Regenerative medicine for cardiovascular disorders-new milestones: adult stem cells

Long-term follow-up of patients with Buerger's disease after autologous stem cell therapy

Objective:

We investigated the long-term results of autologous bone marrow mononuclear cells (ABMMNCs) implantation in patients with Buerger’s disease (BD).

Methods:

Twenty-eight patients (25 males and 3 females) who had BD and critical unilateral limb ischemia were investigated between April 2003 and August 2005. The patients were administered multiple injections of CD34+ and CD45+ positive ABMMNCs into the gastrocnemius muscle, the intermetatarsal region, and the dorsum of the foot (n=26) or forearm (n=2) and saline injection into the contralateral limb.

Results:

The mean follow-up time was 139.6±10.5 months. No complication related to stem cell therapy was observed during the follow-up. The ankle–brachial pressure index evaluated at 6 months and 120 months was compared to the baseline scores (p<0.001 and p=0.021, respectively). Digital subtraction angiography (DSA) was performed for all patients at baseline, 6 months, and 120 months. The angiographic improvement was 78.5% and 57.1% at 6 and 120 months, respectively. Patients demonstrated a significant improvement in the quality of life parameters at 6 months compared to baseline (p=0.008) and 120 months compared to the baseline (p=0.009). The 10-year amputation-free rate was 96% (95% CI=0.71-1) in ABMMNC-implanted limbs and 93% (95% CI=0.33–0.94) in saline-injected limbs (p=1).

Conclusion:

Autologous stem cell therapy could be an alternative therapeutic method for BD at long-term follow-up.

Nanoparticle labeling of bone marrow-derived rat mesenchymal stem cells: their use in differentiation and tracking

Mesenchymal stem cells (MSCs) are promising candidates for cellular therapies due to their ability to migrate to damaged tissue without inducing immune reaction. Many techniques have been developed to trace MSCs and their differentiation efficacy; however, all of these methods have limitations. Conjugated polymer based water-dispersible nanoparticles (CPN) represent a new class of probes because they offer high brightness, improved photostability, high fluorescent quantum yield, and noncytotoxicity comparing to conventional dyes and quantum dots. We aimed to use this tool for tracing MSCs' fate in vitro and in vivo. MSC marker expression, survival, and differentiation capacity were assessed upon CPN treatment. Our results showed that after CPN labeling, MSC markers did not change and significant number of cells were found to be viable as revealed by MTT. Fluorescent signals were retained for 3 weeks after they were differentiated into osteocytes, adipocytes, and chondrocytes in vitro. We also showed that the labeled MSCs migrated to the site of injury and retained their labels in an in vivo liver regeneration model. The utilization of nanoparticle could be a promising tool for the tracking of MSCs in vivo and in vitro and therefore can be a useful tool to understand differentiation and homing mechanisms of MSCs.

Hydrogel based injectable scaffolds for cardiac tissue regeneration

Tissue engineering promises to be an effective strategy that can overcome the lacuna existing in the current pharmacological and interventional therapies and heart transplantation. Heart failure continues to be a major contributor to the morbidity and mortality across the globe. This may be attributed to the limited regeneration capacity after the adult cardiomyocytes are terminally differentiated or injured. Various strategies involving acellular scaffolds, stem cells, and combinations of stem cells, scaffolds and growth factors have been investigated for effective cardiac tissue regeneration. Recently, injectable hydrogels have emerged as a potential candidate among various categories of biomaterials for cardiac tissue regeneration due to improved patient compliance and facile administration via minimal invasive mode that treats complex infarction. This review discusses in detail on the advances made in the field of injectable materials for cardiac tissue engineering highlighting their merits over their preformed counterparts.

