Progression and regression in renal vascular and glomerular fibrosis

CURRENT STATUSREVIEW

Progression and regression in renal vascular and glomerular fibrosis

Christos Chatziantoniou, Jean-Jacques Boffa, Pierre-Louis Tharaux, Martin Flamant, Pierre Ronco and

Jean-Claude Dussaule

Inserm U489, Tenon Hospital, Paris, France

I N T E R N AT I O N A LJOURNAL OFE X P E R I M E N TA LPAT H O L O G Y

Summary

End-stage renal disease (ESRD) is characterized by the development of fibrotic lesions in

the glomerular, interstitial and vascular compartments. Renal fibrogenesis, a common

complication of diabetes and hypertension, is a complex dynamic process involving

several players such as inflammatory agents, cytokines, vasoactive agents and enzymes

participating in extracellular matrix assembly, anchoring or degradation. The only

available treatment today against chronic renal failure is dialysis or kidney transplant-

ation, making thus ESRD one of the most expensive diseases to treat on a per-patient

basis. An emerging challenge for clinicians, maybe the nephrologist’s Holy Grail in the

21st century, is to stop definitively the decline of renal function and, if possible, to

achieve regression of renal fibrosis and restoration of renal structure. Over the last 5

years, different approaches have been tested in experimental models of nephropathy

with variable degree of success. In this review, we will focus on the mechanisms of the

hypertension-associated fibrosis and the few recent studies that gave promising results

for a therapeutic intervention.

Keywords

angiotensin II, collagen I, progression, regression, renal vascular remodelling

Diabetes and hypertension are amongst the leading causes of end-

stage renal failure (ESRF), accounting for more than 60% of new

cases (United States Renal Data System 1998; Valderrabano et al.

1996). Kidney disease can also develop from infection, inflamma-

tion of renal blood vessels and glomeruli, kidney stones and cysts.

ESRF is characterized by the development of fibrotic lesions in the

glomerular, interstitial and vascular compartments. These lesions

are defined by the abnormal accumulation of extracellular matrix

(mainly fibrillar collagens) that substitutes normal kidney struc-

ture. Under normal conditions, the formation of extracellular

matrix is a dynamic equilibrium between systems that promote

its synthesis and those that favour its degradation. In pathophysio-

logical conditions that lead to the development of fibrosis, this

equilibrium is broken due to exaggerated rates of extracellular

matrix synthesis, to diminished capacity of degradation or to a

combination of both. This process appears irrespective of the

underlying disease and originating compartment, pointing out a

final common pathway, independently of the primary cause.

Under this view, identifying and targeting the systems participating

in this pathway may provide an efficient treatment against renal

fibrosis and failure regardless of the initiating pathology. Over the

last years, an important progress has been made towards this

Received for publication 7 January

2004

Accepted for publication 19 February

2004

Correspondence:

Christos Chatziantoniou

Inserm U489

Tenon Hospital

4 rue de la Chine

75020 Paris, France

Tel.: +33 1 56016658

Fax: +33 143645448

E-mail: christos.chatziantoniou@tnn.

ap-hop-paris.fr

Int. J. Exp. Path. (2004), 85, 1–11

� 2004 Blackwell Publishing Ltd 1

direction, and it is now well established that various therapeutic

interventions can prevent the development of renal damage in

several experimental models. The challenge, however, remains to

go beyond slowing down the decline of renal function, and to

attempt to achieve regression of renal fibrosis and restoration of

the renal structure. Our group has contributed to the understand-

ing of the fibrotic mechanisms by focusing on experimental models

in which renal fibrosis originates from vascular dysfunction. The

present work aimed to review some of the most significant recent

developments concerning the mechanisms of progression and

regression of renal fibrosis.

Progression of renal fibrosis of vascular origin

One of the most common complications associated with hyper-

tension is the development of renal sclerotic injury (Weistuch &

Dworkin 1992). For several years, the general belief was that

renal vascular and glomerular sclerosis were consequences of

the high blood pressure and that the exaggerated extracellular

matrix formation inmesangial and vascular smoothmuscle cells

was an adaptive response to the increased tension within the

renal vasculature (Figure1). This hypothesis postulates that the

systemic blood pressure increase is transmitted within renal

resistance vessels and glomeruli initiating an adaptive mechan-

ism that is subsequently extended to renal interstitium and that

ultimately leads to the development of renal fibrosis. Under this

schema, circulating or locally generated vasoconstrictors have a

primary (if not exclusive) action on the blood pressure increase.

However, over the last years, this belief was evolved to the

concept that vasoconstrictors have fibrogenic effects indepen-

dently of their constrictor action (Figure 1) and that an efficient

treatment against hypertension and its complications should

also address the issue of pathological structural remodelling (in

addition to simply lowering blood pressure). This concept is

based on data obtained mainly in the cardiac tissue with block-

ers of the renin–angiotensin system (Weber 2000). The follow-

ing lines will examine whether this concept can also apply to the

renal vasculature; the focus will be on the data concerning the

fibrogenic action of the most extensively studied peptides in this

field, angiotensin II, and endothelin and of the beneficial effects

of their inhibitors or antagonists; in addition, it will be exam-

ined whether inhibitors of the different growth factors (consid-

ered to mediate the fibrogenic action of vasoconstrictors) such

as transforming growth factor-b (TGFb) and tyrosine kinase

growth factors can be used against renal fibrosis.

Angiotensin II

A central role for the renin–angiotensin system in the vascular

remodelling and fibrosis is well established. Its involvement in

renal fibrosis was suggested from studies using pharmacological

blockade of the angiotensin II action. Thus, inhibition of the

angiotensin-converting enzyme (ACE) or antagonism of the

angiotensin AT1 receptors slowed or stopped the progression

of renal fibrosis in several models of experimental or genetic

hypertension. In the nitric oxide (NO) deficiency model of

hypertension (L-NAME model) for instance, inhibition or

antagonism of angiotensin II preserved kidney function and

morphology in addition to normalizing systolic pressure (Case-

llas et al. 1999; Michel et al. 1996). Treatment with a calcium

blocker and/or an ACE inhibitor improved renal haemody-

namics and protected against nephrosclerosis in spontaneously

hypertensive rat (SHR) treated with L-NAME (Francischetti

et al. 1998). To understand the underlying cellular mechan-

ism(s), we examined the hypothesis of whether angiotensin II

specifically activates genes of extracellular matrix proteins (such

as collagen I) within the renal cortical vasculature (Boffa et al.

