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(Circulation. 1999;100:II-216.)
© 1999 American Heart Association, Inc.
Thoracic Transplantation and Ventricular Assist Devices |
Myocardial Gene Expression of Regulators of Myocyte Apoptosis and Myocyte Calcium Homeostasis During Hemodynamic Unloading by Ventricular Assist Devices in Patients With End-Stage Heart Failure
From the Institute of Pathophysiology (B.B., H.S., D.D., J.H.) and the Clinic for Cardiothoracic Surgery (H.M., H.-R.Z.), Martin Luther University Halle-Wittenberg, Halle/Saale, Germany; the Department of Thoracic and Cardiovascular Surgery (L.A., M.M.K., A.E.-B., R.K.), Heart and Diabetes Center North Rhine-Westphalia, Ruhr University Bochum, Bad Oeynhausen, Germany; and the Clinic for Cardio-Thoracic Surgery (H.-R.Z.), University of Basel, Kantonspital, Basel, Switzerland.
Correspondence to Babett Bartling, Institut für Pathophysiologie, Martin-Luther-Universität Halle-Wittenberg, Magdeburger Str 18, D-06097 Halle/Saale, Germany. E-mail babett.bartling{at}medizin.uni-halle.de
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Abstract |
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Background—In patients with end-stage heart failure, characterized by an increased susceptibility to cardiomyocyte apoptosis and a labile cardiomyocyte calcium homeostasis, a ventricular assist device (VAD) is implanted for bridging to cardiac transplantation and results in myocardial unloading. Although phenotype changes in the failing heart are assumed to result from hemodynamic overload, the reversibility of these changes under unloading is unknown.
Methods and Results—By use of quantitative reverse-transcription polymerase chain reaction, mRNA expression analyses were performed on left ventricular specimens obtained from 10 nonfailing donor hearts (from 8 patients with dilated cardiomyopathy and 2 patients with coronary heart disease) at the time of VAD implantation and 36 to 169 days later during VAD removal with subsequent cardiac transplantation. In terminally failing hearts before VAD support, left ventricular mRNA analyses revealed increased Pro-ANP, reduced antiapoptotic Bcl-xL and antiapoptotic Fas isoform FasExo6Del, and a decreased ratio of sarcoplasmic reticulum Ca2+-ATPase per sarcolemmal Na+-Ca2+ exchanger in comparison with nonfailing ventricles. After VAD unloading, ventricular transcription of Pro-ANP was immediately normalized, and apoptotic DNA fragmentation was attenuated. In patients with dilated cardiomyopathy, mRNAs of Bcl-xL and FasExo6Del/Fas were enhanced depending on time on VAD. The Bcl-xL mRNA level correlated positively with that of the Bcl-xL protein. Transcription of sarcoplasmic reticulum Ca2+-ATPase/Na+-Ca2+ exchanger demonstrated recovery in only 4 of 10 patients.
Conclusions—Mechanical support of the failing heart induces a time-dependent change in myocardial gene expression compatible with a decreased susceptibility to apoptosis.
Key Words: apoptosis • calcium • heart failure • heart-assist device
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Introduction |
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Currently, ventricular assist devices (VADs) are implanted for mechanical support of a failing human heart and function reliably for weeks or months without complications even outside the hospital.1 A shortage of organ donors for heart transplantation has led to the increased application of VADs for patients in end-stage heart failure (HF); the VAD serves as a bridge to transplantation. This bridging also improves the outcome after the subsequent heart transplantation.2 3
The overload-induced distension of the heart is a critical factor promoting the progression of HF.4 Therefore, it has been postulated that some myocardial recovery should occur in the failing heart hemodynamically unloaded by an implanted VAD, and several clinical reports indicate some ventricular recovery under VAD support.5 6
Experimental investigations revealed that mechanical distension of the myocardium induces apoptotic death of cardiomyocytes.7 Furthermore, apoptosis is demonstrable in ventricles of patients with a terminally failing, overloaded heart,8 9 which is associated with mRNA downregulation of antiapoptotic regulators, such as Bcl-xL10 and FasExo6Del.11 In human myocardium, FasExo6Del is the most abundant11 of several soluble antagonistic isoforms of the apoptosis-triggering surface receptor Fas,12 and it is assumed to function by competing with Fas for the Fas ligand. In contrast, the antiapoptotic Bcl-2 family member Bcl-xL is an intracellular protein localized at the outer mitochondrial membrane.13 It prevents the apoptosis-associated disruption of the mitochondrial transmembrane potential,14 the release of cytochrome c from the mitochondrial intermembrane space, and the cytochrome c–mediated activation of the apoptotic process.15 Heterodimerization with the antiapoptotic Bcl-2–related protein Bak through homology domains, characteristic for members of the Bcl-2 family, inhibits the effect of Bcl-xL.13 Like Bcl-xL, Bcl-2 and Mcl-1 exert an analogous apoptosis-preventing function, whereas their action is antagonized by Bax.16 17
Presently, the clinical importance of myocardial recovery under VADs remains unclear. Therefore, we investigated whether a reduction of this distension by VAD unloading6 18 19 abolishes the fatal trend toward ongoing myocardial apoptosis with normalization of the apoptosis-susceptible myocardial phenotype. Accordingly, we obtained left ventricular specimens from the same heart-failure patients during VAD implantation (ie, in the state of maximal hemodynamic overload) and later, during the transplantation with VAD removal (ie, in the state of substantial temporal unloading by the VAD). The left ventricles of HF patients who were successfully transplanted but without previous VAD support were additionally investigated for comparison.
