Dynamic imaging of allogeneic mesenchymal stem cells trafficking to myocardial infarction

The life and fate of mesenchymal stem cells

Mesenchymal stem cells (MSC) are present throughout the body and are thought to play a role in tissue regeneration and control of inflammation. MSC can be easily expanded in vitro and their potential as a therapeutic option for degenerative and inflammatory disease is therefore intensively investigated. Whilst it was initially thought that MSC would replace dysfunctional cells and migrate to sites of injury to interact with inflammatory cells, experimental evidence indicates that the majority of administered MSC get trapped in capillary networks and have a short life span. In this review, we discuss current knowledge on the migratory properties of endogenous and exogenous MSC and confer on how culture-induced modifications of MSC may affect these properties. Finally, we will discuss how, despite their limited survival, administered MSC can bring about their therapeutic effects.

Mesenchymal stromal cells for organ transplantation: different sources and unique characteristics?

PURPOSE OF THE REVIEW

In this review, recent findings on the effects of tissue and donor origin, culturing conditions and preconditioning regimens on the therapeutic effect of mesenchymal stem cells (MSC) in organ transplantation are discussed and the importance of understanding the characteristics of MSC for developing efficient therapy is stressed.

RECENT FINDINGS

MSC research in organ transplantation is currently moving from safety-feasibility studies to efficacy studies and finding the optimal MSC for therapy is therefore highly relevant. Although sharing basic properties, there are subtle differences between MSC from different tissue sources that may affect their efficacy. Furthermore, the use of MSC from diseased organ recipients, donor or third party may affect their therapeutic effect. The importance of these differences in MSC properties may however be overshadowed by the impact of culture conditions on MSC. Culture conditions dramatically change the characteristics of MSC, and this situation can be exploited by exposing MSC to preconditioning treatment to bring about the desired properties in MSC. As MSC appear to be short-lived after infusion, the specific characteristics of MSC are mostly relevant for short-term interactions between MSC and host cells, which will subsequently take over the effects of MSC. The multiple effects of MSC are by no means unique, but the full spectrum of the effects in combination with their easy isolation and expansion make MSC a suitable cell type for therapy.

SUMMARY

Tissue source, donor source and culture conditions affect the phenotypical and functional properties of MSC. The efficacy of MSC therapy will therefore depend on the source and manipulation of MSC.

Optimization of the therapeutic efficacy of human umbilical cord blood-mesenchymal stromal cells in an NSG mouse xenograft model of graft-versus-host disease

BACKGROUND AIMS

Although in vitro studies have demonstrated the immunosuppressive capacity of mesenchymal stromal cells (MSCs), most in vivo studies on graft-versus-host disease (GVHD) have focused on prevention, and the therapeutic effect of MSCs is controversial. Moreover, optimal time intervals for infusing MSCs have not been established.

METHODS

We attempted to evaluate whether human umbilical cord blood-MSCs (hUCB-MSCs) could either prevent or treat GVHD in an NSG mouse xenograft model by injection of MSCs before or after in vivo clearance. Mice were infused with either a single dose or multiple doses of 5 × 10(5) hUCB-MSCs (3- or 7-day intervals) before or after GVHD onset.

RESULTS

Before onset, hUCB-MSCs significantly improved the survival rate only when repeatedly injected at 3-day intervals. In contrast, single or repeated injections after GVHD onset significantly increased the survival rate and effectively attenuated tissue damage and inflammation. Furthermore, the levels of prostaglandin E2 and transforming growth factor-β1 increased significantly, whereas the level of interferon-γ decreased significantly in all MSC treatment groups.

CONCLUSIONS

These data establish the optimal time intervals for preventing GVHD and show that hUCB-MSCs effectively attenuated symptoms and improved survival rate when administered after the onset of GVDH.

Adult stem cells and heart regeneration

Cardiovascular disease remains the single greatest cause of death in the Western world, claiming more lives in the USA than the next four leading causes combined. Among these diseases, the incidence of heart failure continues to rise at a staggering rate. Recent advances in medical and device therapies have dramatically improved both the survival and quality of life of many of these patients; however, limited strategies are available to address the central pathophysiology underlying the development of heart failure, namely, the loss of functional cardiomyocytes. Therefore, one recent strategy has been the development of cell-based therapies, aiming towards the replacement of injured or lost cardiomyocytes and thereby improved cardiac function. In this review, we will examine the cell types undergoing investigation as potential cell-based therapies and provide an overview of current clinical trials utilizing cell-based therapeutic approaches in patients with heart disease.

Transendocardial cell injection is not superior to intracoronary infusion in a porcine model of ischaemic cardiomyopathy: a study on delivery efficiency

Stem cell therapy is a new strategy for chronic ischaemic heart disease in patients. However, no consensus exists on the most optimal delivery strategy. This randomized study was designed to assess cell delivery efficiency of three clinically relevant strategies: intracoronary (IC) and transendocardial (TE) using electromechanical mapping guidance (NOGA) compared to surgical delivery in a chronic pig model of ischaemic cardiomyopathy. Twenty-four animals underwent delivery of 10(7) autologous Indium-oxine-labelled bone marrow-derived mesenchymal stem cells (MSC) 4 weeks after infarction and were randomized to one of three groups (n = 8 each group): IC, TE or surgical delivery (reference group). Primary endpoint was defined as percentage (%) of injected dose per organ and assessed by in vivo gamma-emission counting. In addition, troponin and coronary flow were assessed before and after MSC injection. Blinded endpoint analysis showed no significant difference in efficiency after surgical (16 ± 4%), IC (11 ± 1%) and TE (11 ± 3%) (P = 0.52) injections. IC showed less variability in efficiency compared with TE and surgical injection. Overall, TE injection showed less distribution of MSC to visceral organs compared with other modalities. Troponin rise and IC flow did not differ between the percutaneous groups. This randomized study showed no significant difference in cell delivery efficiency to the myocardium in a clinically relevant ischaemic large animal model between IC and TE delivery. In addition, no differences in safety profile were observed. These results are important in view of the choice of percutaneous cell delivery modality in future clinical stem cell trials.

Organic nanoparticles with aggregation-induced emission for tracking bone marrow stromal cells in the rat ischemic stroke model

Fluorescent nanoparticles with aggregation-induced emission were successfully used for tracking bone marrow-derived mesenchymal stromal cells in rats with ischemic stroke.

