Transcatheter injection-induced changes in human bone marrow-derived mesenchymal stem cells

Optimal Intravenous Administration Procedure for Efficient Delivery of Canine Adipose-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) are currently being investigated for their therapeutic applications in a wide range of diseases. Although many studies examined peripheral venous administration of MSC, few have investigated the detailed intravenous administration procedures of MSC from their preparation until they enter the body. The current study therefore aimed to explore the most efficient infusion procedure for MSC delivery by preparing and infusing them under various conditions. Canine adipose-derived mesenchymal stem cells (cADSC) were infused using different infusion apparatuses, suspension solutions, allogenic serum supplementation, infusion time and rates, and cell densities, respectively. Live and dead cell counts were then assessed by manual measurements and flow cytometry. Efficiency of live- and dead-cell infusion and cell viability were calculated from the measured cell counts and compared under each condition. Efficiency of live-cell infusion differed significantly according to the infusion apparatus, infusion rate, and combination of cell density and serum supplementation. Cell viability after infusion differed significantly between the infusion apparatuses. The optimal infusion procedure resulting in the highest cell delivery and viability involved suspending cADSC in normal saline supplemented with 5% allogenic serum at a density of 5 × 10⁵ cells/mL, and infusing them using an automatic infusion device for 15 min. This procedure is therefore recommended as the standard procedure for the intravenous administration of ADSC in terms of cell-delivery efficiency.

Modifying strategies for SDF-1/CXCR4 interaction during mesenchymal stem cell transplantation

Mesenchymal stem cell (MSC) transplantation is regarded as a promising candidate for the treatment of ischaemic heart disease. The major hurdles for successful clinical translation of MSC therapy are poor survival, retention, and engraftment in the infarcted heart. Stromal cell-derived factor-1/chemokine receptor 4 (SDF-1/CXCR4) constitutes one of the most efficient chemokine/chemokine receptor pairs regarding cell homing. In this review, we mainly focused on previous studies on how to regulate the SDF-1/CXCR4 interaction through various priming strategies to maximize the efficacy of mesenchymal stem cell transplantation on ischaemic hearts or to facilitate the required effects. The strengthened measures for enhancing the therapeutic efficacy of the SDF-1/CXCR4 interaction for mesenchymal stem cell transplantation included the combination of chemokines and cytokines, hormones and drugs, biomaterials, gene engineering, and hypoxia. The priming strategies on recipients for stem cell transplantation included ischaemic conditioning and device techniques.

Intravascular Application of Labelled Cell Spheroids: An Approach for Ischemic Peripheral Artery Disease

Mesenchymal stem cells (MSC) are known for their vascular regeneration capacity by neoangiogenesis. Even though, several delivery approaches exist, particularly in the case of intravascular delivery, only limited number of cells reach the targeted tissue and are not able to remain on site. Applicated cells exhibit poor survival accompanied with a loss of functionality. Moreover, cell application techniques lead to cell death and impede the overall MSC function and survival. 3D cell spheroids mimic the physiological microenvironment, thus, overcoming these limitations. Therefore, in this study we aimed to evaluate and assess the feasibility of 3D MSCs spheroids for endovascular application, for treatment of ischemic peripheral vascular pathologies. Multicellular 3D MSC spheroids were generated at different cell seeding densities, labelled with ultra-small particles of iron oxide (USPIO) and investigated in vitro in terms of morphology, size distribution, mechanical stability as well as ex vivo with magnetic resonance imaging (MRI) to assess their trackability and distribution. Generated 3D spheroids were stable, viable, maintained stem cell phenotype and were easily trackable and visualized via MRI. MSC 3D spheroids are suitable candidates for endovascular delivery approaches in the context of ischemic peripheral vascular pathologies.