Apart from the apoptosis-sensitive myocardial phenotype, the left ventricular expression of proteins involved in the myocyte calcium homeostasis is altered in failing human myocardium. In detail, a decreased expression of the sarcoplasmic reticulum (SR) Ca2+-ATPase20 is associated with an enhanced expression of the sarcolemmal Na+-Ca2+ exchanger21 in end-stage HF. Therefore, we additionally analyzed the left ventricular mRNA levels of both calcium-regulatory determinants under VAD support of the overloaded heart.
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Methods |
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Patient Population
We obtained left ventricular specimens from 10 male patients undergoing VAD implantation as a bridge to transplantation at the time of surgery and at removal of the VAD with subsequent orthotopic cardiac transplantation. Eight patients suffered from dilated cardiomyopathy (DCM), and 2 patients demonstrated end-stage coronary artery disease (CAD). At the time of VAD implantation, patients were 53±12 years old and clinically characterized as shown in Table 1
.
The hemodynamic data in Table 1 result from the
date when the last echocardiographic determination of
the ejection fraction was performed. For left ventricular
unloading, either TCI HeartMate (Thermo Cardiosystems, Inc), Novacor
(Baxter Healthcare Corp, Novacor Division), or Thoratec (Thoratec
Laboratories, Inc) assist devices were used. For
biventricular support in case of TCI or Novacor use, an
additional right ventricular assist device of Thoratec was
implanted.
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In addition, explanted left ventricular specimens of 22 male and 2 female patients (54±8 years old) from the Halle and Hamburg Cardiac Transplant Program exhibiting end-stage HF and treated without VAD unloading were investigated. They had a mean ejection fraction of 25±15%. Thirteen patients suffered from DCM; 11 patients, from CAD. Left ventricular tissues from 10 organ donors (8 men and 2 women, 39±5 years old) served as controls. These hearts were not transplanted for technical reasons. The local ethics committee approved the study of these human cardiac tissues.
DNA Preparation and Gel Electrophoresis
Genomic DNA was prepared from human left ventricular
specimens by use of the Puregene DNA Isolation Kit (Biozym). DNA (1.5
µg) was electrophoretically separated in a SYBR Green–stained
agarose gel (Biozym). Apoptotic DNA fragmentation was
determined by scanning with a laser densitometer that incorporated an
evaluation system (Molecular Dynamics).
TUNEL Assay
Terminal
deoxynucleotidyltransferase-mediated
dUTP-biotin nick end labeling (TUNEL)-positive
cardiomyocytes were detected in left
ventricular cryosections by using the protocol described in
the Apoptaq Peroxidase Kit (Oncor). Positive and negative control
sections were included. Microscopic evaluations were performed by using
an IMT-2 inverted research microscope (Olympus).
Construction of cRNA Standards and Competitive
Reverse-Transcription Polymerase Chain Reaction
The standard cRNA for each human gene under study was
constructed by introducing a definite deletion of 
100 bp into the
respective cDNA target molecules of the polymerase chain reaction (PCR)
amplification. Each standard cDNA was cloned into the pCR-Script SK 197
plasmid (Stratagene) and in vitro–transcribed from the flanking T3 or
T7 promotor to yield cRNA.