1999). To this end, we used a transgenic strain of mice har-

bouring two reporter genes, the firefly luciferase and the

Escherichia coli B-galactosidase, under the control of the

promoter of the a2-chain of mouse collagen type I gene.

The choice of these mice was based on data showing that

the expression pattern of the two reporter genes closely

correlated with cell and tissue distribution of collagen I

(Bou-Gharios et al. 1996; Chatziantoniou et al. 1998). Due

to the sensibility of reporter gene assays, this model allows

changes in the expression of the collagen I gene to be

detected in a highly sensitive manner. Thus, the sensitivity

and reproducibility of luciferase activity measurements pro-

vided us with accurate estimates of tissular (afferent arter-

ioles or glomeruli vs. heart and aorta) and temporal

(before, during and after the establishment of pathology)

activation of collagen I gene. Hypertension and renal failure

were induced in these mice by inhibiting endogenous NO

synthesis in presence or absence of angiotensin blockade for

Intrinsic factors

Renal fibrogenesis

High blood pressureExtrinsic factors

NO ET-1 ANG II

–? +? +?

Figure 1 Classically, the development of renal fibrosis of vascular

origin was considered as an adaptive response to blood pressure

increase. This notion has been challenged lately by the concept

that vasoactive agents can control extracellular martrix synthesis

through a genetic action independent of their constrictor effects.

2 C. Chatziantoniou et al.

� 2004 Blackwell Publishing Ltd, International Journal of Experimental Pathology, 85, 1–11

a period of up to 14 weeks (Boffa et al. 1999). Systolic

blood pressure was increased after 6 weeks of treatment

and reached a plateau after 10 weeks (around 160mmHg).

Collagen I gene activity was increased in freshly isolated

afferent arterioles and glomeruli earlier than systolic pressure

(4 weeks of L-NAME treatment), indicating that the two phe-

nomena could be controlled by distinct mechanisms. The acti-

vation of collagen I gene became more pronounced with time,

and at 14 weeks, increased 10-fold compared with controls in

afferent arterioles and glomeruli. This activation of collagen I

gene was accompanied by the progressive accumulation of extra-

cellular matrix within glomeruli as evidenced by classical morpho-

logical methods. The kinetics of collagen I gene activation was

different in aorta and heart; it remained unchanged up to 8 weeks

and was increased slowly thereafter (in parallel with the systolic

pressure increase), suggesting that the early activation of col-

lagen I gene in renal resistance vessels and glomeruli was specific

to the renal tissue (Chatziantoniou et al. 1998). Pharmacologi-

cal blockade of angiotensin II action inhibited collagen I gene

activation in the renal cortical tissue and prevented the develop-

ment of renal vascular and glomerular fibrosis. This study,

summarized in Figure 2, provided an in vivo evidence that

angiotensin II is involved in the fibrogenic process by inducing

collagen gene activation within the renal tissue by a cellular

mechanism(s) partly independent of its systemic haemodynamic

actions (Boffa et al. 1999).

Endothelin

Several recent studies point to a major role for endothelin in

mediating renal fibrosis. Transgenic mice overexpressing human

endothelin 1 gene developed glomerulosclerosis and interstitial

fibrosis without change in arterial pressure (Hocher et al. 1997);

conversely, selective blockade of ETA receptors prevented pro-

teinuria and glomerular ischaemia and blunted the degree of

vascular and tubulointerstitial injuries during inhibition of NO

synthesis without normalizing blood pressure (Verhagen et al.

1998). These results corroborate the hypothesis that the

endothelin-mediated fibrogenic mechanisms are independent

of systemic haemodynamics. We have observed that mRNA

175

150

125

100

75

200

150

100

50

0

Without AT1 antagonistWith AT1 antagonist

Glomeruli

Control LN 8 w LN 14 w

Control LN 8 w LN 14 w

Col

lage

n I g

ene

activ

atio

nS

ysto

lic p

ress

ure

(mm

Hg)

L-NAME 14 w

L-NAME + AT1 antagonist 14 w

Figure 2 Antagonism of angiotensin II action inhibited collagen I gene activation within the renal vasculature (glomeruli and afferent

arterioles) and prevented the development of glomerulosclerosis without normalizing systolic pressure increase (Boffa et al. 1999).

Renal vascular and glomerular fibrosis 3


expression and peptide content of endothelin in renal resistance

vessels and endothelin urinary excretion rate were increased in

rats developing renal vascular fibrosis (Tharaux et al. 1999). We

pursued the hypothesis of an endothelin–collagen I gene inter-

action using the same transgenic strain and a similar to the

above-described protocol with the exception that an endothelin

receptor blocker was used instead of the AT1 receptor antago-

nist. Endothelin blockade prevented the collagen I gene activa-

tion and protected kidneys from the development of fibrosis

without altering the blood pressure increase induced by NO

inhibition (Chatziantoniou et al. 1998). These studies provided

an additional support to the hypothesis that the fibrogenic

action of vasoactive peptides is local and independent of sys-

temic haemodynamics; on the other hand, these findings raised a

number of important questions such as to identify the way (if

any) of the interaction between angiotensin II and endothelin

that leads to collagen I gene activation and the development of

renal fibrosis. We have addressed this issue in subsequent

experiments by investigating the role of some pro-fibrogenic

and/or mitogenic transduction pathways that are known to

interact with angiotensin II, such as TGF-b/SMAD, MAP/ERK

and tyrosine kinase receptors of growth factors.

