A novel sub-population of bone marrow-derived myocardial stem cells: potential autologous cell therapy in myocardial infarction

Nitrosylation of β2-Tubulin Promotes Microtubule Disassembly and Differentiated Cardiomyocyte Beating in Ischemic Mice

BACKGROUND

Beating cardiomyocyte regeneration therapies have revealed as alternative therapeutics for heart transplantation. Nonetheless, the importance of nitric oxide (NO) in cardiomyocyte regeneration has been widely suggested, little has been reported concerning endogenous NO during cardiomyocyte differentiation.

METHODS

Here, we used P19CL6 cells and a Myocardiac infarction (MI) model to confirm NO-induced protein modification and its role in cardiac beating. Two tyrosine (Tyr) residues of β2-tubulin (Y106 and Y340) underwent nitrosylation (Tyr-NO) by endogenously generated NO during cardiomyocyte differentiation from pre-cardiomyocyte-like P19CL6 cells.

RESULTS

Tyr-NO-β2-tubulin mediated the interaction with Stathmin, which promotes microtubule disassembly, and was prominently observed in spontaneously beating cell clusters and mouse embryonic heart (E11.5d). In myocardial infarction mice, Tyr-NO-β2-tubulin in transplanted cells was closely related with cardiac troponin-T expression with their functional recovery, reduced infarct size and thickened left ventricular wall.

CONCLUSION

This is the first discovery of a new target molecule of NO, β2-tubulin, that can promote normal cardiac beating and cardiomyocyte regeneration. Taken together, we suggest therapeutic potential of Tyr-NO-β2-tubulin, for ischemic cardiomyocyte, which can reduce unexpected side effect of stem cell transplantation, arrhythmogenesis.

Left ventricle radio-frequency ablation in the rat: a new model of heart failure due to myocardial infarction homogeneous in size and low in mortality

BACKGROUND

The purpose of the current study was to create a model of myocardial infarction (MI) that is homogeneous in size with a low immediate (24 hours) mortality.

METHODS AND RESULTS

Male and female rats (n = 256) underwent left ventricle (LV) ablation (Ab) by a radiofrequency current (1000 kHz; 12 watts for 12 seconds) to promote a MI. A transmural MI occurred in all rats. Post-Ab complex arrhythmias were frequent (atrioventricular block, ventricular tachycardia, and fibrillation), which rapidly and spontaneously reverted to sinus rhythm. Among 66 male rats, immediate mortality occurred in 7.5%. Small MI size dispersion was characterized by smaller variability following Ab (x +/- SD: 45 +/- 8%) when compared with coronary occlusion (Oc; 40 +/- 19%). The histopathologic evaluations identified lesions similar to those which occurred following Oc, with scarring complete at 4 weeks. The hemodynamic and Doppler echocardiograms showed comparable increases in LV dimension, end-diastolic pressure, and pulmonary water content 1 and 4 weeks post-MI. Papillary muscle mechanics 6 weeks post-MI had matched inotropic and lusitropic dysfunction.

CONCLUSIONS

LV Ab gave rise to a MI within a narrow size limit and with a low immediate mortality. LV Ab resulted in histopathologic evolution, ventricular dilation, and dysfunction, impairment in myocardial mechanics, and congestive outcome that reproduced a MI from Oc.

Donor-derived human bone marrow cells contribute to solid organ cancers developing after bone marrow transplantation

Bone marrow-derived stem cells have been shown to participate in solid organ repair after tissue injury. Animal models suggest that epithelial malignancies may arise as aberrant stem cell differentiation during tissue repair. We hypothesized that if bone marrow stem cells participate in human neoplasia, then solid organ cancers developing after allogeneic bone marrow transplantation (ABMT) might include malignant cells of donor origin. We identified four male patients who developed solid organ cancers (lung adenocarcinoma, laryngeal squamous cell carcinoma, glioblastoma, and Kaposi sarcoma) after myeloablation, total body irradiation, and ABMT from female donors. Donor-derived malignant cells comprised 2.5%-6% of the tumor cellularity The presence of donor-derived malignant cells in solid organ cancers suggests that human bone marrow-derived stem cells have a role in solid organ cancer's carcinogenesis. However, the nature of this role is yet to be defined.

Cardiac myocyte transplantation does not increase global epicardial repolarization heterogeneity in a rat infarct model

BACKGROUND

Using a rat in vivo infarct model we tested the hypothesis that fetal cardiomyocyte (FCM) implantation would increase repolarization heterogeneity.

METHODS

Four groups of rats were studied: two groups served as controls and underwent injection with FCM or culture medium in a region of the left ventricle (LV) supplied by the left anterior descending artery (LAD), and two groups underwent LAD ligation followed 3 weeks later by the injection of either FCM or culture medium. Epicardial monophasic action potential (MAP) recordings were obtained 4 to 5 weeks after cell injection from the right ventricle (RV), LV infarction region and LV region remote from the LAD. The maximum difference in action potential duration (MAPD90) between the three sites was defined as repolarization heterogeneity.

RESULTS

LAD ligation (in the control media injection group) resulted in an increase in repolarization heterogeneity from 6.9 +/- 0.9 to 13.8 +/- 1.2 ms (p < 0.005). Similarly, injection of FCM without coronary ligation resulted in an increase in heterogeneity from 6.9 +/- 3.9 to 20.7 +/- 1.3 ms (p = 0.001). However, injection of FCM into regions of infarction did not result in an increase in heterogeneity when compared with the control media group (13.8 +/- 1.9 vs 13.0 +/- 2.6 ms, respectively, p = 0.752).

CONCLUSIONS

Both fetal cardiomyocyte engraftment in the normal myocardium and coronary ligation increased repolarization heterogeneity. However, fetal cardiomyocyte engraftment in an infarcted region did not further increase repolarization heterogeneity.

