Isolation, Maintenance and Expansion of Adult Hematopoietic Stem/Progenitor Cells and Leukemic Stem Cells.

Hematopoietic stem cells (HSCs) are rare, self-renewing cells that perch on top of the hematopoietic tree. The HSCs ensure the constant supply of mature blood cells in a tightly regulated process producing peripheral blood cells. Intense efforts are ongoing to optimize HSC engraftment as therapeutic strategy to treat patients suffering from hematopoietic diseases. Preclinical research paves the way by developing methods to maintain, manipulate and expand HSCs ex vivo to understand their regulation and molecular make-up. The generation of a sufficient number of transplantable HSCs is the Holy Grail for clinical therapy. Leukemia stem cells (LSCs) are characterized by their acquired stem cell characteristics and are responsible for disease initiation, progression, and relapse. We summarize efforts, that have been undertaken to increase the number of long-term (LT)-HSCs and to prevent differentiation towards committed progenitors in ex vivo culture. We provide an overview and compare methods currently available to isolate, maintain and enrich HSC subsets, progenitors and LSCs and discuss their individual advantages and drawbacks.

A robust approach for the generation of functional hematopoietic progenitor cell lines to model leukemic transformation.

Studies of molecular mechanisms of hematopoiesis and leukemogenesis are hampered by the unavailability of progenitor cell lines that accurately mimic the situation in vivo. We now report a robust method to generate and maintain LSK (Lin-, Sca-1+, c-Kit+) cells, which closely resemble MPP1 cells. HPCLSKs reconstitute hematopoiesis in lethally irradiated recipient mice over >8 months. Upon transformation with different oncogenes including BCR/ABL, FLT3-ITD, or MLL-AF9, their leukemic counterparts maintain stem cell properties in vitro and recapitulate leukemia formation in vivo. The method to generate HPCLSKs can be applied to transgenic mice, and we illustrate it for CDK6-deficient animals. Upon BCR/ABLp210 transformation, HPCLSKsCdk6-/- induce disease with a significantly enhanced latency and reduced incidence, showing the importance of CDK6 in leukemia formation. Studies of the CDK6 transcriptome in murine HPCLSK and human BCR/ABL+ cells have verified that certain pathways depend on CDK6 and have uncovered a novel CDK6-dependent signature, suggesting a role for CDK6 in leukemic progenitor cell homing. Loss of CDK6 may thus lead to a defect in homing. The HPCLSK system represents a unique tool for combined in vitro and in vivo studies and enables the production of large quantities of genetically modifiable hematopoietic or leukemic stem/progenitor cells.

Intact sensory-motor network structure and function in far from onset premanifest Huntington's disease.

Structural and functional changes attributable to the neurodegenerative process in Huntington's disease (HD) may be evident in HTT CAG repeat expansion carriers before the clinical manifestations of HD. It remains unclear, though, how far from motor onset a consistent signature of the neurodegenerative process in HD can be detected. Twelve far from onset preHD and 22 age-matched healthy control participants underwent volumetric structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and resting-state functional MRI (11 preHD, 22 controls) as well as electrophysiological measurements (12 preHD, 13 controls). There were no significant differences in white matter macro- and microstructure between far from onset preHD participants and controls. Functional connectivity in a basal ganglia-thalamic and motor networks, all measures of the motor efferent and sensory afferent pathways as well as sensory-motor integration were also similar in far from onset preHD and controls. With the methods used in far from onset preHD sensory-motor neural macro- or micro-structure and brain function were similar to healthy controls. This suggests that any observable structural and functional change in preHD nearer to onset, or in manifest HD, at least using comparable techniques such as in this study, most likely reflects an ongoing neurodegenerative process.

Neurophysiology in Huntington's disease: an update.

Huntington's disease (HD) is a hereditary movement disorder with dementia and behavioral difficulties caused by a mutation in the HTT gene. Age-at-onset, clinical phenotype and disease evolution vary and are not explained by the mutation alone. Electrophysiological techniques, like transcranial magnetic stimulation and electroencephalography, have advanced our understanding of the pathophysiology but have not revealed any consistent abnormalities suitable as biomarkers. The most promising candidate may be somatosensory or visual evoked potentials, which repeatedly had reduced amplitudes in manifest HD. To test their potential, large cohorts of clinically homogeneous patients need to be studied with electrophysiological in conjunction with neuroimaging techniques to delineate neural network function in relation to micro- and macro-structural brain changes.