Reporter gene technologies for imaging cell fates in hematopoiesis

Advances in noninvasive imaging technologies that allow for in vivo dynamic monitoring of cells and cellular function in living research subjects have revealed new insights into cell biology in the context of intact organs and their native environment. In the field of hematopoiesis and stem cell research, studies of cell trafficking involved in injury repair and hematopoietic engraftment have made great progress using these new tools. Stem cells present unique challenges for imaging since after transplantation, they proliferate dramatically and differentiate. Therefore, the imaging modality used needs to have a large dynamic range, and the genetic regulatory elements used need to be stably expressed during differentiation. Multiple imaging technologies using different modalities are available, and each varies in sensitivity, ease of data acquisition, signal to noise ratios (SNR), substrate availability, and other parameters that affect utility for monitoring cell fates and function. For a given application, there may be several different approaches that can be used. For mouse models, clinically validated technologies such as magnetic resonance imaging (MRI) and positron emission tomography (PET) have been joined by optical imaging techniques such as in vivo bioluminescence imaging (BLI) and fluorescence imaging (FLI), and all have been used to monitor bone marrow and stem cells after transplantation into mice. Photoacoustic imaging that utilizes the sound created by the thermal expansion of absorbed light to generate an image best represents hybrid technologies. Each modality requires that the cells of interest be marked with a genetic reporter that acts as a label making them uniquely visible using that technology. For each modality, there are several labels to choose from. Multiple methods for applying these different labels are available. This chapter provides an overview of the imaging technologies and commonly used labels for each, as well as detailed protocols for gene delivery into hematopoietic cells for the purposes of applying these specific labels to cell trafficking. The goal of this chapter is to provide adequate background information to allow the design and implementation of an experimental system for in vivo imaging in mice.

Challenges facing in vivo tracking of mesenchymal stem cells used for tissue regeneration

Bone marrow-derived mesenchymal stem cells (MSCs) are increasingly being investigated in the field of regenerative medicine. In vivo monitoring of MSCs can be performed with MRI, which is a non-invasive, non-toxic and clinically acceptable modality. In order to track these MSCs, cells must be labeled with detectable magnetic nanoparticles. However, they 'leak' from labeled cells, limiting their surveillance to a 3-week period. Li et al. developed a rodent model in order to evaluate MRI monitoring of intramuscularly injected aminopropyltriethoxysilane iron oxide-labeled MSCs. Both in vivo tracking and histological analysis were undertaken. Seeded MSCs demonstrated increased MRI signal in the labeled test group over 3 weeks compared with the unlabeled controls. Histological Prussian blue staining of posttermination tissues confirmed these findings. The authors conclude that successful labeling of MSCs is possible with aminopropyltriethoxysilane - magnetic nanoparticles and that these cells can be monitored in vivo. They offer this form of labeling as an alternative to more common dextran-coated magnetic nanoparticles.

Mesenchymal Stromal Cells: Updates and Therapeutic Outlook in Rheumatic Diseases

Multipotent mesenchymal stromal cells or mesenchymal stem cells (MSCs) are adult stem cells exhibiting functional properties that have opened the way for cell-based clinical therapies. MSCs have been reported to exhibit immunosuppressive as well as healing properties, improving angiogenesis and preventing apoptosis or fibrosis through the secretion of paracrine mediators. This review summarizes recent progress on the clinical application of stem cells therapy in some inflammatory and degenerative rheumatic diseases. To date, most of the available data have been obtained in preclinical models and clinical efficacy needs to be evaluated through controlled randomized double-blind trials.

Mesenchymal stem cells migration homing and tracking

In this review, we discuss the migration and homing ability of mesenchymal stem cells (MSCs) and MSC-like cells and factors influencing this. We also discuss studies related to the mechanism of migration and homing and the approaches undertaken to enhance it. Finally, we describe the different methods available and frequently used to track and identify the injected cells in vivo.

Healthy bone marrow cells reduce progression of kidney failure better than CKD bone marrow cells in rats with established chronic kidney disease

Chronic kidney disease (CKD) is a major health care problem. New interventions to slow or prevent disease progression are urgently needed. We studied functional and structural effects of infusion of healthy and CKD bone marrow cells (BMCs) in a rat model of established CKD. CKD was induced by 5/6 nephrectomy (SNX) in Lewis rats, and disease progression was accelerated with L-NNA and 6% NaCl diet. Six weeks after SNX, CKD rats received healthy eGFP(+) BMCs, CKD eGFP(+) BMCs, or vehicle by single renal artery injection. Healthy BMCs were functionally effective 6 weeks after administration: glomerular filtration rate (GFR; inulin clearance) (0.48±0.16 vs. 0.26±0.14 ml/min/100 g) and effective renal plasma flow (RPF; PAH clearance) (1.6±0.40 vs. 1.0±0.62 ml/min/100 g) were higher in healthy BMC- versus vehicle-treated rats (both p < 0.05). Systolic blood pressure (SBP) and proteinuria were lower 5 weeks after treatment with healthy BMCs versus vehicle (SBP, 151±13 vs. 186±25 mmHg; proteinuria, 33±20 vs. 59±39 mg/day, both p < 0.05). Glomerular capillary density was increased, and less sclerosis was detected after healthy BMCs (both p < 0.05). Tubulointerstitial inflammation was also decreased after healthy BMCs. eGFP(+) cells were present in the glomeruli and peritubular capillaries of the remnant kidney in all BMC-treated rats. CKD BMCs also reduced SBP, proteinuria, glomerulosclerosis, and tubular atrophy versus vehicle in CKD rats. However, CKD BMC therapy was not functionally effective versus vehicle [GFR: 0.28±0.09 vs. 0.26±0.16 ml/min/100 g (NS), RPF: 1.15±0.36 vs. 0.78±0.44 ml/min/100 g (NS)], and failed to decrease tubulointerstitial inflammation and fibrosis. Single intrarenal injection of healthy BMCs in rats with established CKD slowed progression of the disease, associated with increased glomerular capillary density and less sclerosis, whereas injection of CKD BMCs was less effective.

Pulp cell tracking by radionuclide imaging for dental tissue engineering

Pulp engineering with dental mesenchymal stem cells is a promising therapy for injured teeth. An important point is to determine the fate of implanted cells in the pulp over time and particularly during the early phase following implantation. Indeed, the potential engraftment of the implanted cells in other organs has to be assessed, in particular, to evaluate the risk of inducing ectopic mineralization. In this study, our aim was to follow by nuclear imaging the radiolabeled pulp cells after implantation in the rat emptied pulp chamber. For that purpose, indium-111-oxine (¹¹¹In-oxine)-labeled rat pulp cells were added to polymerizing type I collagen hydrogel to obtain a pulp equivalent. This scaffold was implanted in the emptied pulp chamber space in the upper first rat molar. Labeled cells were then tracked during 3 weeks by helical single-photon emission computed tomography (SPECT)/computed tomography performed on a dual modality dedicated small animal camera. Negative controls were performed using lysed radiolabeled cells obtained in a hypotonic solution. In vitro data indicated that ¹¹¹In-oxine labeling did not affect cell viability and proliferation. In vivo experiments allowed a noninvasive longitudinal follow-up of implanted living cells for at least 3 weeks and indicated that SPECT signal intensity was related to implanted cell integrity. Notably, there was no detectable systemic release of implanted cells from the tooth. In addition, histological analysis of the samples showed mitotically active fibroblastic cells as well as neoangiogenesis and nervous fibers in pulp equivalents seeded with entire cells, whereas pulp equivalents prepared from lysed cells were devoid of cell colonization. In conclusion, our study demonstrates that efficient labeling of pulp cells can be achieved and, for the first time, that these cells can be followed up after implantation in the tooth by nuclear imaging. Furthermore, it appears that grafted cells retained the label and are viable to follow the repair process. This technique is expected to be of major interest for monitoring implanted cells in innovative therapies for injured teeth.