Novel Techniques to Improve Precise Cell Injection

We noted recently that the injection of cells with a needle through a cystoscope in the urethral sphincter muscle of pigs failed to deposit them nearby or at the intended target position in about 50% of all animals investigated (n > 100). Increasing the chance for precise cell injection by shotgun approaches employing several circumferential injections into the sphincter muscle bears the risk of tissue injury. In this study, we developed and tested a novel needle-free technique to precisely inject cells in the urethral sphincter tissue, or other tissues, using a water-jet system. This system was designed to fit in the working channels of endoscopes and cystoscopes, allowing a wide range of minimally invasive applications. We analyze key features, including the physical parameters of the injector design, pressure ranges applicable for tissue penetration and cell injections and biochemical parameters, such as different compositions of injection media. Our results present settings that enable the high viability of cells post-injection. Lastly, the method is suitable to inject cells in the superficial tissue layer and in deeper layers, required when the submucosa or the sphincter muscle of the urethra is targeted.

Shear-Resistant, Biological Tethering of Nanostimulators for Enhanced Therapeutic Cell Paracrine Factor Secretion

Mesenchymal stromal cells (MSCs) secreting multiple growth factors and immunomodulatory cytokines are promising for regenerative medicine. To further enhance their secretory activity, efforts have emerged to tether nanosized carriers of secretory stimuli, named nanostimulators, to the MSC surface by forming nonchemical bonds. Despite some successes, there is a great need to improve the retention of nanostimulators during transport through a syringe needle, where high shear stress exerted on the cell surface separates them. To this end, we hypothesize that poly(lactic-co-glycolic acid)-block-hyaluronic acid (PLGA-HA) conjugated with integrin-binding RGD peptides, denoted PLGA-HA-RGD, can form nanostimulators that remain on the cell surface stably during the injection. The resulting HA-CD44 and RGD-integrin bonds would synergistically increase the adhesion strength of nanostimulators. Interestingly, nanostimulators prepared with PLGA-HA-RGD show 3- to 6-fold higher retention than those made with PLGA-HA. Therefore, the PLGA-HA-RGD nanostimulators induced MSCs to secrete 1.5-fold higher vascular endothelial growth factors and a 1.2-fold higher tissue inhibitor of matrix metalloproteinase-1 as compared to PLGA-HA nanostimulators. Consequently, MSCs tethered with PLGA-HA-RGD nanostimulators served to stimulate endothelial cell activities to form a blood vessel-like endothelial lumen with increased length and number of junctions. The nanostimulator design strategy would also be broadly applicable to regulate, protect, and home a broad array of therapeutic or immune cells by tethering carriers with bioactive molecules of interest.

Injection of Porcine Adipose Tissue-Derived Stromal Cells by a Novel Waterjet Technology

Previously, we developed a novel, needle-free waterjet (WJ) technology capable of injecting viable cells by visual guided cystoscopy in the urethral sphincter. In the present study, we aimed to investigate the effect of WJ technology on cell viability, surface markers, differentiation and attachment capabilities, and biomechanical features. Porcine adipose tissue-derived stromal cells (pADSCs) were isolated, expanded, and injected by WJ technology. Cell attachment assays were employed to investigate cell-matrix interactions. Cell surface molecules were analyzed by flow cytometry. Cells injected by Williams Needle (WN), normal cannula, or not injected cells served as controls. Biomechanical properties were assessed by atomic force microscopy (AFM). pADSCs injected by the WJ were viable (85.9%), proliferated well, and maintained their in vitro adipogenic and osteogenic differentiation capacities. The attachment of pADSCs was not affected by WJ injection and no major changes were noted for cell surface markers. AFM measurements yielded a significant reduction of cellular stiffness after WJ injections (p < 0.001). WJ cell delivery satisfies several key considerations required in a clinical context, including the fast, simple, and reproducible delivery of viable cells. However, the optimization of the WJ device may be necessary to further reduce the effects on the biomechanical properties of cells.

Ex vivo biomechanical characterization of syringe-needle ejections for intracerebral cell delivery

Intracerebral implantation of cell suspensions is finding its clinical translation with encouraging results in patients with stroke. However, the survival of cells in the brain remains poor. Although the biological potential of neural stem cells (NSCs) is widely documented, the biomechanical effects of delivering cells through a syringe-needle remain poorly understood. We here detailed the biomechanical forces (pressure, shear stress) that cells are exposed to during ejection through different sized needles (20G, 26G, 32G) and syringes (10, 50, 250 µL) at relevant flow rates (1, 5, 10 µL/min). A comparison of 3 vehicles, Phosphate Buffered Saline (PBS), Hypothermosol (HTS), and Pluronic, indicated that less viscous vehicles are favorable for suspension with a high cell volume fraction to minimize sedimentation. Higher suspension viscosity was associated with greater shear stress. Higher flow rates with viscous vehicle, such as HTS reduced viability by ~10% and also produced more apoptotic cells (28%). At 5 µL/min ejection using a 26G needle increased neuronal differentiation for PBS and HTS suspensions. These results reveal the biological impact of biomechanical forces in the cell delivery process. Appropriate engineering strategies can be considered to mitigate these effects to ensure the efficacious translation of this promising therapy.

