Christian Klopsch

Bcl‐2 Engineered MSCs Inhibited Apoptosis and Improved Heart Function

Engraftment of mesenchymal stem cells (MSCs) derived from adult bone marrow has been proposed as a potential therapeutic approach for postinfarction left ventricular dysfunction. However, limited cell viability after transplantation into the myocardium has restricted its regenerative capacity. In this study, we genetically modified MSCs with an antiapoptotic Bcl‐2 gene and evaluated cell survival, engraftment, revascularization, and functional improvement in a rat left anterior descending ligation model via intracardiac injection. Rat MSCs were manipulated to overexpress the Bcl‐2 gene. In vitro, the antiapoptotic and paracrine effects were assessed under hypoxic conditions. In vivo, the Bcl‐2 gene‐modified MSCs (Bcl‐2‐MSCs) were injected after myocardial infarction. The surviving cells were tracked after transplantation. Capillary density was quantified after 3 weeks. The left ventricular function was evaluated by pressure‐volume loops. The Bcl‐2 gene protected MSCs against apoptosis. In vitro, Bcl‐2 overexpression reduced MSC apoptosis by 32% and enhanced vascular endothelial growth factor secretion by more than 60% under hypoxic conditions. Transplantation with Bcl‐2‐MSCs increased 2.2‐fold, 1.9‐fold, and 1.2‐fold of the cellular survival at 4 days, 3 weeks, and 6 weeks, respectively, compared with the vector‐MSC group. Capillary density in the infarct border zone was 15% higher in Bcl‐2‐MSC transplanted animals than in vector‐MSC treated animals. Furthermore, Bcl‐2‐MSC transplanted animals had 17% smaller infarct size than vector‐MSC treated animals and exhibited functional recovery remarkably. Our current findings support the premise that transplantation of antiapoptotic gene‐modified MSCs may have values for mediating substantial functional recovery after acute myocardial infarction.

Cell Origin of Human Mesenchymal Stem Cells Determines a Different Healing Performance in Cardiac Regeneration

The possible different therapeutic efficacy of human mesenchymal stem cells (hMSC) derived from umbilical cord blood (CB), adipose tissue (AT) or bone marrow (BM) for the treatment of myocardial infarction (MI) remains unexplored. This study was to assess the regenerative potential of hMSC from different origins and to evaluate the role of CD105 in cardiac regeneration. Male SCID mice underwent LAD-ligation and received the respective cell type (400.000/per animal) intramyocardially. Six weeks post infarction, cardiac catheterization showed significant preservation of left ventricular functions in BM and CD105+-CB treated groups compared to CB and nontreated MI group (MI-C). Cell survival analyzed by quantitative real time PCR for human GAPDH and capillary density measured by immunostaining showed consistent results. Furthermore, cardiac remodeling can be significantly attenuated by BM-hMSC compared to MI-C. Under hypoxic conditions in vitro, remarkably increased extracellular acidification and apoptosis has been detected from CB-hMSC compared to BM and CD105 purified CB-derived hMSC. Our findings suggests that hMSC originating from different sources showed a different healing performance in cardiac regeneration and CD105+ hMSC exhibited a favorable survival pattern in infarcted hearts, which translates into a more robust preservation of cardiac function.

Intracardiac injection of erythropoietin induces stem cell recruitment and improves cardiac functions in a rat myocardial infarction model