TGF-�

TGF-b is a well-known agent promoting extracellular matrix

synthesis and is considered to play a major role as mediator of

the fibrogenic action of several vasoconstrictor peptides, parti-

cularly of the angiotensin II (Border & Noble 1998). The angio-

tensin II–TGF-b interaction does not appear to depend on

systemic haemodymamics. In the L-NAME model, TGF-bmRNA expression was increased locally in the renal cortex;

treatment with an ACE inhibitor, but not with hydralazine,

reduced the exaggerated expression of TGF-b and improved

renal histology, despite a similar reduction of systolic blood

pressure with both treatments (Kashiwagi et al. 2000). More

controversial is the issue of whether TGF-b mediates the fibro-

genic actions of endothelin. In two models of experimental

fibrotic nephropathy (the streptozotocin-induced diabetes or

the 5/6 nephrectomy), ETA/B antagonism had no effect on the

exaggerated expression of TGF-b or collagen IV and the pro-

gression of fibrosis in glomeruli and tubules (Kelly et al. 2000).

In other studies that used similar models of chronic renal failure

(5/6 nephrectomy), ETA/B antagonismmarkedly reduced extra-

cellular matrix synthesis, protected renal structure and

improved the survival of 5/6 nephrectomized rats (Benigni et al.

1993). We studied the interactions between angiotensin II,

endothelin and TGF-b on collagen I gene activation in acute in

vivo experiments. To this end, we tested whether exogenous

administration of angiotensin II, endothelin or TGF-b activated

collagen I gene in the aortic and renal cortical tissue andwhether

a cross-reaction of blockers of these systems affected collagen I

gene activation (Fakhouri et al. 2001). The main conclusion of

these studies was that cooperation and/or synergy between

endothelin and TGF-b are required and mediate the fibrogenic

action of angiotensin II. The molecular events that lead from the

angiotensin II receptor to collagen I gene activation were

subsequently examined by focusing on the role ofMAPKpathway.

MAP kinases and intracellular signalling mediators of

fibrogenesis

The MAP/ER kinase cascade is considered as a major intracel-

lular signalling pathway mediating the mitogenic actions of

most vasoconstrictors. We tested if this pathway could also

mediate fibrogenesis in the renal and vascular tissues in col-

lagen I gene transgenic mice. Angiotensin II produced an early

stimulation of collagen I gene activity in freshly isolated aortas

and renal cortical slices followed by similar increase in col-

lagen I gene mRNA levels (Tharaux et al. 2000). This effect of

angiotensin II was inhibited by AT1 receptor antagonism and

blockade of the MAPK/ERK cascade, but not by inhibition of

the P38 kinase pathway or blockade of the transcription factor

NFkB. The angiotensin II-induced increase of the MAPK/ERK

activity was accompanied by increased expression of the c-fos

proto-oncogene; inversely, inactivation of the transcriptional

factor AP-1 cancelled the effect of angiotensin II on the col-

lagen I gene (Figure 3). Similar data have been obtained in a

transgenic model of rat harbouring both human renin and

angiotensinogen genes (Muller et al. 2000). In this model,

characterized by angiotensin II–induced end-organ damage in

heart and kidney, AP-1 expression and several genes regulated

by this complex (such as intercellular adhesion molecule-1 and

vascular cell adhesion molecule-1) were locally overexpressed

in the renal and cardiac tissues; treatment with angiotensin II

or endothelin antagonists, but not with hydralazine, improved

albuminuria and renal injury and reduced mortality rates;

these functional improvements were independent of blood

pressure effects and were associated to significant reduction

of AP-1 (and AP-1-regulated genes) expression in the kidney.

Tyrosine kinase receptors of growth factors

A relatively novel concept regarding the signalling pathways of

potent vasoconstrictors such as angiotensin II or endothelin is

that they can transactivate the receptors of growth factors

(Berk 1999). Increased expression or levels, or activation of

these receptors have been observed during the development of

several forms of nephropathies (Klahr & Morrisey 2000),

making thus attractive the hypothesis that this activation



could participate in the progression of renal fibrotic disease.

To this end, a tyrosine kinase inhibitor attenuated the devel-

opment of fibrosis in the model of unilateral ureteral obstruc-

tion (Ludewig et al. 2000). More recently, use of nuclease

resistant high-affinity aptamers that neutralized the effects of

PDGF-B inhibited glomerular and interstitial fibrosis in a rat

model of mesangioproliferative glomerulosclerosis (Ostendorf

et al. 2001). We tested the interaction between vasoconstrict-

ors, epidermal growth factor (EGF) receptor transactivation

and collagen I gene (Flamant et al. 2003), and we found that

endothelin induced a rapid phosphorylation of the EGF recep-

tor associated to activation of the MAP/ERK pathway and to

increased collagen I gene activity in freshly isolated aortic and

renal cortical tissue (Figure 3). In subsequent in vivo studies,

we observed that EGF receptor was activated within glomeruli

concomitantly to the development of glomerulosclerosis in the

NO deficiency model. In this model, an EGF receptor-tyrosine

kinase inhibitor, normalized the MAPK activation, inhibited

the abnormal increase of collagen I gene expression, decreased

proteinuria and creatininaemia and prevented the develop-

ment of renal vascular and glomerular fibrosis (Francois et al.

2003). It appears, thus, that EGF receptor activation is a major

step in the fibrogenic process, at least in the model of NO

deficiency. These observations provide a novel perspective for

the eventual use of growth factor receptor inhibitors as anti-

fibrotic agents.

