Abstract
BackgroundMutation in the ubiquitously expressed cytoplasmic superoxide dismutase (SOD1) causes an inherited form of Amyotrophic Lateral Sclerosis (ALS). Mutant synthesis in motor neurons drives disease onset and early disease progression. Previous experimental studies have shown that spinal grafting of human fetal spinal neural stem cells (hNSCs) into the lumbar spinal cord of SOD1G93A rats leads to a moderate therapeutical effect as evidenced by local α-motoneuron sparing and extension of lifespan. The aim of the present study was to analyze the degree of therapeutical effect of hNSCs once grafted into the lumbar spinal ventral horn in presymptomatic immunosuppressed SOD1G93A rats and to assess the presence and functional integrity of the descending motor system in symptomatic SOD1G93A animals.Methods/Principal FindingsPresymptomatic SOD1G93A rats (60–65 days old) received spinal lumbar injections of hNSCs. After cell grafting, disease onset, disease progression and lifespan were analyzed. In separate symptomatic SOD1G93A rats, the presence and functional conductivity of descending motor tracts (corticospinal and rubrospinal) was analyzed by spinal surface recording electrodes after electrical stimulation of the motor cortex. Silver impregnation of lumbar spinal cord sections and descending motor axon counting in plastic spinal cord sections were used to validate morphologically the integrity of descending motor tracts. Grafting of hNSCs into the lumbar spinal cord of SOD1G93A rats protected α-motoneurons in the vicinity of grafted cells, provided transient functional improvement, but offered no protection to α-motoneuron pools distant from grafted lumbar segments. Analysis of motor-evoked potentials recorded from the thoracic spinal cord of symptomatic SOD1G93A rats showed a near complete loss of descending motor tract conduction, corresponding to a significant (50–65%) loss of large caliber descending motor axons.Conclusions/SignificanceThese data demonstrate that in order to achieve a more clinically-adequate treatment, cell-replacement/gene therapy strategies will likely require both spinal and supraspinal targets.
Highlights
Amyotrophic lateral sclerosis (ALS), known as Lou Gehrig’s disease, is characterized by the progressive development of motor dysfunction, a-motoneuron degeneration and death, in turn producing progressive fatal paralysis
Grafted human fetal spinal neural stem cells show long term survival, develop neuronal morophologies and form synapses with host amotoneurons Twenty-four, SOD1G93A rats (12 male, 12 female; 60–65 days old) received 10 bilateral injections of hNSCs targeted into ventral horn of L2–L5 spinal segments (Fig. 1A, B)
The pattern of engraftment identified by antibodies selective for human neuron-specific enolase (Fig. 1D) or doublecortin (DCX; Fig. 1E), an early postmitotic neuronal marker, closely matched that seen with hNUMA
Summary
Amyotrophic lateral sclerosis (ALS), known as Lou Gehrig’s disease, is characterized by the progressive development of motor dysfunction, a-motoneuron degeneration and death, in turn producing progressive fatal paralysis. The role of non-motor neurons in the evolution of a-motoneuron degeneration in ALS was initially validated by analysis of chimeric mouse models that were mixtures of normal and mutant SOD1 expressing cells. Those studies revealed that normal motor neurons within an ALS-causing mutant cell environment develop diseaserelated damage [6]. The aim of the present study was to analyze the degree of therapeutical effect of hNSCs once grafted into the lumbar spinal ventral horn in presymptomatic immunosuppressed SOD1G93A rats and to assess the presence and functional integrity of the descending motor system in symptomatic SOD1G93A animals
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