Neuroprotective Effects of Glial Cell Line-Derived Neurotrophic Factor Mediated by an Adeno-Associated Virus Vector in a Transgenic Animal Model of Amyotrophic Lateral Sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive lethal disease that involves selective annihilation of motoneurons. Glial cell line-derived neurotrophic factor (GDNF) is proposed to be a promising therapeutic agent for ALS and other motor neuron diseases. Because adeno-associated virus (AAV) has been developed as an attractive gene delivery system with proven safety, we explored the therapeutic efficacy of intramuscular delivery of the GDNF gene mediated by an AAV vector (AAV-GDNF) in the G93A mouse model of ALS. We show here that AAV-GDNF leads to substantial and long-lasting expression of transgenic GDNF in a large number of myofibers with its accumulation at the sites of neuromuscular junctions. Detection of GDNF labeled with FLAG in the anterior horn neurons, but not beta-galactosidase expressed as a control, indicates that most of the transgenic GDNF observed there is retrogradely transported GDNF protein from the transduced muscles. This transgenic GDNF prevents motoneurons from their degeneration, preserves their axons innervating the muscle, and inhibits the treated-muscle atrophy. Furthermore, four-limb injection of AAV-GDNF postpones the disease onset, delays the progression of the motor dysfunction, and prolongs the life span in the treated ALS mice. Our finding thus indicates that AAV-mediated GDNF delivery to the muscle is a promising means of gene therapy for ALS.

Antiapoptotic activity maintenance of Brain Derived Neurotrophic Factor and the C fragment of the tetanus toxin genetic fusion protein

“…At present, treatment for ALS is mainly palliative [1], although the administration of neurotrophic growth factors as a means to protect motorneurons is being analysed [2]. In vitro studies demonstrated that several neurotrophic factors delay motorneuron degeneration [3][4][5][6]. However, clinical trials using subcutaneous and intrathecal neurotrophic factors caused several side effects such as weight loss, fever, cough, fatigue and behavioural changes [7][8][9][10][11][12].…”

Glycinergic and GABAergic Synaptic Activity Differentially Regulate Motoneuron Survival and Skeletal Muscle Innervation

“…During embryonic development, approximately half of the motoneurons generated undergo programmed cell death (PCD) (Oppenheim, 1991). Motoneuron survival and differentiation depend on trophic factors secreted from target muscle fibers and Schwann cells surrounding motor axons (Bordet et al, 2001;Acsadi et al, 2002;Wang et al, 2002;Lu et al, 2003). Reductions in skeletal muscle activity improve the access of a motoneuron to target-derived trophic factors by increasing the extent to which motor axons branch and form neuromuscular synapses (Oppenheim et al, 2000b;Millecamps et al, 2001Millecamps et al, , 2002.…”

Current developments in gene therapy for amyotrophic lateral sclerosis

“…A number of neurotrophic factors have been proposed as being a promising avenue for gene therapy in light of their beneficial effects on animal models of ALS. Among the factors which have shown promise in facilitating neuroprotection in animal models are vascular endothelial growth factor (VEGF) [81][82][83][84], hepatocyte growth factor (HGF) [85], glial-derived neurotrophic factor (GDNF) [84,86,87], insulin-like growth factor 1 (IGF-1) [88][89][90] and granulocyte-colony stimulating factor (G-CSF) [91,92]. The delivery of these neurotrophic factors can be carried out by using different approaches, with emerging viral vector-based and cell-based therapies among some of the most promising techniques.…”

“…Engineering AAV viruses to drive neurotrophic factor expression has been successfully tested in ALS mouse models. In the early 2000s it was reported that the intramuscular delivery of GDNF or IGF-1 to SOD1-G93A mice delayed the disease onset, improving behavioural tasks and prolonging lifespan [87,90]. Vascular endothelial growth factor (VEGF) is another promising candidate which has been used as a therapeutic tool in ALS.…”