TRANSPLANT STUDIES IN GLOBOID CELL LEUKODYSTROPHY

Lysosomal storage diseases are associated with significant morbidity and
mortality in affected patients. Transplantation of normal bone marrow
cells in these conditions may provide long-term enzyme replacement and lead
to attenuation or reversal of organ system deterioration attributable to
accumulated substrate. Preclinical studies of bone marrow transplantation
(BMT) in storage diseases have hitherto been precluded by the lack of
appropriate animal models. The twitcher mouse is a recently-described
model of human globoid cell leukodystrophy (Krabbe disease;
galactosylceramidase deficiency), a sphingolipidosis. Initial studies have
shown that hematopoietic cell transplantation (HCT) from enzymatically
normal congenic mice into 10-day-old twitcher mice is associated with
prolonged survival and some remyelination in peripheral nerves. The
proposed comprehensive studies will further examine the clinical,
histopathological, neurochemical, and neurophysiological effects of HCT in
twitcher mice. The survival and clinical course of groups of twitcher mice
that receive HCT at various ages (2, 5, 7, or 10 days) will be compared
with those of untreated twitchers. The activity of galactosylceramidase
will be determined in brain, nerve, liver, kidney, spleen, spinal cord and
plasma of untreated twitchers, normal littermates, and HCT-treated twitcher
mice at selected times after HCT to determine the temporal course and
extent of enzyme replacement. Levels of substrate (galactosylceramide and
psychosine) will be analyzed in tissues and plasma after HCT.
Histopathological and ultrastructural alterations in brain, spinal cord,
and sciatic nerves in untreated and HCT-treated twitcher mice will be
assessed by light and electron microscopy. The effects of HCT on the
neurophysiologic status of twitcher mice will be studied by serial
nerve-conduction measurements, using standard neurometric techniques, and
compared with similar studies in untreated twitchers and normal
littermates. The effects of injection of Sindbis virus, which erturbs the
blood-brain barrier (BBB) by production of intense CNS inflammation, will
be evaluated in untreated and HCT-treated twitcher mice; their clinical,
biochemical, and neurometric status will be compared to those with mice
that do not receive BBB disruption. The information thus obtained with HCT
in a prototypic animal model of human sphingolipidosis is applicable to
strategies for clinical enzyme replacement therapy, whether by cellular
allotransplantation or gene insertion, in human lysosomal storage diseases.