Glial aging and its impact on central nervous system myelin regeneration

Aging is a major risk factor for several neurodegenerative diseases and is associated with cognitive decline. In addition to affecting neuronal function, the aging process significantly affects the functional phenotype of the glial cell compartment, comprising oligodendrocyte lineage cells, astrocytes, and microglia. These changes result in a more inflammatory microenvironment, resulting in a condition that is favorable for neuron and synapse loss. In addition to facilitating neurodegeneration, the aging glial cell population has negative implications for central nervous system remyelination, a regenerative process that is of particular importance to the chronic demyelinating disease multiple sclerosis. This review will discuss the changes that occur with aging in the three main glial populations and provide an overview of the studies documenting the impact these changes have on remyelination.

Somatic mutation rates scale with lifespan across mammals

The rates and patterns of somatic mutation in normal tissues are largely unknown outside of humans1-7. Comparative analyses can shed light on the diversity of mutagenesis across species, and on long-standing hypotheses about the evolution of somatic mutation rates and their role in cancer and ageing. Here we performed whole-genome sequencing of 208 intestinal crypts from 56 individuals to study the landscape of somatic mutation across 16 mammalian species. We found that somatic mutagenesis was dominated by seemingly endogenous mutational processes in all species, including 5-methylcytosine deamination and oxidative damage. With some differences, mutational signatures in other species resembled those described in humans8, although the relative contribution of each signature varied across species. Notably, the somatic mutation rate per year varied greatly across species and exhibited a strong inverse relationship with species lifespan, with no other life-history trait studied showing a comparable association. Despite widely different life histories among the species we examined-including variation of around 30-fold in lifespan and around 40,000-fold in body mass-the somatic mutation burden at the end of lifespan varied only by a factor of around 3. These data unveil common mutational processes across mammals, and suggest that somatic mutation rates are evolutionarily constrained and may be a contributing factor in ageing.

Systematic approach to selecting licensed drugs for repurposing in the treatment of progressive multiple sclerosis

OBJECTIVE

To establish a rigorous, expert-led, evidence-based approach to the evaluation of licensed drugs for repurposing and testing in clinical trials of people with progressive multiple sclerosis (MS).

METHODS

We long-listed licensed drugs with evidence of human safety, blood-brain barrier penetrance and demonstrable efficacy in at least one animal model, or mechanistic target, agreed by a panel of experts and people with MS to be relevant to the pathogenesis of progression. We systematically reviewed the preclinical and clinical literature for each compound, condensed this into a database of summary documents and short-listed drugs by scoring each one of them. Drugs were evaluated for immediate use in a clinical trial, and our selection was scrutinised by a final independent expert review.

RESULTS

From a short list of 55 treatments, we recommended four treatments for immediate testing in progressive MS: R-α-lipoic acid, metformin, the combination treatment of R-α-lipoic acid and metformin, and niacin. We also prioritised clemastine, lamotrigine, oxcarbazepine, nimodipine and flunarizine.

CONCLUSIONS

We report a standardised approach for the identification of candidate drugs for repurposing in the treatment of progressive MS.

Schwann cell remyelination of the central nervous system: why does it happen and what are the benefits?

Myelin sheaths, by supporting axonal integrity and allowing rapid saltatory impulse conduction, are of fundamental importance for neuronal function. In response to demyelinating injuries in the central nervous system (CNS), oligodendrocyte progenitor cells (OPCs) migrate to the lesion area, proliferate and differentiate into new oligodendrocytes that make new myelin sheaths. This process is termed remyelination. Under specific conditions, demyelinated axons in the CNS can also be remyelinated by Schwann cells (SCs), the myelinating cell of the peripheral nervous system. OPCs can be a major source of these CNS-resident SCs—a surprising finding given the distinct embryonic origins, and physiological compartmentalization of the peripheral and central nervous system. Although the mechanisms and cues governing OPC-to-SC differentiation remain largely undiscovered, it might nevertheless be an attractive target for promoting endogenous remyelination. This article will (i) review current knowledge on the origins of SCs in the CNS, with a particular focus on OPC to SC differentiation, (ii) discuss the necessary criteria for SC myelination in the CNS and (iii) highlight the potential of using SCs for myelin regeneration in the CNS.