Mesenchymal stem cells induce an inflammatory response after intravenous infusion

Mesenchymal stem cells (MSCs) have potent immunosuppressive effects in vitro and are considered as a therapeutic option for autoimmune disease and organ transplantation. While MSCs show beneficial effects on immune disease progression and transplant survival in animal models, the immunomodulatory mechanisms involved are largely unknown. In the present study, we show that intravenously infused C57BL/6- green fluorescent protein (GFP) MSCs home to the lungs in C57BL/6 recipient mice and induce an inflammatory response. This response was characterized by increased mRNA expression of monocyte chemoattractant protein-1 (MCP1), IL1-β, and TNF-α and an increase in macrophages in lung tissue 2 h after MSC infusion. Simultaneously, serum levels of proinflammatory IL6, CXCL1, and MCP1 protein increased, demonstrating systemic immune activation after MSC infusion. In liver tissue, no C57BL/6-GFP MSCs were detected, but MCP1 and TNF-α mRNA levels peaked 4 h after MSC infusion. The expression of the anti-inflammatory cytokines TGF-β, IL4, and IL10 was only marginally affected. Nevertheless, 3 days after MSC infusion, animals developed a milder inflammatory response to lipopolysaccharides. Our results suggest that the in vivo immunomodulatory effects of MSCs originate from an inflammatory response that is induced by the infusion of MSCs, which is followed by a phase of reduced immune reactivity.

A transgenic tri-modality reporter mouse

Transgenic mouse with a stably integrated reporter gene(s) can be a valuable resource for obtaining uniformly labeled stem cells, tissues, and organs for various applications. We have generated a transgenic mouse model that ubiquitously expresses a tri-fusion reporter gene (fluc2-tdTomato-ttk) driven by a constitutive chicken β-actin promoter. This “Tri-Modality Reporter Mouse” system allows one to isolate most cells from this donor mouse and image them for bioluminescent (fluc2), fluorescent (tdTomato), and positron emission tomography (PET) (ttk) modalities. Transgenic colonies with different levels of tri-fusion reporter gene expression showed a linear correlation between all three-reporter proteins (R²=0.89 for TdTomato vs Fluc, R²=0.94 for Fluc vs TTK, R²=0.89 for TdTomato vs TTK) in vitro from tissue lysates and in vivo by optical and PET imaging. Mesenchymal stem cells (MSCs) isolated from this transgenics showed high level of reporter gene expression, which linearly correlated with the cell numbers (R²=0.99 for bioluminescence imaging (BLI)). Both BLI (R²=0.93) and micro-PET (R²=0.94) imaging of the subcutaneous implants of Tri-Modality Reporter Mouse derived MSCs in nude mice showed linear correlation with the cell numbers and across different imaging modalities (R²=0.97). Serial imaging of MSCs transplanted to mice with acute myocardial infarction (MI) by intramyocardial injection exhibited significantly higher signals in MI heart at days 2, 3, 4, and 7 (p<0.01). MSCs transplanted to the ischemic hindlimb of nude mice showed significantly higher BLI and PET signals in the first 2 weeks that dropped by 4^th week due to poor cell survival. However, laser Doppler perfusion imaging revealed that blood circulation in the ischemic limb was significantly improved in the MSCs transplantation group compared with the control group. In summary, this mouse can be used as a source of donor cells and organs in various research areas such as stem cell research, tissue engineering research, and organ transplantation.

Comparison of the sorting efficiency and influence on cell function between the sterile flow cytometry and immunomagnetic bead purification methods

Currently, flow cytometry and immunomagnetic bead purification are the most commonly used cell sorting methods. We performed this study because there are few reports that directly compare the sorting efficiency and influence on cell functions of these two methods. The in vitro cultured third-generation bone marrow mesenchymal cells from newborn Sprague-Dawley rats were sorted and purified using sterile flow cytometry and immunomagnetic beads to obtain CXCR4-positive bone marrow mesenchymal stem cells (CXCR4(+)-MSCs). The yield and purity (detected by flow cytometry), in vitro viability (detected by the MTT method), and in vitro chemotactic capacity (detected by stromal cell-derived factor-1α [SDF-1α] induction) of sorted target cells using these two methods were compared. The purity of CXCR4(+)-MSCs obtained using sterile flow cytometry was higher than that using immunomagnetic bead purification. The MTT method and growth curves showed that the viability of cells was lower and that the amplification rate of cells decreased using sterile flow cytometry, whereas the cell viability was higher after cells were sorted using immunomagnetic beads (p < 0.01). The number of CXCR4(+)-MSCs cells that underwent chemotactic migration induced by SDF-1α after sorting using sterile flow cytometry was smaller than that using immunomagnetic bead purification (15.60 ± 1.14 vs. 26.40 ± 1.67, p < 0.01). Although the purity of CXCR4(+)-MSCs sorted by the immunomagnetic bead purification method was lower than that by sterile flow cytometry, the influence on cell activity of the former was smaller, including improved cell viability and improved SDF-1α -induced chemotactic migration in vitro.

Differential biodistribution of intravenously administered endothelial progenitor and cytotoxic T-cells in rat bearing orthotopic human glioma

BACKGROUND

A major challenge in the development of cell based therapies for glioma is to deliver optimal number of cells (therapeutic dose) to the tumor. Imaging tools such as magnetic resonance imaging (MRI), optical imaging, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) has been used in cell tracking and/or biodistribution studies. In this study, we evaluate the dynamic biodistribution of systemic injected labeled cells [human cord blood derived endothelial progenitor cells (EPCs) and cytotoxic T-cells (CTLs)] in rat glioma model with in vivo SPECT imaging.

METHODS

Human cord blood EPCs, T-cells and CD14⁺ cells (monocytes/dendritic cells) were isolated using the MidiMACS system. CD14⁺ cells were converted to dendritic cells (DC) and also primed with U251 tumor cell line lysate. T-cells were co-cultured with irradiated primed DCs at 10:1 ratio to make CTLs. Both EPCs and CTLs were labeled with In-111-oxine at 37°C in serum free DMEM media. Glioma bearing animals were randomly assigned into three groups. In-111 labeled cells or In-111 oxine alone were injected through tail vein and SPECT imaging was performed on day 0, 1, and 3. In-111 oxine activity in various organs and tumor area was determined. Histochemical analysis was performed to further confirm the migration and homing of injected cells at the tumor site.

