Download Role of miRNAs in cardiac fibrosis

Scriptie.
Role of miRNAs in cardiac fibrosis.
Sjoukje I. Lok1, Daniëlle Mensink2, Nicolaas de Jonge1, Roel A. de Weger2.
1
2
Department of Cardiology, University Medical Center, Utrecht, the Netherlands
Department of Pathology, University Medical Center, Utrecht, the Netherlands
Corresponding author:
Sjoukje Lok, MD
University Medical Centre Utrecht
Huispostnummer H04.312
Postbus 85500
3508 GA Utrecht
Abstract
Heart failure is a common problem in developed countries. During heart failure, cardiac remodelling
takes place which leads to cardiac fibrosis. TGF-β is at a key central position in mediating fibrosis.
Anti-fibrotic strategies are increasingly recognized as a promising approach in the prevention and
treatment of heart failure. Targeting the TGF-β axis in developing anti-fibrotic therapies, will
influence the immune regulation and accelerate plaque formation. Therefore, specific intervention
points downstream of TGF-β ligand and receptors are required. New evidence is showing that
microRNAs may have a potential influence in the pathway of cardiac fibrosis. These microRNAs can
give new directions for a future therapeutic for heart failure and can have a function a biomarker for
better diagnostics.
Keywords: miRNA, Fibrosis, Remodeling, Heart Failure.
Introduction
Heart failure is one of the leading causes of hospital admission and mortality in industrialized
countries [1][13]. Heart failure is characterised by cardiac remodeling. There are two important
processes to appoint: the hypertrophic reaction of the cardiomyocytes and the deposition of
extracellular matrix (ECM) by fibroblasts. The ECM deposition by the fibroblasts causes cardiac
fibrosis. Recent evidence suggests that microRNAs (miRNAs, miRs) are differentially expressed in the
failing heart and play an important role in progression of cardiac remodeling. This review focuses on
the function of miRs in relation to their role in cardiac remodeling, especially the process of cardiac
fibrosis.
Ras and Angiotensine II
The Ras (renin angiotensin system) is the body’s hormonal system that regulates blood pressure and
water balance [2][18]. The RAS is activated during heart failure in response to hemodynamic
overload and contributes to myocardial hypertrophy, fibrosis and dysfunction [3][30]. The effector
molecule of the RAS, Angiotensine II (Ang II), directly induces cellular responses in the heart. Ang II
stimulates the secretion of transforming growth factor (TGF)-β by cardiac fibroblasts [3,4][28, 30].
(see Figure 1)
TGF-β signalling
After induction of the secretion of TGF-β by Ang II, TGF-β will activate the Smad pathway which
regulates the transcription of several fibrosis-related genes, including those encoding connective
tissue growth factor (CTGF), osteopontin (OPN) and endothelin-1 (ET-1) [4-7][14, 26, 28, 42]. CTGF is
overexpressed during cardiac fibrosis and is correlated with the severity of fibrosis [4][28]. OPN
controls the CTGF expression [7][42]. ET-1 induces a program of ECM synthesis and contraction
[4][28].
CTGF, OPN and ET-1 induce the differentiation from fibroblasts into myofibroblasts [6,8,9][26, 32, 43].
This cell type is not part of the normal cardiac tissue and is only present after cardiac injury [10][10].
The myofibroblasts produce different proteins that play an important role in the ECM and this leads
to cardiac fibrosis during cardiac remodeling resulting in heart failure. (see Figure 1)
Since the TGF- β is involved in cardiac remodelling, it can be a promising therapeutic target. However,
this strategy is challenging due to the broad range of effects of TGF-β and its important role in tissue
homeostasis [11][0]. Recent studies suggest TGF-β exerts antiatherogenic actions [11][0]. Chronic
inhibition of TGF-β signalling may accelerate plaque formation [11][0]. Furthermore, inhibition of the
TGF-β pathway in patients with cardiomyopathy in order to attenuate hypertrophy and fibrosis will
also likely interfere with immune regulation [11][0].
A new approach for identification of a suitable therapeutic for patients with heart failure is needed
to selectively inhibit pro-fibrotic signalling.
miRNAs
Recently the interest in small non-coding miRs has increased enormously. MiRs are small regulatory
RNAs, about 22 nucleotide in length, that act as negative regulators of genes by inhibiting mRNA
translation or degradation of mRNA through binding to their 3’-UTR region [12-14][3, 12, 17]. The
importance of these small molecules has been shown in plant biology, cancer, viral diseases and
developmental processes [1][13]. Research showed that some miR levels seemed to be increased or
decreased in cardiac fibrosis. Potential target genes were identified for some regulatory miRs and
their possible role in cardiac fibrosis has been validated [1][13].
