Thermosensitive, near-infrared-labeled nanoparticles for topotecan delivery to tumors.

Liposomal nanoparticles have proven to be versatile systems for drug delivery. However, the progress in clinic has been slower and less efficient than expected. This suggests a need for further development using carefully designed chemical components to improve usefulness under clinical conditions and maximize therapeutic effect. For cancer chemotherapy, PEGylated liposomes were the first nanomedicine to reach the market and have been used clinically for several years. Approaches toward targeted drug delivery using next generation "thermally triggered" nanoparticles are now in clinical trials. However, clinically tested thermosensitive liposomes (TSLs) lack the markers that allow tumor labeling and improved imaging for tissue specific applied hyperthermia. Here we describe the development of optically labeled TSLs for image guidance drug delivery and proof-of-concept results for their application in the treatment of murine xenograft tumors using the anticancer drug topotecan. These labeled TSLs also allow the simultaneous, real-time diagnostic imaging of nanoparticle biodistribution using a near-infrared (NIR; 750-950 nm) fluorophore coupled to a lipidic component of the lipid bilayer. When combined with multispectral fluorescence analysis, this allows for specific and high sensitivity tracking of the nanoparticles in vivo. The application of NIR fluorescence-labeled TSLs could have a transformative effect on future cancer chemotherapy.

Peripheral facial nerve axotomy in mice causes sprouting of motor axons into perineuronal central white matter: time course and molecular characterization.

Generation of new axonal sprouts plays an important role in neural repair. In the current study, we examined the appearance, composition and effects of gene deletions on intrabrainstem sprouts following peripheral facial nerve axotomy. Axotomy was followed by the appearance of galanin(+) and calcitonin gene-related peptide (CGRP)(+) sprouts peaking at day 14, matching both large, neuropeptide(+) subpopulations of axotomized facial motoneurons, but with CGRP(+) sprouts considerably rarer. Strong immunoreactivity for vesicular acetylcholine transporter (VAChT) and retrogradely transported MiniRuby following its application on freshly cut proximal facial nerve stump confirmed their axotomized motoneuron origin; the sprouts expressed CD44 and alpha7beta1 integrin adhesion molecules and grew apparently unhindered along neighboring central white matter tracts. Quantification of the galanin(+) sprouts revealed a stronger response following cut compared with crush (day 7-14) as well as enhanced sprouting after recut (day 8 + 6 vs. 14; 14 + 8 vs. 22), arguing against delayed appearance of sprouting being the result of the initial phase of reinnervation. Sprouting was strongly diminished in brain Jun-deficient mice but enhanced in alpha7 null animals that showed apparently compensatory up-regulation in beta1, suggesting important regulatory roles for transcription factors and the sprout-associated adhesion molecules. Analysis of inflammatory stimuli revealed a 50% reduction 12-48 hours following systemic endotoxin associated with neural inflammation and a tendency toward more sprouts in TNFR1/2 null mutants (P = 10%) with a reduced inflammatory response, indicating detrimental effects of excessive inflammation. Moreover, the study points to the usefulness of the facial axotomy model in exploring physiological and molecular stimuli regulating central sprouting.

DNA instability in postmitotic neurons.

Huntington's disease (HD) is caused by a CAG repeat expansion that is unstable upon germ-line transmission and exhibits mosaicism in somatic tissues. We show that region-specific CAG repeat mosaicism profiles are conserved between several mouse models of HD and therefore develop in a predetermined manner. Furthermore, we demonstrate that these synchronous, radical changes in CAG repeat size occur in terminally differentiated neurons. In HD this ongoing mutation of the repeat continuously generates genetically distinct neuronal populations in the adult brain of mouse models and HD patients. The neuronal population of the striatum is particularly distinguished by a high rate of CAG repeat allele instability and expression driving the repeat upwards and would be expected to enhance its toxicity. In both mice and humans, neurons are distinguished from nonneuronal cells by expression of MSH3, which provides a permissive environment for genetic instability independent of pathology. The neuronal mutations described here accumulate to generate genetically discrete populations of cells in the absence of selection. This is in contrast to the traditional view in which genetically discrete cellular populations are generated by the sequence of random variation, selection, and clonal proliferation. We are unaware of any previous demonstration that mutations can occur in terminally differentiated neurons and provide a proof of principle that, dependent on a specific set of conditions, functional DNA polymorphisms can be produced in adult neurons.

Mouse models of triplet repeat diseases.

Triplet repeat expansions were first discovered in 1991 and since then have been found to be the mutation underlying a range of neurodegenerative, neuromuscular, and cognitive disorders including fragile X syndrome, myotonic dystrophy, Friedreich's ataxia, and the polyglutamine disorders that include Huntington's disease. The repeats exert their detrimental effects through different molecular mechanisms dependent on whether they are located in coding or noncoding regions of the gene in question. During the past 10 yr, a wide range of strategies have been used to successfully establish mouse models for all of these disorders. This review presents an overview of these mouse models, discusses the insights into the molecular pathogenesis of these disorders that have been gained from their analysis and the strategies that are being used to uncover novel therapeutic options.