Translational considerations in injectable cell-based therapeutics for neurological applications: concepts, progress and challenges

Significant progress has been made during the past decade towards the clinical adoption of cell-based therapeutics. However, existing cell-delivery approaches have shown limited success, with numerous studies showing fewer than 5% of injected cells persisting at the site of injection within days of transplantation. Although consideration is being increasingly given to clinical trial design, little emphasis has been given to tools and protocols used to administer cells. The different behaviours of various cell types, dosing accuracy, precise delivery, and cell retention and viability post-injection are some of the obstacles facing clinical translation. For efficient injectable cell transplantation, accurate characterisation of cellular health post-injection and the development of standardised administration protocols are required. This review provides an overview of the challenges facing effective delivery of cell therapies, examines key studies that have been carried out to investigate injectable cell delivery, and outlines opportunities for translating these findings into more effective cell-therapy interventions.

Stem Cell Delivery With Polymer Hydrogel for Treatment of Intervertebral Disc Degeneration: From 3D Culture to Design of the Delivery Device for Minimally Invasive Therapy

Nucleus pulposus (NP) tissue damage can induce detrimental mechanical strain on the biomechanical performance of intervertebral discs (IVDs), causing subsequent disc degeneration. A novel, photocurable, injectable, synthetic polymer hydrogel (pHEMA-co-APMA grafted with PAA) has already demonstrated success in encapsulating and differentiating human mesenchymal stem cells (hMSCs) toward an NP phenotype during hypoxic conditions. After demonstration of promising results in our previous work, in this study we have further investigated the inclusion of mechanical stimulation and its impact on hMSC differentiation toward an NP phenotype through the characterization of matrix markers such as SOX-9, aggrecan, and collagen II. Furthermore, investigations were undertaken in order to approximate delivery parameters for an injection delivery device, which could be used to transport hMSCs suspended in hydrogel into the IVD. hMSC-laden hydrogel solutions were injected through various needle gauge sizes in order to determine its impact on postinjection cell viability and IVD tissue penetration. Interpretation of these data informed the design of a potential minimally invasive injection device, which could successfully inject hMSCs encapsulated in a UV-curable polymer into NP, prior to photo-cross-linking in situ.

A Detailed Assessment of Varying Ejection Rate on Delivery Efficiency of Mesenchymal Stem Cells Using Narrow-Bore Needles

As the number of clinical trials exploring cell therapy rises, a thorough understanding of the limits of cell delivery is essential. We used an extensive toolset comprising various standard and multiplex assays for the assessment of cell delivery postejection. Primary human mesenchymal stem cell (hMSC) suspensions were drawn up into 100-µl Hamilton syringes with 30- and 34-gauge needles attached, before being ejected at rates ranging from 10 to 300 µl/minute. Effects of ejection rate, including changes in viability, apoptosis, senescence, and other key aspects of cellular health, were evaluated. Ejections at slower flow rates resulted in a lower percentage of the cell dose being delivered, and apoptosis measurements of samples ejected at 10 µl/minute were significantly higher than control samples. Immunophenotyping also revealed significant downregulation of CD105 expression in samples ejected at 10 µl/minute (p < .05). Differentiation of ejected hMSCs was investigated using qualitative markers of adipogenesis, osteogenesis, and chondrogenesis, which revealed that slower ejection rates exerted a considerable effect upon the differentiation capacity of ejected cells, thereby possibly influencing the success of cell-based therapies. The findings of this study demonstrate that ejection rate has substantial impact on the percentage of cell dose delivered and cellular health postejection.