Stem cell mediated cardiovascular repair

Recent increase in the interest in stem and progenitor cells may be attributed to their behavioural characteristics. A consensus has been reached that embryonic or adult stem cells have therapeutic potential. As cardiovascular health issues are still the major culprits in many developed countries, stem and progenitor cell driven approaches may give the clinicians a new arsenal to tackle many significant health issues. However, stem and progenitor cell mediated cardiovascular regeneration can be achieved via complex and dynamic molecular mechanisms involving a variety of cells, growth factors, cytokines, and genes. Functional contributions of transplanted cells on target organs and their survival are still critical problems waiting to be resolved. Moreover, the regeneration of contracting myocardial tissue has controversial results in human trials. Thus, moderately favourable clinical results should be interpreted carefully. Determining the behavioural programs, genetic and transcriptional control of stem cells, mechanisms that determine cell fate, and functional characteristics are the primary targets. In addition, ensuring the long-term follow-up of cells with efficient imaging techniques in human clinical studies may provide a resurgence of the initial enthusiasm, which has faded over time. Here, we provide a brief historical perspective on stem cell driven cardiac regeneration and discuss cardiac and vascular repair in the context of translational science.

Human blood-vessel-derived stem cells for tissue repair and regeneration

Multipotent stem/progenitor cells with similar developmental potentials have been independently identified from diverse human tissue/organ cultures. The increasing recognition of the vascular/perivascular origin of mesenchymal precursors suggested blood vessels being a systemic source of adult stem/progenitor cells. Our group and other laboratories recently isolated multiple stem/progenitor cell subsets from blood vessels of adult human tissues. Each of the three structural layers of blood vessels: intima, media, and adventitia has been found to include at least one precursor population, that is, myogenic endothelial cells (MECs), pericytes, and adventitial cells (ACs), respectively. MECs and pericytes efficiently regenerate myofibers in injured and dystrophic skeletal muscles as well as improve cardiac function after myocardial infarction. The applications of ACs in vascular remodeling and angiogenesis/vasculogenesis have been examined. Our recent finding that MECs and pericytes can be purified from cryogenically banked human primary muscle cell culture further indicates their potential applications in personalized regenerative medicine.

Long-term results of autologous stem cell transplantation in the treatment of patients with congestive heart failure

BACKGROUND

The aim of this study was to assess the long-term efficacy of stem cell transplantation with revascularization for patients with ischemic cardiomyopathy.

METHODS

We enrolled 17 patients with ischemic cardiomyopathy who had undergone autologous stem cell treatment. To assess myocardial ischemia and viability they underwent coronary angiography, stress tests with dobutamine, echocardiography, and positron emission tomography. Peripheral stem cells mobilized using granulocyte colony-stimulating factor (G-CSF) were collected by aphseresis for transplantation transmyocardially into the areas of injury during coronary artery bypass surgery to increase blood flow to the engrafted areas.

RESULTS

Three patients died in the early follow-up period and 4 patients with cardiac failure died during mid-term follow-up; they all underwent stem cell transplantation at 6 months after acute myocardial infarction. The mean follow-up period of the remaining 10 patients was 85.8 ± 9.2 months (range, 70-100). Mean left ventricular ejection fraction improved to 30.0 ± 6.7, whereas the preoperative mean left ventricular ejection fraction of the surviving patients was 25.6 ± 4.5 (P = .035). Mean New York Heart Association (NYHA) functional class decreased from 3.2 to 1.5 (P = .006). When the study population was divided into 2 subgroups according to the interval between acute myocardial infraction and surgery, the patients who underwent autologous stem cell transplantation within the first 6 months after myocardial infraction (Group 1) showed significantly lower NYHA scores at the last follow-up (P = .024 in Group 1 and P = .102 in Group 2). No side effects were observed to be due to the stem cell or G-CSF injections.

CONCLUSION

Treatment of ischemic cardiomyopathy with autologous stem cell transplantation is easy and safe, opening a new window in the treatment of "no hope" patients.