Regression of renal fibrosis

Blockade of the renin–angiotensin system

Figure 3 summarizes the signalling pathways that have been

characterized by our studies as mediators of the angiotensin II-

induced activation of collagen I gene. These studies were

mainly focused on the mechanisms leading to the progression

of renal vascular fibrosis. From a therapeutic point of view,

however, the challenge remains to go beyond prevention and

to attempt to achieve regression of renal fibrosis and restor-

ation of the renal structure. Over the last years, several studies

in humans gave promising results indicating that anti-

hypertensive treatments can have beneficial effects regarding

renoprotection. Thus, blockade of the angiotensin II action

protected against the progression of renal insufficiency in

patients with various renal diseases (such as glomerulopathies,

interstitial nephritis, nephrosclerosis, polycystic kidney disease

or diabetic nephropathy) (Maschio et al. 1996). This initial

Figure 3 Angiotensin II-induced signalling pathways that lead to activation of collagen I gene. Interruption of one of these cascades is

sufficient to inhibit collagen I synthesis and to prevent the development of fibrosis (dash arrows indicate the targets used in experimental

studies to block collagen I formation).



report was validated with the publication of three large-scale

studies concerning hypertensive patients with type 2 diabetes

(Brenner et al. 2001; Lewis et al. 2001; Parving et al. 2001).

Angiotensin II receptor antagonism was effective in protecting

against the progression of nephropathy by reducing micro-

albuminuria and slowing down the rate of decline of filtration

rate; interestingly, these renoprotective effects were independ-

ent of the blood-pressure-lowering effect, providing an add-

itional argument supporting the dissociation between the

contractile and the fibrotic actions of angiotensin II in the

renal tissue. These observations are corroborated by a mor-

phometric analysis performed in a limited number of type 2

diabetic patients with glomerulosclerosis. After 2 years of

follow-up, mean cortical interstitial fractional volume (a marker

of progression of renal fibrosis) was increased significantly

in the placebo group, whereas it remained unchanged in the

ACE inhibitor-treated patients (Cordonnier et al. 1999).

We have addressed the issue of renoprotection by investigat-

ing the mechanisms by which AT1 receptor antagonists make

possible the regression of renal vascular and glomerular fibro-

sis (Boffa et al. 2003). To this end, hypertension and renal

failure were induced by inhibiting NO synthesis. After 1

month of hypertension, animals displayed a decline of renal

function (evidenced by increased levels of proteinuria and

plasma creatinine), an exaggerated gene and protein expres-

sion of TGF-b, collagen I and collagen IV within the renal

vasculature and an abnormal accumulation of extracellular

matrix in glomeruli (Figure 4). These structural and functional

alterations were accompanied by increased activities of matrix

metalloproteinases (MMPs) 2 and 9. Administration of an

angiotensin II receptor antagonist immediately decreased col-

lagen I, collagen IV and TGF-b gene and protein expressions,

without affecting activities of metalloproteinases 2 and 9.

These cellular alterations were accompanied by a gradual

regression of glomerulosclerosis and restoration of renal func-

tion; after 1 month of anti-hypertensive treatment, all func-

tional and structural parameters of kidney were normalized

(Figure 4). Hydralazine failed to improve renal function and/or

structure despite a similar degree of systolic pressure decrease,

providing another element to support the hypothesis that sys-

temic pressure regulation and renal vascular fibrosis follow

distinct mechanisms. These data are among the first studies

2.5

2.0

1.5

1.0

0.5

0

150

125

100

75

50

25

4

3

2

1

0Protein/creatinine (mg/µmol) Plasma creatinine (µmol/l) Sclerotic index

Control L-NAME 4w L-NAME 4w +L-NAME 4w + Los 4w

Figure 4 Chronic inhibition of nitric oxide is accompanied by the development of renal failure as evidenced by the increase of urinary

protein excretion, plasma creatinine and the exaggerated extracellular matrix accumulation in renal cortex. Treatment of the diseased

animals with an angiotensin receptor antagonist normalized renal functional and structural parameters indicating that renal fibrosis is a

reversible phenomenon, at least in this experimental model (white, black and grey bars represent control animals and animals treated for

4 weeks with L-NAME or 4 weeks with L-NAME followed by 4 weeks L-NAME+ losartan, respectively; L-NAME: a NO synthase

inhibitor; Los: losartan, an AT1 receptor antagonist; w: weeks (Boffa et al. 2003).



implying that the progression of renal vascular fibrosis is a

reversible process. The mechanism of the regression (at least in

the NO deficiency model) appears to be dual: inhibition of

collagen synthesis due to AT1 receptor antagonism and acti-

vation of metalloproteinases that is probably associated with

the degree of fibrosis independently of AT1 blockade. In a

subsequent study, other investigators confirmed the reversibil-

ity of vascular lesions after angiotensin II blockade in the

model of 5/6 nephrectomy (Adamczak et al. 2003). In this

study, delayed treatment with an ACE inhibitor regressed

preexisting glomerular, tubular and vascular lesions, and

reversed glomerular hypertrophy. However, the initially

decreased number of podocytes (following renal ablation)

was not restored by the pharmacological treatment indicating

that the limiting step of glomerular regeneration depends on

the degree of damage of glomerular podocytes. In agreement

to this notion, mesangial proliferation was reduced and inter-

stitial changes were reversed after favourable treatment,

whereas the number of sclerotic glomeruli remained

unchanged in biopsies of immunoglobulin A (IgA) nephro-

pathy patients (Hotta et al. 2002). These observations are con-

sistent with the notion that the no-return point is associated to

podocyte alterations and underline the importance of finding

markers to detect these alterations as early as possible.

Blockade of the TGF-� pathway

Despite the reservations, exposed in the first part of the

review, of whether TGF-b is a common fibrogenic mediator

of all vasoconstrictor peptides, its involvement in the angio-

tensin II-induced fibrogenesis is well established. For this rea-

son, anti-fibrogenic strategies have been proposed that block

the action of TGF-b. Exogenous administration of decorin

mimicked the effect of chronic anti-TGF-b antibody infusion

by blunting the formation of extracellular matrix within the

renal cortex and protecting rat kidneys from the development

of glomerulonephritis (Border et al. 1992). In addition, endo-

genous overexpression of decorin in the skeletal muscle of rats

by gene transfer technology inhibited the fibrogenic action of

TGF-b and protected kidneys against glomerulosclerosis

(Isaka et al. 1996). However, an important limitation for the

generalized use of decorin is that increased concentrations of

decorin lack the anti-TGF-b specificity and can produce sec-

ondary effects. An alternative approach could be to block the

TGF-b action at the receptor level (exogenous administration of

anti-TGF-b receptor antibody or soluble receptors of TGF-b) orat the intracellular signalling pathway (SMADs, the intracellu-

lar mediators of TGF-b actions); both treatments gave promis-

ing results by preventing the development of renal and cardiac

fibrosis (Kasuga et al. 2001; Wang et al. 2002).

