  52. Kramann R, Dirocco DP, Maarouf OH, Humphreys BD. Matrix Producing Cells in Chronic Kidney Disease: Origin, Regulation, and Activation. Curr Pathobiol Rep 2013 Dec;1(4):10.1007/s40139-013-0026-7.
  53. Chalkia A, Gakiopoulou H, Theohari I, Foukas PG, Vassilopoulos D, Petras D. Transforming Growth Factor-β1/Smad Signalling in Glomerulonephritis and Its Association with Progression to Chronic Kidney Disease. Am J Nephrol 2021 Sep 8:1-13. doi: 10.1159/000517619. Epub ahead of print.
  54. Y. Shi, Massague J. Mechanisms of TGF-β signalling from cell membrane to the nucleus. Cell 2003;113:685-700.
  55. K. Sharma. Obesity, oxidative stress, and fibrosis in chronic kidney disease, Kidney Int 2014;4:113-7.
  56. Kitamura M, Sütö TS. TGF-beta and glomerulonephritis: anti-inflammatory versus prosclerotic actions. Nephrol Dial Transplant 1997;12:669-79.
  57. Goumenos DS, Tsakas S, El Nahas AM, Alexandri S, Oldroyd S, Kalliakmani P, et al. Transforming growth factor- beta (1) in the kidney and urine of patients with glomerular disease and proteinuria. Nephrol Dial Transplant 2002;17:2145-52.
  58. Shimizu M, Kondo S, Urushihara M, Takamatsu M, Kanemoto K, Nagata M, et al. Role of integrin-linked kinase in epithelial mesenchymal transition in crescent formation of experimental glomerulonephritis. Nephrol Dial Transplant 2006;21:2380-90.
  59. Ito Y, Goldschmeding R, Kasuga H, Claessen N, Nakayama M, Yuzawa Y, et al. Expression patterns of connective tissue growth factor and of TGF-beta isoforms during glomerular injury recapitulate glomerulogenesis. Am J Physiol Renal Physiol 2010 Sep;299(3):F545-58.
  60. Yoshioka K, Takemura T, Murakami K, Okada M, Hino S, Miyamoto H, et al. Transforming growth factor-beta protein and mRNA in glomeruli in normal and diseased human kidneys. Lab Invest 1993; 68:154-63.
  61. Ka SM, Huang XR, Lan HY, Tsai PY, Yang SM, Shui HA, et al. Smad7 Gene Therapy Ameliorates an Autoimmune Crescentic Glomerulonephritis in Mice. J Am Soc Nephrol 2007;18(6):1777-88.
  62. Zhou H, Hasni SA, Perez P, Tandon M, Jang SI, Zheng C, et al. MiR-150 promotes renal fibrosis in lupus nephritis by downregulating SOCS1. J Am Soc Nephrol 2013;24:1073-87.
  63. Qi H, Cao Q, Liu Q. MicroRNA-183 exerts a protective role in lupus nephritis through blunting the activation of TGF-β/Smad/TLR3 pathway via reducing Tgfbr1. Exp Cell Res 2020;394:112-38.
  64. Du Y, Xie C, Ravikumar S, Orme J, Li L, Zhou XJ, et al. Heightened Crescentic Glomerulonephritis in Immune Challenged 129sv Mice Is TGF-β/Smad3 Dependent. Int J Mol Sci 2021; 22(4):2059.
  65. Koutroutsos K, Kassimatis TI, Nomikos A, Giannopoulou I, Theohari I, Nakopoulou L. Effect of Smad pathway activation on podocyte cell cycle regulation: an immunohistochemical evaluation. Ren Fail 2014 Sep;36(8):1310-6.