Metformin Restores CNS Remyelination Capacity by Rejuvenating Aged Stem Cells

The age-related failure to produce oligodendrocytes from oligodendrocyte progenitor cells (OPCs) is associated with irreversible neurodegeneration in multiple sclerosis (MS). Consequently, regenerative approaches have significant potential for treating chronic demyelinating diseases. Here, we show that the differentiation potential of adult rodent OPCs decreases with age. Aged OPCs become unresponsive to pro-differentiation signals, suggesting intrinsic constraints on therapeutic approaches aimed at enhancing OPC differentiation. This decline in functional capacity is associated with hallmarks of cellular aging, including decreased metabolic function and increased DNA damage. Fasting or treatment with metformin can reverse these changes and restore the regenerative capacity of aged OPCs, improving remyelination in aged animals following focal demyelination. Aged OPCs treated with metformin regain responsiveness to pro-differentiation signals, suggesting synergistic effects of rejuvenation and pro-differentiation therapies. These findings provide insight into aging-associated remyelination failure and suggest therapeutic interventions for reversing such declines in chronic disease.

Niche stiffness underlies the ageing of central nervous system progenitor cells

Ageing causes a decline in tissue regeneration owing to a loss of function of adult stem cell and progenitor cell populations1. One example is the deterioration of the regenerative capacity of the widespread and abundant population of central nervous system (CNS) multipotent stem cells known as oligodendrocyte progenitor cells (OPCs)2. A relatively overlooked potential source of this loss of function is the stem cell 'niche'-a set of cell-extrinsic cues that include chemical and mechanical signals3,4. Here we show that the OPC microenvironment stiffens with age, and that this mechanical change is sufficient to cause age-related loss of function of OPCs. Using biological and synthetic scaffolds to mimic the stiffness of young brains, we find that isolated aged OPCs cultured on these scaffolds are molecularly and functionally rejuvenated. When we disrupt mechanical signalling, the proliferation and differentiation rates of OPCs are increased. We identify the mechanoresponsive ion channel PIEZO1 as a key mediator of OPC mechanical signalling. Inhibiting PIEZO1 overrides mechanical signals in vivo and allows OPCs to maintain activity in the ageing CNS. We also show that PIEZO1 is important in regulating cell number during CNS development. Thus we show that tissue stiffness is a crucial regulator of ageing in OPCs, and provide insights into how the function of adult stem and progenitor cells changes with age. Our findings could be important not only for the development of regenerative therapies, but also for understanding the ageing process itself.

Transforming growth factor-beta renders ageing microglia inhibitory to oligodendrocyte generation by CNS progenitors

It is now well-established that the macrophage and microglial response to CNS demyelination influences remyelination by removing myelin debris and secreting a variety of signaling molecules that influence the behaviour of oligodendrocyte progenitor cells (OPCs). Previous studies have shown that changes in microglia contribute to the age-related decline in the efficiency of remyelination. In this study, we show that microglia increase their expression of the proteoglycan NG2 with age, and that this is associated with an altered micro-niche generated by aged, but not young, microglia that can divert the differentiation OPCs from oligodendrocytes into astrocytes in vitro. We further show that these changes in ageing microglia are generated by exposure to high levels of TGFβ. Thus, our findings suggest that the rising levels of circulating TGFβ known to occur with ageing contribute to the age-related decline in remyelination by impairing the ability of microglia to promote oligodendrocyte differentiation from OPCs, and therefore could be a potential therapeutic target to promote remyelination.

