Intralingual Administration of AAVrh10-miR^SOD1 Improves Respiratory But Not Swallowing Function in a Superoxide Dismutase-1 Mouse Model of Amyotrophic Lateral Sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal disease characterized by degeneration of motor neurons and muscles, and death is usually a result of impaired respiratory function due to loss of motor neurons that control upper airway muscles and/or the diaphragm. Currently, no cure for ALS exists and treatments to date do not significantly improve respiratory or swallowing function. One cause of ALS is a mutation in the superoxide dismutase-1 (SOD1) gene; thus, reducing expression of the mutated gene may slow the progression of the disease. Our group has been studying the SOD1 G93A transgenic mouse model of ALS that develops progressive respiratory deficits and dysphagia. We hypothesize that solely treating the tongue in SOD1 mice will preserve respiratory and swallowing function, and it will prolong survival. At 6 weeks of age, 11 SOD1 G93A mice (both sexes) received a single intralingual injection of gene therapy (AAVrh10-miR SOD1). Another 29 mice (both sexes) were divided into two control groups: (1) 12 SOD1 G93A mice that received a single intralingual vehicle injection (saline); and (2) 17 non-transgenic littermates. Starting at 13 weeks of age, plethysmography (respiratory parameters) at baseline and in response to hypoxia (11% O 2) + hypercapnia (7% CO 2) were recorded and videofluoroscopic swallow study testing were performed twice monthly until end-stage disease. Minute ventilation during hypoxia + hypercapnia and mean inspiratory flow at baseline were significantly reduced (p < 0.05) in vehicle-injected, but not AAVrh10-miR SOD1-injected SOD1 G93A mice as compared with wild-type mice. In contrast, swallowing function was unchanged by AAVrh10-miR SOD1 treatment (p > 0.05). AAVrh10-miR SOD1 injections also significantly extended survival in females by *1 week. In conclusion, this study indicates that intralingual AAVrh10-miR SOD1 treatment preserved respiratory (but not swallowing) function potentially via increasing upper airway patency, and it is worthy of further exploration as a possible therapy to preserve respiratory capacity in ALS patients.

Gene delivery to the hypoglossal motor system: preclinical studies and translational potential

“…These treatments represent strategies to help improve or compensate for lingual motor dysfunction, but they do not address the underlying pathology. In this regard, gene therapy may represent a novel therapeutic option, but there has been limited work on this topic [32]. Obstructive sleep apnea (OSA) is present in 10% of the population and lingual mechanisms figure prominently in the etiology.…”

“…Intralingual vector delivery effectively drives gene and protein expression in the tongue [32,[45][46][47] and can reverse tongue muscle histopathology in neuromuscular disease [45][46][47]. Pompe disease is a neuromuscular disorder associated with mutations in a single gene (acid alpha glucosidase or GAA), macroglossia, dysphagia, and dysarthria [48].…”

“…Intralingual AAV therapy also shows promise in treating amyotrophic lateral sclerosis (ALS). In the SOD1 G93A mouse model of ALS, a single intralingual treatment with AAV driving expression of microRNA targeting the superoxide dismutase 1 (SOD1) gene (AAVrh10-H1-miR SOD1 ) dramatically reduced SOD1 mRNA expression in the tongue, and caused a small (~1 wk) but statistically significant increase in lifespan in females [ 32 ]. The lingual treatment also improved aspects of breathing function but did not impact swallow as studied using videofluoroscopy.…”

Laying the Foundation for Neuromuscular Disease Gene Therapy

“…Despite the lack of improvement in swallowing, respiration was significantly enhanced. 5 These results suggest that intralingual injection may be used to supplement systemic injection. Concomitant local and systemic therapy will likely maximize therapeutic benefits.…”

“…Nicole Nichols and colleagues hypothesized that intralingual injection can lead to mutant SOD1 silencing in the tongue and, through retrograde transport, in the hypoglossal motor neurons in the medulla. 5 This is expected to improve ventilation and swallowing. The authors detected abundant AAV in the tongue but not the medulla.…”