Bone marrow-derived stem cell interactions with adult cardiomyocytes and skeletal myoblasts in vitro

BACKGROUND AND OBJECTIVES

Secreted growth factors and cell-to-cell contact are both required to elicit cellular functions. We tested the hypothesis that bone-marrow-derived growth factors, together with cell-to-cell contact between bone-marrow-derived stem cells and cardiomyocytes or myoblasts, promote the proliferation of cardiomyocytes and myoblasts.

METHODS

Human cardiomyocytes or skeletal myoblasts were cultured for 4 days in the presence of low and high concentrations of bone-marrow-derived mononuclear cell conditioned medium (MNC-CM) or marrow stromal cell conditioned medium (MSC-CM). The concentrations of vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), hepatocyte growth factor (HGF), and insulin-like growth factor-1 in their respective conditioned media were assayed by enzyme-linked immunosorbent assay. Stem cells were mixed with cardiomyocytes or skeletal myoblasts at a 1:1 ratio and cultured for 7 days to assess the proliferation of these cells. In parallel experiments, equal numbers of various cell types were cultured alone.

RESULTS

The concentrations of VEGF, MCP-1, and HGF increased in MNC-CM and MSC-CM. MNC-CM showed no effect on cardiomyocyte proliferation. A low concentration of MSC-CM increased cardiomyocyte proliferation by 60% (P<.05). Low concentrations of MNC-CM or MSC-CM showed a trend toward an increased proliferation of myoblasts. A high concentration of either conditioned medium showed a toxic effect. In contact coculture, the proliferation of cardiomyocytes and MNC showed no synergistic effect; instead, there was some evidence of inhibition. The proliferation of cardiomyocytes and stromal cells showed an additive effect. Myoblasts in contact coculture with MNC or MSC showed no synergistic effect.

CONCLUSION

These in vitro results suggest that paracrine effects may be the mechanism by which stromal cells become beneficial in cardiac therapy. MNC do not induce the proliferation of cardiomyocytes. Stem-cell-secreted growth factors induce the proliferation of myoblasts, which is not influenced by cell-to-cell contact.

Potential of mesenchymal stem cells in gene therapy approaches for inherited and acquired diseases

The intriguing biology of stem cells and their vast clinical potential is emerging rapidly for gene therapy. Bone marrow stem cells, including the pluripotent haematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs) and possibly the multipotent adherent progenitor cells (MAPCs), are being considered as potential targets for cell and gene therapy-based approaches against a variety of different diseases. The MSCs from bone marrow are a promising target population as they are capable of differentiating along multiple lineages and, at least in vitro, have significant expansion capability. The apparently high self-renewal potential makes them strong candidates for delivering genes and restoring organ systems function. However, the high proliferative potential of MSCs, now presumed to be self-renewal, may be more apparent than real. Although expanded MSCs have great proliferation and differentiation potential in vitro, there are limitations with the biology of these cells in vivo. So far, expanded MSCs have failed to induce durable therapeutic effects expected from a true self-renewing stem cell population. The loss of in vivo self-renewal may be due to the extensive expansion of MSCs in existing in vitro expansion systems, suggesting that the original stem cell population and/or properties may no longer exist. Rather, the expanded population may indeed be heterogeneous and represents several generations of different types of mesenchymal cell progeny that have retained a limited proliferation potential and responsiveness for terminal differentiation and maturation along mesenchymal and non-mesenchymal lineages. Novel technology that allows MSCs to maintain their stem cell function in vivo is critical for distinguishing the elusive stem cell from its progenitor cell populations. The ultimate dream is to use MSCs in various forms of cellular therapies, as well as genetic tools that can be used to better understand the mechanisms leading to repair and regeneration of damaged or diseased tissues and organs.

Induction of umbilical cord blood-derived beta2m-c-Met+ cells into hepatocyte-like cells by coculture with CFSC/HGF cells

Several studies have indicated that adult stem cells derived from bone marrow (BM) and cord blood (CB) can differentiate into hepatocyte-like cells. This ability is important for the treatment of hepatic diseases with BM or CB as a potential approach. However, methods are still being developed for the efficient induction of stem cell differentiation and expansion to get enough cells to be useful. In the present study, we enriched a subset of umbilical cord blood beta(2)m(-)c-Met(+) cells (UCBCCs) and investigated the combination effect of liver nonparenchymal cells (cirrhotic fat-storing cells [CFSCs]) and hepatocyte growth factor (HGF) on the induction of UCBCCs into hepatocyte-like cells. UCBCCs were cocultured with CFSC/HGF feeder layers either directly or separately using insert wells. Flow cytometric analysis showed that most UCBCCs were CD34(+/-)CD90(+/-)CD49f(+)CD29(+)Alb(+)AFP(+). After cocultured with transgenic feeder layers for 7 days, UCBCCs displayed some morphologic characteristics of hepatocytes. Reverse-transcription polymerase chain reaction (RT-PCR) and immunofluorescence cell staining proved that the induced UCBCCs expressed several hepatocyte specific genes including AFP, Alb, CYP1B1 and cytokeratins CK18 and CK19. Furthermore, the induced cells displayed liver specific functions of indocyanine green (ICG) uptake, ammonium metabolism and albumin secretion. Hence, our data have demonstrated that UCBCCs might represent a novel subpopulation of CB-derived stem/progenitor cells capable of successful differentiation into hepatocyte-like cells when incubated with CFSC/HGF cells. In conclusion, not only HGF but also CFSCs and/or the secreted extracellular matrix (ECM) have been shown to be able to serve as essential microenvironment for hepatocyte differentiation.