Cord blood cell therapy alters LV remodeling and cytokine expression but does not improve heart function after myocardial infarction in rats

Survival, integration, and differentiation of unrestricted somatic stem cells in the heart

Unrestricted somatic stem cells (USSCs) derived from human umbilical cord blood represent an attractive cell source to reconstitute the damaged heart. We have analyzed the cardiomyogenic potential and investigated the fate of USSCs after transplantation into rat heart in vivo. USSCs demonstrated cardiomyogenic differentiation properties characterized by the spontaneously beating activity and the robust expression of cardiac α-actinin and troponin T (cTnT) at protein and mRNA level after cocultivation with neonatal rat cardiomyocytes. To study the fate in vivo, eGFP⁺ USSCs were injected transcoronarily into immunosuppressed rats via a catheter-based technique. Nearly 80% USSCs were retained within the myocardium without altering cardiac hemodynamics. After 7 days, 20% of the transplanted cells survived in the host myocardium and showed elongated morphology with weak expression of cardiac-specific markers, while some eGFP⁺ USSCs were found to integrate into the vascular wall. After 21 days, only a small fraction of USSCs were found in the myocardium (0.13%); however, the remaining cells clearly exhibited a sarcomeric structure similar to mature cardiomyocytes. Identical results were also obtained in nude rats. In addition, we found some cells stained positively for activated caspase 3 paralleled by the massive infiltration of CD11b⁺ cells into the myocardium. In summary, USSCs can differentiate into beating cardiomyocytes by cocultivation in vitro. After coronary transplantation in vivo, however, long-term survival of differentiated USSCs was rather low despite a high initial fraction of trapped cells.

Human unrestricted somatic stem cell administration fails to protect nude mice from cisplatin-induced acute kidney injury

BACKGROUND

Kidney failure is a debilitating disorder with limited treatment options. The kidney-protective effects of stem cells have been vastly investigated and promising results have been achieved with various sources of stem cells. However, in spite of beneficial effects on other disease models, the renoprotective potential of human cord blood-derived unrestricted somatic stem cells (USSC) has not been examined so far.

METHODS

In the present study, acute kidney failure was induced in female nude mice and the effect of USSC transplantation on kidney function and structure was assessed. Furthermore, the expression of some cytokine genes was examined by real-time PCR. Homing of the transplanted cells into kidneys was assessed by flow cytometry, immunohistochemistry, and real-time PCR.

RESULTS

USSC-conditioned medium did not attenuate the in vitro nephrotoxic effects of cisplatin. Transplantation of USSC to nude mice did not protect kidney function and was associated with worsened kidney structural damage. USSC transplantation was also associated with a decline in the renal expression of VEGF-A gene. In spite of these effects, the transplanted cells could not be detected in the kidneys by any of the exploited methods and they were mainly entrapped in the lungs.

CONCLUSION

These data indicate that USSC are not suitable for cell therapy in the setting of acute kidney injury. Also, this study shows that these stem cells are able to affect damaged kidneys even if they are not homed there.

Xenon and isoflurane reduce left ventricular remodeling after myocardial infarction in the rat

BACKGROUND

Xenon and isoflurane are known to have cardioprotective properties. We tested the hypothesis that these anesthetics positively influence myocardial remodeling 28 days after experimental perioperative myocardial infarction and compared their effects.

METHODS

A total of 60 male Sprague-Dawley rats were subjected to 60 min of coronary artery occlusion and 120 min of reperfusion. Prior to ischemia, the animals were randomized for the different narcotic regimes (0.6 vol% isoflurane, 70 vol% xenon, or intraperitoneal injection of s-ketamine). Acute injury was quantified by echocardiography and troponin I. After 4 weeks, left ventricular function was assessed by conductance catheter to quantify hemodynamic compromise. Cardiac remodeling was characterized by quantification of dilatation, hypertrophy, fibrosis, capillary density, apoptosis, and expression of fetal genes (α/β myosin heavy chains, α-skeletal actin, periostin, and sarco/endoplasmic reticulum Ca2+-ATPase).

RESULTS

Whereas xenon and isoflurane impeded the acute effects of ischemia-reperfusion on hemodynamics and myocardial injury at a comparable level, differences were found after 4 weeks. Xenon in contrast to isoflurane or ketamine anesthetized animals demonstrated a lower remodeling index (0.7 ± 0.1 vs. 0.9 ± 0.3 and 1.0 ± 0.3g/ml), better ejection fraction (62 ± 9 vs. 49 ± 7 and 35 ± 6%), and reduced expression of β-myosin heavy chain and periostin. The effects on hypertrophy, fibrosis, capillary density, and apoptosis were comparable.