For competitive reverse-transcription PCR (RT-PCR), a dilution series
of the respective cRNA standard molecules was added to 4 RT reactions
containing the same amount of total RNA (Table 2) and simultaneously
reverse-transcribed by using SuperScript Plus reverse transcriptase
(GIBCO-BRL). Total RNA was isolated from left ventricular
specimens after mechanical pulverization in liquid nitrogen using the
protocol of Chirgwin et al.22 The RNA concentration was
calculated from the absorption at 260 nm.
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Five microliters of the first-strand cDNA reaction (RT) was used as the
template for PCR, with each containing the following components: 10
pmol of each primer, 1x complete buffer, 12 µmol/L of each
dNTP, and 2 U of rTaqDNA polymerase (Pharmacia) in a final
volume of 50 µL. After an initial denaturation at 95°C for 2
minutes, PCR cycles were performed in a thermocycler (Biometra
Trioblock) corresponding to the following protocol: 30 seconds at
94°C, 30 seconds at the primer-specific annealing temperature (Table 2
), and 30 seconds at 72°C. After extension of the cDNA
amplification at 72°C for 5 minutes, the PCR products were
electrophoretically separated in an agarose gel containing ethidium
bromide (Sigma-Aldrich) for detection. The RT-PCR was evaluated by
scanning with a laser densitometer and computer-based imaging system
(Molecular Dynamics).
The nucleotide sequences of cDNA clones and PCR fragments were identified by cycle sequencing using the ABI Prism Dye Terminator Cycle Sequencing Kit (Perkin-Elmer) and subsequent automated analysis (Perkin-Elmer, Applied Biosystems Division).
Western Blot
After mechanical pulverization in liquid nitrogen, total protein
from left ventricular tissues was extracted in lysis buffer
(10 mmol/L Tris-HCl [pH 7.4], 1% SDS, and complete protease
inhibitor [Boehringer]) by
homogenization and subsequent incubation at 95°C
for 15 minutes. Protein concentration was measured by the Bio-Rad
protein assay, and samples containing 80 µg of total protein were
mixed with 2x loading buffer (250 mmol/L Tris-HCl [pH 7.4],
20% glycerol, 4% SDS, 40 mmol/L dithiothreitol, 2 mmol/L
Na-EDTA, and 0.1% bromophenol blue), boiled for 2 minutes, and loaded
onto a 10% SDS polyacrylamide gel. Proteins were
electroblotted onto polyvinylidene fluoride membranes (Pall
Gelman), blocked with 6% nonfat dry milk in TBST (200 mmol/L
Tris-HCl [pH 7.5], 300 mmol/L NaCl, and 0.1% Tween 20) at room
temperature for 1 hour, and incubated with 5 µg/mL of the primary
human antibodies for Bcl-xL (rabbit polyclonal,
H-62; Santa Cruz Biotechnology) and for Bcl-2 (mouse monoclonal, 124;
DAKO) at room temperature for 4 hours. Blots were subsequently washed
in TBST and incubated with peroxidase-conjugated antibodies
(anti-rabbit or anti-mouse IgG, respectively; Amersham). Bound
antibodies were detected with enhanced chemiluminescence detection
reagents (Amersham), quantified by use of a laser-densitometer with an
imaging system (Molecular Dynamics), and normalized in comparison with
the densitometrically determined value of the total protein loading per
lane. In control reactions, immunodetection occurred without the
primary antibodies. In all cases, control reactions were negative.
Data Analysis
Clinical data and results of molecular investigations are given
as mean±SD. Student’s paired or unpaired t test was used
for statistical comparison as appropriate. The correlation coefficient
r of the linear regression analysis for significance
was tested by a 2-sided test. A value of P<0.05 was
considered statistically significant.
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Results |
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Data of HF Patients Without VAD Support
Compared with the myocardium of organ donors, the myocardium of HF patients is characterized by an increased mRNA expression of Pro-ANP and a decrease in FasExo6Del, Bcl-xL, and Bak (Table 3
). Furthermore, we observed elevated
apoptotic oligonucleosome-sized DNA fragmentation in left
ventricles (Table 3, Figure 1A)
associated with an increased abundance of apoptotic
cardiomyocytes observed by the TUNEL assay (Figure 1B).
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Influence of ACE Inhibitor Therapy on
Bcl-xL and Bcl-2 Expression
Whereas patients without therapy by inhibitors of the
angiotensin-converting enzyme (ACE) showed low mRNA levels
of Bcl-xL (92.0 amol/µg RNA) and of Bcl-2 (10.1
amol/mg RNA) (n=8), patients under ACE inhibitor treatment
(n=16) revealed partial normalization of Bcl-xL
mRNA (147.8 amol/µg RNA) and Bcl-2 mRNA (20.9 amol/mg RNA)
(P<0.01 and P<0.05, respectively). These mRNA
data could be confirmed on the protein level, which was observed by
Western blot analysis (Figure 2).
