The endothelium is a dynamic component of the cardiovascular system that plays an important role in health and disease. This study tested the hypothesis that targeted delivery of endothelial cells (ECs) overexpressing neutrophil membrane IL-8 receptors IL8RA and IL8RB reduces acute myocardial infarction (MI)-induced left ventricular (LV) remodeling and dysfunction and increases neovascularization in the area at risk surrounding the infarcted tissue. MI was created by ligating the left anterior descending coronary artery in 12-wk-old male Sprague-Dawley rats. Four groups of rats were studied: group 1: sham-operated rats without MI or EC transfusion; group 2: MI rats with intravenous vehicle; group 3: MI rats with transfused ECs transduced with empty adenoviral vector (Null-EC); and group 4: MI rats with transfused ECs overexpressing IL8RA/RB (1.5 × 106 cells post-MI). Two weeks after MI, LV function was assessed by echocardiography; infarct size was assessed by triphenyltetrazolium chloride (live tissue) and picrosirus red (collagen) staining, and capillary density and neutrophil infiltration in the area at risk were measured by CD31 and MPO immunohistochemical staining, respectively. When compared with the MI + vehicle and MI-Null-EC groups, transfusion of IL8RA/RB-ECs decreased neutrophil infiltration and pro-inflammatory cytokine expression and increased capillary density in the area at risk, decreased infarct size, and reduced MI-induced LV dysfunction. These findings provide proof of principle that targeted delivery of ECs is effective in repairing injured cardiac tissue. Targeted delivery of ECs to infarcted hearts provides a potential novel strategy for the treatment of acute MI in humans.
- myocardial infarction
- cell therapy
- endothelial cells
- interleukin-8 receptors
cell-based therapies for cardiovascular diseases have proliferated over the past decade, but with limited success (13, 30). Cell-based therapies have been shown to alleviate left ventricular (LV) remodeling and dysfunction after acute myocardial infarction (MI) in animal models and in humans (1, 2, 4, 5, 15, 16, 19, 20, 22, 26, 31, 32). Intracoronary administration of stem cells (e.g., bone marrow-derived cells or circulating cardiac progenitor cells) can be effective in regenerating cardiac tissue and ameliorating LV remodeling and dysfunction in rodent models of acute MI, both in the setting of permanent coronary occlusion and as a result of transient occlusion followed by reperfusion (15, 16, 26, 31, 32). An important limitation of this approach is that because these cells lack a selective homing device targeting ischemic/infarcted tissues, they must be injected directly into the affected myocardium or infused into the aortic root, procedures that are invasive, costly, and difficult to adapt for widespread clinical use. Other major hurdles for successful cell therapies include 1) cell type selection (e.g., progenitor vs. differentiated), 2) cell delivery mode (e.g., peripheral vs. directly into tissue), 3) timing of cell delivery (e.g., acute vs. delayed), 4) rejection of transplanted cells (e.g., autologous vs. heterologous), and most importantly, 5) targeting delivery of cells to damaged organs to maximize therapeutic effects.
The neutrophil chemoattractant IL-8 [cytokine-induced neutrophil chemoattractant-2β (CINC2β) in rat] is expressed in the setting of cardiovascular injury. Neutrophils migrate to and interact with injured tissue, triggering an initial pro-inflammatory response and facilitating the influx of other classes of inflammatory cells, e.g., monocytes/macrophages in the setting of acute ischemic myocardial injury. Selective receptors (IL8RA and IL8RB; also named CXCR1 and CXCR2) on the neutrophil surface bind to IL-8 or N-acetylated proline-glycine-proline (a specific collagen-derived tripeptide fragment expressed in injured tissue and 3-dimensional structurally similar to IL-8) (28, 29) and serve as homing devices to orient neutrophils to target injured tissue.