RESULTS

EPCs and CTLs showed an In-111 labeling efficiency of 87.06 ± 7.75% and 70.8 ± 12.9% respectively. Initially cell migration was observed in lung following inravenous administration of In-111 labeled cells and decreased on day 1 and 3, which indicate re-distribution of labeled cells from lung to other organs. Relatively higher In-111 oxine activity was observed in tumor areas at 24 hours in animals received In-111 labeled cells (EPCs or CTLs). Histiological analysis revealed iron positive cells in and around the tumor area in animals that received labeled cells (CTLs and EPCs).

CONCLUSION

We observed differential biodistribution of In-111-oxine labeled EPCs and CTLs in different organs and intracranial glioma. This study indicates In-111 oxine based SPECT imaging is an effective tool to study the biodistribution of therapeutically important cells.

Recruitment of exogenous mesenchymal stem cells in mandibular distraction osteogenesis by the stromal cell-derived factor-1/chemokine receptor-4 pathway in rats

Distraction osteogenesis is widely used in orthopaedic and craniofacial surgery. However, its exact mechanism is still poorly understood. The purpose of this study was to find out whether there is systemic recruitment of mesenchymal stem cells (MSC) to the neocallus in the distraction gap by the stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) axis during osteogenesis. We examined the migration of MSC towards a gradient of SDF-1 in vitro. We also transplanted MSC labelled with green fluorescent protein (GFP) intravenously, with or without treatment with CXCR4-blocking antibody, into rats that had had unilateral mandibular distraction osteogenesis, and investigated the distribution of cells labelled with GFP in the soft callus after 24 h. We found that SDF-1 facilitated the migration potency of MSC both in vitro and in vivo, and this migration could be inhibited by AMD3100, an antagonist of CXCR4, and promoted by local infusion of exogenous SDF-1 into the distraction gap. This study provides a new insight into the molecular basis of how new bone is regenerated during distraction osteogenesis.

Delayed Intranasal Delivery of Hypoxic-Preconditioned Bone Marrow Mesenchymal Stem Cells Enhanced Cell Homing and Therapeutic Benefits after Ischemic Stroke in Mice

Stem cell transplantation therapy has emerged as a potential treatment for ischemic stroke and other neurodegenerative diseases. Effective delivery of exogenous cells and homing of these cells to the lesion region, however, have been challenging issues that hinder the efficacy and efficiency of cell-based therapy. In the present investigation, we tested a delayed treatment of noninvasive and brain-targeted intranasal delivery of bone marrow mesenchymal stem cells (BMSCs) in a mouse focal cerebral ischemia model. The investigation tested the feasibility and effectiveness of intranasal delivery of BMSCs to the ischemic cortex. Hypoxia preconditioning (HP) of BMSCs was performed before transplantation in order to promote their survival, migration, and homing to the ischemic brain region after intranasal transplantation. Hoechst dye-labeled normoxic- or hypoxic-pretreated BMSCs (1 × 106 cells/animal) were delivered intranasally 24 h after stroke. Cells reached the ischemic cortex and deposited outside of vasculatures as early as 1.5 h after administration. HP-treated BMSCs (HP-BMSCs) showed a higher level of expression of proteins associated with migration, including CXC chemokine receptor type 4 (CXCR4), matrix metalloproteinase 2 (MMP-2), and MMP-9. HP-BMSCs exhibited enhanced migratory capacities in vitro and dramatically enhanced homing efficiency to the infarct cortex when compared with normoxic cultured BMSCs (N-BMSCs). Three days after transplantation and 4 days after stroke, both N-BMSCs and HP-BMSCs decreased cell death in the peri-infarct region; significant neuroprotection of reduced infarct volume was seen in mice that received HP-BMSCs. In adhesive removal test of sensorimotor functional assay performed 3 days after transplantation, HP-BMSC-treated mice performed significantly better than N-BMSC- and vehicle-treated animals. These data suggest that delayed intranasal administration of stem cells is feasible in the treatment of stroke and hypoxic preconditioning of transplanted cells, significantly enhances cell's homing to the ischemic region, and optimizes the therapeutic efficacy.

Human adipose-derived mesenchymal stem cells can survive and integrate into the adult rat eye following xenotransplantation

BACKGROUND

Novel threads of discovery provide the basis for optimism for the development of a stem-cell-based strategy for the treatment of retinal blindness. Accordingly, achievement to suitable cell source with potential-to-long-term survival and appropriate differentiation can be an effective step in this direction.

METHODS

After derivation of human adipose-derived mesenchymal stem cells (HAD-MSCs), they were stably transfected with a vector containing Turbo-green fluorescent protein (GFP) and JRed to be able to trace them after transplantation. Labeled HAD-MSCs were transplanted into the intact adult rat eye and their survival, integration, and migration during 6 months post-transplantation were assessed.

RESULTS

The transplanted cells were traceable in the rat vitreous humor (VH) up until 90 days after transplantation, with gradual reduction in numbers, their adhesion and expansion capacity after recovery. These cells were also integrated into the ocular tissues. Nonetheless, some of the implanted cells succeeded to cross the blood-retina barrier (BRB) and accumulate in the spleen with time.

CONCLUSIONS

The survival of the HAD-MSCs for a period of 90 days in VH and even longer period of up to 6 months in other eye tissues makes them a promising source to be considered in regenerative medicine of eye diseases. However, the potency of crossing the BRB by the implanted cells suggests that use of HAD-MSCs must be handled with extreme caution.

Specific chemotaxis of magnetically labeled mesenchymal stem cells: implications for MRI of glioma

PURPOSE

Glioblastoma multiforme (GBM) is a lethal disease marked by infiltration of cancerous cells into the surrounding normal brain. The dire outcome of GBM patients stems in part from the limitations of current neuroimaging methods. Notably, early cancer detection methodologies are lacking, without the ability to identify aggressive, metastatic tumor cells. We propose a novel approach for tumor detection using magnetic resonance imaging (MRI) based on imaging specific tumor tropism of mesenchymal stem cells (MSCs) labeled with micron-sized iron oxide particles (MPIOs).

PROCEDURES

MPIO labeled and unlabeled MSCs were compared for viability, multi-lineage differentiation, and migration, where both chemotactic and chemokinetic movement were assessed in the presence of serum-free medium, serum-containing medium, and glioma-conditioned medium. MRI was performed on agarose samples, consisting of MPIO-labeled single MSCs, to confirm the capability to detect single cells.