Another more recent option is to use bone morphogenic

protein-7 (BMP-7), a 35-kDa homodimeric protein and a

member of the TGF-b superfamily that antagonizes the action

of TGF-b. BMP-7 is highly expressed in the kidney, and its

genetic deletion in mice leads to severe impairment of eye,

skeletal and kidney development (Hogan 1996). Ischaemic

kidneys showed a marked decrease of BMP-7 mRNA, whereas

BMP-7 enhanced recovery when infused into rats with ischaemia-

induced acute renal failure (Simon et al. 1999). More

importantly, BMP-7 treatment in a preventive or curative

way preserved or restored renal histology and renal func-

tion in a rat model of unilateral ureteral obstruction; these

effects of BMP-7 were slightly better compared to the pro-

tection obtained with an ACE inhibitor (Hruska et al.

2000; Morrissey et al. 2002). In addition, systemic admin-

istration of recombinant human BMP-7 in mice with

nephrotoxic serum nephritis leads to repair of severely

damaged renal tubular epithelial cells, in association with

reversal of chronic renal injury (Zeisberg et al. 2003). These

results indicate the potential of BMP-7 to reverse the TGF-

b-induced injury and to repair renal tissue in a variety of

experimental models.

An additional endogenous ligand antagonizing the effects of

TGF-b is the ‘Hepatocyte Growth Factor’ (HGF). The therapeu-

tic potential of HGF has been tested in the unilateral ureteral

obstruction model, a model of renal interstitial fibrosis (Yang&

Liu 2003). Delayed administration of recombinant HGF

retarded the progression of renal lesions by blunting the myofi-

broblast accumulation and collagen deposition within the

kidney. This action of HGF is probably related to a mitogen-

activated protein kinase-dependent blockade of TGF-b-inducednuclear translocation of SMADs (Yang et al. 2003). Continuous

infusion of HGF in the rat remnant kidney model decreased

tubulointerstitial collagen deposition and ameliorated renal

fibrosis; in contrast, blocking of endogenous HGF by an anti-

HGF-neutralizing antibody increased interstitial collagen and

aggravated the degree of renal fibrosis. Interestingly, HGF infu-

sion increased, and conversely HGF antibody suppressed, the in

situ gelatinolytic activity in remnant kidneys thus, supporting

our hypothesis that MMPs play a beneficial role in renal fibrosis

by facilitating collagen degradation (Gong et al. 2003)

Stem cells

A very important issue when one addresses the problem of

regression of renal fibrosis is whether sclerotic glomeruli can

regenerate, and if so, what cells are or can be used as progeni-

tors. As mentioned above, a limiting step factor for the rever-

sibility of renal fibrosis appears to be podocyte differentiation.

Considerable progress has been made over the last years to this



direction, and emerging data demonstrated that bone marrow

cells can serve as progenitors for a variety of cells such as

vascular smooth, endothelial, hepatic or osteoblastic cells

(Prockop 1997). Furthermore, it has been demonstrated that

these marrow-derived cells can migrate into areas of induced

tissue degeneration, undergo differentiation and participate in

the regeneration of the damaged tissue (Asahara et al. 1997;

Ferrari et al. 1998). This innovative therapeutic approach has

been successfully applied in myocardial ischaemia (Kawamoto

et al. 2001) and in osteogenesis imperfecta, a genetic disorder

in which osteoblasts produce defective type I collagen (Horwitz

et al. 1999).

Bone marrow-derived cells may have the potential to differ-

entiate into glomerular mesangial cells (Imasawa et al. 2001).

However, this efficiency to differentiate can act as double-edge

feature, depending on whether the conditions favour hyper-

plasia and/or proliferation or recovery and/or regeneration.

Thus, the sclerotic phenotype was carried by mesangial cell

progenitors, and this phenotype could be derived from the

bone marrow in a genetic model of diffuse glomerulosclerosis

and glomerular hypertrophy (Cornacchia et al. 2001), or in

IgA nephropathy (Imasawa et al. 1999). Inversely, healthy

bone marrow cells gave rise to mesangial cells in vivo and

participated in the regeneration of glomeruli in the anti-Thy1

antibody-mediated glomerulonephritis (Ito et al. 2001); in

addition, use of genetically modified bone marrow-derived

cells to deliver an interleukin-1 receptor antagonist prevented

the phenotypic alterations of interstitial cells and protected kid-

neys in the model of unilateral ureteral obstruction (Yamagishi

et al. 2001).

Perspectives

Figure 5 summarizes the factors that have been identified to

play a crucial role in the mechanisms controlling extracellular

matrix formation in the renal vascular and glomerular tissue.