We have recently developed an innovative strategy to overcome the hurdles of cell-based therapy by intravenously transfusing endothelial cells (ECs) overexpressing IL8RA and IL8RB into rats with balloon injury of the carotid artery (35). We have demonstrated that acute intravenous transfusion of ECs equipped with the neutrophil IL-8 receptors results in targeting and adherence of the transformed ECs to injured carotid arteries, decreasing infiltration of activated neutrophils, inhibiting pro-inflammatory responses, and reducing neointima formation (adverse remodeling) (35).
With the use of the rat left anterior descending (LAD) coronary artery ligation-induced model of MI, this study tested the hypothesis that acute administration of ECs equipped with IL8RA and ILRB alleviates post-MI LV remodeling and dysfunction by decreasing neutrophil infiltration and pro-inflammatory cytokine production, as well as enhancing regeneration of microvessels in the area at risk (border zone, ischemic but not dead region) surrounding the infarcted tissue. Rat aortic ECs transduced with adenoviral vectors carrying neutrophil IL8RA and RB and were transfused from the femoral vein into rats 1 to 5 h after LAD coronary artery ligation. We demonstrated that, when compared with that of the control groups, administration of ECs overexpressing IL8Rs increased capillary density in the area at risk, decreased infarct size, promoted structural recovery, and reduced MI-induced LV dysfunction in rats following experimentally induced MI.
MATERIALS AND METHODS
Animals and procedures.
Eleven-wk-old male Sprague-Dawley rats were obtained from Charles River Breeding Laboratories and maintained at constant humidity (60 ± 5%), temperature (24 ± 1°C), and light cycle (6 AM to 6 PM) and fed a standard rat pellet diet ad libitum. All protocols were approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Alabama at Birmingham and were consistent with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health “Public Health Service Policy on Humane Care and Use of Animals, DHEW Publication No. 96-01, PHS Policy revised in 2002.” Body weights were determined before and after 2 wk LAD coronary artery ligation surgery.
After a 5-day acclimatization period and 1 day before LAD coronary artery ligation, rats were subjected to cannulation of a femoral vein for ECs transfusion. To perform the femoral vein catheterization, rats were anesthetized with ketamine (80 mg/kg ip) and xylazine (15 mg/kg ip), and the right femoral vein was isolated. A PE catheter (PE-10 fused with PE-50) was implanted into right femoral vein for transfusion of ECs (23, 35). During the surgery, respiratory rate were monitored continuously and toe pinch reflex was tested every 3 to 5 min to verify the depth of anesthesia. If animal showed any sign of irregular respiration of reflex pain, additional doses of anesthetics were given to the animal during operation. Analgesic agent buprenorphine (0.05 mg/kg sc) was given twice a day for 3 days postsurgery. After surgery, rats were kept on a warming pad to maintain body temperature until waking up. Rats were housed in individual cage postsurgery and monitored daily including weekends. Any rats that showed signs of infection, weight loss, avoidance behavior, lack of grooming, or any other health problems were euthanized by carbon dioxide followed by bilateral thoracotomy.
On the next day, rats were subjected to LAD coronary artery ligation. Briefly, rats were anesthetized with ketamine-xylazine (80–15 mg/kg ip), intubated, ventilated with a rodent respirator, and laid on a heating pad to keep body temperature at 37°C. A left intercostal thoracotomy through the 4th intercostal space was performed. The heart was exposed, and the pericardium was removed for identification of the LAD coronary artery. The LAD coronary artery was ligated 2 mm below the left atrium using a tapered needle and a 5-0 polyprophylene ligature. Occlusion was confirmed by a sudden change in color (pale) of the anterior wall of the LV (6). The chest cavity was then closed, and the rat was allowed to recover. Analgesic agent buprenorphine (0.05 mg/kg sc) was given twice a day for 3 days postsurgery.
To confirm the consistency of infarct injury generated by the LAD coronary artery ligation, eight rats were injected with Evans blue dye (2%, 1 ml/kg iv) and euthanized 24 h after the ligation without any other treatment. The heart was removed and washed with ice-cold saline. The LV below the ligation was sliced into 5 to 6 transverse sections (2 mm) and stained with triphenyltetrazolium chloride (TTC; 1%, pH 7.4) at 37°C for 20 min. The stained slices were photographed for infarct region measurement. The mean infarct area was 31.1 ± 1.5% of LV area (n = 8, coefficient of variation = 13%).