The novel findings of the role of miR in cardiac remodeling reveal a future therapeutic target for
treatment of cardiac remodeling.
Role of miRNAs in cardiac fibrosis
Several miRs have so far been implicated in the control of cardiac fibrosis. The molecular pathways
targeted by those miRs are depicted in Figure 2.
Angiotensine II
Ang II is a key hormone in cardiovascular homeostasis and is involved in multiple cardiac diseases.
Ang II functions as a stimulator of fibrosis and also stimulates myocardial cell growth and
hypertrophy. The increased myocardial tissue levels of Ang II are consistent with the increase in
collagen content after Left ventricular assist device (LVAD) support [15][44]. However, a reduction
toward normal in myocyte diameter and regression of hypertrophy in patients after LVAD support
has been seen [15][44]. This suggests that the hemodynamic effect of unloading the LV overwhelms
the effect of Ang II in hypertrophy but not in fibrosis [15][44]. Evidence in mice supports our concept
that Ang II could affect fibrosis without inducing hypertrophy [15][44].
Research identified five miRs (miR-29b, miR-129-3p, miR-132, miR-132*, miR-212) which are induced
by Ang II in cardiac fibroblasts through the Angiotensin II type 1 receptor (AT1R) [16][7]. Several of
these miRs have previously been linked to cardiovascular disease [16][7]. The regulation of these
miRs relies on Gαq/11 and Erk1/2 dependent signalling [16][7].
ERK-MAP signalling
MiR-21 regulates the extracellular signal-regulated kinase-mitogen activated protein kinase (ERKMAP) signalling in cardiac fibroblast and thereby it seems to have influence on global cardiac
structure and function [17][21]. MiR-21 levels are increased in heart failure and increases the ERKMAP signalling by inhibition of sprouty homologue 1 (Spry1) [17][21]. Due to an increased ERK-MAP
signalling there is an increased survival, proliferation and growth factor secretion of the fibroblasts
leading to fibrosis, hypertrophy and cardiac dysfunction [17] [21]. Therefore miR-21 seems to be an
important regulator of fibrosis and fibroblast functions in heart failure [17][21].Silencing of miR-21
reduces cardiac ERK-MAP kinase activity, inhibits interstitial fibrosis and attenuates cardiac function
[17][21]. These results validate miR-21 as a disease target in heart failure and establish the
therapeutic efficacy of miR therapeutic intervention in cardiovascular disease.
CTGF
CTGF is a pro-fibrotic factor and is considered to play a key role in cardiac fibrosis in the failing heart.
Several studies have indicated that miR-133 and miR-30 are both negative regulators of CTGF
expression [12][3]. MiR-133 and miR-30 can influence the protein level of CTGF directly by binding to
the 3’-UTR of the CTGF mRNA [12][3]. In a normal heart miR-133 and miR-30 importantly regulate
the amount of CTGF by repressing the translation and also by degradation of the mRNA [12][3]. In
heart failure, miR-113 and miR-30 are downregulated, thereby losing the negative regulation on
CTGF and resulting in an increase in CTGF levels [12][3].
Furthermore, regulation of CTGF and TSP-1 (thrombospodin-1), an ECM protein, seems to be
regulated by the miR-17~92 cluster during cardiac remodeling in age-related heart failure [18][11].
An inhibition of miR-18a, miR-19a and miR-19b seem to result in an increased expression of CTGF
and TSP-1, both of which contribute to cardiac fibrosis [18][11]. However, in cardiac fibroblast,
overexpression of miR-18a and miR-19b also decreases the CTGF and TSP-1 transcription, but
inhibition of these miRs was not sufficient to increase CTGF and TSP-1 [18][11]. This may be due to
the fact that a fibroblast produces large amounts of CTGF and TSP-1 while it contains relatively low
amounts of miR-18a and miR-19b [18][11]. The age related regulation of CTGF and TSP-1 expression
by miR-18a, miR-19a and miR-19b in the heart seem to be restricted to the cardiomyocytes to
control their surrounding ECM [18][11].