RESULTS

We determined that MPIO-labeled MSCs exhibit specific and significant chemotactic migration towards glioma-conditioned medium in vitro. Confocal fluorescence microscopy confirmed that MPIOs are internalized and do not impact important cell processes of MSCs. Lastly, MPIO-labeled MSCs appear as single distinct, dark spots on T(2)*-weighted MRI, supporting the robustness of this contrast agent for cell tracking.

CONCLUSIONS

This is the first study to show that MPIO-labeled MSCs exhibit specific tropism toward tumor-secreted factors in vitro. The potential for detecting single MPIO-labeled MSCs provides rationale for in vivo extension of this methodology to visualize GBM in animal models.

Molecular imaging: the key to advancing cardiac stem cell therapy

Cardiac stem cell therapy continues to hold promise for the treatment of ischemic heart disease despite the fact that early promising pre-clinical findings have yet to be translated into consistent clinical success. The latest human studies have collectively identified a pressing need to better understand stem cell behavior in humans and called for more incorporation of noninvasive imaging techniques into the design and evaluation of human stem cell therapy trials. This review discusses the various molecular imaging techniques validated to date for studying stem cells in living subjects, with a particular emphasis on their utilities in assessing the acute retention and the long-term survival of transplanted stem cells. These imaging techniques will be essential for advancing cardiac stem cell therapy by providing the means to both guide ongoing optimization and predict treatment response in humans.

Intramyocardial transplantation and tracking of human mesenchymal stem cells in a novel intra-uterine pre-immune fetal sheep myocardial infarction model: a proof of concept study

Although stem-cell therapies have been suggested for cardiac-regeneration after myocardial-infarction (MI), key-questions regarding the in-vivo cell-fate remain unknown. While most available animal-models require immunosuppressive-therapy when applying human cells, the fetal-sheep being pre-immune until day 75 of gestation has been proposed for the in-vivo tracking of human cells after intra-peritoneal transplantation. We introduce a novel intra-uterine myocardial-infarction model to track human mesenchymal stem cells after direct intra-myocardial transplantation into the pre-immune fetal-sheep. Thirteen fetal-sheep (gestation age: 70–75 days) were included. Ten animals either received an intra-uterine induction of MI only (n = 4) or MI+intra-myocardial injection (IMI;n = 6) using micron-sized, iron-oxide (MPIO) labeled human mesenchymal stem cells either derived from the adipose-tissue (ATMSCs;n = 3) or the bone-marrow (BMMSCs;n = 3). Three animals received an intra-peritoneal injection (IPI;n = 3; ATMSCs;n = 2/BMMSCs;n = 1). All procedures were performed successfully and follow-up was 7–9 days. To assess human cell-fate, multimodal cell-tracking was performed via MRI and/or Micro-CT, Flow-Cytometry, PCR and immunohistochemistry. After IMI, MRI displayed an estimated amount of 1×10⁵–5×10⁵ human cells within ventricular-wall corresponding to the injection-sites which was further confirmed on Micro-CT. PCR and IHC verified intra-myocardial presence via detection of human-specific β-2-microglobulin, MHC-1, ALU-Sequence and anti-FITC targeting the fluorochrome-labeled part of the MPIOs. The cells appeared viable, integrated and were found in clusters or in the interstitial-spaces. Flow-Cytometry confirmed intra-myocardial presence, and showed further distribution within the spleen, lungs, kidneys and brain. Following IPI, MRI indicated the cells within the intra-peritoneal-cavity involving the liver and kidneys. Flow-Cytometry detected the cells within spleen, lungs, kidneys, thymus, bone-marrow and intra-peritoneal lavage, but not within the heart. For the first time we demonstrate the feasibility of intra-uterine, intra-myocardial stem-cell transplantation into the pre-immune fetal-sheep after MI. Utilizing cell-tracking strategies comprising advanced imaging-technologies and in-vitro tracking-tools, this novel model may serve as a unique platform to assess human cell-fate after intra-myocardial transplantation without the necessity of immunosuppressive-therapy.

Choice of cell-delivery route for successful cell transplantation therapy for the heart

The cell-delivery route is one of the major factors influencing the therapeutic effect and complications of cell transplantation therapy for cardiac diseases. There are four major clinically practical routes, with each method having its own advantages and disadvantages. First, intramyocardial injection allows targeted cell delivery into the areas of interest, although this induces mechanical injury, inflammation and islet-like donor cell clusters, leading to limited donor cell survival and arrhythmogenicity. Second, intracoronary injection is less likely to induce inflammation, whereas poor initial cell retention in the heart is a concern. Third, intravenous injection is easy and economical, but cell recruitment into the heart is not frequent. Finally, epicardial placement of 'cell sheets' enables higher efficiency of cell engraftment, but poor integration into the myocardium may be an issue. This review summarizes up-to-date clinical and preclinical knowledge regarding these cell-delivery methods. We further discuss the ways to refine these methods towards optimizing cell transplantation therapy for the heart.

Photostable fluorescent organic dots with aggregation-induced emission (AIE dots) for noninvasive long-term cell tracing

Long-term noninvasive cell tracing by fluorescent probes is of great importance to life science and biomedical engineering. For example, understanding genesis, development, invasion and metastasis of cancerous cells and monitoring tissue regeneration after stem cell transplantation require continual tracing of the biological processes by cytocompatible fluorescent probes over a long period of time. In this work, we successfully developed organic far-red/near-infrared dots with aggregation-induced emission (AIE dots) and demonstrated their utilities as long-term cell trackers. The high emission efficiency, large absorptivity, excellent biocompatibility, and strong photobleaching resistance of the AIE dots functionalized by cell penetrating peptides derived from transactivator of transcription proteins ensured outstanding long-term noninvasive in vitro and in vivo cell tracing. The organic AIE dots outperform their counterparts of inorganic quantum dots, opening a new avenue in the development of fluorescent probes for following biological processes such as carcinogenesis.

Intranasal Delivery of Neural Stem Cells: A CNS-specific, Non-invasive Cell-based Therapy for Experimental Autoimmune Encephalomyelitis

The therapeutic potential of adult neural stem cells (aNSCs) has been shown in EAE, an animal model of MS, administered by either i.c.v. or i.v. injection. However, i.c.v. is an invasive approach, while the i.v. route of aNSCs is associated with a non-specific immune suppression in the periphery. Here we demonstrate that intranasal (i.n.) delivery of fluorescently labeled aNSCs resulted in their appearance in the olfactory bulb, cortex, hippocampus, striatum, brainstem, and spinal cord. These cells induce functional recovery from ongoing EAE similar to that achieved with i.v. injected aNSCs, with comparable anti-inflammatory and remeylination effects in CNS inflammatory foci. Importantly, unlike the peripheral immune suppression brought about by i.v. NSCs, intranasal delivery did not influence peripheral immune responses. We conclude that aNSCs can be reliably delivered to the CNS via the nasal route to induce functional recovery and confer immunomodulation and remyelination in EAE. Intranasal administration of NSCs provides a highly promising, noninvasive and CNS-specific alternative to current cell-based approaches in treating EAE.