After LAD coronary artery ligation, rats were randomly divided into four groups: group 1: sham-operated (no MI) control rats without EC transfusion; group 2: MI rats transfused intravenously with vehicle (vehicle group, 500 μl saline at 1, 3, and 5 h post-MI); group 3: MI rats transfused intravenously with rat aortic ECs transduced with empty adenoviral vector (Null-EC group, 0.5 × 106 cells at 1, 3, and 5 h post-MI, total 1.5 × 106 per rat); and group 4: MI rats transfused intravenously with ECs overexpressing IL8RA/RB (IL8RA/RB-EC group, 0.5 × 106 cells at 1, 3, and 5 h post-MI). ECs transduced with adenoviral vectors carrying IL8RA/RB and the green fluorescent protein (GFP) marker gene or with an empty adenoviral vector (Null) with a GFP gene were prepared as described previously (35). Transduced ECs or vehicle were transfused through the femoral venous catheter that had been implanted one day before the LAD coronary artery ligation surgery. The femoral venous catheter was removed 1 day after the MI injury and intravenous cell transfusion under ketamine-xylazine (80–15 mg/kg ip) anesthesia.
Adenoviral vector generation and in vitro characterization of the ECs transduced with IL8RA and IL8RB adenoviral vectors.
Rat aortic ECs (purchased from VEC Technologies, Cat No. RAEC/T-75) that overexpress IL8RA-GFP, IL8RB-GFP, or Null-GFP (empty adenoviral vector control) were generated using adenoviral vectors that contain human IL8RA and/or IL8RB cDNAs and the GFP gene using the AdEasy Adenoviral Vector System (Stratagene) as reported previously (35).
To examine the expression of GFP (IL8RA/RB-EC marker) and the EC biomarkers vWF (von Willebrand factor) and CD31 in IL8RA/RB transduced ECs, cells were fixed in 4% paraformaldehyde, permeabilized in 0.1% Triton X-100 in PBS, and stained with selective primary antibodies against vWF or CD31 and a Texas Red-labeled goat anti-mouse IgG secondary antibody. After additional nuclear staining with 4,6-diamidino-2-phenylindole, ECs were mounted for confocal fluorescent microscopic analysis with a computerized Zeiss-Axioskop system.
Immunohistochemical analysis of neutrophil, monocyte/macrophage, and transfused EC infiltration into MI-injured hearts.
One day after EC transfusion, hearts were harvested. Immunohistochemical techniques were used to detect GFP-labeled IL8RA/RB-ECs, neutrophils, and monocytes/macrophages in frozen or formalin-fixed paraffin-embedded sections of hearts using a Vector Laboratories kit (Biotechnology) as described previously (33). Transfused ECs, neutrophils, and monocytes/macrophages were recognized by specific primary antibodies against GFP (an IL8RA/RB-EC marker), CD31 (an EC marker), MPO (a neutrophil marker), and ED1 (a monocyte/macrophage marker), respectively.
Real-time quantitative RT-PCR analysis of pro-inflammatory mediators.
RNA was extracted from the area at risk (within 2 mm adjacent to the infarct region) of MI-injured hearts, reverse transcribed to cDNA, and amplified by PCR with specific primers for TNF-α, cytokine induced neutrophil chemoattractant-2β (CINC-2β; equivalent to human IL-8), monocyte chemotactic protein-1 (MCP-1), vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and IL-10 and quantified using the iCycler (Applied Biosystems) (35). Levels of specific mRNAs were normalized using 18S RNA.
Echocardiographic and hemodynamic studies.