In patients treated with ACE inhibitors compared with
patients with no ACE inhibitor treatment, the
Bcl-xL protein level was determined to be 1.0
versus 0.51 relative units (P<0.001), respectively, and the
Bcl-2 protein level was 0.79 versus 0.32 relative units
(P<0.09), respectively. Furthermore, we observed a
significantly positive correlation between Bcl-xL
or Bcl-2 protein and the mRNA levels in the group of all HF patients
and donors (r=0.488 [P<0.05] and
r=0.461 [P<0.05], respectively). However,
these HF patients showed no significant left ventricular
alterations either in apoptotic DNA fragmentation or in Pro-ANP
mRNA expression or ejection fraction depending on the therapy with ACE
inhibitors.
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Data of HF Patients Supported by VAD
Clinical data of the 10 VAD patients revealed a highly critical
hemodynamic state before VAD implantation (Table 1). During the time of ventricular support, a
tendency to improved cardiac function could be assumed in these
patients from decreasing cardiothoracic x-ray ratios or
transthoracic echocardiography.
However, these putative improvements could not be exactly quantified
because the VAD was not temporarily turned off for measurements of the
genuine hemodynamic parameters. This
potentially risky procedure was avoided, since this observational study
was not designed to prove the potential of cardiac recovery under VAD.
Nevertheless, shortly before the orthotopic cardiac transplantation, a
decrease in pulmonary capillary wedge pressure and an absence
of deterioration or even an increase in the cardiac index (determined
either by pulmonary artery catheter or
transthoracic echocardiography)
indicated the beneficial effects on hemodynamic
unloading by VAD (Table 1).
Transcription of Pro-ANP
In left ventricular specimens, we observed a decrease
in Pro-ANP mRNA expression under hemodynamic unloading
approaching the mRNA levels of donor ventricles (Table 3 and
Figure 3). This downregulation of
Pro-ANP mRNA did not depend on time elapsed on VAD: it reached 23±18
amol/ng RNA in patients with <100 days (n=4) and 31±30 amol/ng RNA in
patients with >100 days (n=6) of VAD support compared with the
starting level of 180±207 amol/ng RNA.
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Apoptotic DNA Laddering
No or minimal signs of DNA fragmentation could be observed in left
ventricles of donors in accordance with TUNEL-negative
cardiomyocytes (Figure 1). The left ventricles of
VAD-supported patients showed an intensive DNA fragmentation before VAD
unloading. This DNA laddering tended to be attenuated after the time on
VAD (P=0.07, Tables 1 and 3 and Figure 3).
Transcription of Apoptosis-Associated Genes
Before VAD support of terminally failing hearts, left
ventricular transcription of Bcl-xL,
FasExo6Del, and Bak was reduced compared with that in nonfailing left
ventricles of organ donors. These data are comparable to those of HF
patients without VAD support (Table 3). After VAD unloading, the
Bcl-xL mRNA expression was enhanced by 29±30%
(P<0.05), and this improvement revealed a significant
dependence on duration of VAD support (Figure 4A). Furthermore, Figure 4A
indicates that the left ventricular
Bcl-xL mRNA expression reached the mean value of
donor ventricles after 130 days of VAD unloading.
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Similarly, an increase in mRNA expression of FasExo6Del in relation to
Fas correlated with the duration of ventricular support in
DCM patients (Figure 4B). However, this time-dependent increase
in the ratio of FasExo6Del per Fas did not reach the level of increase
exhibited by donor ventricles during the period of VAD unloading. In
addition, the mRNA level of Mcl-1 was slightly elevated (20±26%)
under VAD support (P<0.05). For Bcl-2 and the
Bcl-2–related Bak and Bax, we did not observe any transcriptional
changes under support by VAD (Table 3). Consequently, the left
ventricular mRNA level of Bcl-xL was
increased in relation to its heterodimerization partner Bak by 42±46%
(P<0.06).