CONCLUSIONS

Compared to isoflurane and s-ketamine, xenon limited progressive adverse cardiac remodeling and contractile dysfunction 28 days after perioperative myocardial infarction.

Direct contact of umbilical cord blood endothelial progenitors with living cardiac tissue is a requirement for vascular tube-like structures formation

The umbilical cord blood derived endothelial progenitor cells (EPCs) contribute to vascular regeneration in experimental models of ischaemia. However, their ability to participate in cardiovascular tissue restoration has not been elucidated yet. We employed a novel coculture system to investigate whether human EPCs have the capacity to integrate into living and ischaemic cardiac tissue, and participate to neovascularization. EPCs were cocultured with either living or ischaemic murine embryonic ventricular slices, in the presence or absence of a pro-angiogenic growth factor cocktail consisting of VEGF, IGF-1, EGF and bFGF. Tracking of EPCs within the cocultures was performed by cell transfection with green fluorescent protein or by immunostaining performed with anti-human vWF, CD31, nuclei and mitochondria antibodies. EPCs generated vascular tube-like structures in direct contact with the living ventricular slices. Furthermore, the pro-angiogenic growth factor cocktail reduced significantly tubes formation. Coculture of EPCs with the living ventricular slices in a transwell system did not lead to vascular tube-like structures formation, demonstrating that the direct contact is necessary and that the soluble factors secreted by the living slices were not sufficient for their induction. No vascular tubes were formed when EPCs were cocultured with ischaemic ventricular slices, even in the presence of the pro-angiogenic cocktail. In conclusion, EPCs form vascular tube-like structures in contact with living cardiac tissue and the direct cell-to-cell interaction is a prerequisite for their induction. Understanding the cardiac niche and micro-environmental interactions that regulate EPCs integration and neovascularization are essential for applying these cells to cardiovascular regeneration.

Cord blood transplantation and stem cell regenerative potential

The past 20 years of experience with umbilical cord blood transplantation have demonstrated that cord blood is effective in the treatment of a spectrum of diseases, including hematological malignancies, bone marrow failure, hemoglobinopathies, and inborn errors of metabolism. Cord blood can be obtained with ease and then safely cryopreserved for either public or private use without loss of viability. As compared to other unrelated donor cell sources, cord blood transplantation allows for greater human leukocyte antigen disparity without a corresponding increase in graft-vs.-host disease. Moreover, cord blood has a lower risk of transmitting infections by latent viruses and is less likely to carry somatic mutations than other adult cells. Recently, multiple populations of stem cells with primitive stem cell properties have been identified from cord blood. Meanwhile, there is an increasing interest in applying cord blood mononuclear cells or enriched stem cell populations to regenerative therapies. Accumulating evidence has suggested functional improvements after cord blood transplantation in various animal models for treatments of cardiac infarction, diabetes, neurological diseases, etc. In this review, we will summarize the most recent updates on clinical applications of cord blood transplantation and the promises and limitations of cell-based therapies for tissue repair and regeneration.

Integration of functional bacterial artificial chromosomes into human cord blood-derived multipotent stem cells

Stem cells from a patient with a genetic disease could be used for cell therapy if it were possible to insert a functional copy of the defective gene. In this study, we investigate the transfection and subsequent integration of large genomic fragments into human cord blood-derived multipotent stem cells. We describe for the first time the creation of clonal stem cells carrying a human bacterial artificial chromosome (BAC) containing the Friedreich ataxia locus with an enhanced green fluorescent protein (EGFP) reporter gene fused to exon 5a of the frataxin (FXN) gene. Integration of the BAC into the host cell genome was confirmed by PCR, Southern blot and fluorescent in situ hybridization analysis. Reverse transcription-PCR and flow cytometry confirmed expression of FXN-EGFP. Correct mitochondrial localization of the protein was confirmed using fluorescent microscopy. The transfected stem cells also retained the ability to differentiate into cells from all three germline layers, as demonstrated by the capacity to form neuron-specific beta-tubulin-expressing cells, Alizarin Red S-positive bone-like cells, and epithelial-like cells expressing surfactant protein C. This is the first study to demonstrate that cord blood-derived multipotent stem cells may be useful targets for gene therapy applications using large genomic loci.