Decidua mesenchymal stem cells migrated toward mammary tumors in vitro and in vivo affecting tumor growth and tumor development

Mesenchymal stem cells (MSCs) have affinity to tumor sites where they home, affecting their biology and growth. Previously, we have isolated mesenchymal cells from the decidua of the human placenta named as decidua-derived MSCs (DMSCs). The aims of the present study were to investigate the migration capacity of DMSCs in vitro, and in vivo in a preclinical model of mammary tumors induced by N-nitroso-N-methylurea (NMU). Additionally, we assessed the safety of DMSC administration in vivo and their effect on tumor growth. In vitro studies showed that DMSCs significantly migrate toward both, healthy human breast tissue and breast adenocarcinoma. Nevertheless, the effect on DMSC migration was significantly higher in the presence of tumor tissue. DMSCs also significantly migrated in vitro in the presence of NMU-mammary tumor homogenate when compared with control media alone. In vivo studies showed both migration and engraftment of DMSCs into NMU-induced tumors. Interestingly, DMSCs showed an inhibitory effect on the growth of primary tumors and in the development of new tumors. DMSCs did not affect the growth of secondary tumors, although secondary tumors appeared 2 weeks later, and the number of secondary tumors was lower in the DMSC-treated rats as compared with vehicle-treated rats. To our knowledge, this is the first report showing placental MSCs effect on tumor growth. In conclusion, DMSCs could serve as a therapeutic agent themselves and as a cellular vehicle of anticancer drugs.

The application of super paramagnetic iron oxide-labeled mesenchymal stem cells in cell-based therapy

Mesenchymal stem cell (MSC)-based therapy has great potential for tissue regeneration. However, being able to monitor the in vivo behavior of implanted MSCs and understand the fate of these cells is necessary for further development of successful therapies and requires an effective, non-invasive and non-toxic technique for cell tracking. Super paramagnetic iron oxide (SPIO) is an idea label and tracer of MSCs. MRI can be used to follow SPIO-labeled MSCs and has been proposed as a gold standard for monitoring the in vivo biodistribution and migration of implanted SPIO-labeled MSCs. This review discusses the biological effects of SPIO labeling on MSCs and the therapeutic applications of local or systemic delivery of these labeled cells.

Nanotechnology and stem cell therapy for cardiovascular diseases: potential applications

The use of stem cell therapy for the treatment of cardiovascular diseases has generated significant interest in recent years. Limitations to the clinical application of this therapy center on issues of stem cell delivery, engraftment, and fate. Nanotechnology-based cell labeling and imaging techniques facilitate stem cell tracking and engraftment studies. Nanotechnology also brings exciting new opportunities to translational stem cell research as it enables the controlled engineering of nanoparticles and nanomaterials that can properly relate to the physical scale of cell-cell and cell-niche interactions. This review summarizes the most relevant potential applications of nanoscale technologies to the field of stem cell therapy for the treatment of cardiovascular diseases.

Fate of intravenously injected mesenchymal stem cells and significance for clinical application

Mesenchymal stromal cells (MSCs) have initially been characterized as a fibroblastlike cell population that can be expanded readily in vitro, and is able to support hematopoiesis in vitro and in vivo. By serendipity it was discovered that MSCs can also be administered into the bloodstream. This mode of application formed a major breakthrough in the clinical use of MSCs, because MSC transplantation was found to cure severe immune hyperactivation states such as graft-versus-host disease after allogeneic bone marrow transplantation, or bacterial sepsis. However, MSCs were found difficult to trace and consensus to date is lacking in the scientific community as to where transplanted MSCs end up in the body and which major principles are responsible for the therapeutic effects of MSCs. This chapter gives an overview of the current knowledge on interactions of freshly transplanted MSCs with the cells in the blood stream and the vessel wall, with major organs such as lung, liver, gut, and spleen, and discusses the limitations of the methodologies used to trace transplanted MSCs. The findings will be put into perspective on how therapeutically applied, culture-expanded MSCs may exert beneficial effects.

Direct in vitro comparison of six three-dimensional positive contrast methods for susceptibility marker imaging

PURPOSE

To compare different techniques for positive contrast imaging of susceptibility markers with MRI for three-dimensional visualization. As several different techniques have been reported, the choice of the suitable method depends on its properties with regard to the amount of positive contrast and the desired background suppression, as well as other imaging constraints needed for a specific application.

MATERIALS AND METHODS

Six different positive contrast techniques are investigated for their ability to image at 3 Tesla a single susceptibility marker in vitro. The white marker method (WM), susceptibility gradient mapping (SGM), inversion recovery with on-resonant water suppression (IRON), frequency selective excitation (FSX), fast low flip-angle positive contrast SSFP (FLAPS), and iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) were implemented and investigated.

RESULTS

The different methods were compared with respect to the volume of positive contrast, the product of volume and signal intensity, imaging time, and the level of background suppression. Quantitative results are provided, and strengths and weaknesses of the different approaches are discussed.

CONCLUSION

The appropriate choice of positive contrast imaging technique depends on the desired level of background suppression, acquisition speed, and robustness against artifacts, for which in vitro comparative data are now available.

Stem cell therapy in ischemic stroke: role of IV and intra-arterial therapy

OBJECTIVE

Cell-based therapies are being investigated as an adjunct to IV thrombolysis or mechanical thrombectomy in ischemic stroke. This review summarizes the potential applications as well as challenges of intravascular cell delivery in ischemic stroke.

METHOD

We conducted a search of Medline as well as the clinicaltrials.gov Web site for all ongoing human clinical studies using stem cells in ischemic stroke patients.

RESULT

The pros and cons of the various donor cell types and routes of cell delivery, including intravascular delivery, in ischemic stroke are discussed. In addition, the potential challenges in translation from bench to bedside, the optimal techniques for intravascular cell delivery, and an updated comprehensive list of ongoing clinical trials in ischemic stroke are highlighted.

CONCLUSIONS

Stem cells have shown a promising role in ischemic stroke, in preclinical studies as well as initial pilot studies. Further studies are needed to assess intravascular cell therapy as a potential adjunct to thrombolysis or mechanical thrombectomy in ischemic stroke.

Tracking of In-111-labeled human umbilical tissue-derived cells (hUTC) in a rat model of cerebral ischemia using SPECT imaging

BACKGROUND

In order to increase understanding of how infused cells work, it becomes important to track their initial movement, localization, and engraftment efficiency following transplantation. However, the available in vivo cell tracking techniques are suboptimal. The study objective was to determine the biodistribution of intravenously administered Indium-111 (In-111) oxine labeled human umbilical tissue-derived cells (hUTC) in a rat model of transient middle cerebral occlusion (tMCAo) using single photon emission computed tomography (SPECT).