Two weeks after MI, echocardiography was performed in isoflurane (1.5%) anesthetized rats using a Phillips Sonos 5500 ultrasound system equipped with a 15-MHz transducer as described previously (10, 18). LV end-diastolic dimension (LVEDD) and LV end-systolic dimension (LVESD) were measured by two-dimensional-guided M-mode echocardiography from the parasternal short-axis view below the mitral valve. LV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and fractional shortening (FS) were calculated as EDV = 7 × LVEDD3/(2.4 + LVEDD), ESV = 7 × LVESD3/(2.4 + LVESD), FS = (LVEDD − LVESD)/LVEDD × 100, EF = (EDV − ESV)/EDV × 100. A single examiner, blinded to treatment, performed and interpreted all studies.
Assessment of infarct size and capillary density in the area at risk of the MI-injured hearts.
Rats were euthanized after echocardiographic analysis with an overdose of ketamine-xylazine. Hearts were quickly removed, weighed, and cut into 2-mm slices (average 6 transverse slices/heart at the level below the LAD coronary artery ligation) perpendicular to the apex-base axis (32). Tissue slices were first stained with 1% TTC at 37°C, pH 7.0, for 20 min to assess the area of live/necrotic tissue. TTC-stained slices were photographed and then fixed with 4% paraformaldehyde, embedded in paraffin, cut into 5 μm sections and stained with picrosirius red (0.1%) for assessment of collagen area (index of replacement fibrosis and infarct size) and for CD31 (immunostaining) for assessment of capillary density, respectively, as described previously (18).
For infarct size measurement, the necrotic/live tissue area ratios of the TTC-stained slices and collagen/total tissue area ratios of the picrosirius red-stained sections (6 slices or 6 sections from each heart) were measured. For capillary density measurement, tissue sections from the injured posterior wall (areas immediate adjacent to the infarct/fibrotic region) and from the unaffected septum (remote region) were immunostained with antibody against CD31. Quantitative morphometric analysis of TTC, collagen, and CD31-stained tissue sections was carried out by light microscopy with a Qimaging QiCam digital camera (Qimaging) interfaced with a computer system running Metamorph 6.2v4 software (Universal Imaging).
In each in vivo experiment, rats were age-matched to minimize individual differences. Results were expressed as means ± SE. Statistical analysis was carried out using the SigmaStat statistical package (version 3.5). The primary statistical test was two-way and one-way ANOVA. When the overall F test result of ANOVA was significant, a multiple-comparison Tukey test was applied. Student's t-test was used in two-mean comparisons. Differences were reported as significant when P values were <0.05.
Adenoviral transduction did not change EC phenotype.
Adenoviral transduction of IL8RA/RB and GFP genes did not change the cell shape or expression of EC markers (vWF and CD31) in rat aortic ECs (Fig. 1, A1−A3). The intensity of expression and number of ECs expressed GFP peaked (∼90%) at 3 days after transduction and gradually decreased during cell proliferation (50% at passage 1 and <10% at passage 2; Fig. 1, B1−B3). Our previous study demonstrated that IL8RA and IL8RB are expressed on the EC membrane, suggesting that these receptors can detect extracellular signals (35). IL8RA/RB-ECs had the same proliferative and apoptotic activities as untransduced ECs or Null ECs (35). Thus adenoviral transduction and overexpression of IL8RA and IL8RB did not alter the basal phenotype of rat aortic ECs.
Transfusion of IL8RA/RB-ECs inhibited neutrophil and monocyte/macrophage infiltration and production of pro-inflammatory cytokines in the area at risk of the MI-injured hearts.
There were no significant differences in body weight [348 ± 12 g (8), 342 ± 14 g (10), 350 ± 12 g (15), and 357 ± 2 g (9), among MI + vehicle, MI + Null-EC, MI + IL8RA/RB-EC, and sham (no MI control)-operated groups, respectively] at 2 wk post-MI. Immunohistochemical staining demonstrated large numbers of MPO+ neutrophils and ED1+ monocytes/macrophages in the area at risk domains of 24-h MI-injured hearts from vehicle-treated and Null-EC-treated rats; neutrophil and monocyte/macrophage numbers were greatly reduced by IL8RA/RB-EC treatment (Fig. 2). The number of neutrophils in the area at risk of injured heart was positively correlated with the number of monocytes/macrophages.