Erythropoietin (EPO) protects the myocardium from ischaemic injury and promotes beneficial remodelling. We assessed the therapeutic efficacy of intracardiac EPO injection and EPO‐mediated stem cell homing in a rat myocardial infarction (MI) model. Following MI, EPO (3000 U/kg) or saline was delivered by intracardiac injection. Compared to myocardial infarction control group (MIC), EPO significantly improved left ventricular function (n= 11–14, P< 0.05) and decreased right ventricular wall stress (n= 8, P< 0.05) assessed by pressure‐volume loops after 6 weeks. MI‐EPO hearts exhibited smaller infarction size (20.1 ± 1.1%versus 27.8 ± 1.2%; n= 6–8, P< 0.001) and greater capillary density (338.5 ± 14.7 versus 259.8 ± 9.2 vessels per mm; n= 6–8, P< 0.001) than MIC hearts. Direct EPO injection reduced post‐MI myocardial apoptosis by approximately 41% (0.27 ± 0.03%versus 0.42 ± 0.03%; n= 6, P= 0.005). The chemoattractant SDF‐1 was up‐regulated significantly assessed by quantitative realtime PCR and immunohistology. c‐Kit+ and CD34+ stem cells were significantly more numerous in MI‐EPO than in MIC at 24 hrs in peripheral blood (n= 7, P< 0.05) and 48 hrs in the infarcted hearts (n= 6, P< 0.001). Further, the mRNAs of Akt, eNOS and EPO receptor were significantly enhanced in MI‐EPO hearts (n= 7, P< 0.05). Intracardiac EPO injection restores myocardial functions following MI, which may attribute to the improved early recruitment of c‐Kit+ and CD34+ stem cells via the enhanced expression of chemoattractant SDF‐1.

A transformed cell population derived from cultured mesenchymal stem cells has no functional effect after transplantation into the injured heart.

Bone marrow-derived mesenchymal stem cells (MSCs) are multipotent cells characterized by their self-renewal and differentiation potential. Accumulating clinical and preclinical evidence indicate MSCs are a promising cell source for regenerative medical therapies. However, undesirable immortalization, spontaneous transformation, and tumorigenic potential from long-term cultured MSCs have been reported in human and mouse. We report rat MSCs isolated from young donors could undergo transformation in early passage culture. We aimed to characterize the transformed population and determine their therapeutic effects after intracardiac transplantation in the infarcted myocardium. MSCs were isolated from bone marrow of Lewis rats according to standard protocols and cultured under standard conditions. Phenotype of growing cells was assessed by flow cytometry. Following acute myocardial infarction in rats, cells were delivered by intracardiac injection. Cardiac functions were assessed by pressure–volume loops. Infarction size and pathologic effects were evaluated after 6 weeks. The abnormal colonies were detected in culture as early at passage 3. They were noted to appear as distinctly different morphology from typical MSCs, which changed from a normal elongated spindle shape to a compact abnormal morphology. They exhibited rapid cell proliferation. Some subclones lost contact inhibition of cell division and formed multilayer aggregates. Chromosomal instability was detected. They were devoid of surface markers CD29, CD44, CD90, and CD117. Furthermore, there was no significant improvement on infarction size and cardiac function 6 weeks after cell transplantation. Our study highlights the need for establishment of biosafety criteria in regulating culture-expanded MSCs to achieve the full clinical therapeutic benefits.

Autologous umbilical cord blood mononuclear cell transplantation preserves right ventricular function in a novel model of chronic right ventricular volume overload.

We aimed to evaluate the feasibility and efficacy of autologous umbilical cord blood mononuclear cell (UCMNC) transplantation on right ventricular (RV) function in a novel model of chronic RV volume overload. Four-month-old sheep (n = 20) were randomized into cell (n = 10) and control groups (n = 10). After assessment of baseline RV function by the conductance catheter method, a transannular patch (TAP) was sutured to the right ventricular outflow tract (RVOT). Following infundibulotomy the ring of the pulmonary valve was transected without cardiopulmonary bypass. UCMNC implantation (8.22 ± 6.28 × 107) in the cell group and medium injection in the control group were performed into the RV myocardium around the TAP. UCMNCs were cultured for 2 weeks after fluorescence-activated cell sorting (FACS) analysis for CD34 antigen. Transthoracic echocardiography (TTE) and computed tomography were performed after 6 weeks and 3 months, respectively. RV function was assessed 3 months postoperatively before the hearts were excised for immunohistological examinations. FACS analysis revealed 1.2 ± 0.22% CD34+ cells within the isolated UCMNCs from which AcLDL+ endothelial cells were cultured in vitro. All animals survived surgery. TTE revealed grade II–III pulmonary regurgitation in both groups. Pressure-volume loops under dobutamine stress showed significantly improved RV diastolic function in the cell group (dP/dtmin: p = 0.043; Eed: p = 0.009). CD31 staining indicated a significantly enhanced number of microvessels in the region of UCMNC implantation in the cell group (p < 0.001). No adverse tissue changes were observed. TAP augmentation and pulmonary annulus distortion without cardiopulmonary bypass constitutes a valid large animal model mimicking the surgical repair of tetralogy of Fallot. Our results indicate that the chronically volume-overloaded RV profits from autologous UCMNC implantation by enhanced diastolic properties with a probable underlying mechanism of increased angiogenesis.