Timing of induction of cardiomyocyte differentiation for in vitro cultured mesenchymal stem cells: a perspective for emergencies

Mesenchymal stem cells (MSCs) have the capacity to differentiate into osteoblasts, chondrocytes, adipocytes, myocytes, and cardiomyocytes. Several established methods are presently available for in vitro isolation of MSCs from bone marrow. However, the duration necessary to culture them can be a major handicap to cell-based therapies needed for such urgent cardiovascular conditions as acute myocardial infarction and acute hindlimb ischemia. The best timing of cardiomyocyte differentiation induction after MCS isolation and expansion is still an unresolved issue. Our goal was to investigate the possibility of obtaining functional cardiomyocytes from rat MSC within a shorter time period. We examined MSCs' colony-forming capacity, CD90 and CD34 immunoreactivity during the 14 days of culturing. Cardiomyocyte differentiation was induced by 5-azacytidine. Immunohistochemic staining, together with intracellular Ca2+ measurement experiments, revealed that MSCs do not differentiate into any specific cell lineage but show the characteristics of MSCs on both the 9th and 14th days of the culture. To check the potential for differentiation into cardiomyocytes, experiments with caffeine application and depolarization with KCl were performed. The cells possessed some of the specific biochemical features of contracting cells, with slightly higher capacities on the 14th day. Cells from 9th and 14th days of the culture that were treated with 5-azacytidine had a higher expression of cardiac-specific markers such as troponin I, alpha-sarcomeric actin, and MEF2D compared with the control groups. This study illustrates that it is possible to get functional cardiomyocytes from in vitro MSC culture in a shorter time period than previously achieved. This reduction in time may provide emergency cases with access to cell-based therapies that may have previously been unavailable.

Material-based deployment enhances efficacy of endothelial progenitor cells

Cell-based therapies are attractive for revascularizing and regenerating tissues and organs, but clinical trials of endothelial progenitor cell transplantation have not resulted in consistent benefit. We propose a different approach in which a material delivery system is used to create a depot of vascular progenitor cells in vivo that exit over time to repopulate the damaged tissue and participate in regeneration of a vascular network. Microenvironmental conditions sufficient to maintain the viability and outward migration of outgrowth endothelial cells (OECs) have been delineated, and a material incorporating these signals improved engraftment of transplanted cells in ischemic murine hindlimb musculature, and increased blood vessel densities from 260 to 670 vessels per mm(2), compared with direct cell injection. Further, material deployment dramatically improved the efficacy of these cells in salvaging ischemic murine limbs, whereas bolus OEC delivery was ineffective in preventing toe necrosis and foot loss. Finally, material deployment of a combination of OECs with another cell population commonly isolated from peripheral or cord blood, endothelial progenitor cells (EPCs) returned perfusion to normal levels in 40 days, and prevented toe and foot necrosis. Direct injection of an EPC/OEC combination was minimally effective in improving limb perfusion, and untreated limbs underwent autoamputation in 3 days. These results demonstrate that vascular progenitor cell utility is highly dependent on the mode of delivery, and suggest that one can create new vascular beds for a variety of applications with this material-controlled deployment of cells.

Comparison of different needle diameters and flow rates on bone marrow mononuclear stem cell viability: an ex vivo experimental study

Considerable information is available regarding the experimental and clinical applications of bone marrow derived stem cells (BMDSC) for regenerative medicine. Optimized stem cell delivery systems might help to maintain better stem cell viability. We have investigated whether needle diameters and flow rates through the needles cause any difference in terms of BMDSC viability.

Impact of harvest product volume in erythrocyte depletion of allogeneic or autologous bone marrow using COBE spectra

Depletion of bone marrow (BM) from erythrocytes is used to prevent early hemolysis in major ABO incompatible allogeneic hematopoietic cell transplantation (Allo-HCT). This method was also strongly recommended before storing of autologous and even allo-BM for volume reduction in order to prevent early hemolysis and DMSO toxicity after infusion. In our center, erythrocyte depletion of BM harvests has been performed on a continuous flow cell separator, which used a closed system with a high mononuclear cell (MNC) yield and low rate of erythrocyte contamination. According to the protocol of a cellular therapy approach in a cardiovascular collaborative study we have to adopt the process to lower volumes. We aimed to compare our results with standard volume (SV) (historical control) to low volume ED procedures.