Collagen and other ECM proteins
Collagen is one of the most important proteins of the ECM. Several factors like TGF-β indirectly
induce the production of collagen during cardiac remodeling. A study by van Rooij et al showed that
TGF-β represses the miR-29 expression [19][4]. MiR-29 regulates a broad spectrum of mRNAs
involved in fibrosis and ECM remodeling, like collagen, fibrillins and elastins [12,19][4, 3].
MiR-29 inhibits the fibrotic respons in a normal heart [19][4]. When TGF-β is overexpressed during
heart failure, it will represses the expression of miR-29 and thereby the negative regulation of
mRNAs involved in fibrosis and ECM remodeling will be lost [19][4]. As result it will give more fibrosis
and ECM proteins that contribute to further development of heart failure.
MiRNA in fibrosis of other organs
MicroRNA dysregulation has also been studied in pulmonary, hepatic and renal fibrosis. The
mechanism in which fibrosis occurs is similar to all organs. The possible role of miRs in fibrosis could
also have similarities between different organs and therefore be a promising approach for
development of new therapeutics.
MiR-21
A study of patients with idiopathic pulmonary fibrosis (IPF) showed an increased expression of miR21 and this expression was primarily localized to myofibroblasts [20,21][20, 9]. The data present that
miR-21 is a central mediator during lung fibrosis and could be a potential target for developing novel
therapeutics in treating fibro tic diseases, including IPF and heart failure [20][20].
MiR-29
MiR-29 correlates with increased expression of collagens and ECM-related genes in pulmonary,
hepatic and renal fibrosis [22-24][37, 40, 41]. Research showed a significant reduction of miR-29
correlating with a increased ECM deposition. Furthermore, the results show that TGF-β is a repressor
of the miR-29 expression. The low levels of miR-29 correlate with advanced stages of hepatic fibrosis
[25][34]. The precise dysregulation of miR-29 during renal fibrosis has not been clarified yet.
Discussion
Heart failure is characterised by cardiac remodeling. Cardiac remodeling is characterised by cardiac
fibrosis and hypertrophy. During cardiac fibrosis the TGF-β pathway is an important regulator of the
ECM deposition. However, TGF-β has not seemed to be a possible therapeutic target because of its
role during immune regulation and plaque formation. Therefore the interest in miRs has increased
enormously for their potential role in cardiac fibrosis.
MiR-21, -29, -30 and -133 seem to be key regulators in the fibrotic response. MiR-21 inhibits Spry1
and thereby induces the ERK-MAP pathway resulting in an increased cardiac fibrosis.
Mir-30 and miR-133 influence the protein level of CTGF. During cardiac remodeling these miRs are
inhibited by TGF-β resulting in a higher CTGF level.
Another miR with a notable influence in cardiac fibrosis is miR-29. This miR can influence the
production of collagens and other ECM proteins. During cardiac fibrosis, miR-29 is suppressed by
TGF-β resulting in a higher ECM synthesis.
Furthermore the miR-17~92 cluster seemed to play a role in controlling CTGF and TSP-1. However,
the role of the miRs from this cluster has not seemed to have important influence in the fibroblasts.
Finally, Ang II is playing an important role in the regulation of miRs. Ang II seemed to influence the
miR expression in a way it is resulting in an increased cardiac fibrosis.
Nowadays there is more evidence that miRs regulate fibrosis in multiple organs including the heart,
lung, kidney and liver. Particulary miR-21 and miR-29 seem to show similarities between their
function in fibrosis in different organs. Some potential therapeutic strategies have already been
shown for targeting these two miRs and thereby they show a potential therapeutic approach for
treatment of fibrosis in all these different organs.
AntimiRs, or antagomiRs, are modified antisense oligtonucleotides that target the mature miR
sequence and thereby increase the mRNA levels that are normally targeted by the miR [26][23]. In
contrast, miR mimics elevate the expression levels of the miRs in the target tissue and thereby
decreasing the expression of the mRNAs controlled by that miR [26][23]. Even though miR based
therapies are promising for the treatment of heart failure, there are limitations to overcome before
these promising therapies can be safely and successfully applied in patients. miRs have a broad
spectrum of mRNA target and it is likely that modulation of a single miR lead to unintended adverse
effects and pathological consequences through regulation of other, sometimes unknown mRNAs.
Secondly, the miR-based therapeutics needs to be improved in their pharmacokinetics,
biodistribution and tissue penetration to achieve target tissue specificity.