METHODS

Rats received 3 million In-111 labeled hUTC (i.v.) 48 hrs after tMCAo. Following the administration of either hUTC or equivalent dose of In-111-oxine (18.5 MBq), animals underwent SPECT imaging on days 0, 1, and 3. Radioactivity in various organs as well as in the stroke area and contralateral hemisphere was determined, decay corrected and normalized to the total (whole body including head) radioactivity on day 0. Immunohistochemical analysis was also performed to confirm the beneficial effects of hUTC on vascular and synaptic density, and apoptosis.

RESULTS

Most of the radioactivity (43.36±23.07% on day 0) trafficked to the lungs immediately following IV administration of In-111 labeled hUTC (day 0) and decreased drastically to 8.81±7.75 and 4.01±4.52% on days 1 and 3 post-injection, respectively. In contrast, radioactivity measured in the lung of animals that received In-111-oxine alone remained relatively unchanged from day 0 to day 1 (18.38±5.45% at day 0 to 12.59±5.94%) and decreased to 8.34±4.25% on day 3. Significantly higher radioactivity was observed in stroke areas of animals that received In-111 labeled hUTC indicating the presence of cells at the site of injury representing approximately 1% of total administered dose. In addition, there was significant increase in vascular and synaptophysin immunoreactivity in stroke areas of rats that received In-111 labeled hUTC.

CONCLUSIONS

The present studies showed the tracking of In-111 labeled hUTC to the sites of stroke in a rat model of tMCAo using SPECT. Animals treated with In-111 labeled hUTC showed histological improvements, with higher vascular and synaptic densities observed in the ischemic boundary zone (IBZ).

Different routes of administration of human umbilical tissue-derived cells improve functional recovery in the rat after focal cerebral ischemia

Human umbilical tissue-derived cells (hUTC) are a potential neurorestorative candidate for stroke treatment. Here, we test the effects of hUTC treatment in a rat model of stroke via various routes of administration. Rats were treated with hUTC or phosphate-buffered saline (PBS) via different routes including intraarterial (IA), intravenous (IV), intra-cisterna magna (ICM), lumber intrathecal (IT), or intracerebral injection (IC) at 24h after stroke onset. Treatment with hUTC via IV and IC route led to significant functional improvements starting at day 14, which persisted to day 60 compared with respective PBS-treated rats. HUTC administered via IA, ICM, and IT significantly improved neurological functional recovery starting at day 14 and persisted up to day 49 compared with PBS-treated rats. Although IA administration resulted in the highest donor cell number detected within the ischemic brain compared to the other routes, hUTC treatments significantly increased ipsilateral bromodeoxyuridine incorporating subventricular zone (SVZ) cells and vascular density in the ischemic boundary compared with PBS-treated rats regardless of the route of administration. While rats received hUTC treatment via IA, IV, IC, and ICM routes showed greater synaptophysin immunoreactivity, significant reductions in TUNEL-positive cells in the ipsilateral hemisphere were observed in IA, IV, and IC routes compared with PBS-treated rats. hUTC treatments did not reduce infarct volume when compared to the PBS groups. Our data indicate that hUTC administered via multiple routes provide therapeutic benefit after stroke. The enhancement of neurorestorative events in the host brain may contribute to the therapeutic benefits of hUTC in the treatment of stroke.

Mesenchymal stem cells are short-lived and do not migrate beyond the lungs after intravenous infusion

Mesenchymal stem cells (MSC) are under investigation as a therapy for a variety of disorders. Although animal models show long term regenerative and immunomodulatory effects of MSC, the fate of MSC after infusion remains to be elucidated. In the present study the localization and viability of MSC was examined by isolation and re-culture of intravenously infused MSC. C57BL/6 MSC (500,000) constitutively expressing DsRed-fluorescent protein and radioactively labeled with Cr-51 were infused via the tail vein in wild-type C57BL/6 mice. After 5 min, 1, 24, or 72 h, mice were sacrificed and blood, lungs, liver, spleen, kidneys, and bone marrow removed. One hour after MSC infusion the majority of Cr-51 was found in the lungs, whereas after 24 h Cr-51 was mainly found in the liver. Tissue cultures demonstrated that viable donor MSC were present in the lungs up to 24 h after infusion, after which they disappeared. No viable MSC were found in the other organs examined at any time. The induction of ischemia-reperfusion injury in the liver did not trigger the migration of viable MSC to the liver. These results demonstrate that MSC are short-lived after i.v. infusion and that viable MSC do not pass the lungs. Cell debris may be transported to the liver. Long term immunomodulatory and regenerative effects of infused MSC must therefore be mediated via other cell types.

Cell tracking and the development of cell-based therapies: a view from the Cardiovascular Cell Therapy Research Network

Cell-based therapies are being developed for myocardial infarction (MI) and its consequences (e.g., heart failure) as well as refractory angina and critical limb ischemia. The promising results obtained in preclinical studies led to the translation of this strategy to clinical studies. To date, the initial results have been mixed: some studies showed benefit, whereas in others, no benefit was observed. There is a growing consensus among the scientific community that a better understanding of the fate of transplanted cells (e.g., cell homing and viability over time) will be critical for the long-term success of these strategies and that future studies should include an assessment of cell homing, engraftment, and fate as an integral part of the trial design. In this review, different imaging methods and technologies are discussed within the framework of the physiological answers that the imaging strategies can provide, with a special focus on the inherent regulatory issues.

A novel suture-based method for efficient transplantation of stem cells

Advances in regenerative medicine have improved the potential of using cellular therapy for treating several diseases. However, the effectiveness of new cellular therapies is largely limited by low cell engraftment and inadequate localization. To improve on these limitations, we developed a novel delivery mechanism using cell-seeded biological sutures. We demonstrate the ability of cell-seeded biological sutures to efficiently implant human mesenchymal stem cells (hMSCs) to specific regions within the beating heart; a tissue known to have low cell retention and engraftment shortly after delivery. Cell-seeded biological sutures were developed by bundling discrete microthreads extruded from extracellular matrix proteins, attaching a surgical needle to the bundle and seeding the bundle with hMSCs. During cell preparation, hMSCs were loaded with quantum dot nanoparticles for cell tracking within the myocardium. Each biological suture contained an average of 5903 ± 1966 hMSCs/cm suture length. Delivery efficiency was evaluated by comparing cell-seeded biological suture implantation with intramyocardial (IM) cell injections (10,000 hMSCs in 35 μL) into the left ventricle of normal, noninfarcted rat hearts after 1 h. Delivery efficiency of hMSCs by biological sutures (63.6 ± 10.6%) was significantly higher than IM injection (11.8 ± 6.2%; p < 0.05). Cell-tracking analysis indicated suture-delivered hMSCs were found throughout the thickness of the ventricular myocardium: along the entire length of the biological suture track, localizing closely with native myocardium. These results suggest cell-seeded biological sutures can deliver cells to the heart more efficiently than conventional methods, demonstrating an effective delivery method for implanting cells in soft tissue.