Real-time quantitative RT-PCR analysis of pro-inflammatory mediator mRNA levels in area at risk of 24-h injured hearts showed that pro-inflammatory mediators measured (TNF-α, CINC-2β, MCP-1, VCAM-1, ICAM-1, and IL-10) were expressed at very low levels in sham-operated (no MI control) hearts and increased markedly after injury (Fig. 3). IL8RA/RB-EC transfusion resulted in significant reductions in mRNA levels of the inflammatory cytokine TNF-α and chemoattractants CINC-2β and MCP-1, as well as adhesion molecules VCAM-1 and ICAM-1 compared with MI + vehicle and MI + Null-EC groups. Expression of IL-10 mRNA in injured hearts was not altered by IL8RA/RB-EC treatment and did not differ significantly from levels in injured hearts of Null-EC and vehicle-treated rats. The mRNA levels of TNF-α, CINC-2β, and MCP-1 in the area at risk of injured heart were positively correlated with the number of neutrophils and monocytes/macrophages.
Transfusion of ECs overexpressing IL8RA and IL8RB reduced LV dysfunction at 2 wk post-MI.
Echocardiographic examination showed that LVEDD, EDV, LVESD, and ESV were significantly increased in MI rats transfused with vehicle compared with their sham-operated (no MI) controls (Fig. 4). The MI-induced increases in LVEDD/EDV and LVESD/ESV were significantly reduced in IL8RA/RB-EC-treated rats, but not in Null-EC treated rats compared with vehicle controls (Fig. 4, B–E). LV EF and FS were significantly decreased after MI in vehicle-treated rats compared with sham-operated (no MI control) animals (Fig. 4, F and G). Transfusion with IL8RA/RB-EC, but not Null-EC or vehicle, significantly attenuated the MI-induced decreases in EF and FS. Heart rates were not different among experimental groups.
Transfusion of ECs overexpressing IL8RA and IL8RB reduced infarct size in rat heart at 2 wk post-MI.
For quantitative analysis of MI size, LV below the LAD coronary artery ligation was first cut into six slices (2 mm thickness; Fig. 5A) for TTC (necrotic tissue) staining (Fig. 5B, top) and then each slice was fixed, paraffin embedded, and cut into 5 μm sections for picrosirius red (collagen) staining (Fig. 5B, bottom). Both TTC and collagen staining showed smaller infarct areas in LV of rats transfused with IL8RA/RB-ECs compared with vehicle-treated or Null-EC-treated rats (Fig. 5, C and D). Ratios of fibrotic/necrotic area to total area of 4 to 6 cross sections of each heart showed that transfusion of IL8RA/RB-ECs reduced infarct size by 24.4% and 29.8%, compared with MI + vehicle control rats and MI rats transfused with Null-ECs, respectively, at 2 wk post-MI.
Transfusion of ECs overexpressing IL8RA and IL8RB increased capillary density in the area at risk surrounding the infarct zone in rat heart post-MI.
GFP and CD31 double immunostaining of 24-h MI hearts (frozen section) of rats transfused with vehicle, Null-ECs, and IL8RA/RB-ECs was performed to detect IL8RA/RB-ECs targeting to the area at risk of injured hearts. GFP (green color) and CD31 (red color) positive (double stained) cells were detected in the area at risk of MI + IL8RA/RB-ECs hearts, but not in the MI + vehicle or MI + Null-EC hearts (Fig. 6A), or the remote region (e.g., septum or right ventricular wall) in the MI + IL8RA/RB-EC hearts. Furthermore, no GFP-positive cells were detected in lung, liver, kidney, and spleen in MI rats at 24 h post-IL8RA/RB-EC transfusion.