Although encouraging data have been obtained lately, the

issue still remains open on how to cure renal fibrosis. In this

context, some critical steps of the fibrotic mechanisms need to

be first well defined. Can the same treatment, for instance, be

applied to all stages of renal fibrosis, or does it depend on the

degree, severity and nature (type and supramolecular organi-

zation of collagen) of lesions? Are all stages of fibrosis rever-

sible or is there a no-return point, and in this case, how this

point will be clinically defined and what markers can be used

for its definition? Because the abnormal formation of col-

lagens is a common phenomenon of chronic renal failure

independently of cause and initiating mechanisms, is it possi-

ble to achieve regression by targeting a common step (blocking

collagen synthesis)? In that sense, angiotensin II appears as an

appropriate target, and the recently obtained data point to this

direction. However, anti-angiotensin treatments have been

widely used for several years now, and it becomes clear that

blocking angiotensin II action alone is not as much efficient in

regressing renal fibrosis in humans as it is in animals. Does this

mean that the prescribed doses of angiotensin blockers (based

on anti-hypertensive efficency) are not sufficient enough to

block the locally generated angiotensin? Or, may it be better

to associate angiotensin blockade to specific anti-fibrotic treat-

ments (anti-TGF-b or anti-tyrosine kinase growth factors) and/

or to agents that can degrade specifically the abnormally

formed extracellular matrix? Is it reasonable to believe that

the technological advance based on stem cells will permit to

reconstruct and regenerate completely a fibrotic kidney, even

if it is beyond on what we call today a no-return point?

Certainly, it is still a long way to go before making a fibrotic

kidney operational again; however, the progress made over the

last years and the continuously novel options emerging in the

horizon are sufficient reasons for optimism that is not far from

the day in which the regression of renal fibrosis will no more

considered as a myth but as a reality.

Factors involved in progression Factors facilitating regression

Angiotensin II

Endothelin

TGFβTyrosine kinase growth factors

NO

Activation of MMPs

BMP-7

Hepatic growth factor

Stem cells?

Extracellular matrix formation

Figure 5 Factors controlling the formation of extracellular matrix and the development of renal vascular and glomerular fibrosis.

Inhibition of pro-fibrogenic agents and/or activation of anti-fibrogenic systems have been accompanied by regression of fibrosis and

restoration of renal function in experimental nephropathies.



References

Adamczak M., Gross M.L., Krtil J., Koch A., Tyralla K., Amann K.,

Ritz E. (2003) Reversal of glomerulosclerosis after high-dose

enalapril treatment in subtotally nephrectomized rats. J. Am.

Soc. Nephrol. 14, 2833–2842.

Asahara T., Murohara T., Sullivan A., Silver M., van der Zee R.,

Li T., Witzenbichler B., Schatteman G., Isner J.M. (1997)

Isolation of putative progenitor endothelial cells for angiogen-

esis. Science 275, 964–967.

Benigni A., Zoja C., Corna D., Orisio S., Longaretti L., Bertani T.,

Remuzzi G. (1993) A specific endothelin subtype A receptor

antagonist protects against injury in renal disease progression.

Kidney Int. 44, 440–444.

Berk B.C. (1999) Angiotensin II signal transduction in vascular

smooth muscle: pathways activated by specific tyrosine kinases.

J. Am. Soc. Nephrol. 10 (Suppl. 11), S62–S68.

Boffa J.J., Tharaux P.L., Placier S., Ardaillou R., Dussaule J.C.,

Chatziantoniou C. (1999) Angiotensin II activates collagen type

I gene in the renal vasculature of transgenic mice during

inhibition of nitric oxide synthesis: evidence for an endothelin-

mediated mechanism. Circulation 100, 1901–1908.

Boffa J.J., Ying L., Placier S., Stefanski A., Dussaule J.C.,

Chatziantoniou C. (2003) Regression of renal vascular and

glomerular fibrosis: Role of angiotensin II receptor antagonism

and metalloproteinases. J. Am. Soc. Nephrol. 14, 1132–1144

(editorial comment 1411–1414).

Border W.A. & Noble N.A. (1998) Interactions of transforming

growth factor-b and angiotensin II in renal fibrosis. Hyperten-

sion 31, 181–188.

Border W.A., Noble N.A., Yamamoto T., Harper J.R.,

Yamaguchi Y., Pierschbacher M.D., Ruoslahti E. (1992) Natural

inhibitor of transforming growth factor-b protects against

scarring in experimental kidney disease. Nature 360, 361–364.

Bou-Gharios G., Garrett L.A., Rossert J., Niederreither K.,

Eberspaecher H., Smith C., Black C., de Crombrugghe B.

(1996) A potent far-upstream enhancer in the mouse proa2 (I)

collagen gene regulates expression of reporter genes in

transgenic mice. J. Cell Biol. 134, 1333–1344.

Brenner B.M., Cooper M.E., de Zeeuw D., KeaneW.F., Mitch W.E.,

Parving H.H., Remuzzi G., Snapinn S.M., Zhang Z., Shahinfar S.,

RENAAL Study Investigators. (2001) Effects of losartan on renal

and cardiovascular outcomes in patients with type 2 diabetes and

nephropathy. N. Engl. J. Med. 345, 861–869.

Casellas D., Benhamed S., Artuso A., Jover B. (1999) Candesartan

and progression of preglomerular lesions in L-NAME hyper-

tensive rats. J. Am. Soc. Nephrol. 10, S230–S233.

Chatziantoniou C., Boffa J.J., Ardaillou R., Dussaule J.C. (1998)

Nitric oxide inhibition induces early activation of type I

collagen gene in renal resistance vessels and glomeruli in

transgenic mice: role of endothelin. J. Clin. Invest. 101,

2780–2789.

Cordonnier D.J., Pinel N., Barro C., Maynard M., Zaoui P.,

Halimi S., Hurault de Ligny B., Reznic Y., Simon D., Bilous R.W.

(1999) Expansion of cortical interstitium is limited by

converting enzyme inhibition in type 2 diabetic patients with

glomerulosclerosis. The Diabiopsies Group. J. Am. Soc.

Nephrol. 10, 1253–1263.

Cornacchia F., Fornoni A., Plati A.R., Thomas A., Wang Y.,

Inverardi L., Striker L.J., Striker G.E. (2001) Glomerulo-

sclerosis is transmitted by bone marrow-derived mesangial cell

progenitors. J. Clin. Invest. 108, 1649–1656.

Fakhouri F., Placier S., Ardaillou R., Dussaule J.C.,

Chatziantoniou C. (2001) Angiotensin II activates collagen

type I gene in the renal cortex and aorta of transgenic mice

through interaction with endothelin and TGFb. J. Am. Soc.