Use of MR cell tracking to evaluate targeting of glial precursor cells to inflammatory tissue by exploiting the very late antigen-4 docking receptor

PURPOSE

To determine if glial precursor cells can be targeted to inflamed brain through overexpression of very late antigen-4 (VLA-4) and whether this docking process can be monitored with magnetic resonance (MR) cell tracking after intraarterial injection.

MATERIALS AND METHODS

All experimental procedures were performed between August 2010 and February 2012 and were approved by the institutional animal care and use committee. Human glial precursor cells (hGPs) were transfected with VLA-4 and labeled with superparamagnetic iron oxide that contained rhodamine. A microfluidic adhesion assay was used for assessing VLA-4 receptor-mediated cell docking in vitro. A rat model of global lipopolysaccharide (LPS)-mediated brain inflammation was used to induce global vascular cell adhesion molecule-1 (VCAM-1) expression. hGPs were infused into the carotid artery in four animal cohorts (consisting of three rats each): rats that received VLA-4-naive hGPs but did not receive LPS, rats that received VLA-4-expressing hGPs but not LPS, rats that received VLA-4-naive hGPs and LPS, and rats that received VLA-4-expressing hGPs and LPS. MR imaging was performed at 9.4 T before and 1, 10, 20, and 30 minutes after injection. Brain tissue was processed for histologic examination. Quantification of low-signal-intensity pixels was performed with pixel-by-pixel analysis for MR images obtained before and after cell injection.

RESULTS

With use of the microfluidic adhesion assay, cell binding to activated brain endothelium significantly increased compared with VLA-4-naive control cells (71.5 cells per field of view±11.7 vs 36.4 cells per field of view±3.3, respectively; P<.05). Real-time quantitative in vivo MR cell tracking revealed that VLA-4-expressing cells docked exclusively within the vascular bed of the ipsilateral carotid artery and that VLA-4-expressing cells exhibited significantly enhanced homing as compared with VLA-4-naive cells (1448 significant pixels±366.5 vs 113.3 significant pixels±19.88, respectively; P<.05). Furthermore, MR cell tracking was crucial for correct cell delivery and proper ligation of specific arteries.

CONCLUSION

Targeted intraarterial delivery and homing of VLA-4-expressing hGPs to inflamed endothelium is feasible and can be monitored in real time by using MR imaging in a quantitative, dynamic manner.

A novel strategy to enhance mesenchymal stem cell migration capacity and promote tissue repair in an injury specific fashion

Mesenchymal stem cells (MSCs) of bone marrow origin appear to be an attractive candidate for cell-based therapies. However, the major barrier to the effective implementation of MSC-based therapies is the lack of specific homing of exogenously infused cells and overall the inability to drive them to the diseased or damaged tissue. In order to circumvent these limitations, we developed a preconditioning strategy to optimize MSC migration efficiency and potentiate their beneficial effect at the site of injury. Initially, we screened different molecules by using an in vitro injury-migration setting, and subsequently, we evaluated the effectiveness of the different strategies in mice with acute kidney injury (AKI). Our results showed that preconditioning of MSCs with IGF-1 before infusion improved cell migration capacity and restored normal renal function after AKI. The present study demonstrates that promoting migration of MSCs could increase their therapeutic potential and indicates a new therapeutic paradigm for organ repair.

Mesenchymal Stem Cells Home to Sites of Injury and Inflammation

BACKGROUND

Mesenchymal stem cells (MSCs) have shown significant therapeutic potential in preclinical animal models of wound healing. However, the translation of MSC-based therapeutics to clinical practice has been delayed by questions including the mechanisms of MSC homing, engraftment, and ultimate function.

THE PROBLEM

Experimental models of MSC-based wound therapies often involve intravenous injection of cells followed by sacrifice of animals at various time points and detection of MSCs in wounds by histological methods. However, this methodology is limited by its sampling of only specific tissue at a single time point and provides no information about how exogenously transplanted MSCs home to the wound environment.

BASIC/CLINICAL SCIENCE ADVANCES

Most systemically injected MSCs initially become entrapped within the lungs before migrating out to the liver and spleen in the normal state. When an injury is present, after the initial lung entrapment, MSCs migrate in response to inflammatory mediators and home to sites of wounding.

CLINICAL CARE RELEVANCE

As MSC-based wound therapies continue to advance toward clinical trials, the availability of noninvasive methods to track cells after injection into patients affords the opportunity to monitor stem cell behavior post-transplantation.

CONCLUSION

MSCs have demonstrated great promise as an emerging therapeutic for wound management. However, further preclinical studies will be needed to elucidate the reparative mechanisms of these cells and to determine how to optimize their regenerative potential.

Stem cells as a tool for breast imaging

Stem cells are a scientific field of interest due to their therapeutic potential. There are different groups, depending on the differentiation state. We can find lonely stem cells, but generally they distribute in niches. Stem cells don't survive forever. They are affected for senescence. Cancer stem cells are best defined functionally, as a subpopulation of tumor cells that can enrich for tumorigenic property and can regenerate heterogeneity of the original tumor. Circulating tumor cells are cells that have detached from a primary tumor and circulate in the bloodstream. They may constitute seeds for subsequent growth of additional tumors (metastasis) in different tissues. Advances in molecular imaging have allowed a deeper understanding of the in vivo behavior of stem cells and have proven to be indispensable in preclinical and clinical studies. One of the first imaging modalities for monitoring pluripotent stem cells in vivo, magnetic resonance imaging (MRI) offers high spatial and temporal resolution to obtain detailed morphological and functional information. Advantages of radioscintigraphic techniques include their picomolar sensitivity, good tissue penetration, and translation to clinical applications. Radionuclide imaging is the sole direct labeling technique used thus far in human studies, involving both autologous bone marrow derived and peripheral stem cells.

The role of chemokines in mesenchymal stem cell homing to myocardium

A growing body of preclinical evidence suggests that mesenchymal stem cells (MSCs) are effective for the structural and functional recovery of the infracted heart. Accordingly, clinical trials are underway to determine the benefit of MSC-based therapies. While systemic administration of MSCs is an attractive strategy, and is the route currently used for the administration of MSCs in clinical studies for myocardial infarction, the majority of infused cells do not appear to localize to infracted myocardium in animal studies. Recently, important progress has been made in identifying chemokine receptors critical for the migration and homing of MSCs. Here, we review recent literature regarding mechanisms of MSC homing and recruitment to the ischemic myocardium, and discuss potential influences of low engraftment rates of systemically administered MSCs to the infracted heart tissue on the effects of MSC-based therapies on myocardial infarction.