Endothelial (CD31) immunohistochemical staining of 2-wk MI hearts (formalin-fixed, paraffin-embedded) of rats transfused with vehicle, Null-ECs, and IL8RA/RB-ECs was performed to elucidate the effects of IL8RA/RB-EC transfusion on neo-vascularization. In rats that received IL8RA/RB-ECs, capillary density was significantly greater in the area at risk between normal and infarcted myocardium, compared with that in the remote region of the septum (Fig. 6, B and C). Vehicle and Null-EC treatment did not increase capillary density in the area at risk compared with the remote control area and the septal and posterior wall areas of the sham-operated control rats. The capillary density in the remote region of the septum was the same in all treatment groups.
This study has shown for the first time that intravenous transfusion of ECs transduced with IL8RA and IL8RB significantly inhibits production of pro-inflammatory mediators and infiltration of neutrophils and monocytes/macrophages and enhances capillary density in the area at risk of infarcted rat hearts. These anti-inflammatory and neo-vascularization-promoting effects of targeting ECs to the area at risk effectively reduced infarct size and prevented loss of LV function in the infarcted hearts following experimentally induced (LAD coronary artery ligation) MI. These results support our hypothesis that ECs that overexpress IL8RA and/or IL8RB mimic the behavior of neutrophils that target acutely injured tissues, thus inhibiting pro-inflammatory responses, accelerating neo-vascularization and decreasing necrosis of myocardium in the area at risk, thus preserving LV function after acute MI (Fig. 7). Targeting delivery of ECs equipped with the homing device (IL-8 receptors) to the site of cardiac injury, as demonstrated in this study, provides a novel strategy for the treatment of ischemic heart disease.
Coronary artery disease is a leading cause of death in the United States. Acute MI is a catastrophic acute coronary event that strikes nearly 1.5 million Americans each year (17, 21). MI caused by rupture of atherosclerotic plaque occludes coronary arteries and induces thrombosis, resulting in myocardial ischemia and necrosis at the core of the infarction. In the area at risk (ischemic border zone surrounding the infarct/necrotic region) blood vessels are damaged and the blood supply to the injured tissues is impaired. Enhancing regeneration of microvessels in the area at risk is a therapeutic option to rescue tissue from critical ischemia (33). After severe myocardial ischemia occurs in MI, restoration of the blood supply to the area at risk can rescue ischemic but still viable tissue, prevent progressive cardiomyocyte death, and reduce expansion of the infarct region and adverse cardiac remodeling, thus improving cardiac function and reducing mortality. Therapeutic neovascularization (vasculogenesis and angiogenesis) has thus become a promising new method of treatment for patients with ischemic heart disease and acute MI.
Several strategies including growth factor delivery (7, 38), gene therapy (12), and cell-based therapy (25, 33) have been developed to promote neovascularization in the ischemic myocardium. Among them, cell-based therapy has emerged as the most promising therapeutic tool for vascular growth and treatment of ischemic cardiovascular disease. Studies in animals and humans suggest that bone marrow-derived mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) have regenerative potential in ischemic tissue. Both endogenous nonselective MSCs and selective EPCs have been demonstrated to enhance capillary growth and participate in the formation of collateral vessels in ischemic heart (34, 36). These effects led to improved perfusion and functional recovery of myocardial ischemia. EPCs also contribute to endothelial repair and may impede the development or progression of arteriosclerosis (3). However, a critical limitation for the therapeutic application of endogenous MSCs or EPCs is their low number in the circulation, which is further reduced during aging and in patients with cardiovascular risk factors (8). One strategy to overcome this limitation is to introduce large numbers of exogenous ECs or EC-like cells with vascular regenerating and repairing capacities into the ischemic myocardium. Our current findings suggest that intravenous administration of mature ECs targeted to injured tissues may be useful in reaching the therapeutic goal of reducing MI-induced tissue injury.
