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Magnetic resonance imaging (MRI) provides a unique tool for in vivo visualization and tracking of stem cells in the brain. This is of particular importance when assessing safety of experimental cell treatments in the preclinical or clinical setup. Yet, specific imaging requires an efficient and non-perturbing cellular magnetic labeling which precludes adverse effects of the tag, e.g., the impact of iron-oxide-nanoparticles on the critical differentiation and integration processes of the respective stem cell population investigated. In this study we investigated the effects of very small superparamagnetic iron oxide particle (VSOP) labeling on viability, stemness, and neuronal differentiation potential of primary human adult neural stem cells (haNSCs). Cytoplasmic VSOP incorporation massively reduced the transverse relaxation time T2, an important parameter determining MR contrast. Cells retained cytoplasmic label for at least a month, indicating stable incorporation, a necessity for long-term imaging. Using a clinical 3T MRI, 1 × 103 haNSCs were visualized upon injection in a gel phantom, but detection limit was much lower (5 × 104 cells) in layer phantoms and using an imaging protocol feasible in a clinical scenario. Transcriptional analysis and fluorescence immunocytochemistry did not reveal a detrimental impact of VSOP labeling on important parameters of cellular physiology with cellular viability, stemness and neuronal differentiation potential remaining unaffected. This represents a pivotal prerequisite with respect to clinical application of this method.

Aiming at iron-related T2-hypointensity, which is related to normal aging and neurodegenerative processes, we here present two practicable approaches, based on Bayesian inference, for preprocessing and statistical analysis of a complex set of structural MRI data. In particular, Markov Chain Monte Carlo methods were used to simulate posterior distributions. First, we rendered a segmentation algorithm that uses outlier detection based on model checking techniques within a Bayesian mixture model. Second, we rendered an analytical tool comprising a Bayesian regression model with smoothness priors (in the form of Gaussian Markov random fields) mitigating the necessity to smooth data prior to statistical analysis. For validation, we used simulated data and MRI data of 27 healthy controls (age: [Formula: see text]; range, [Formula: see text]). We first observed robust segmentation of both simulated T2-hypointensities and gray-matter regions known to be T2-hypointense. Second, simulated data and images of segmented T2-hypointensity were analyzed. We found not only robust identification of simulated effects but also a biologically plausible age-related increase of T2-hypointensity primarily within the dentate nucleus but also within the globus pallidus, substantia nigra, and red nucleus. Our results indicate that fully Bayesian inference can successfully be applied for preprocessing and statistical analysis of structural MRI data.

Experimental treatment strategies using human umbilical cord blood mononuclear cells (hUCB MNCs) represent a promising option for alternative stroke therapies. An important point for clinical translation of such treatment approaches is knowledge on the therapeutic time window. Although expected to be wider than for thrombolysis, the exact time window for hUCB MNC therapy is not known. Our study aimed to determine the time window of intravenous hUCB MNC administration after middle cerebral artery occlusion (MCAO). Male spontaneously hypertensive rats underwent MCAO and were randomly assigned to hUCB MNC administration at 4, 24, 72, and 120 or 14 days. Influence of cell treatment was observed by magnetic resonance imaging on days 1, 8, and 29 following MCAO and by assessment of functional neurological recovery. On day 30, brains were screened for glial scar development and presence of hUCB MNCs. Further, influence of hUCB MNCs on necrosis and apoptosis in postischemic neural tissue was investigated in hippocampal slices cultures. Transplantation within a 72-h time window resulted in an early improvement of functional recovery, paralleled by a reduction of brain atrophy and diminished glial scarring. Cell transplantation 120 h post-MCAO only induced minor functional recovery without changes in the brain atrophy rate and glial reactivity. Later transplantation (14 days) did not show any benefit. No evidence for intracerebrally localized hUCB MNCs was found in any treatment group. In vitro hUCB MNCs were able to significantly reduce postischemic neural necrosis and apoptosis. Our results for the first time indicate a time window of therapeutic hUCB MNC application of at least 72 h. The time window is limited, but wider than compared to conventional pharmacological approaches. The data furthermore confirms that differentiation and integration of administered cells is not a prerequisite for poststroke functional improvement and lesion size reduction.

Purpose. We analyzed our experience with the phenox clot retriever as part of a multimodal mechanical thrombectomy (MTE) approach in acute ischemic stroke. Methods. 56 patients were treated by MTE with the phenox clot retriever alone or in combination with other modalities. Results. Overall we achieved TICI 2b/3 reperfusion rates of 61,9%. In multimodally treated patients we achieved reperfusion rates of 72,8%. There were 3 (5,5%) severe adverse events, all symptomatic intracranial hemorrhages. The mean angio to reperfusion times (ART) were 74 minutes for phenox-only procedures and 51 minutes for multimodal procedures. A chronological analysis showed a reduction of ART from 70,5 to 49,4 minutes and an increase of TICI 2b/3 recanalizations from 53,8% to 81,8%. Throughout the observation period there was a significant shift towards multimodal procedures with simultaneous increase of TICI 2b/3 reperfusions. Both effects are partially attributable to our institutional learning curve. NIHSS improvement could be seen in 54% (𝑛=28) overall and in 73% (𝑛=15) of MCA recanalizations. Conclusions. The phenox clot retriever is a safe and effective tool for MTE in acute stroke patients, with faster and better reperfusion results when used as part of a multimodal strategy. Clinical improvement is more frequent in MCA recanalizations.

BACKGROUND: After ischemia of the CNS, extracellular adenosine 5'-triphosphate (ATP) can reach high concentrations due to cell damage and subsequent increase of membrane permeability. ATP may cause cellular degeneration and death, mediated by P2X and P2Y receptors. METHODOLOGY/PRINCIPAL FINDINGS: The effects of inhibition of P2 receptors by pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on electrophysiological, functional and morphological alterations in an ischemia model with permanent middle cerebral artery occlusion (MCAO) were investigated up to day 28. Spontaneously hypertensive rats received PPADS or vehicle intracerebroventricularly 15 minutes prior MCAO for up to 7 days. The functional recovery monitored by qEEG was improved by PPADS indicated by an accelerated recovery of ischemia-induced qEEG changes in the delta and alpha frequency bands along with a faster and sustained recovery of motor impairments. Whereas the functional improvements by PPADS were persistent at day 28, the infarct volume measured by magnetic resonance imaging and the amount of TUNEL-positive cells were significantly reduced by PPADS only until day 7. Further, by immunohistochemistry and confocal laser scanning microscopy, we identified both neurons and astrocytes as TUNEL-positive after MCAO. CONCLUSION: The persistent beneficial effect of PPADS on the functional parameters without differences in the late (day 28) infarct size and apoptosis suggests that the early inhibition of P2 receptors might be favourable for the maintenance or early reconstruction of neuronal connectivity in the periinfarct area after ischemic incidents.