Acute and chronic response of the right ventricle to surgically induced pressure and volume overload--an analysis of pressure-volume relations.

We aimed to determine the response of the right ventricle (RV) to surgically induced pressure and volume overload in both acute and chronic settings. Four-month-old sheep were operated via left anterior thoracotomy. Pressure overload of the RV was established by banding of the pulmonary trunk. Volume overload was induced by the implantation of a transannular patch to the right ventricular outflow tract. Right ventricular function was obtained with conductance catheters before and after surgery as well as three months postoperatively. Acute pressure overload resulted in an increase of end-systolic volume (ESV) (P=0.002) and end-diastolic volume (EDV) (P=0.004), increments in contractile indexes [maximal slope of systolic pressure increment (dP/dt(max)), P=0.002; slope of end-systolic pressure volume relation (Ees), P=0.002; preload recruitable stroke work (PRSW), P=0.002] and an acceleration of early diastole [relaxation time (tau), P=0.012; maximal slope of diastolic pressure decrement (dP/dt(min)), P=0.002]. Acute volume overload revealed better contractility and more prominent increases in preload (ESV, EDV; both P=0.008). Three months postoperatively, pressure overloaded hearts demonstrated superior systolic (Ees, P=0.022; PRSW, P=0.013) and diastolic reserves (dP/dt(min), P=0.013; slope of end-diastolic pressure volume relation (Eed), P=0.005; P(20), P=0.003) than volume overloaded hearts. Acute pressure overload leads to enhanced contractility of the RV as a result of the Anrep effect and the Frank-Starling mechanism whereas volume overload institutes only the latter. The chronically pressure overloaded RV exposes more contractile and elastic reserves than the chronically volume overloaded RV under stress conditions.

Intracardiac Erythropoietin Injection Reveals Antiinflammatory Potential and Improved Cardiac Functions Detected by Forced Swim Test

Systemic administration of erythropoietin (Epo) protects the myocardium from an ischemic insult and promotes beneficial remodeling. We hypothesized that intracardiac injection of Epo may exhibit cardioprotective potential with reduced systemic toxicity. Following myocardial infarction (MI), Epo was injected directly into the border of the infarction. Six weeks after an MI, we evaluated infarction size, angiogenesis, and pathologic effects of the treatment. Myocardial performance was assessed with a Forced Swim Test adapted to the study. Anti-inflammatory and cellular proliferative effects of Epo were analyzed by measuring expression of integrin-beta and CdK4 by reverse transcriptase-polymerase chain reaction (RT-PCR). The findings indicated improved cardiac status with direct Epo administration. Exercise capacity detected by the Forced Swim Test was significantly increased. There was radical reduction of absolute infarction size, ventricular dilatation, and hypertrophy in the Epo group. Integrin-beta was down-regulated and CdK4 expression was increased significantly with Epo. In conclusion, the study demonstrated that intramyocardial Epo injection, following MI, reduced inflammation, enhanced angiogenesis and proliferation, improved myocardial functions, and did not lead to intramural thrombus formation.