The left ventricular mRNA expression of the 
subunit of
the leukocyte-specific adhesion glycoprotein p150.95, an
indicator of inflammatory cell infiltration, did not change during time
on VAD (0±7%).
mRNA Expression of Na+-Ca2+ Exchanger and
SR Ca2+-ATPase
mRNA expression of the
Na+-Ca2+ exchanger tended
to be elevated in the left ventricles of HF patients before VAD support
compared with the left ventricles of donor hearts, whereas mRNA of the
SR Ca2+-ATPase tended to be lowered, and the
ratio of SR Ca2+-ATPase per
Na+-Ca2+ exchanger was
significantly reduced. Under hemodynamic unloading,
left ventricular transcription of the SR
Ca2+-ATPase as well as of the
Na+-Ca2+ exchanger remained
at failing levels despite this mechanical support (Table 3).
However, in the left ventricles of 4 patients (Nos. 3, 4, 6, and 8; see
Table 1), an improvement of the mRNA ratio of SR
Ca2+-ATPase per
Na+-Ca2+ exchanger (
40%;
ie, larger than the SD of pre-VAD values) could be observed. These 4
patients suffered from DCM, and post hoc comparison with the remaining
4 DCM patients without such improvement of the SR
Ca2+-ATPase/Na+-Ca2+
exchanger mRNA level under VAD indicated that they also showed more
improved gene expressions of antiapoptotic factors. Their
myocardial mRNA levels of FasExo6Del were increased by 94±45%
(P=0.05), of Mcl-1 by 42±9% (P=0.07), and of
Bcl-xL/Bak by 59±49% (P=0.05) during
the time on VAD. Similar elevations were not observed in the other
subgroup for FasExo6Del (7±80%), Mcl-1 (9±41%), or
Bcl-xL/Bak (33±52%), although the duration of
VAD support was not significantly different in both subgroups (102±52
versus 84±52 days in patients with versus without increased SR
Ca2+-ATPase/Na+-Ca2+
exchanger mRNA level). The subgroup without a VAD-induced increase in
SR
Ca2+-ATPase/Na+-Ca2+
exchanger mRNA expression may have been in a worse condition
immediately before VAD implantation: their cumulative dosage of
phosphodiesterase inhibitors, needed for positive inotropic
treatment, was 564±356 mg milrinone equivalents (in case of the use of
enoximone, the enoximone dosage in milligrams was divided by 5.5), and
the last monitored pulmonary wedge pressure was determined to
be 35±5 mm Hg. These values tended to be lowered in the subgroup
with an improved expression of the mentioned genes under VAD: the
pulmonary wedge pressure was 25±6 mm Hg
(P=0.06 versus the other subgroup) and the cumulative
milrinone equivalent dosage was 233±191 mg.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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In the present study, we report that the HF patients who required VAD support exhibited an apoptosis-susceptible myocardial phenotype and an abnormal myocardial mRNA expression of calcium-regulatory proteins before VAD insertion that were comparable to those of other HF patients who were not treated by VAD unloading.
Compared with donor hearts, the hearts of the HF patients exhibited
increased cardiac DNA fragmentation with more abundant TUNEL-positive
cardiomyocytes; these data are in agreement with the data
of Olivetti et al,9 which additionally showed that in
overloaded human myocardium apoptosis mainly
affects cardiomyocytes. Thus, the reduction in myocardial
DNA laddering under VAD (Tables 1 and 3) probably
reflects the decrease in the ongoing apoptotic loss of cardiac
myocytes, because mRNA expression of the leukocyte adhesion molecule
p150.95,23 an indicator of inflammatory cell invasion,
remained constant during time on VAD. This reduction in myocardial
apoptosis occurs in association with upregulation of the
apoptosis-preventing determinants Bcl-xL,
Mcl-1, and FasExo6Del/Fas (Table 3 and Figures 3 and 4). The quantitative PCR method revealed that Mcl-1 and
Bcl-xL are highly transcribed Bcl-2 relatives in
the human left ventricle. In DCM patients, the time-dependent increase
in Bcl-xL and FasExo6Del/Fas indicates the
gradual reinduction of these antiapoptotic regulators under
hemodynamic unloading. Since the leukocyte p150.95 mRNA
level was not altered under VAD, it is unlikely that a changing
myocardial content of inflammatory cells influences the cardiac mRNA
expression of apoptosis-associated genes.
The enhanced ventricular Pro-ANP transcription is more rapidly renormalized than is Bcl-xL or FasExo6Del/Fas, confirming the ventricular level of Pro-ANP mRNA as an indicator of overload.24 Furthermore, this could explain the mRNA upregulation of the antiapoptotic Mcl-1: in vitro experiments have shown that ANP treatment of cardiomyocytes increased signs of apoptosis associated with a reduction in Mcl-1 mRNA.25 However, since Mcl-1 mRNA is not altered between donors and excessive Pro-ANP–expressing HF patients, this VAD-associated induction of Mcl-1 mRNA could be a rather transient effect.