Accelerated adipogenic differentiation of hMSCs in a microfluidic shear stimulation platform

The use of transplanted adipose tissue to repair crucial defects is clinically interesting for surgical reconstruction. Terminally differentiated adipocytes are utilized to promote the healthy regeneration of defective tissue. Use of differentiated mesenchymal stem cells, capable of differentiation into adipocytes, is advantageous because of their regenerative properties. Conventionally, the differentiation of hMSCs toward adipocytes occurs through chemical stimulation. We designed a microfluidic system, consisting of plastic tubing and a syringe pump, to create an environment of shear to accelerate this differentiation process. This system employed a flow rate equivalent to the accelerated flow rates found within the arterial system in order to promote and activate intracellular and extracellular proteins associated with the adipogenic lineage. Confirmation of sustained viability following shear exposure was obtained using a fluorescent live-dead assay. Visualization of intracellular lipid accumulation was achieved via Oil Red O staining. When placed into culture, shear stimulated hMSCs were further induced toward brown adipose tissue, as evidenced by a greater quantity of lipid triglycerides, relative to unstimulated hMSCs. qRT-PCR analysis validated the phenotypic changes observed when the hMSCs were later cultured in adipogenic differentiation media. Additionally, increased fold change for adipogenic markers such as LPL1, CFL1, and SSP1 were observed as a result of shear stimulation. The significance of this work lies in the demonstration that transient fluid shear exposure of hMSCs in suspension can influence differentiation into adipocytes. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:440-446, 2016.

The effect of injection using narrow-bore needles on mammalian cells: administration and formulation considerations for cell therapies

Objectives

This study focuses on the effect of the injection administration process on a range of cell characteristics.

Methods

Effects of different ejection rates, needle sizes and cell suspension densities were assessed in terms of viability, membrane integrity, apoptosis and senescence of NIH 3T3 fibroblasts. For ratiometric measurements, a multiplex assay was used to verify cell viability, cytotoxicity and apoptosis independent of cell number. Co‐delivery with alginate hydrogels and viscosity‐modifying excipients was also assessed.

Key findings

Ejections at 150 μl/min resulted in the highest percentage of dose being delivered as viable cells among ejection rates tested. The difference in proportions of apoptotic cells became apparent 48 h after ejection, with proportions being higher in samples ejected at slower rates. Co‐delivery with alginate hydrogels demonstrated a protective action on the cell payload.

Conclusions

This study demonstrates the importance of careful consideration of administration protocols required for successful delivery of cell suspensions, according to their nature and cellular responses post‐ejection.

Emerging medical devices for minimally invasive cell therapy

The past decade has seen the first wave of cell-based therapeutics undergo clinical trials with varying degrees of success. Although attention is increasingly focused on clinical trial design, owing to spiraling regulatory costs, tools used in delivering cells and sustaining the cells' viability and functions in vivo warrant careful scrutiny. While the clinical administration of cell-based therapeutics often requires additional safeguarding and targeted delivery compared with traditional therapeutics, there is significant opportunity for minimally invasive device-assisted cell therapy to provide the physician with new regenerative options at the point of care. Herein we detail exciting recent advances in medical devices that will aid in the safe and efficacious delivery of cell-based therapeutics.

Impact of passing mesenchymal stem cells through smaller bore size needles for subsequent use in patients for clinical or cosmetic indications

Background

Numerous preclinical and clinical studies have investigated the regenerative potential and the trophic support of mesenchymal stem cells (MSCs) following their injection into a target organ. Clinicians favor the use of smallest bore needles possible for delivering MSCs into vascular organs like heart, liver and spleen. There has been a concern that small needle bore sizes may be detrimental to the health of these cells and reduce the survival and plasticity of MSCs.

Methods

In this report, we aimed to investigate the smallest possible bore size needle which would support the safe delivery of MSCs into various tissues for different clinical or cosmetic applications. To accomplish this we injected cells via needle sizes 24, 25 and 26 G attached to 1 ml syringe in the laboratory and collected the cells aseptically. Control cells were ejected via 1 ml syringe without any needle. Thereafter, the needle ejected cells were cultured and characterized for their morphology, attachment, viability, phenotypic expression, differentiation potential, cryopreservation and in vivo migration abilities. In the second phase of the study, cells were injected via 26 G needle attached to 1 ml syringe for 10 times.