PATIENTS AND METHOD

Data has been collected from the last five years. We analyzed 28 cases in the SV group (BM volume >750ml) and 39 cases in the low volume (LV) group. Nineteen of these cases were allogeneic, and 48 were autologous procedures. We used the software COBE PBSC coll vers 5.1 and a standard disposable set (Gambro BCT, Lakewood, USA) for the procedure, and simultaneously, a double bag system with intermediate connectors were used to overcome re-circulation (COBE Spectra Bone Marrow Processing Set, Lakewood USA).

RESULTS

The mean volume reduction was 88% (range, 84.4-93.5%) for SV and 90.8% (range, 87.2-91.3%) for the LV group. We did not find any significant difference for MNC yield, volume reduction rate and CD34+ cell recovery between the SV and LV group. There were no complications experienced with regards to device or technical difficulties during procedures. Acute massive intravascular hemolysis was not observed in allogeneic recipients.

CONCLUSION

ED and volume reduction with COBE spectra produced successful results in standard and low harvest volumes. This process can be successfully applied to lower volumes and comparable results to the SV harvest can be achieved for the ED rate, reduction of volume and recovery of MNCs and CD34+ cells.

Autologous bone-marrow mononuclear cell implantation for patients with Rutherford grade II-III thromboangiitis obliterans

BACKGROUND

This study investigated the efficacy and safety of autologous bone marrow-mononuclear cells (ABMMNC) implantation in patients with critical limb ischemia (CLI) due to thromboangiitis obliterans (Buerger's disease).

METHODS

The study comprised 28 patients (25 men and 3 women) with a median age of 44 years (range, 25-54 years) who had thromboangiitis obliterans and unilateral critical limb ischemia, defined as ischemic rest pain in a limb with or without nonhealing ulcers. The patients received multiple injections of erythrocyte-depleted and volume-reduced ABMMNC into the gastrocnemius muscle, the intermetatarsal region, and the feet dorsum (n = 26) or forearm (n = 2) vs saline injections into the less ischemic contralateral limbs. The patients were nonresponders to previous Iloprost infusion and smoking cessation >or=6 months and were not candidates for nonsurgical or surgical revascularization. Primary end points were the total healing of the most important lesion while avoiding major or minor amputation, the relief of rest pain without the need for analgesics from baseline to 6 months' follow-up, and the safety and feasibility of the treatment. Secondary end points were the changes in ankle-brachial pressure index and peak walking time, the angiographic evidence of collateral vessel formation or remodeling, and the quality-of-life assessment. Two investigators blinded for treatment assignment performed image analyses.

RESULTS

Unilateral intramuscular administration of ABMMNC was not associated with any complications. The mean follow-up time was 16.6 +/- 7.8 months (range, 7.6 to 33.8 months). Only one patient required toe amputation during follow-up. A change in the ankle-brachial pressure index >0.15 was achieved in 8 patients at 3 months and in 14 patients at 6 months compared with baseline values. At 6 months, patients demonstrated a significant improvement in rest pain scores (P < .0001), peak walking time (P < .0001), and quality of life (P < .0083). Total healing of the most important lesion was achieved in 15 patients (83%) with ischemic ulcers, and relief of rest pain without the need of narcotic analgesics improved in all patients. Digital subtraction angiography studies before and 6 months after the ABMMNC implantation showed vascular collateral networks had formed across the affected arteries in 22 patients (78.5%).

CONCLUSIONS

ABMMNC implantation could be a safe alternative to achieve therapeutic angiogenesis in patients with thromboangiitis obliterans and critical limb ischemia refractory to other treatment modalities.