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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.

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

We investigated the kinetics of human mesenchymal stem cells (MSCs) after intravascular administration into SCID mouse cremaster vasculature by intravital microscopy. MSCs were injected into abdominal aorta through left femoral artery at two different concentrations (1 x 10(6) or 0.2 x 10(6) cell). Arterial blood velocity decrease by 60 and 18% 1 min after high/low dose MSCs injection respectively. The blood microcirculation was interrupted after 174+/-71 and 485+/-81 s. Intravital microscopy observation and histopathologic analysis of cremaster muscles indicated MSCs were entrapped in capillaries in both groups. 40 and 25% animals died of pulmonary embolism respectively in both high and low MSCs dose groups, which was detected by histopathologic analysis of the lungs. Intraarterial MSCs administration may lead to occlusion in the distal vasculature due to their relatively large cell size. Pulmonary sequestration may cause death in small laboratory animals. MSCs should be used cautiously for intravascular transplantation.

The heart has long been regarded as a post-mitotic organ. Since many years, physicians have focused on developing strategies to restore the myocardium after ischemic damage followed by ventricular dysfunction. Restoration is generally achieved through the redirection of blood flow or by supporting contractile performance. The discovery of stem cells capable of generating angiogenic or contractile cells and structures offers new horizons to patients suffering from myocardial disease. Experimental studies indicate that the delivery or mobilization of stem and progenitor cells may improve tissue perfusion and the contractile performance of the damaged heart. Another aspect of restoration is based on cardiovascular tissue engineering and the creation of three-dimensional biological conformations to replace the artificial materials frequently used during operations, i.e., valves and grafts, or even a portion of the nonfunctional myocardial tissue. At present, the underlying intra- and intercellular molecular mechanisms controlling myocardiogenesis and cardiomyocyte replacement during regenerative processes are not very well understood. In this brief review we try to give the answers to questions on certain aspects of myocardial tissue regeneration and engineering procedures.

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.

Erythropoietin has been shown to promote tissue regeneration after ischaemic injury in various organs. Here, we investigated whether Erythropoietin could ameliorate ischaemic spinal cord injury in the mouse and sought an underlying mechanism. Spinal cord ischaemia was developed by cross-clamping the descending thoracic aorta for 7 or 9 min. in mice. Erythropoietin (5000 IU/kg) or saline was administrated 30 min. before aortic cross-clamping. Neurological function was assessed using the paralysis score for 7 days after the operation. Spinal cords were histologically evaluated 2 and 7 days after the operation. Immunohistochemistry was used to detect CD34+ cells and the expression of brain-derived neurotrophic factor and vascular endothelial growth factor. Each mouse exhibited either mildly impaired function or complete paralysis at day 2. Erythropoietin-treated mice with complete paralysis demonstrated significant improvement of neurological function between day 2 and 7, compared to saline-treated mice with complete paralysis. Motor neurons in erythropoietin-treated mice were more preserved at day 7 than those in saline-treated mice with complete paralysis. CD34+ cells in the lumbar spinal cord of erythropoietin-treated mice were more abundant at day 2 than those of saline-treated mice. Brain-derived neurotrophic factor and vascular endothelial growth factor were markedly expressed in lumbar spinal cords in erythropoietin-treated mice at day 7. Erythropoietin demonstrated neuroprotective effects in the ischaemic spinal cord, improving neurological function and attenuating motor neuron loss. These effects may have been mediated by recruited CD34+ cells, and enhanced expression of brain-derived neurotrophic factor and vascular endothelial growth factor.

Because human lungs are unlikely to repair or regenerate beyond the cellular level, cell therapy has not previously been considered for chronic irreversible obstructive lung diseases. To explore whether cell therapy can restore lung function, we administered allogenic intratracheal mesenchymal stem cells (MSCs) in the trachea of rats with chronic thromboembolic pulmonary hypertension (CTEPH), a disease characterized by single or recurrent pulmonary thromboembolic obliteration and progressive pulmonary vascular remodeling. MSCs were retrieved only in high pressure-exposed lungs recruited via a homing stromal derived factor-1α/ CXCR4 pathway. After MSC administration, a marked and long-lasting improvement of all clinical parameters and a significant change of the proteome level were detected. Beside a variation of liver proteome, such as caspase-3, NF-κB, collagen1A1, and α-SMA, we also identified more than 300 resident and nonresident lung proteins [e.g., myosin light chain 3 (P16409) or mitochondrial ATP synthase subunit alpha (P15999)]. These results suggest that cell therapy restores lung function and the therapeutic effects of MSCs may be related to protein-based tissue reconstituting effects.

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.

This article is being retracted because another article was published using the same data, but under a different title, in Microvascular Research.

Objectives: Cardiovascular diseases are the most common causes of mortality and morbidity in the developed countries. More than just a promoter of erythropoiesis, Erythropoietin (EPO) has a much broader range of action on cardioprotective effects. We aimed to assess the functional improvement of EPO on both left and right ventricles in a rat myocardial infarction model. Methods: Adult male rats were divided into three groups as Sham, myocardial infarction treated with EPO (MI-EPO) and untreated MI control group (MI-C). Myocardial infarction was achieved by ligation of the LAD. MI-EPO group received four intramyocardial injections of Epoetin-α along the infarction border. Cardiac functions were investigated by pressure-volume (P-V) loop in both ventricles six weeks after the procedure. Infarction size and adverse effects of the treatment were evaluated by histological analysis. Results: Mortality was remarkably reduced with EPO treatment in the follow up period. Mean survival was 13 and 21 days in MI-C and MI-EPO groups, respectively. EPO treatment leads to significantly improved cardiac function. Left ventricular dp/dt max (baseline, 7374.84±1742.71mmHg/s vs. 5815.23±1257.10mmHg/s), ejection fraction (40,05±8,04 vs. 27,12±6,65), cardiac output (51331,77±16065,48 vs. 31083,60 ±15985,72) were enhanced and right ventricular pressure (23.08±4.10mmHg vs. 31.31±6.61mmHg) and end-systolic pressure (20,56±3,27 vs. 30,02±6,30) decreased. In the MI-EPO group infarction size was significantly smaller (27.8±3.4% vs. 20.1±2.8%) and intramural thrombosis was not observed in the myocardium. Conclusion: Our findings indicate directly intramyocardial administration of EPO has low adverse effect profile and improves cardiac functions in infarcted myocardium.