Results

Similar phenotypic and functional characteristics were observed between ejected and control group of cells. MSCs maintained their cellular and functional properties after single and multiple injections.

Conclusions

This study proves that 26 G bore size needles can be safely used to inject MSCs for clinical/therapeutics purposes.

G-CSF stimulation and coronary reinfusion of mobilized circulating mononuclear proangiogenic cells in patients with chronic ischemic heart disease:five-year results of the TOPCARE-G-CSF trial

Prognosis of patients with heart failure remains poor despite improved conventional and interventional treatment regimens. The improvement of neovascularization and repair processes by administration of bone marrow-derived cells modestly improved the recovery after acute myocardial infarction. However, circulating patient-derived cells are reduced in number and function particularly in chronic heart failure. Therefore, we tested the hypothesis whether the mobilization of circulating mononuclear proangiogenic cells (CPCs) by G-CSF may overcome some of these limitations. In the present pilot study, 32 patients with at least 3-month-old myocardial infarction were randomized to G-CSF alone (G-CSF group) or intracoronary infusion of G-CSF-mobilized and cultured CPCs into the infarct-related artery (G-CSF/CPC group). Primary endpoint of the study was safety. Efficacy parameters included serial assessment of LV function, NT-proBNP levels, and cardiopulmonary exercise testing. G-CSF effectively mobilized circulating CD34(+)CD45(+) cells after 5 days in all patients (408 ± 64%) without serious adverse events. At 3 months, NYHA class and global LV function did not show significant improvements in both treatment groups (G-CSF: ΔLVEF 1.6 ± 2.4%; p = 0.10; G-CSF/CPC: ΔLVEF 1.4 ± 4.1%; p = 0.16). In contrast, target area contractility improved significantly in the G-CSF/CPC group. During 5-year follow-up, one patient died after rehospitalization for worsening heart failure. Eleven patients underwent further revascularization procedures. NT-proBNP levels, cardiopulmonary exercise capacity, and NYHA class remained stable in both treatment groups. The results from our pilot trial indicate that administration of G-CSF alone or G-CSF-mobilized and cultured CPCs can be performed safely in patients with chronic ischemic heart disease. However, only minor effects on LV function, NT-proBNP levels, and NYHA classification were observed during follow-up, suggesting that the enhancement of CPCs by G-CSF alone does not substantially improve intracoronary cell therapy effects in patients with chronic ischemic heart failure.

The sensitivity of human mesenchymal stem cells to vibration and cold storage conditions representative of cold transportation

In the current study, the mechanical and hypothermic damage induced by vibration and cold storage on human mesenchymal stem cells (hMSCs) stored at 2-8°C was quantified by measuring the total cell number and cell viability after exposure to vibration at 50 Hz (peak acceleration 140 m s(-2) and peak displacement 1.4 mm), 25 Hz (peak acceleration 140 m s(-2), peak displacement 5.7 mm), 10 Hz (peak acceleration 20 m s(-2), peak displacement 5.1 mm) and cold storage for several durations. To quantify the viability of the cells, in addition to the trypan blue exclusion method, the combination of annexin V-FITC and propidium iodide was applied to understand the mode of cell death. Cell granularity and a panel of cell surface markers for stemness, including CD29, CD44, CD105 and CD166, were also evaluated for each condition. It was found that hMSCs were sensitive to vibration at 25 Hz, with moderate effects at 50 Hz and no effects at 10 Hz. Vibration at 25 Hz also increased CD29 and CD44 expression. The study further showed that cold storage alone caused a decrease in cell viability, especially after 48 h, and also increased CD29 and CD44 and attenuated CD105 expressions. Cell death would most likely be the consequence of membrane rupture, owing to necrosis induced by cold storage. The sensitivity of cells to different vibrations within the mechanical system is due to a combined effect of displacement and acceleration, and hMSCs with a longer cold storage duration were more susceptible to vibration damage, indicating a coupling between the effects of vibration and cold storage.