Tissue-Engineered Devices in Cardiovascular Surgery

Manufacturing life-long functional cardiovascular (CV) implants is the ultimate goal for researchers and clinicians in the cardiothoracic field. Tissue engineering (TE) is an opportunity to create ideal prostheses that are vital, growing, adaptive, autologous and functionally optimally performing. Today, initial translation from basic science to first clinical trials has begun. The article depicts the state of the art in TE techniques for CV products and describes milestones in the ongoing development of tissue-engineered myocardial, valvular and vascular devices from an experimental and clinical point of view. Artificial CV implants still reveal remarkable limitations but promising advances regarding optimal structural design, the prevention of intimal hyperplasia and the reduction of antigenicity and thrombogenicity. Where applicable, the implantation of vascularized autografts should still be preferred. Apart from that, decellularized allogen bioprostheses currently represent most promising matrix scaffolds that can be autologously cellularized in vitro prior to or in vivo after implantation. Capable biologic alternatives have been described like the decellularized porcine small intestinal submucosa. Rising evidence suggests that in vitro endothelialization might be the minimal requirement for improved long-term results of biological tissue-engineered CV grafts.

The CD4(+)AT2R(+) T cell subpopulation improves post-infarction remodelling and restores cardiac function

Myocardial infarction (MI) is a major condition causing heart failure (HF). After MI, the renin angiotensin system (RAS) and its signalling octapeptide angiotensin II (Ang II) interferes with cardiac injury/repair via the AT1 and AT2 receptors (AT1R, AT2R). Our study aimed at deciphering the mechanisms underlying the link between RAS and cellular components of the immune response relying on a rodent model of HF as well as HF patients. Flow cytometric analyses showed an increase in the expression of CD4+ AT2R+ cells in the rat heart and spleen post‐infarction, but a reduction in the peripheral blood. The latter was also observed in HF patients. The frequency of rat CD4+ AT2R+ T cells in circulating blood, post‐infarcted heart and spleen represented 3.8 ± 0.4%, 23.2 ± 2.7% and 22.6 ± 2.6% of the CD4+ cells. CD4+ AT2R+ T cells within blood CD4+ T cells were reduced from 2.6 ± 0.2% in healthy controls to 1.7 ± 0.4% in patients. Moreover, we characterized CD4+ AT2R+ T cells which expressed regulatory FoxP3, secreted interleukin‐10 and other inflammatory‐related cytokines. Furthermore, intramyocardial injection of MI‐induced splenic CD4+ AT2R+ T cells into recipient rats with MI led to reduced infarct size and improved cardiac performance. We defined CD4+ AT2R+ cells as a T cell subset improving heart function post‐MI corresponding with reduced infarction size in a rat MI‐model. Our results indicate CD4+ AT2R+ cells as a promising population for regenerative therapy, via myocardial transplantation, pharmacological AT2R activation or a combination thereof.

Single high-dose intramyocardial administration of erythropoietin promotes early intracardiac proliferation, proves safety and restores cardiac performance after myocardial infarction in rats

Various studies demonstrate erythropoietin (EPO) as a cardioprotective growth hormone. Recent findings reveal EPO in addition might induce proliferation cascades inside myocardium. We aimed to evaluate whether a single high-dose intramyocardial EPO administration safely elevates early intracardiac cell proliferation after myocardial infarction (MI). Following permanent MI in rats EPO (3000 U/kg) in MI EPO-treatment group (n=99) or saline in MI control group (n=95) was injected along the infarction border. Intramyocardial EPO injection activated the genes of cyclin D1 and cell division cycle 2 kinase (cdc2) at 24 h after MI (n=6, P<0.05) evaluated by real time-PCR. The number of Ki-67+ intracardiac cells analyzed following immunohistochemistry was significantly enhanced by 45% in the peri-infarction zone at 48 h after EPO treatment (n=6, P<0.001). Capillary density was significantly enhanced by 17% as early as seven days (n=6, P<0.001). After six weeks, left ventricular performance assessed by conductance catheters was restored under baseline and dobutamine induced stress conditions (n=11-14, P<0.05). No thrombus formation was observed in the heart and in distant organs. No deleterious systemic adverse effects were apparent. Single high-dose intramyocardial EPO delivery proved safety and promoted early intracardiac cell proliferation, which might in part have contributed to an attenuated myocardial functional decline.