Nephrol. 12, 2701–2710.

Ferrari G., Cusella-De Angelis G., Coletta M., Paolucci E.,

Stornaiuolo A., Cossu G., Mavilio F. (1998) Muscle regener-

ation by bone marrow-derived myogenic progenitors. Science

279, 1528–1530.

Flamant M., Tharaux P.L., Placier S., Henrion D., Coffman T.,

Chatziantoniou C., Dussaule J.C. (2003) Epidermal Growth

Factor Transactivation Mediates the Tonic and Fibrogenic

Effects of Endothelin in the Aortic Wall of Transgenic Mice.

FASEB J. 17, 327–329 (Epub 02–0115fje, December 2002).

Francischetti A., Ono H., Frohlich E.D. (1998) Renoprotective

effects of felodipine and/or enalapril in spontaneously hyper-

tensive rats with and without L-NAME. Hypertension 31,

795–801.

Francois H., Placier S., Parvez-Braun L., Dussaule J.C., Chat-

ziantoniou C. (2003) Prevention of renal vascular and

glomerular fibrosis by inhibiting tyrosine-kinase growth factor

receptors. J. Am. Soc. Nephrol. 14, 20A.

Gong R., Rifai A., Tolbert E.M., Centracchio J.N., Dworkin L.D.

(2003) Hepatocyte growth factor modulates matrix metallo-

proteinases and plasminogen activator/plasmin proteolytic

pathways in progressive renal interstitial fibrosis. J. Am. Soc.

Nephrol. 14, 3047–3060.

Hocher B., Thone-Reineke C., Rohmeiss P., Schmager F.,

Slowinski T., Burst V., Siegmund F., Quertermous T., Bauer C.,

Neumayer H.H., Schleuning W.D., Theuring F. (1997)

Endothelin-1 transgenic mice develops glomerulosclerosis,

interstitial fibrosis, and renal cysts but not hypertension.

J. Clin. Invest. 99, 1380–1389.

Hogan B.L. (1996) Bone morphogenic proteins in development

Curr. Opin. Genet. Dev. 6, 432–438.

Horwitz E.M., Prockop D.J., Fitzpatrick L.A., Koo W.W.,

Gordon P.L., Neel M., Sussman M., Orchard P., Marx J.C.,

PyeritZ. R.E., Brenner M.K. (1999) Transplantability and

therapeutic effects of bone marrow-derived mesenchymal cells

in children with osteogenesis imperfecta. Nat. Med. 5,

309–313.



Hotta O., Furuta T., Chiba S., Tomioka S., Taguma Y. (2002)

Regression of IgA nephropathy: a repeat biopsy study. Am. J.

Kidney Dis. 39, 493–502.

Hruska K.A., Guo G., Wozniak M., Martin D., Miller S., Liapis H.,

Loveday K., Klahr S., Sampath T.K., Morrissey J. (2000)

Osteogenic protein-1 prevents renal fibrogenesis associated

with ureteral obstruction. Am. J. Physiol. Renal Physiol. 279,

F130–F143.

Imasawa T., Nagasawa R., Utsunomiya Y., Kawamura T., Zhong Y.,

Makita N., Muso E., Miyawaki S., Maruyama N., Hosoya T.,

Sakai O., Ohno T. (1999) Bone marrow transplantation

attenuates murine IgA nephropathy: The role of a stem cell

disorder. Kidney Int. 56, 1809–1817.

Imasawa T., Utsunomiya Y., Kawamura T., Zhong Y., Nagasawa R.,

Okabe M., Maruyama N., Hosoya T., Ohno T. (2001) The

potential of bone marrow-derived cells to differentiate to

glomerular mesangial cells. J. Am. Soc. Nephrol. 12,

1401–1409.

Isaka Y., Brees D., Ikegaya K., Kaneda Y., Imai E., Noble N.A.,

Border W.A. (1996) Gene therapy by skeletal muscle expres-

sion of decorin prevents fibrotic disease in rat kidney. Nat.

Med. 2, 418–423.

Ito T., Suzuki A., Imai E., Okabe M., Hori M. (2001) Bone

marrow is a reservoir of repopulating mesangial cells during

glomerular remodeling. J. Am. Soc. Nephrol. 12, 2625–2635.

Kashiwagi M., Shinozaki M., Hirakata H., Tamaki K., Hirano T.,

Tokumoto M., Goto H., Okuda S., Fujishima M. (2000)

Locally activated renin-angiotensin system associated with

TGFb as a major factor for renal injury induced by chronic

inhibition of nitric oxide synthase in rats. J. Am. Soc. Nephrol.

11, 616–624.

Kasuga H., Ito Y., Sakamoto S., Kawachi H., Shimizu F., Yuzawa Y.,

Matsuo S. (2001) Effects of anti-TGF-beta type II receptor

antibody on experimental glomerulonephritis. Kidney Int. 60,

1745–1755.

Kawamoto A., Gwon H.C., Iwaguro H., Yamaguchi J.I., Uchida S.,

Masuda H., Silver M., Ma H., Kearney M., Isner J.M., Asahara T.

(2001) Therapeutic potential of ex vivo expanded endothelial

progenitor cells for myocardial ischemia. Circulation 103,

634–637.

Kelly D.J., Skinner S.L., Gilbert R.E., Cox A.J., Cooper M.E.,

Wilkinson-Berka J.L. (2000) Effects of endothelin or angio-

tensin II receptor blockade on diabetes in the transgenic (mRen-2),

27 rat. Kidney Int. 57, 1882–1894.

Klahr S. & Morrisey J.J. (2000) The role of vasoactive

compounds, growth factors and cytokines in the progression

of renal disease. Kidney Int. 57 (Suppl. 75), S7–S14.

Lewis E.J., Hunsicker L.G., Clarke W.R., Berl T., Pohl M.A.,

Lewis J.B., Ritz E., Atkins R.C., Rohde R., Raz I. (2001)

Renoprotective effect of the angiotensin-receptor antagonist

irbesartan in patients with nephropathy due to type 2 diabetes.