Injectable solid peptide hydrogel as a cell carrier: effects of shear flow on hydrogels and cell payload

β-hairpin peptide-based hydrogels are a class of injectable solid hydrogels that can deliver encapsulated cells or molecular therapies to a target site via syringe or catheter injection as a carrier material. These physical hydrogels can shear-thin and consequently flow as a low-viscosity material under a sufficient shear stress but immediately recover back into a solid upon removal of the stress, allowing them to be injected as preformed gel solids. Hydrogel behavior during flow was studied in a cylindrical capillary geometry that mimicked the actual situation of injection through a syringe needle in order to quantify effects of shear-thin injection delivery on hydrogel flow behavior and encapsulated cell payloads. It was observed that all β-hairpin peptide hydrogels investigated displayed a promising flow profile for injectable cell delivery: a central wide plug flow region where gel material and cell payloads experienced little or no shear rate, and a narrow shear zone close to the capillary wall where gel and cells were subject to shear deformation. The width of the plug flow region was found to be weakly dependent on hydrogel rigidity and flow rate. Live-dead assays were performed on encapsulated MG63 cells 3 h after injection flow and revealed that shear-thin delivery through the capillary had little impact on cell viability and the spatial distribution of encapsulated cell payloads. These observations help us to fundamentally understand how the gels flow during injection through a thin catheter and how they immediately restore mechanically and morphologically relative to preflow, static gels.

Targeted Intra-arterial Transplantation of Stem Cells to the Injured CNS is more Effective than Intravenous Administration: Engraftment is Dependent on Cell Type and Adhesion Molecule Expression

Stem cell transplantation procedures using intraparenchymal injections cause tissue injury in addition to associated surgical risks. Intravenous cell administration give engraftment in parenchymal lesions although the method has low efficacy and specificity. In pathological conditions with inflammation, such as traumatic brain injury, there is a transient up-regulation of ICAM-1 and VCAM-1 which might provide environmental cues for migration of stem cells from blood to parenchyma. The aim of this study was to i) analyze the effect of intra-arterial administration on cellular engraftment, ii) compare engraftment and side effects between three different stem cell systems, and iii) analyze gene expression in these three systems. We performed specific intra-arterial transplantations with human mesenchymal stem cells (hMSCs), human neural progenitor cells (hNPCs), and rat neural progenitor cells (rNPCs) in a rat model of traumatic brain injury. These results were compared to the intravenous route for each cell type, respectively. Analysis of engraftment and recipient characterization was performed by immunohistochemistry. We further characterized the different types of cells by microarray and RT-qPCR analysis. Specific intra-arterial transplantations produced significantly higher engraftment compared to intravenous transplantation with hMSCs and rNPCs. No engraftment was detected after intra-arterial or intravenous administration of hNPCs. Characterization of integrin expression indicated that CD49dVCAM-1 and possibly ICAM-1 interactions through CD18 and CD11a, respectively, are important for engraftment after intravascular cell administration. No side effects, such as thromboembolic complications, were detected. When translating stem cell therapies to clinical practice, the route of transplantation and the properties of the cell lines (homing, diapedesis, and migration) become important. This study supports the use of selective intra-arterial transplantation for improving engraftment after traumatic brain injury. In addition, we conclude that careful analysis of cells intended for local, intra-arterial transplantation with respect to integrin expression is important.

Platelet lysate consisting of a natural repair proteome supports human mesenchymal stem cell proliferation and chromosomal stability

With favorable regenerative and immunotolerant profiles, patient-derived human mesenchymal stem cells (hMSCs) are increasingly considered in cell therapy. Derived from bone marrow (BM) and standardized with culture in fetal bovine serum (FBS), translation of hMSC-based approaches is impeded by protracted expansion times, risk of xenogenic response, and exposure to zoonoses. Here, human platelet lysate adherent to good manufacturing practices (GMP-hPL) provided a nonzoonotic adjuvant that enhanced the capacity of BM-hMSC to proliferate. The nurturing benefit of GMP-hPL was generalized to hMSC from adipose tissue evaluated as an alternative to bone marrow. Long-term culture in GMP-hPL maintained the multipotency of hMSC, while protecting against clonal chromosomal instability detected in the FBS milieu. Proteomic dissection identified TGF-β, VEGF, PDGF, FGF, and EGF as highly ranked effectors of hPL activity, revealing a paradigm of healing that underlies platelet lysate adjuvancy. Thus, GMP-adherent human platelet lysate accelerates hMSC proliferation with no chromosomal aberrancy, through an innate repair paradigm.