High-density Mapping Guided Pulmonary Vein Isolation for Treatment of Atrial Fibrillation - Two-year clinical outcome of a single center experience

Pulmonary vein isolation (PVI) as interventional treatment for atrial fibrillation (AF) aims to eliminate arrhythmogenic triggers from the PVs. Improved signal detection facilitating a more robust electrical isolation might be associated with a better outcome. This retrospective cohort study compared PVI procedures using a novel high-density mapping system (HDM) with improved signal detection vs. age- and sex-matched PVIs using a conventional 3D mapping system (COM). Endpoints comprised freedom from AF and procedural parameters. In total, 108 patients (mean age 63.9 ± 11.2 years, 56.5% male, 50.9% paroxysmal AF) were included (n = 54 patients/group). Our analysis revealed that HDM was not superior regarding freedom from AF (mean follow-up of 494.7 ± 26.2 days), with one- and two-year AF recurrence rates of 38.9%/46.5% (HDM) and 38.9%/42.2% (COM), respectively. HDM was associated with reduction in fluoroscopy times (18.8 ± 10.6 vs. 29.8 ± 13.4 min; p < 0.01) and total radiation dose (866.0 ± 1003.3 vs. 1731.2 ± 1978.4 cGy; p < 0.01) compared to the COM group. HDM was equivalent but not superior to COM with respect to clinical outcome after PVI and resulted in reduced fluoroscopy time and radiation exposure. These results suggest that HDM-guided PVI is effective and safe for AF ablation. Potential benefits in comparison to conventional mapping systems, e.g. arrhythmia recurrence rates, have to be addressed in randomized trials.

Corrigendum: Violent Behavior During Psychiatric Inpatient Treatment in a German Prison Hospital

[This corrects the article DOI: 10.3389/fpsyt.2019.00762.].

Violent Behavior During Psychiatric Inpatient Treatment in a German Prison Hospital

Violent behavior in correctional facilities is common and differs substantially in type, target, implication, and trigger. Research on frequency and characteristics of violent behavior in correctional facilities and psychiatric hospitals is limited. Results from recent research suggest that comorbidity of severe mental disorder, personality disorder, and diagnosis of substance abuse is related to a higher risk of violent behavior. In the Berlin prison hospital, a database was created to collect data from all violent incidences (n=210) between 1997 and 2006 and between 2010 and 2016. In a retrospective, case-control study, we analyzed specific socioeconomic data and psychiatric diagnosis and compared the group of prisoners with violent behavior with randomly selected prisoners of the same department without violent behavior (n = 210). Diagnosis of schizophrenia, non-German nationality, no use of an interpreter, no children, and no previous sentence remained significantly associated with the dependent variable violent behavior. There were no significant differences regarding age and legal statuses. Practical implications for clinical work are discussed.

Development, preclinical evaluation and validation of a novel quick vascular closure device for transluminal, cardiac and radiological arterial catheterization

Following percutaneous coronary intervention, vascular closure devices (VCDs) are increasingly used to reduce time to ambulation, enhance patient comfort, and reduce potential complications compared with traditional manual compression. Newer techniques include complicated, more or less automated suture devices, local application of pads or the use of metal clips and staples. These techniques often have the disadvantage of being time consuming, expensive or not efficient enough. The VCD failure rate in association with vascular complications of 2.0-9.5%, depending on the type of VCD, is still not acceptable. Therefore, the aim of this study is to develop a self-expanding quick vascular closure device (QVCD) made from a bioabsorbable elastic polymer that can be easily applied through the placed introducer sheath. Bioabsorbable block-co-polymers were synthesized and the chemical and mechanical degradation were determined by in vitro tests. The best fitting polymer was selected for further investigation and for microinjection moulding. After comprehensive haemocompatibility analyses in vitro, QVCDs were implanted in arterial vessels following arteriotomy for different time points in sheep to investigate the healing process. The in vivo tests proved that the new QVCD can be safely placed in the arteriotomy hole through the existing sheath instantly sealing the vessel. The degradation time of 14 days found in vitro was sufficient for vessel healing. After 4 weeks, the remaining QVCD material was covered by neointima. Overall, our experiments showed the safety and feasibility of applying this novel QVCD through an existing arterial sheath and hence encourage future work with larger calibers.