N. Engl. J. Med. 345, 851–860.

Ludewig D., Kosmehl H., Sommer M., Bohmer F.D., Stein G.

(2000) PDGF receptor kinase blocker AG1295 attenuates

interstitial fibrosis in rat kidney after unilateral obstruction.

Cell Tissue Res. 299, 97–103.

Maschio G., Alberti D., Janin G., Locatelli F., Mann J.F.,

Motolese M., Ponticelli C., Ritz E., Zucchelli P. (1996) Effect

of the angiotensin-converting-enzyme inhibitor benazepril on

the progression of chronic renal insufficiency. The Angiotensin-

Converting-Enzyme Inhibition in Progressive Renal Insuffi-

ciency Study Group. N. Engl. J. Med. 334, 939–945.

Michel J.B., Xu Y., Blot S., Philippe M., Chatelier G. (1996)

Improved survival in rats administered L-NAME due to

converting enzyme inhibition. J. Cardiovasc. Pharmacol. 28

(142–148), 1996.

Morrissey J., Hruska K., Guo G., Wang S., Chen Q., Klahr S.

(2002) Bone morphogenetic protein-7 improves renal fibrosis

and accelerates the return of renal function. J. Am. Soc.

Nephrol. 13 Suppl, S14–S21.

Muller D.N., Mervaala E.M., Schmidt F., Park J.K., Dechend R.,

Genersch E., Breu V., Loffler B.M., Ganten D., Schneider W.,

Haller H., Luft F.C. (2000) Effect of bosentan on NF-kB,inflammation, and tissue factor in angiotensin II-induced end-

organ damage. Hypertension 36, 282–290.

Ostendorf T., Kunter U., Grone H.J., Bahlmann F., Kawachi H.,

Shimizu F., Koch K.M., Janjic N., Floege J. (2001) Specific

antagonism of PDGF prevents renal scarring in experimental

glomerulonephritis. J. Am. Soc. Nephrol. 12, 909–918.

Parving H.H., Lehnert H., Brochner-Mortensen J., Gomis R.,

Andersen S., Arner P., Irbesartan in Patients with Type 2

Diabetes and Microalbuminuria Study Group. (2001) The

effect of irbesartan on the development of diabetic nephropathy

in patients with type 2 diabetes. N. Engl. J. Med. 345,

870–878.

Prockop D.J. (1997) Marrow stromal cells as stem cells for

nonhematopoietic tissues. Science 276, 71–74.

Simon M., Maresh J.G., Harris S.E., HernandeZ. J.D., Arar M.,

Olson M.S., Abboud H.E. (1999) Expression of bone

morphogenetic protein-7 mRNA in normal and ischemic adult

rat kidney. Am. J. Physiol. 276, F382–F389.

Tharaux P.L., Chatziantoniou C., Casellas D., Fouassier L.,

Ardaillou R., Dussaule J.C. (1999) Vascular endothelin-1 gene

expression, synthesis and effect on renal type I collagen

synthesis and nephroangiosclerosis during nitric oxide synthase

inhibition in rats. Circulation 99, 2185–2191.

Tharaux P.L., Chatziantoniou C., Fakhouri F., Dussaule J.C.

(2000) Angiotensin II activates collagen I gene through a

mechanism involving the MAP/ER kinase pathway. Hyperten-

sion 36, 330–336.

United States Renal Data System. (1998) Incidence and pre-

valence of ESRD. Am. J. Kidney Dis. 32 (Suppl. 1), S38–S49.

Valderrabano F., Berthoux F.C., Jones E.H., Mehls O. (1996)

Report on management of renal failure in Europe, XXV, 1994



end stage renal disease and dialysis report. The EDTA-ERA

Registry. Nephrol. Dial. Transplant. 11 (Suppl. 1), 2–21.

Verhagen A.M., Rabelink T.J., Braam B., Opgenorth T.J.,

Grone H.J., Koomans H.A., Joles J.A. (1998) Endothelin A

receptor blockade alleviates hypertension and renal lesions

associated with chronic nitric oxide synthase inhibition. J. Am.

Soc. Nephrol. 9, 755–762.

Wang B., Hao J., Jones S.C., Yee M.S., Roth J.C., Dixon I.M.

(2002) Decreased Smad 7 expression contributes to cardiac

fibrosis in the infarcted rat heart. Am. J. Physiol. Heart Circ.

Physiol. 282, H1685–H1696.

Weber K.T. (2000) Targeting pathological remodelling: concepts

of cardioprotection and reparation. Circulation 102,

1342–1345.

Weistuch J.M. & Dworkin L.D. (1992) Does essential hyperten-

sion cause end- stage renal disease? Kidney Int. 41, S33–S37.

Yamagishi H., Yokoo T., Imasawa T., Mitarai T., Kawamura T.,

Utsunomiya Y. (2001) Genetically modified bone marrow-

derived vehicle cells site specifically deliver an anti-inflammatory

cytokine to inflamed interstitium of obstructive nephropathy.

J. Immunol. 166, 609–616.

Yang J., Dai C., Liu Y. (2003) Hepatocyte growth factor

suppresses renal interstitial myofibroblast activation and

intercepts Smad signal transduction. Am. J. Pathol. 163,

621–632.

Yang J. & Liu Y. (2003) Delayed administration of hepatocyte

growth factor reduces renal fibrosis in obstructive nephro-

pathy. Am. J. Physiol. Renal Physiol. 284, F349–F357.

Zeisberg M., Hanai J., Sugimoto H., Mammoto T., Charytan D.,

Strut Z.F., Kalluri R. (2003) BMP-7 counteracts TGF-beta

1-inducedepithelial-to-mesenchymal transitionandreverses

chronic renal injury. Nat. Med. 9, 964–968.



Progression and regression in renal vascular and glomerular fibrosis

Documents

Transcript of Progression and regression in renal vascular and glomerular fibrosis