Acute inflammatory responses after MI play a pathogenic role by adversely influencing cardiac contractility, promoting apoptosis, and inducing matrix degradation/fibrosis and myocardial remodeling (11, 37). Neutrophils migrate to injured tissue in response to the IL-8 and N-acetylated proline-glycine-proline that are expressed and released in large amounts by injured tissues (28, 29). Interactions between IL-8 and its cognate receptors play a key role in host defense and disease responses following recruitment of activated neutrophils to sites of inflammation (27). IL-8 binds to selective IL8RA and IL8RB receptors on the neutrophil surface (9, 29), and activated IL8RA and/or IL8RB induce expression of chemotactic mediators that trigger local inflammation. Neutrophils are the main leukocyte subset that interacts with the damaged endothelium, triggers the initial pro-inflammatory response, and facilitates the influx of other classes of inflammatory cells, e.g., monocytes/macrophages and T cells in the setting of acute vascular injury (14, 24). Using this background knowledge, we have developed an innovative strategy to equip ECs with the neutrophil homing device to target their delivery to injured tissues.
An important limitation of current cell-based therapy of cardiovascular injury is that because the introduced cells lack a selective homing device to target ischemic/infarcted tissues, they must be injected directly into the affected tissue (e.g., injured myocardium or vessels) or infused into the aortic root to reach cardiac tissue directly, procedures that are invasive and may be hazardous for patients. In the current study, the injured/dysfunctional endothelium is the therapeutic target for treatment of MI-induce tissue injury. We have generated ECs overexpressing IL8RA and IL8RB that can mimic the behavior of neutrophils in binding to IL-8 that is produced by injured tissues (35). We have demonstrated that IL8RA/RB-ECs can compete with neutrophils to attach to activated endothelial monolayers in vitro and that intravenous transfusion of these transduced ECs into rats with balloon injured carotid arteries resulted in targeting and adhesion of the transduced ECs to injured vessels (35). Transfusion of IL8RA/RB bearing ECs resulted in decreased neutrophil infiltration and inflammatory mediator expression, accelerated re-endothelializtion, and reduced neointima formation in injured arteries (35).
In the current study, we demonstrated that, when compared with MI + vehicle and MI + Null-EC rats, transfusion with ECs overexpressing IL8RA and IL8RB on the day of LAD coronary artery ligation (acute MI) decreased neutrophil and monocyte/macrophage infiltration and pro-inflammatory mediator production and increased the amount of viable myocardium and capillary density in the area at risk region and reduced fibrosis in the noninfarcted region in association with improved global LV function (increased LVEDD, LVESD, EF, and FS) in the infarcted rat heart. These data indicate that transfusion of IL8-RA/RB-EC has cardioprotective effects after an acute ischemic cardiac injury. It should be noted that the current study was performed in young male rats. We do not know whether these cardioprotective effects of IL8RA/RB-EC can be found in aged or female rats. In summary, these findings provide proof of principle that targeted delivery of ECs is effective in repairing injured cardiac tissue. We suggest that this strategy may be a novel cell-based therapy for ischemic myocardial injury in humans.
This work was supported, in part, by National Heart, Lung, and Blood Institute Grants RO1HL-080017, RO1HL-044195 (to Y.-F. Chen), and T32 HL-079888 (to P. Li) and by American Heart Association Grants 10POST3180007 (to K. Gong) and 09BGIA2250367 (D. Xing).
No conflicts of interest, financial or otherwise, are declared by the author(s).
Author contributions: X.Z., D.X., K.G., F.G.H., S.O., and Y.-F.C. provided conception and design of research; X.Z., W.Z., D.X., P.L., J.F., K.G., and Y.-F.C. performed experiments; X.Z., S.O., and Y.-F.C. analyzed data; X.Z., D.X., F.G.H., S.O., and Y.-F.C. interpreted results of experiments; X.Z. and Y.-F.C. prepared figures; X.Z., S.O., and Y.-F.C. drafted manuscript; X.Z. and Y.-F.C. edited and revised manuscript; X.Z., S.O., and Y.-F.C. approved final version of manuscript.
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