Intrajugular balloon catheter reduces air embolism in vitro and in vivo

Background

Neurosurgical procedures requiring a sitting position may put the patient at risk of a potentially life-threatening air embolism. Transient manual jugular venous compression limits further air entry in this situation. This study presents an alternative technique aimed at reducing the risk of air embolism.

Methods

In an in vitro model, an intrajugular balloon catheter was inserted to demonstrate that this device prevents air embolism. In an in vivo study, this device was bilaterally placed into jugular vessels in pigs. Using an ultrasound technique, blood flow was monitored and jugular venous pressure was recorded before and during cuff inflation. Air was applied proximally to the inflated cuffs to test the hypothesis that this novel device blocks air passage.

Results

In vitro, the intrajugular balloon catheter reliably prevented further air entry (n=10). Additionally, accumulated air could be aspirated from an orifice of the catheter (n=10). In vivo, inflation of the catheter balloon completely obstructed venous blood flow (n=8). Bilateral inflation of the cuff significantly increased the proximal jugular venous pressure from 9.8 (2.4) mm Hg to 14.5 (2.5) mm Hg (n=8, P<0.05). Under conditions mimicking an air embolism, air passage across the inflated cuffs was prevented and 78 (20%) (n=6) of the air dose could be aspirated by the proximal orifice of the catheter.

Conclusions

These findings may serve as a starting point for the development of intrajugular balloon catheters designed to reduce the risk of air embolism in patients undergoing neurosurgery in a sitting position.

Preclinical evaluation of the thrombogenicity and endothelialization of bare metal and surface-coated neurovascular stents

BACKGROUND AND PURPOSE

Stent-assisted coiling is routinely used for the endovascular treatment of complex or wide-neck intracranial aneurysms. However, in-stent thrombosis, thromboembolic events, and ischemic complications remain a major concern associated with stent implants. Therefore, a novel low-profile neurovascular stent with a bare metal surface was investigated with regard to thrombogenicity and endothelialization and compared with the same stent coated with albumin or heparin.

MATERIALS AND METHODS

The bare metal and heparin- or albumin-coated stents were loaded in heparin-coated tubing, which was then filled with heparinized human blood (n = 5) and circulated at 150 mL/min and 37°C for 60 minutes. Before and after circulation, measurement of various inflammation and coagulation markers and scanning electron microscopy were performed. Endothelialization of the stents was investigated in an in vitro model including human umbilical vascular endothelial cells.

RESULTS

Our results showed that platelet loss and platelet activation and activation of the coagulation cascade, which are induced by the bare metal stents, were significantly reduced by heparin or albumin coating. Adverse effects on erythrocytes, leukocytes, and the complement cascade were not induced by the bare metal or coated stents. Moreover, the bare metal and albumin-coated stents showed good endothelialization properties.

CONCLUSIONS

Albumin and heparin coatings clearly improve the thrombogenicity of the stents and thus may represent fundamental progress in the treatment of intracranial aneurysms. Moreover, preclinical evaluation of neurovascular stents under physiologic conditions supports and accelerates the development of more biocompatible neurovascular stents.

Evolution of the optical releasers for aggressive behavior in cave-dwelling Astyanax fasciatus (Teleostei, Characidae)

Epigean and blind cave-dwelling populations of the characid Astyanax fasciatus differ in their agonistic behavior. Epigean specimens are characterized by intense aggressive behavior and territoriality in the laboratory, whereas the blind cave fishes are rarely aggressive and have totally lost the territorial behavior. These behavioral changes are genetically based. In the present study, a comparative analysis of the optical releasers for aggressive behavior has been performed in both epigean and cave-dwelling populations. It was expected that the regression of aggressive behavior should be accompanied by the regression of the genetically fixed optical releasers for aggression in the cave specimens. For the analysis of cave fishes, well-eyed F1-hybrids of cave and epigean specimens (Pachon × Teapao) as well as phylogenetically young cave specimens (Micos) selected for large eyes, have been used. In epigean specimens, aggression is most intensely released by a combination of the signals 'natural shape' and 'locomotion'. The cave populations exhibit a partial regression of the releaser 'natural shape'. 'Locomotion', however, has become a more effective releaser for aggression in cave fishes than it has in their epigean relatives. The results are discussed with respect to their evolutionary significance.