Stem cell research in cell transplantation: sources, geopolitical influence, and transplantation

If the rapidly progressing field of stem cell research reaches its full potential, successful treatments and enhanced understanding of many diseases are the likely results. However, the full potential of stem cell science will only be reached if all possible avenues can be explored and on a worldwide scale. Until 2009, the US had a highly restrictive policy on obtaining cells from human embryos and fetal tissue, a policy that pushed research toward the use of adult-derived cells. Currently, US policy is still in flux, and retrospective analysis does show the US lagging behind the rest of the world in the proportional increase in embryonic/fetal stem cell research. The majority of US studies being on either a limited number of cell lines, or on cells derived elsewhere (or funded by other sources than Federal) rather than on freshly isolated embryonic or fetal material. Neural, mesenchymal, and the mixed stem cell mononuclear fraction are the most commonly investigated types, which can generally be classified as adult-derived stem cells, although roughly half of the neural stem cells are fetal derived. Other types, such as embryonic and fat-derived stem cells, are increasing in their prominence, suggesting that new types of stem cells are still being pursued. Sixty percent of the reported stem cell studies involved transplantation, of which over three quarters were allogeneic transplants. A high proportion of the cardiovascular systems articles were on allogeneic transplants in a number of different species, including several autologous studies. A number of pharmaceutical grade stem cell products have also recently been tested and reported on. Stem cell research shows considerable promise for the treatment of a number of disorders, some of which have entered clinical trials; over the next few years it will be interesting to see how these treatments progress in the clinic.

The effect of transcatheter injections on cell viability and cytokine release of mononuclear cells

BACKGROUND AND PURPOSE

Several studies suggest that various types of cellular therapies enhance recovery after stroke in animal models. IA-based delivery of cells to the brain is under investigation for stroke, but it is unknown whether cells are injured as a result of being injected through a catheter or exposed to iodinated contrast medium or solutions containing heparin.

MATERIALS AND METHODS

We assessed the effect of catheterization with the Excelsior SL-10 catheter or exposure to heparin or iodine contrast on human bone marrow MNCs. Viability and cell injury were assessed by trypan blue exclusion, caspase-3 activity, and lipid peroxidation. Cellular function of MNCs was assessed by their production and release of VEGF, IL-10, and IGF-1.

RESULTS

Flow rates of 10 million cells from 0.5 to 2 mL/min did not alter MNC viability; however, 5 mL/min of MNCs did reduce viability by 19%. Iodine and low-dose heparin exposure did not affect cell viability; however, high-dose heparin was cytotoxic. Catheter delivery at 2 mL/min did not affect levels of VEGF, IL-10, or IGF-1.

CONCLUSIONS

MNCs do not appear to be damaged by heparin, iodine contrast, and the Excelsior SL-10 catheter at flow rates up to 2 mL/min. However, higher flow rates did reduce viability, and high-dose heparin did cause cell death.

In Vivo MRI Stem Cell Tracking Requires Balancing of Detection Limit and Cell Viability

Cell-based therapy using adult mesenchymal stem cells (MSCs) has already been the subject of clinical trials, but for further development and optimization the distribution and integration of the engrafted cells into host tissues have to be monitored. Today, for this purpose magnetic resonance imaging (MRI) is the most suitable technique, and micron-sized iron oxide particles (MPIOs) used for labeling are favorable due to their low detection limit. However, constitutional data concerning labeling efficiency, cell viability, and function are lacking. We demonstrate that cell viability and migratory potential of bone marrow mesenchymal stromal cells (BMSCs) are negatively correlated with incorporated MPIOs, presumably due to interference with the actin cytoskeleton. Nevertheless, labeling of BMSCs with low amounts of MPIOs results in maintained cellular function and sufficient contrast for in vivo observation of single cells by MRI in a rat glioma model. Conclusively, though careful titration is indicated, MPIOs are a promising tool for in vivo cell tracking and evaluation of cell-based therapies.