Significant correction of pathology in brains of twitcher mice following injection of genetically modified mouse neural progenitor cells.

Krabbe disease or globoid cell leukodystrophy is an autosomal recessive disorder resulting from mutations in the galactocerebrosidase (GALC) gene. These mutations lead to deficient GALC activity, storage of substrates of the enzyme, including psychosine, death to oligodendrocytes, decreased myelination, production of globoid cells and eventually death to the individual. While most affected individuals are infants, late-onset forms are also recognized. In addition to human patients, several animal models have been well characterized, including the twitcher mouse. A spontaneously transformed progenitor cell line was isolated from an astrocyte-enriched fraction of normal mice, partially characterized and transduced with a retrovirus-containing mouse GALC cDNA to produce increased GALC activity (20-30-fold above baseline). These cells, called MAR-52, were injected into the brains of newborn affected twitcher mice. While there was only a modest increase in lifespan and body weight, there was clear evidence for the correction of the astrocytic gliosis, normal appearing oligodendrocytes and evidence for remyelination. We demonstrate that the exogenously supplied neural progenitor cells can donate GALC enzyme to oligodendrocytes in the brains of affected mice resulting in normal myelination in the area of donor cells. At this time, hematopoietic stem cell transplantation provides the best outcome in affected mice and is the only treatment available for human patients, but it does not result in a cure even when performed in asymptomatic newborns. Complete correction probably will require a combined approach to effectively treat patients with Krabbe disease. With developments in the isolation and characterization of stem cells, this approach may improve the outcome for individuals diagnosed in the future.