Controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells using porphyrin conjugated nanoparticles.

Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(II) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(II) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn(II) porphyrin and high numbers of irradiations of excitation light were found to generate greater amounts of ROS. A novel dye, which is transformed into fluorescent 7-hydroxy-4-trifluoromethyl-coumarin in the presence of hydrogen peroxide, provided an indirect indicator for cumulative ROS production. The mitochondrial membrane potential was monitored to investigate the destructive effect of increased intracellular ROS production. Flow cytometric analysis of nanoparticle treated hMSCs suggested irradiation with excitation light signalled controlled apoptotic cell death, rather than uncontrolled necrotic cell death. Increased intracellular ROS production did not induce phenotypic changes in hMSC subcultures.

Hematopoietic stem cell (CD34+) uptake of superparamagnetic iron oxide is enhanced by but not dependent on a transfection agent.

BACKGROUND AIMS: Tracking the fate of cells after infusion would be a valuable asset for many stem cell therapies, but very few (cell) labels are approved for human therapeutic use. Superparamagnetic iron oxide particles (SPIO) can be internalized into stem cells in vitro to allow real-time tracking with gradient echo magnetic resonance imaging, but SPIO are approved for (diagnostic) imaging and not for (therapeutic) cell labeling in vivo. In this study, we investigated the possibility of labeling stem cells with an SPIO approved for patient use, albeit in a novel manner by enhancing uptake with the use of a transfection agent, also approved for patient use. Although there are many reports of hematopoietic stem cells being labeled with SPIO, there is some controversy regarding the efficiency of this and whether undifferentiated CD34+ progenitor (stem) cells are able to take up iron in the absence of a transfection agent to enhance the process. METHODS: Human CD34+ cells were treated in vitro as follows: incubation with (i) medium only (control), (ii) ferumoxide (Endorem) and (iii) ferumoxide (Endorem) plus exposure to a transfection agent (protamine sulfate). Cells were incubated for 2, 4 and 24 hours and assessed for viability, differentiation capacity and visualized in vitro with 3-T magnetic resonance imaging. The cells were also analyzed by means of flow cytometry and morphology examined by electron microscopy. RESULTS: CD34+ hematopoietic progenitor cells can internalize ferumoxide (Endorem) independently of a transfection agent. However, uptake of ferumoxide is enhanced after exposure to protamine sulfate. Iron labeling of CD34+ cells in this manner does not affect cell viability and does not appear to affect the potential of the cells to grow in culture. Iron-labeled CD34+ cells can be visualized in vitro on 3-T magnetic resonance image scanning. CONCLUSIONS: Endorem and protamine sulfate can be combined to promote iron oxide nanoparticle uptake by CD34+ cells, and this methodology can potentially be used to track the fate of cells in a clinical trial setting because both compounds are (separately) approved for clinical use.

Mesenchymal stem cells in the human corneal limbal stroma.

PURPOSE: Peripheral and limbal corneal stromal cells (PLCSCs), which contain keratocytes, have a complex phenotype. Knowledge of keratocyte cell properties, function, and origin is limited. Evidence available thus far has suggested both mesenchymal stromal and hematopoietic characteristics. Multipotent mesenchymal stromal cells (MSCs) are found in an increasing number of tissues and are the subject of considerable interest and investigation in the disciplines of tissue engineering, immunology, gene therapy, and oncology. METHODS: Isolated PLCSCs were characterized by markers aldehyde dehydrogenase and keratocan, cultured, and analyzed against a set of criteria for the identification of MSCs developed by the International Society of Cellular Therapy (ISCT). PLCSCs were directly compared to fetal liver MSCs (flMSCs). Additional cell surface markers were also used to quantify differentiation, which was also performed on both cell types. RESULTS: PLCSCs were found to be plastic adherent, displayed the correct profile and proportions of CSMs, and demonstrated trilineage potential in accordance with the ISCT guidelines. Furthermore, PLCSCs displayed a high degree of similarity to flMSCs and this likeness extended into the non-ISCT MSC cell surface markers and trilineage differentiation, which were often but not always comparable. CONCLUSIONS: Herein we report a novel observation that PLCSCs conform to all the ISCT criteria and are therefore MSCs. Furthermore, this study has identified the limbal stroma as yet another MSC niche and presents a new perspective on the role of the PLCSC.