Automatic cell segmentation in strongly agglomerated cell networks for different cell types

This paper presents a method of separating cells that are connected to each other forming clusters. The difference to many other publications covering similar topics is that the cell types we are dealing with form clusters of highly varying morphology. An advantage of our method is that it can be universally used for different cell types. The segmentation method is based on a growth simulation starting from the nuclei areas. To start the evaluation, the cells need to be made visible with a histological stain, in our case with the May-Grünwald solution. After the staining process has been completed, the nuclei areas can be distinguished from the other cell areas by a histogram backprojection algorithm. The presented method can, in addition to histological stained cells, also be applied to fluorescent-stained cells.

Sol-gel preparation of alumina stabilized rare earth areo- and xerogels and their use as oxidation catalysts

A new sol-gel synthesis route for rare earth (Ce and Pr) alumina hybrid aero- and xerogels is presented which is based on the so-called epoxide addition method. The resulting materials are characterized by TEM, XRD and nitrogen adsorption. The results reveal a different crystallization behavior for the praseodymia/alumina and the ceria/alumina gel. Whereas the first remains amorphous until 875°C, small ceria domains form already after preparation in the second case which grow with increasing calcination temperature. The use of the calcined gels as CO oxidation catalysts was studied in a quartz tube (lab) reactor and in a (slit) microreactor and compared to reference catalysts consisting of the pure rare earth oxides. The Ce/Al hybrid gels exhibit a good catalytic activity and a thermal stability against sintering which was superior to the investigated reference catalyst. In contrast, the Pr/Al hybrid gels show lower CO oxidation activity which, due to the formation of PrAlO3, decreased with increasing calcination temperature.

Pentacoordinate silicon(IV): cationic, anionic and neutral complexes derived from the reaction of NHC→SiCl4 with highly Lewis acidic (C2F5)2SiH2

Addition of NHC→SiCl4 to the highly Lewis acidic bis(pentafluoroethyl)silane ((C2F5)2SiH2) afforded the salt [(NHC)2SiCl2H][(C2F5)2SiCl3] with pentacoordinate silicon in the cation and the anion. The anion represents the first example of a chlorosilicate structurally characterized in the solid state. In this reaction, the long sought pentacoordinate NHC-adduct of silicochloroform was identified as an intermediate and its crystal structure is presented.

Self-diffusion of carbon dioxide in samaria/alumina aerogel catalyst using high field NMR diffusometry

Pulsed field gradient (PFG) NMR was used to investigate the self-diffusion of carbon dioxide in alumina stabilized samaria aerogel catalyst, a promising porous catalyst for gas-phase reactions featuring high porosity and high surface area. For diffusion studies, the catalyst was prepared in two sample packing types, macroscopic monoliths (i.e., macroscopic cylindrical particles) and powder beds with particle sizes around 200 μm that are considered for catalytic applications. Studies of diffusion in these samples revealed how macroscopic packing influences the catalyst transport properties. Application of a high magnetic field of 17.6 T in the reported PFG NMR studies enabled diffusion measurements for relatively low carbon dioxide densities in the catalyst samples corresponding to a gas loading pressure of around 0.1 atm. As a result, it was possible to perform diffusion measurements for a large range of carbon dioxide loading pressures between 0.1 and 10 atm. The measured carbon dioxide diffusivities in the beds of catalyst particles are interpreted in the context of a simple diffusion-mediated exchange model previously used for zeolites and other porous materials.

