Myelin Regeneration in Multiple Sclerosis: Targeting Endogenous Stem Cells

Regeneration of myelin sheaths (remyelination) after central nervous system demyelination is important to restore saltatory conduction and to prevent axonal loss. In multiple sclerosis, the insufficiency of remyelination leads to the irreversible degeneration of axons and correlated clinical decline. Therefore, a regenerative strategy to encourage remyelination may protect axons and improve symptoms in multiple sclerosis. We highlight recent studies on factors that influence endogenous remyelination and potential promising pharmacological targets that may be considered for enhancing central nervous system remyelination.     

Prevalence of Transfusion Transmitted Infections in Voluntary and Replacement Donors

The aim of the study was to find out the prevalence of transfusion transmitted infections (TTI) in voluntary and replacement donors. A total of 9599 donors were analysed for the prevalence of TTI over a period of 2 years.Of these 61.2% were voluntary donors and 38.8% were replacement donors. Prevalence of TTI in total donors was 0.6%. Prevalence of hepatitis B was highest (0.34%) followed by syphilis (0.11%), HIV&HCV (0.06%) and malaria (0.01%). Prevalence was more in male replacement donors. Extensive donor selection and screening procedures will help in improving the blood safety.     

5-HTT binding in recovered depressed patients and healthy volunteers: a positron emission tomography study with [11C]DASB

OBJECTIVE: The serotonin transporter (5-HTT) is a key target for selective serotonin reuptake inhibitors and may be involved in the pathophysiology of major depression. It is now possible to image 5-HTT directly in the human brain, but results from studies of acutely depressed patients have been inconsistent. The purpose of this study was to determine whether abnormalities in 5-HTT might be present in recovered depressed patients. METHOD: The authors measured the binding potential of 5-HTT using [11C]DASB in conjunction with positron emission tomography (PET) in 24 medication-free, recovered depressed male patients and 20 healthy male comparison subjects. The regional estimates of binding potential were obtained using a metabolite-corrected plasma input function method followed by Logan analysis, with the cerebellum as a reference region. RESULTS: The authors found no significant difference in the binding potential of [11C]DASB between the recovered depressed patients and healthy comparison subjects in any of the brain regions (amygdala, anterior cingulate cortex, caudate nucleus, frontal cortex, hippocampus, insula, thalamus, and dorsal raphe) studied. CONCLUSIONS: Men who recover from depression have normal availability of 5-HTT in brain regions thought to be involved in the pathophysiology of depression. The findings therefore do not support the proposal that recurrent depression is associated with long-standing deficits in 5-HTT.     

Osteopontin is extensively expressed by macrophages following CNS demyelination but has a redundant role in remyelination

Osteopontin (OPN) is a key immunoregulator in the autoimmune-mediated demyelinating disease multiple sclerosis. OPN may also play a role in the remyelination since it is 1) a ligand for αV integrins, several of which regulate the properties of the oligodendrocyte precursor cells (OPCs) primarily responsible for remyelination, and 2) enhances myelin membrane formation in OPC lines. Here we show that OPN is expressed at high levels during remyelination of toxin-induced demyelination. The increased expression is due to mRNA expression in macrophages and follows differences in macrophage responses to demyelination in young and old adult animals. To identify the role of OPN in remyelination focal demyelination was induced in wild-type and OPN^−/− mice. There was no difference in the rate of remyelination between the two groups indicating that OPN is not a critical component of remyelination.     

Correlating hypoxia with insulin secretion using a fluorescent hypoxia detection system

A common obstacle to the survival of encapsulated tissue is oxygen insufficiency. This appears particularly true of encapsulated pancreatic β-cells. Our work investigates a fluorescent hypoxia detection system for early recognition of hypoxic stress in encapsulated pancreatic tissue. Murine insulinoma (MIN6) cells were engineered to produce a red fluorescent protein under the control of hypoxia-inducible-factor-1. Aggregates of these cells were encapsulated in poly(ethylene glycol) hydrogels at densities of 200,000, 600,000, and 1 million cells per capsule then incubated in either a 1% or 20% oxygen environment. Cell function was evaluated by daily measurement of glucose-stimulated insulin secretion. Encapsulated cells were also fluorescently imaged periodically over 72 h for expression of the marker signal. Results indicate that oxygen insufficiency severely impacts insulin release from MIN6 cells, and that large aggregates are especially vulnerable to oxygen limitations. Our marker was found to be successfully indicative of hypoxia and could be used as a predictor of subsequent insulin release. Further work will be required to fully characterize signal dynamics and to evaluate in vivo efficacy. The method presented here represents a unique and valuable approach to detecting hypoxic stress in living tissues which may prove useful to a variety of fields of biological research.     

Uptake, efficacy, and systemic distribution of naked, inhaled short interfering RNA (siRNA) and locked nucleic acid (LNA) antisense

Antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) promise specific correction of disease-causing gene expression. Therapeutic implementation, however, has been forestalled by poor delivery to the appropriate tissue, cell type, and subcellular compartment. Topical administration is considered to circumvent these issues. The availability of inhalation devices and unmet medical need in lung disease has focused efforts in this tissue. We report the development of a novel cell sorting method for quantitative, cell type-specific analysis of siRNA, and locked nucleic acid (LNA) ASO uptake and efficacy after intratracheal (i.t.) administration in mice. Through fluorescent dye labeling, we compare the utility of this approach to whole animal and whole tissue analysis, and examine the extent of tissue distribution. We detail rapid systemic access and renal clearance for both therapeutic classes and lack of efficacy at the protein level in lung macrophages, epithelia, or other cell types. We nevertheless observe efficient redirection of i.t. administered phosphorothioate (PS) LNA ASO to the liver and kidney leading to targeted gene knockdown. These data suggest delivery remains a key obstacle to topically administered, naked oligonucleotide efficacy in the lung and introduce inhalation as a potentially viable alternative to injection for antisense administration to the liver and kidneys.     

Chemistry for the analysis of protein–protein interactions: Rapid and efficient cross-linking triggered by long wavelength light

Chemical cross-linking is a potentially useful technique for probing the architecture of multiprotein complexes. However, analyses using typical bifunctional cross-linkers often suffer from poor yields, and large-scale modification of nucleophilic side chains can result in artifactual results attributable to structural destabilization. We report here the de novo design and development of a type of protein cross-linking reaction that uses a photogenerated oxidant to mediate rapid and efficient cross-linking of associated proteins. The process involves brief photolysis of tris-bipyridylruthenium(II) dication with visible light in the presence of the electron acceptor ammonium persulfate and the proteins of interest. Very high yields of cross-linked products can be obtained with irradiation times of <1 second. This chemistry obviates many of the problems associated with standard cross-linking reagents.