Granulocyte-colony stimulating factor for mobilizing bone marrow stem cells in subacute stroke: the stem cell trial of recovery enhancement after stroke 2 randomized controlled trial.

BACKGROUND AND PURPOSE: Granulocyte-colony stimulating factor (G-CSF) is neuroprotective in experimental stroke and mobilizes CD34(+) peripheral blood stem cells into the circulation. We assessed the safety of G-CSF in recent stroke in a phase IIb single-center randomized, controlled trial. METHODS: G-CSF (10 µg/kg) or placebo (ratio 2:1) was given SC for 5 days to 60 patients 3 to 30 days after ischemic or hemorrhagic stroke. The primary outcome was the frequency of serious adverse events. Peripheral blood counts, CD34(+) count, and functional outcome were measured. MRI assessed lesion volume, atrophy, and the presence of iron-labeled CD34(+) cells reinjected on day 6. RESULTS: Sixty patients were recruited at mean of 8 days (SD ± 5) post ictus, with mean age 71 years (± 12 years) and 53% men. The groups were well matched for baseline minimization/prognostic factors. There were no significant differences between groups in the number of participants with serious adverse events: G-CSF 15 (37.5%) of 40 versus placebo 7 (35%) of 20, death or dependency (modified Rankin Score: G-CSF 3.3 ± 1.3, placebo 3.0 ± 1.3) at 90 days, or the number of injections received. G-CSF increased CD34(+) and total white cell counts of 9.5- and 4.2-fold, respectively. There was a trend toward reduction in MRI ischemic lesion volume with respect to change from baseline in G-CSF-treated patients (P=0.06). In 1 participant, there was suggestion that labeled CD34(+) cells had migrated to the ischemic lesion. CONCLUSIONS: This randomized, double-blind, placebo-controlled trial suggests that G-CSF is safe when administered subacutely. It is feasible to label and readminister iron-labeled CD34(+) cells in patients with ischemic stroke. CLINICAL TRIAL REGISTRATION: URL: www.controlled-trials.com. Unique identifier: ISRCTN63336619.

Internalisation of polymeric nanosensors in mesenchymal stem cells: analysis by flow cytometry and confocal microscopy.

The aim of this study was to demonstrate that flow cytometry and confocal microscopy could be applied in a complementary manner to analyse the internalisation of polymeric nanosensors in mesenchymal stem cells (MSC). The two techniques are able to provide en masse data analysis of nanosensors from large cell populations and detailed images of intracellular nanosensor localisation, respectively. The polyacrylamide nanosensors used in this investigation had been modified to contain free amine groups which were subsequently conjugated to Tat peptide, which acted as a delivery vector for nanosensor internalisation. Flow cytometry was used to confirm the health of MSC culture and assess the impact of nanosensor internalisation. MSC were characterised using fluorescently tagged CD cell surface markers that were also used to show that nanosensor internalisation did not negatively impact on MSC culture. Additionally it was shown that flow cytometry can be used to measure fluorophores located both on the cell surface and internalised within the cell. Complementary data was obtained using confocal microscopy to confirm nanosensor internalisation within MSC.

Hematopoiesis from human embryonic stem cells: overcoming the immune barrier in stem cell therapies.

The multipotency and proliferative capacity of human embryonic stem cells (hESCs) make them a promising source of stem cells for transplant therapies and of vital importance given the shortage in organ donation. Recent studies suggest some immune privilege associated with hESC-derived tissues. However, the adaptability of the immune system makes it unlikely that fully differentiated tissues will permanently evade immune rejection. One promising solution is to induce a state of immune tolerance to a hESC line using tolerogenic hematopoietic cells derived from it. This could provide acceptance of other differentiated tissues from the same line. However, this approach will require efficient multilineage hematopoiesis from hESCs. This review proposes that more efficient differentiation of hESCs to the tolerogenic cell types required is most likely to occur through applying knowledge gained of the ontogeny of complex regulatory signals used by the embryo for definitive hematopoietic development in vivo. Stepwise formation of mesoderm, induction of definitive hematopoietic stem cells, and the application of factors key to their self-renewal may improve in vitro production both quantitatively and qualitatively.