Expression of antimicrobial peptides and toll-like receptors is increased in tinea and pityriasis versicolor

In superficial tinea and pityriasis versicolor, the causative fungi are for the most part confined to the stratum corneum which is barely reached by leukocytes. Therefore, a role of non-cellular components in the epidermal antifungal defence was suggested. To investigate the presence of such factors in these infections, the expression of human beta defensins 2 and 3 (hBD-2, hBD-3), RNase 7, psoriasin, toll-like receptors 2, 4 and 9 (TLR2, TLR4 and TLR9) and dectin 2 was analysed by use of immunostainings in skin biopsies. We found that hBD2, hBD3, psoriasin, RNase7, TLR2 and TLR4 were significantly more often expressed in distinct layers of lesional epidermis as compared with uninfected epidermis. In both infections but not in normal skin, hBD2 and hBD3 were commonly expressed within the stratum corneum and in the stratum granulosum. Similarly, psoriasin was seen more often in the upper skin layers of both infections as compared with normal skin. No significant differences between normal and infected skin were found for the expression of TLR9 and dectin 2. Our findings clearly show the expression of specific antimicrobial proteins and defence-related ligands in superficial tinea as well as in pityriasis versicolor, suggesting that these factors contribute to fungal containment.

Short-acting P2Y12 blockade to reduce platelet dysfunction and coagulopathy during experimental extracorporeal circulation and hypothermia

BACKGROUND

Extracorporeal circulation (ECC) and hypothermia are routinely used in cardiac surgery to maintain stable circulatory parameters and to increase the ischaemic tolerance of the patient. However, ECC and hypothermia cause platelet activation and dysfunction possibly followed by a devastating coagulopathy. Stimulation of the adenosinediphosphate (ADP) receptor P(2)Y(12) plays a pivotal role in platelet activation. This experimental study tested P(2)Y(12) receptor blockade as an approach to protect platelets during ECC.

METHODS

Human blood was treated with the short-acting P(2)Y(12) blocker cangrelor (1 µM, t(1/2)<5 min) or the P(2)Y(12) inhibitor 2-MeSAMP (100 µM) and circulated in an ex vivo ECC model at normothermia (37°C) and hypothermia (28°C). Before and after circulation, markers of platelet activation and of coagulation (thrombin-antithrombin complex generation) were analysed. During hypothermic ECC in pigs, the effect of reversible P(2)Y(12) blockade on platelet function was evaluated by cangrelor infusion (0.075 µg kg(-1) min(-1)).

RESULTS

During ex vivo hypothermic ECC, P(2)Y(12) blockade inhibited platelet granule release (P<0.01), platelet-granulocyte binding (P<0.05), and platelet loss (P<0.001), whereas no effects on platelet-ECC binding, platelet CD42bα expression, glycoprotein IIb/IIIa activation, or thrombin-antithrombin complex generation were observed. During hypothermic ECC in pigs, cangrelor inhibited platelet-fibrinogen binding (P<0.05) and ADP-induced platelet aggregation (P<0.001). Platelet function was rapidly restored after termination of cangrelor infusion.

CONCLUSIONS

P(2)Y(12) blockade by cangrelor prevents platelet activation during ECC and hypothermia. Owing to its short half-life, platelet inhibition can be well controlled, thus potentially reducing bleeding complications. This novel pharmacological strategy has the potential to reduce complications associated with ECC and hypothermia.

Nucleoporin NUP153 guards genome integrity by promoting nuclear import of 53BP1

53BP1 is a mediator of DNA damage response (DDR) and a tumor suppressor whose accumulation on damaged chromatin promotes DNA repair and enhances DDR signaling. Using foci formation of 53BP1 as a readout in two human cell lines, we performed an siRNA-based functional high-content microscopy screen for modulators of cellular response to ionizing radiation (IR). Here, we provide the complete results of this screen as an information resource, and validate and functionally characterize one of the identified 'hits': a nuclear pore component NUP153 as a novel factor specifically required for 53BP1 nuclear import. Using a range of cell and molecular biology approaches including live-cell imaging, we show that knockdown of NUP153 prevents 53BP1, but not several other DDR factors, from entering the nuclei in the newly forming daughter cells. This translates into decreased IR-induced 53BP1 focus formation, delayed DNA repair and impaired cell survival after IR. In addition, NUP153 depletion exacerbates DNA damage caused by replication stress. Finally, we show that the C-terminal part of NUP153 is required for effective 53BP1 nuclear import, and that 53BP1 is imported to the nucleus through the NUP153-importin-β interplay. Our data define the structure-function relationships within this emerging 53BP1-NUP153/importin-β pathway and implicate this mechanism in the maintenance of genome integrity.

