Bone marrow cell migration to the heart in a chimeric mouse model of acute chagasic disease.

BACKGROUND: Chagas disease is a public health problem caused by infection with the protozoan Trypanosoma cruzi. There is currently no effective therapy for Chagas disease. Although there is some evidence for the beneficial effect of bone marrow-derived cells in chagasic disease, the mechanisms underlying their effects in the heart are unknown. Reports have suggested that bone marrow cells are recruited to the chagasic heart; however, studies using chimeric mouse models of chagasic cardiomyopathy are rare. OBJECTIVES: The aim of this study was to investigate the migration of bone marrow cells to the heart after T. cruzi infection in a model of chagasic disease in chimeric mice. METHODS: To obtain chimerical mice, wild-type (WT) C57BL6 mice were exposed to full body irradiation (7 Gy), causing bone marrow ablation. Then, bone marrow cells from green fluorescent protein (GFP)-transgenic mice were infused into the mice. Graft effectiveness was confirmed by flow cytometry. Experimental mice were divided into four groups: (i) infected chimeric (iChim) mice; (ii) infected WT (iWT) mice, both of which received 3 × 104 trypomastigotes of the Brazil strain; (iii) non-infected chimeric (Chim) mice; and (iv) non-infected WT mice. FINDINGS: At one-month post-infection, iChim and iWT mice showed first degree atrioventricular block with decreased heart rate and treadmill exercise parameters compared to those in the non-infected groups. MAIN CONCLUSIONS: iChim mice showed an increase in parasitaemia, myocarditis, and the presence of amastigote nests in the heart tissue compared to iWT mice. Flow cytometry analysis did not detect haematopoietic progenitor cells in the hearts of infected mice. Furthermore, GFP+ cardiomyocytes were not detected in the tissues of chimeric mice.

Therapy with Cardiomyocytes Derived from Pluripotent Cells in Chronic Chagasic Cardiomyopathy.

Chagas disease discovered more than a century ago remains an incurable disease. The objective of this work was to investigate the therapeutic potential of cardiomyocytes derived from mouse embryonic stem cells (CM-mESC) in a model of chronic Chagasic cardiomyopathy (CCC). Mouse embryonic stem cells (mESC) were characterized, transduced with luciferase, and submitted to cardiac differentiation. CM-mESC were labeled with superparamagnetic iron oxide particles. To induce CCC, mice were infected with Brazil strain trypomastigotes. At 150 days post-infection (dpi), infected animals were treated with CM-mESC or PBS. Cells were detected by magnetic resonance imaging (MRI) and bioluminescence. Cardiac function was evaluated by MRI and electrocardiogram at 150 and 196 dpi. CCC mice showed significant differences in MRI and ECG parameters compared to non-infected mice. However, no differences were observed in contractile and electrical parameters between cell and PBS injected groups, 45 days after cell transplantation. Cells were detected 24 h after transplantation by MRI. CM-mESC bioluminescence tracking demonstrated over 90% decrease in signal 8 days after treatment. Nevertheless, the Infected + CM-mESC group showed a significant reduction in the percentage of collagen fibers when compared to the Infected + PBS group. In conclusion, CM-mESC therapy was not effective in reversing cardiac functional changes induced by Chagas disease despite some improvement in myocardial fibrosis.

Cardiosphere-derived cells do not improve cardiac function in rats with cardiac failure.

BACKGROUND: Heart failure represents an important public health issue due to its high costs and growing incidence worldwide. Evidence showing the regenerative potential of postmitotic heart tissue has suggested the existence of endogenous cardiac stem cells in adult hearts. Cardiosphere-derived cells (CDC) constitute a candidate pool of such cardiac stem cells. Previous studies using acute myocardial infarction (MI) models in rodents demonstrated an improvement in cardiac function after cell therapy with CDC. We evaluated the therapeutic potential of CDC 60 days after MI in a rat model. METHODS: CDC were obtained from human discarded myocardial tissue and rat hearts by enzymatic digestion with collagenase II. At 10-15 days after isolation, small, round, phase-bright cells (PBCs) appeared on top of the adherent fibroblast-like cells. The PBCs were collected and placed on a nonadherent plate for 2 days, where they formed cardiospheres which were then transferred to adherent plates, giving rise to CDC. These CDC were characterized by flow cytometry. Wistar rats were submitted to MI through permanent occlusion of the anterior descending coronary artery. After 60 days, they were immunosuppressed with cyclosporine A during 10 days. On the third day, infarcted animals were treated with 5 × 105 human CDC (hCDC) or placebo through intramyocardial injection guided by echocardiogram. Another group of animals was treated with rat CDC (rCDC) without immunosuppression. hCDC and rCDC were stably transduced with a viral construct expressing luciferase under control of a constitutive promoter. CDC were then used in a bioluminescence assay. Functional parameters were evaluated by echocardiogram 90 and 120 days after MI and by Langendorff at 120 days. RESULTS: CDC had a predominantly mesenchymal phenotype. Cell tracking by bioluminescence demonstrated over 85% decrease in signal at 5-7 days after cell therapy. Cardiac function evaluation by echocardiography showed no differences in ejection fraction, end-diastolic volume, or end-systolic volume between groups receiving human cells, rat cells, or placebo. Hemodynamic analyses and infarct area quantification confirmed that there was no improvement in cardiac remodeling after cell therapy with CDC. CONCLUSION: Our study challenges the effectiveness of CDC in post-ischemic heart failure.

Bone marrow cell migration to the heart in a chimeric mouse model of acute chagasic disease

BACKGROUND Chagas disease is a public health problem caused by infection with the protozoan Trypanosoma cruzi. There is currently no effective therapy for Chagas disease. Although there is some evidence for the beneficial effect of bone marrow-derived cells in chagasic disease, the mechanisms underlying their effects in the heart are unknown. Reports have suggested that bone marrow cells are recruited to the chagasic heart; however, studies using chimeric mouse models of chagasic cardiomyopathy are rare. OBJECTIVES The aim of this study was to investigate the migration of bone marrow cells to the heart after T. cruzi infection in a model of chagasic disease in chimeric mice. METHODS To obtain chimerical mice, wild-type (WT) C57BL6 mice were exposed to full body irradiation (7 Gy), causing bone marrow ablation. Then, bone marrow cells from green fluorescent protein (GFP)-transgenic mice were infused into the mice. Graft effectiveness was confirmed by flow cytometry. Experimental mice were divided into four groups: (i) infected chimeric (iChim) mice; (ii) infected WT (iWT) mice, both of which received 3 × 104 trypomastigotes of the Brazil strain; (iii) non-infected chimeric (Chim) mice; and (iv) non-infected WT mice. FINDINGS At one-month post-infection, iChim and iWT mice showed first degree atrioventricular block with decreased heart rate and treadmill exercise parameters compared to those in the non-infected groups. MAIN CONCLUSIONS iChim mice showed an increase in parasitaemia, myocarditis, and the presence of amastigote nests in the heart tissue compared to iWT mice. Flow cytometry analysis did not detect haematopoietic progenitor cells in the hearts of infected mice. Furthermore, GFP+ cardiomyocytes were not detected in the tissues of chimeric mice.