The VAD-induced reduction in left ventricular wall tension18 19 appears to be more relevant for a decrease in myocardial apoptosis of failing hearts under mechanical support. Distension-mediated myocyte apoptosis has been experimentally associated with a p53-mediated enhancement of the renin-angiotensin system, a decreased expression of antiapoptotic versus proapoptotic Bcl-2–related proteins,26 and an elevated translation of the Fas receptor.7 Furthermore, an increase in cardiomyocyte apoptosis and the changed expression of Bcl-2 relatives by experimental overactivity of ACE could be renormalized by angiotensin 1 receptor blockade27 or by long-term therapy with ACE inhibitors.28 Confirming these experimental data, expressions of Bcl-xL and Bcl-2 were partially normalized by ACE inhibitor therapy in the failing human myocardium of our patients. Since nearly all VAD patients were treated with ACE inhibitors, VAD unloading has an additionally stimulatory effect on the mRNA expression of the apoptosis-preventing Bcl-xL, which correlates with the Bcl-xL protein. Furthermore, after ventricular support of patients who had a coronary heart disease, an upregulation of the Bcl-xL protein could be observed, too.29 However, the ventricular unloading, either VAD-mediated or ACE inhibitor–mediated, cannot be the sole stimulus: the overload-indicating Pro-ANP mRNA level was identical in the non–VAD-supported group of patients with and without ACE inhibitor therapy.
Although our data indicate partial apoptotic phenotype normalization under VAD support with cardiac apoptosis reduction of the failing myocardium, these results cannot yet provide an assessment of the quantitative relevance of myocyte apoptosis. Furthermore, they cannot indicate the therapeutic potential of assist devices in terminal HF for several reasons: First, the analysis could not be designed as a treatment study. Second, we analyzed myocardium only from those patients who experienced a clinical stabilization under assist device unloading. Not all patients in such a deteriorated state of terminal HF can be successfully stabilized by a VAD.5 Third, it must be remembered that the myocardium of some patients may have lost this hypothetical potential for recovery because of irreversible remodeling processes, like fibrosis and scar formation.
Finally, it remains to be stressed that a reduction in apoptosis is only one of several basic mechanisms required for a functional recovery of the failing heart. Therefore, mRNA expressions of SR Ca2+-ATPase and Na+-Ca2+ exchanger were additionally determined. However, the mRNA ratio of SR Ca2+-ATPase per Na+-Ca2+ exchanger was normalized in only a few patients. Since a correlation between impaired mRNA and protein levels of the SR Ca2+-ATPase and the decreased SR 45Ca2+ uptake has been demonstrated in the failing human heart,20 30 31 our results are comparable to those of Frazier et al,32 who observed an enhanced myocardial calcium uptake/binding in the SR from some HF patients under chronic VAD support. As mentioned above, the myocardium of only some patients will be capable of renormalizing the expression of calcium-regulatory determinants under VAD for irreversible injuries. Furthermore, VADs are presently used only in patients who cannot be stabilized otherwise, and up to now, only a few selected patients could be weaned from the VAD without a subsequent heart transplantation. The selective use of VADs is necessary because it seems not to be justified to withhold an organ offer from those patients who need it.6 It is plausible to postulate that the VAD application in patients with less deteriorated cardiac function could be more successful. In agreement with this assumption is our observation that the subgroup with VAD-induced improvement of gene expression for antiapoptotic and calcium-handling proteins tends to exhibit a somewhat less deteriorated hemodynamic status immediately before VAD implantation, as can be deduced from a diminished cumulative phosphodiesterase inhibitor dosage and a lower pulmonary wedge pressure.
In conclusion, our findings indicate some potential of VAD as an intervention to interrupt the vicious cycle of distension-induced proapoptotic phenotype shifts, and in the future, VAD may become a treatment option for recovery in a subgroup of patients otherwise undergoing transplantation.
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Acknowledgments |
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This study was supported by grants of the German Bundesministerium für Bildung und Forschung (BMBF, 01ZZ9512.TV3, and TV7). Furthermore, we deeply express our appreciation for the cooperation of the patients and staff of the cardiothoracic surgery clinics at the Heart Center in Bad Oeynhausen and at the Martin Luther University in Halle/Saale, Germany. We thank R. Busath, B. Heinze, R. Gall, and T. Wangemann for their technical assistance.
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