Promising results have been seen with antagomiR-21 in mice. The animals treated with antagomiR21 showed significant attenuation of the impairment of cardiac functions as well as regression of
cardiac hypertrophy and fibrosis [17][21]. This study showed therapeutic efficacy for silencing of miR21 by antogomiRs in a cardiac disease setting.
MiRs may also serve as biomarkers of cardiac fibrosis in patients with heart failure since they can be
measured in the cirvulation. Tijsen and colleagues performed a miR arrays on plasma samples from
patients with heart failure and analyses revealed that serum miR-423-5p level was a powerful
predictor of heart failure diagnosis [26][23]. The source and mechanism of action of miR-423-5p in
patients with heart failure is yet to be determined [26][23]. However, this study provides evidence
that circulating miRs can be utilized as biomarkers in patients with heart failure. Plasma miR profiling
might be useful for evaluating patients with heart failure and may refine current diagnostics. Further
studies are needed to clarify the source and mechanism of action of circulating miRs, as well as their
prognostic value for heart failure patients.
MiRs seem to play an important role during cardiac remodeling. Despite recent advances in miR
research, many gaps remain in the knowledge of miR regulation of gene expression in the normal
and diseased heart. It is necessary to define the potential function of individual miRs. Future research
is necessary to indicate whether miRs can be used as therapeutic entry point and/or as biomarker
during heart failure.
Figure 1: Schematic diagram illustrating the connection between the Ras system, Ang II, TGF-β signalling, OPN,
ET-1 and CTGF, fibroblasts and myofibroblasts in cardiac remodeling resulting in heart failure.
The Ras system induces Ang II, Ang II induces TGF-β and TGF-β induces the fibrotic-related genes. Through
induction of these genes the production of OPN, CTGF and ET-1 will be upregulated during cardiac fibrosis.
These products will induce the differentiation from fibroblasts in myofibroblast. The myofibroblast will produce
different proteins, like collagen, who will contribute to development of the ECM. Through this pathway cardiac
remodeling will be induces and will result in heart failure.
Figure 2: Overview of the role of miRs during cardiac remodeling as discussed in the review. Most of the miRs
suppress the fibrosis in a normal heart. During cardiac remodeling these miRs are inhibited and thereby the
suppression of the miRs has fallen away. MiR-21 is normally available in low amounts. During cardiac
remodeling the levels of miR-21 are increased and induce indirectly the fibrosis.
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Practisch deel.
The effect of LVAD support on the
expression of TGF-β1.
Daniëlle Mensink
Biomedical Sciences - University of Utrecht
Report Practical Part, Bachelor Researchproject
University Medical Centre Utrecht
March - July 2011
ABSTRACT
Heart failure is a complex disorder characterized by cardiac remodeling. During cardiac
remodeling, fibrosis occurs. Transforming growth factor (TGF)-β1 plays an important role in
the fibrotic response. In patients with end-stage heart failure, a left ventricular assist device
(LVAD) can be used as bridge to transplantation. During LVAD support, partial reverse
remodeling takes place. The degree of cardiac fibrosis during LVAD support could predict the
myocardial improvement. We hypothesize that TGF-β1 might be used as a marker to
determine the degree of cardiac fibrosis and therefore it could help to predict the cardiac
improvement of patients during LVAD support.
INTRODUCTION
Heart failure is one of the leading causes of hospital admission and mortality in industrialized
countries [1]. Heart failure is characterised by cardiac remodeling. Cardiac remodeling is
characterised by cardiac fibrosis which occurs through activation of the TGF-β pathway of the
cardiac fibroblast. Activation of the TGF-β pathway leads to an increased production of ECM
components resulting in increased cardiac fibrosis. Until recently, it was widely believed that
cardiac remodeling was irreversible. However, studies with LVAD supported patients showed
otherwise. LVAD support has been linked to ‘reverse remodeling’. Reverse remodeling refers
to the molecular processes of improved cardiac function. Many of the pathological events
associated with heart failure, such as cardiac fibrosis, seem to regress toward normal
parameters. A combination of mechanical unloading through LVAD support and
pharmacological management has increased the frequency of recovery following LVAD
support. Nevertheless, the mechanisms of reverse remodeling during LVAD support have not
been fully characterized. Previous studies show controversy changes in cardiac fibrosis
during LVAD support. Some studies have suggested that cardiac fibrosis increases during
LVAD support. The renin-angiotensin-system (RAS) plays a leading role in the TGF-β
pathway. A study by Klotz et al showed trends towards increased levels of angiotensin I and
II (Ang I and II) in the myocardial tissue after LVAD support and therefore resulting in
ongoing production of new collagen contributing to cardiac fibrosis [2]. Furthermore they
showed an increase of total collagen content after LVAD support, particularly cross-linked
collagen [2]. Drakos et al also showed an increase of interstitial fibrosis [3]. However, other
studies have reported that there is a decrease in cardiac fibrosis during LVAD support.