Veins are no arteries: even moderate arterial pressure induces significant adhesion molecule expression of vein grafts in an ex vivo circulation model

AIM

Coronary artery bypass grafting (CABG) is a standard procedure for treatment of coronary heart disease. Eighty percent of all CABGs are performed with venous grafts which then get exposed to an arterial pressure after surgery. This widely used procedure, however, is complicated by the development of alterations in the vein graft wall, leading to a decreased patency rate and graft failure. This study enlightens the influence of an even moderate arterial pressure on the gene expression of adhesion molecules in venous grafts which play a decisive role for the early induction of atherogenesis.

METHODS

Segments of porcine vena jugularis and arteria carotis were mounted in a simulated bypass circuit and subjected to pulsatile flow. Vessel segments were examined for adhesion molecule expression with quantitative real-time - polymerase chain reaction (qRT-PCR) and adherence of leukocytes was observed by confocal laser scanning microscopy and scanning electron microscopy.

RESULTS

Veins grafts subjected to an even moderate arterial pressure showed a 14-fold increase of ICAM-1 expression already after 4 hours. An arterial pressure of around 100/80 mmHg was enough to stimulate the adhesion molecule expression Furthermore it led to a 9-fold increase of leukocyte adhesion to the venous endothelium, but, in contrast this was not the case in arteries.

CONCLUSION

This study showed, that already 100 mmHg upregulates the expression of several adhesion molecules in pig veins followed by increased adhesion of leukocytes. Therefore, our data demonstrate the advantage of arteries for CABG, and that new therapeutic strategies are urgently necessary to protect vein grafts either physically or pharmacologically if arteries are not available for CABG.

Aptamer-based isolation and subsequent imaging of mesenchymal stem cells in ischemic myocard by magnetic resonance imaging

PURPOSE

Mesenchymal stem cells (MSC) seem to be a promising cell source for cellular cardiomyoplasty. We recently developed a new aptamer-based specific selection of MSC to provide "ready to transplant" cells directly after isolation. We evaluated MRI tracking of newly isolated and freshly transplanted MSC in the heart using one short ex vivo selection step combining specific aptamer-based isolation and labeling of the cells.

MATERIALS AND METHODS

Bone marrow (BM) was collected from healthy pigs. The animals were euthanized and the heart was placed in a perfusion model. During cold ischemia, immunomagnetic isolation of MSC from the BM by MSC-specific aptamers labeled with Dynabeads was performed within 2 h. For histological identification the cells were additionally stained with PKH26. Approx. 3 x 10(6) of the freshly aptamer-isolated cells were injected into the ramus interventricularis anterior (RIVA) and 5 x 10(5) cells were injected directly into myocardial tissue after damaging the respective area by freezing (cryo-scar). 3 x 10(6) of the aptamer-isolated cells were kept for further characterization (FACS and differentiation assays). 20 h after cell transplantation, MRI of the heart using a clinical 3.0 Tesla whole body scanner (Magnetom Trio, Siemens, Germany) was performed followed by histological examinations.

RESULTS

The average yield of sorted cells from 120 ml BM was 7 x 10(6) cells. The cells were cultured and showed MSC-like properties. MRI showed reproducible artifacts within the RIVA-perfusion area and the cryo-scar with surprisingly excellent quality. The histological examination of the biopsies showed PKH26-positive cells within the areas which were positive in the MRI in contrast to the control biopsies.

CONCLUSION

Immunomagnetic separation of MSC by specific aptamers linked to magnetic particles is feasible, effective and combines a specific separation and labeling technique to a "one stop shop" strategy.