Inspiratory muscle conditioning exercise and diaphragm gene therapy in Pompe disease: Clinical evidence of respiratory plasticity
Pompe disease is an inherited disorder due to a mutation in the gene that encodes acid α-glucosidase (GAA). Children with infantile-onset Pompe disease develop progressive hypotonic weakness and cardiopulmonary insufficiency that may eventually require mechanical ventilation (MV). Our team conducted a first in human trial of diaphragmatic gene therapy (AAV1-CMV-GAA) to treat respiratory neural dysfunction in infantile-onset Pompe. Subjects (aged 2-15years, full-time MV: n=5, partial/no MV: n=4) underwent a period of preoperative inspiratory muscle conditioning exercise. The change in respiratory function after exercise alone was compared to the change in function after intramuscular delivery of AAV1-CMV-GAA to the diaphragm with continued exercise. Since AAV-mediated gene therapy can reach phrenic motoneurons via retrograde transduction, we hypothesized that AAV1-CMV-GAA would improve dynamic respiratory motor function to a greater degree than exercise alone. Dependent measures were maximal inspiratory pressure (MIP), respiratory responses to inspiratory threshold loads (load compensation: LC), and physical evidence of diaphragm activity (descent on MRI, EMG activity). Exercise alone did not change function. After AAV1-CMV-GAA, MIP was unchanged. Flow and volume LC responses increased after dosing (p<0.05 to p<0.005), but only in the subjects with partial/no MV use. Changes in LC tended to occur on or after 180days. At Day 180, the four subjects with MRI evidence of diaphragm descent had greater maximal voluntary ventilation (p<0.05) and tended to be younger, stronger, and use fewer hours of daily MV. In conclusion, combined AAV1-CMV-GAA and exercise training conferred benefits to dynamic motor function of the diaphragm. Children with a higher baseline neuromuscular function may have greater potential for functional gains.
Smith, B. K.,
Martin, A. D.,
Lawson, L. A.,
Collins, S. W.,
Byrne, B. J.
(2017). Inspiratory muscle conditioning exercise and diaphragm gene therapy in Pompe disease: Clinical evidence of respiratory plasticity. Experimental Neurology, 287(Pt 2), 216-224.
Available at: https://ecommons.aku.edu/pakistan_fhs_mc_surg_paediatr/103