Bruckner et al showed a reduction of collagen I and III after LVAD support [4, 5].
Furthermore, Jahanyar et al showed a decorin-mediated TGF-β1 inhibition involved in reverse
cardiac remodeling that also indicates a decrease in cardiac fibrosis after LVAD support [6].
Finally, James et al showed a decrease of Ang II at explant which may indicate a decrease in
cardiac fibrosis [7]. These conflicting data regarding the change in fibrosis during LVAD
support can be explained by the biphasic pattern described by Bruggink et al [8]. They show
an increase of ECM volume in the first period of LVAD support. After prolonged LVAD
support, the ECM volume seemed to be reduced which indicates in a later decrease in cardiac
fibrosis.
The goal of this research was to study the expression of the key factor of cardiac fibrosis,
TGF-β1, during LVAD support. The expression of TGF-β1 was measured by comparing
samples of LVAD patients before and after their LVAD support. The mRNA levels of TGFβ1 during LVAD support were measured by qPCR. Furthermore, an ELISA was performed to
measure plasma levels of TGF-β1.
METHODS
Study population
qPCR
The study population consisted of patients with end-stage heart failure supported by a
continuous flow LVAD support as bridge to transplantation. All patients were diagnosed with
non-ischemic dilated cardiomyopathy. Left ventricular tissue samples (apical core) were taken
at time of LVAD implantation (pre LVAD) and compared to tissue samples collected from
the explanted hearts after Heart Transplantation (HTx). Samples were stored at a temperature
of -80°C until isolation of the total RNA. Control tissue samples were obtained from refused
donor hearts.
ELISA
Plasma samples were obtained from patients suffering end-stage heart failure. Samples were
taken before LVAD implantation (pre LVAD), 1 month, 3 months and 6 months after LVAD
implantation and before heart transplantation (pre HTx). EDTA (Ethylenediaminetetraacetic
acid) plasma samples were immediately stored at -80°C. Samples were aliquoted to avoid
freeze-thaw cycles.
RNA isolation and reverse transcription
For the isolation of total RNA from frozen heart tissue, the RNeasy Mini Kit (Qiagen,
Benelux BV, Venlo, Netherlands) was used according to manufacturer’s instructions. Total
RNA was stored at -80°C until further use. For the qPCR, Copy-DNA (cDNA) was
synthesized from 1 μg total RNA using oligodT and random primers. The cDNA samples
were stored at -20°C until use.
qPCR
At first the efficiency of TGF-β1 and GAPDH was determined with cDNA-dilution series.
The efficiency of TGF-β1 was set at 1,81 and the efficiency of GAPDH at 1,96.
The qPCR was performed to determine the change in mRNA levels of TGF-β1. H2O was
used as negative control and the calibrator as positive control. Placenta was used as calibrator.
GAPDH was used as reference gene. Taqman gene-expression (TGEA, Applied Biosystems)
were used to determine TGF- β1 expression. The PCR-mix is composed of 3,13 μl MilliQ
(MQ), 0,625 μl primer/probe (TGEA) and 6,25 μl mastermix per well. The cDNA has to be
diluted five times (1:5) with MQ before use. Every well contains 2,5 μl diluted cDNA and 10
μl PCR-mix. The qPCR was performed on the LightCycler 480-II (Roch Diagnostics, Almere,
Netherlands) using the following thermal profile: 95°C for 10 min, and 40 cycles of 95°C for
15 sec and 60°C for 1 min. The comparative Ct-method was used to determine the relative
quantity.
ELISA
An ELISA (human TGF-β1 Platinum ELISA Kit from eBioscience) was performed to
measure the protein levels of TGF-β1 in the plasma samples of LVAD patients and healthy
controls. All materials for the ELISA were derived from the Kit. The ELISA was performed
according to the protocol in the Kit. The kit was stored at 4°C before use. The plate was
measured at 450 nm.
Statistical analysis
The statistical analysis of the qPCR results were done with Prism software (GraphPad
Software, Inc., San Diego, CA) and p ≤ 0.05 was considered significant. For the statistical
analysis we used the Wilcoxon signed rank test (non-parametric paired t-test).
