Cardiac stem cell therapy. Registered trials and a pilot study in patients with dilated cardiomyopathy

Dose-Independent Therapeutic Benefit of Bone Marrow Stem Cell Transplantation after MI in Mice

Several cell populations derived from bone marrow (BM) have been shown to possess cardiac regenerative potential. Among these are freshly isolated CD133⁺ hematopoietic as well as culture-expanded mesenchymal stem cells. Alternatively, by purifying CD271⁺ cells from BM, mesenchymal progenitors can be enriched without an ex vivo cultivation. With regard to the limited available number of freshly isolated BM-derived stem cells, the effect of the dosage on the therapeutic efficiency is of particular interest. Therefore, in the present pre-clinical study, we investigated human BM-derived CD133⁺ and CD271⁺ stem cells for their cardiac regenerative potential three weeks post-myocardial infarction (MI) in a dose-dependent manner. The improvement of the hemodynamic function as well as cardiac remodeling showed no therapeutic difference after the transplantation of both 100,000 and 500,000 stem cells. Therefore, beneficial stem cell transplantation post-MI is widely independent of the cell dose and detrimental stem cell amplification in vitro can likely be avoided.

Mesenchymal stem cell therapy for heart failure: a meta-analysis

BACKGROUND

Mesenchymal stem cell (MSC) treatment has emerged as an important adjunct therapy for heart failure. However, the use of MSC to treat heart failure has not been well established. We conducted a systematic review and meta-analysis to evaluate the efficacy of MSC treatment for heart failure.

METHODS

PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched. Randomized controlled trials (RCTs) assessing the influence of MSC treatment on cardiac function in heart failure were included in this analysis. Two investigators independently searched the articles, extracted data, and assessed the quality of the included studies. Meta-analysis was performed using the fixed-effect model or random-effect model when appropriate.

RESULTS

Six RCTs involving 625 patients were included in the meta-analysis. Compared with control interventions in heart failure patients, MSC treatment had no significant influence on cardiovascular death (RR = 0.76; 95% CI = 0.38-1.52; p = 0.43); however, it was associated with significantly increased left ventricular ejection fraction (LVEF; mean = 9.64; 95% CI = 7.56-11.71; p < 0.00001) and reduced rehospitalization rate (RR = 0.41; 95% CI = 0.23-0.73; p = 0.003). In addition, no significant difference between the two groups was observed for the incidence of myocardial infarction (RR = 0.72; 95% CI = 0.10-5.02; p = 0.74), the recurrence of heart failure (RR = 0.88; 95% CI = 0.28-2.81; p = 0.83), and total death (RR = 0.68; 95% CI = 0.37-1.25; p = 0.21).

CONCLUSION

Although MSC treatment can significantly improve LVEF and reduce rehospitalization rates, it does not have a significant influence on cardiovascular death, myocardial infarction, heart failure, and total death.

Selective Migration of Subpopulations of Bone Marrow Cells along an SDF-1α and ATP Gradient

Both stem cell chemokine stromal cell-derived factor-1α (SDF-1α) and extracellular nucleotides such as adenosine triphosphate (ATP) are increased in ischemic myocardium. Since ATP has been reported to influence cell migration, we analysed the migratory response of bone marrow cells towards a combination of SDF-1 and ATP. Total nucleated cells (BM-TNCs) were isolated from bone marrow of cardiac surgery patients. Migration assays were performed in vitro. Subsequently, migrated cells were subjected to multicolor flow cytometric analysis of CD133, CD34, CD117, CD184, CD309, and CD14 expression. BM-TNCs migrated significantly towards a combination of SDF-1 and ATP. The proportions of CD34+ cells as well as subpopulations coexpressing multiple stem cell markers were selectively enhanced after migration towards SDF-1 or SDF-1 + ATP. After spontaneous migration, significantly fewer stem cells and CD184+ cells were detected. Direct incubation with SDF-1 led to a reduction of CD184+ but not stem cell marker-positive cells, while incubation with ATP significantly increased CD14+ percentage. In summary, we found that while a combination of SDF-1 and ATP elicited strong migration of BM-TNCs in vitro, only SDF-1 was responsible for selective attraction of hematopoietic stem cells. Meanwhile, spontaneous migration of stem cells was lower compared to BM-TNCs or monocytes.

Impact of short-term liquid storage on human CD133(+) stem cells

Stem cell transplantation is a viable strategy for regenerative medicine. However, it is inevitable to have cells undergo storage for several hours or days due to processing and transportation. Therefore, it is crucial to have rigidly controlled conditions ensuring the therapeutic benefit of isolated stem cells. In the present study, we investigated the impact of short-term storage on human CD133(+) cells. CD133(+) cells were isolated from human bone marrow and kept at standardized nonfreezing storage conditions for up to 72 h. Cell viability (apoptosis/necrosis) and expression of CD133 and CXCR4 were analyzed by flow cytometry. Metabolic activity was determined using an MTT assay; colony-forming ability, as well as endothelial-like differentiation, was further evaluated. A qRT-PCR array was employed to investigate the expression of stemness genes. CD133 and CXCR4 expressions were preserved at all time points. After 30 h, cell number and metabolic activity decreased, although no significant changes were detected in cell viability and proliferation as well as endothelial-like differentiation. Cell viability and proliferation decreased significantly only after 72 h of storage. Our results indicate that storage of isolated human CD133(+) bone marrow stem cells in liquid allows for high viability and functionality. However, storage time should be limited in order to avoid cell loss.

Human Mesenchymal Stem Cells Display Reduced Expression of CD105 after Culture in Serum-Free Medium

Human Mesenchymal Stem Cells (hMSCs) present a promising tool for regenerative medicine. However, ex vivo expansion is necessary to obtain sufficient cells for clinical therapy. Conventional growth media usually contain the critical component fetal bovine serum. For clinical use, chemically defined media will be required. In this study, the capability of two commercial, chemically defined, serum-free hMSC growth media (MSCGM-CD and PowerStem) for hMSC proliferation was examined and compared to serum-containing medium (MSCGM). Immunophenotyping of hMSCs was performed using flow cytometry, and they were tested for their ability to differentiate into a variety of cell types. Although the morphology of hMSCs cultured in the different media differed, immunophenotyping displayed similar marker patterns (high expression of CD29, CD44, CD73, and CD90 cell surface markers and absence of CD45). Interestingly, the expression of CD105 was significantly lower for hMSCs cultured in MSCGM-CD compared to MSCGM. Both groups maintained mesenchymal multilineage differentiation potential. In conclusion, the serum-free growth medium is suitable for hMSC culture and comparable to its serum-containing counterpart. As the expression of CD105 has been shown to positively influence hMSC cardiac regenerative potential, the impact of CD105 expression onto clinical use after expansion in MSCGM-CD will have to be tested.

Stem cell transplantation in cardiovascular disease: an update

Despite the development of novel therapeutic strategies, cardiovascular diseases remain the main cause of morbidity and mortality worldwide. Many phase 1 and 2 clinical trials have reported the safety, feasibility and promising potential of stem cell transplantation, however, the optimal cell types, timing of infusion, cell dosage and routes of administration remain to be determined. This paper reviews the findings of various clinical studies and discusses the challenges facing the delivery of stem cell therapy in cardiovascular diseases.