RESULTS
TGF-β1 mRNA levels
To study the myocardial mRNA expression of TGF-β1 in patients with heart failure on LVAD
support, we compared the mRNA levels of TGF-β1 before (pre) and after (post) LVAD
support. During LVAD support, there is a significant increase in mRNA TGF-β1 (p = 0,001)
(Figure 1).
Figure 1. Relative quantity of mRNA
TGF-β1 at time of LVAD implant (pre)
and at time of LVAD explant (post) (n =
12). *p = 0,001
TGF-β1 plasma levels
Plasma samples of TGF-β1 were measured at different time points during LVAD support with
Elisa. A standard curve was created by plotting the mean absorbance for each standard
concentration. To determine the concentration of circulating human TGF-β1 for each sample,
the mean absorbance had to be calculated and the concentration could be read out of the
standard curve. This concentration value was multiplied by the dilution factor of 30.
Unfortunately, when we corrected the absorption values of our patient samples with the
values of the blanks, most of the absorption values ended up to be negative. This would imply
that there is not any TGF-β1 in the plasma of the patients and the healthy controls.
Other reports show that the TGF-β1 concentration in plasma of healthy human subject is
around 4.1 +/- 2.0 ng/ml [9]. Therefore, our results of the ELISA for the patients and our
healthy controls are unreliable. A possible explanation could be found in the acidification of
the plasma samples before they are used for the ELISA. There are two forms of TGF-β1
available in the plasma: latent TGF-β1 and activated TGF-β1. To activate the latent form of
TGF-β1, the plasma samples must be acidified with HCl and neutralized with NaOH. When
the fluids used for acidification or neutralisation (HCl and NaOH) do not fulfil their role, the
sample will not give any result in the ELISA. We contacted the supplier and we will have to
measure the pH of the HCL and the NaOH to investigate whether this could be the reason for
our results.
DISCUSSION
During LVAD support reverse remodeling takes place resulting in partial recovery of the
heart. Unfortunately, the mechanisms of reverse remodeling after LVAD support have not
been fully characterized. Therefore further research with patients on LVAD support is
necessary.
This article shows an upregulation of the expression of TGF-β1 mRNA in patients with heart
failure after LVAD support. This could indicate an increase in cardiac fibrosis during LVAD
support. However, the results of the ELISA could not confirm our results of the qPCR and
therefore we do not know if the protein levels of TGF-β1 correspond with the increased
mRNA levels of TGF-β1. Further research has to be done to determine the protein levels of
TGF-β1.
Bruckner et al showed that the degree of cardiac fibrosis and hypertrophy at time of LVAD
implantation could predict the myocardial improvement during LVAD support [10]. Whether
or not TGF-β1 can be used as a biomarker to determine the degree of cardiac fibrosis needs
further investigations. Furthermore, if it seems that cardiac fibrosis is increased during LVAD
support, development of a new pharmacologic therapy could help to treat the cardiac fibrosis
when the patients are on LVAD support and thereby will contribute to the recovery of the
patients. Klotz et al are showing a combination of angiotensin-converting enzyme inhibitor
(ACE-I) therapy and LVAD support in patients with heart failure [11]. The ACE-I therapy
was associated with decreased AngII, myocardial collagen content, and myocardial stiffness
during LVAD support. This example demonstrates possible strategies of combining LVAD
support with a pharmacologic therapy to optimize reverse remodeling during LVAD support
to enhance the recovery in patients with LVAD support. However, when a new therapy is
developed based on TGF-β1, it will give a broad spectrum of effect in the rest of the body.
Recent studies suggest that TGF-β exerts anti-atherogenic actions. Chronic inhibition of TGF-
β signalling may accelerate plaque formation. Furthermore, inhibition of the TGF-β pathway
in patients with cardiomyopathy in order to attenuate hypertrophy and fibrosis, causes
immune suppression [12, 13, 14]. When a new therapy will be developed to inhibit TGF-β1,
the effects on the rest of the body need to be studied extensively.
We have showed a possible increase of TGF-β1 during LVAD support that indicates an
increase of cardiac fibrosis. To improve the process of reverse remodeling, this increase of
cardiac fibrosis has to be avoided with, for example, a combination of LVAD support and
pharmacologic therapy. However, the mechanisms of reverse remodeling during LVAD
support are still not fully understood yet. Therefore, further research of reverse remodeling
seems to be a crucial.
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