Characterization of Respiratory Phenotype in Very Long-chain Acyl-CoA Dehydrogenase Deficient Mice.

Rationale: Very Long-chain Acyl-CoA dehydrogenase (VLCAD) deficiency the most common inherited long-chain fatty acid disorder. The VLCAD enzyme catalyzes the first step of mitochondrial fatty acid oxidation and loss of the enzyme results in energy deficiency as well as accumulation of long chain fatty acids. Recently, a related enzyme, Long-chain Acyl-CoA dehydrogensase (LCAD), which unlike VLCAD is not highly expressed in metabolic tissues like liver, heart and skeletal muscle, was found to be expressed in the lung and surfactant and lung dysfunction were observed in LCAD deficient mice. Respiratory distress syndrome has been described in other fatty acid oxidation disorders. VLCAD is expressed in lung, and likely plays an important role in lung compliance. Methods: VLCAD deficient mice and litter-mate controls were fasted for 18 hours, then exercised on a treadmill for 2 hours. Breathing was immediately assessed using whole body plethysmography in unanaesthetized spontaneously breathing mice. After a stable baseline was achieved, mice were given a “respiratory” challenge with 7% hypercapnia. In a subgroup of animals, pulmonary mechanics were assessed using Flexivent (Scireq). Results: Following exercise, VLCAD deficient mice had a decreased tidal volume and minute ventilation compared to their wild type controls. However, post-exercise VLCAD deficient mice were able to stabilize to similar levels as wild-type during baseline. The VLCAD deficient mice had a decreased response to a respiratory challenge with 7% hypercapnia. Early preliminary results suggest that VLCAD deficient animals have lower airway resistance. Conclusions: Respiratory insufficiency was demonstrated in a fasted and exercise challenged VLCAD deficient mice

Gene Therapy 2017: Progress and Future Directions

Introduction: Gene therapy has changed dramatically in the 28 years since the first human gene transfer experiment in 1989. Alipogene tiparvovec, GlyberaR®, a recombinant adeno-associated virus (rAAV) product for lipoprotein lipase deficiency, and Strimvelis®, a lentivirus vector for severe combined immune deficiency are approved in Europe. An rAAV2 product for a congenital form of blindness is currently under review in the United States, likely to be followed by numerous other gene therapies

Airway smooth muscle pathology in Pompe Disease

Pompe disease is a rare autosomal recessive disease which results from a deficiency of acid α-glucosidase (GAA) - an enzyme that degrades lysosomal glycogen. Patients with Pompe disease develop intra-lysosomal accumulation of glycogen in multiple tissues including skeletal muscle, CNS and smooth muscle. Pulmonary dysfunction is a hallmark of Pompe disease and has classically been attributed to muscle weakness and CNS neuropathology. However, the potential role of respiratory smooth muscles in the respiratory pathology is unknown. Therefore we postulated that GAA deficiency results in airway smooth muscle glycogen accumulation that leads to airway smooth muscle dysfunction. Using the Pompe mouse model, the Gaa-/- mouse, we examined the airway smooth muscle structure and function. We used in vivo forced oscillometry measurements (N=7WT, N=7 Gaa-/-) to examine pulmonary physiology and administered methacholine challenges to assess in vivo airway resistance. Also, we used ex-vivo contraction testing (N=6WT, N=5 Gaa-/-) to determine bronchi contractility. In response to the highest dose methacholine challenge (100mg/ml), there was a significant decrease in conducting airway resistance in Gaa-/- versus WT mice (p=0.007). Also, ex vivo bronchi contraction testing demonstrated a significantly weaker response to potassium chloride (p=0.008) and methacholine (2-way ANOVA p=0.005) in Pompe mice compared to WT mice, suggesting impaired smooth muscle contraction. Furtherly, we performed PAS staining on fresh-frozen tissue to examine the degree of glycogen accumulation as a result of GAA deficiency. PAS staining revealed robust glycogen accumulation in the trachea and bronchi of Pompe mice and a disruption of the airway smooth muscle architecture. In conclusion, GAA deficiency results in glycogen accumulation and a disruption of the architecture in the airway smooth muscles of Gaa-/- mice. Furthermore, both in vivo and ex vivo tests reveal that Gaa-/- murine airways have impaired function as evidenced by decreased contractility and a decreased response to methacholine

Intralingual and Intrapleural AAV Gene Therapy Prolongs Survival in a SOD1 ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that results in death from respiratory failure. No cure exists for this devastating disease, but therapy that directly targets the respiratory system has the potential to prolong survival and improve quality of life in some cases of ALS. The objective of this study was to enhance breathing and prolong survival by suppressing superoxide dismutase 1 (SOD1) expression in respiratory motor neurons using adeno-associated virus (AAV) expressing an artificial microRNA targeting the SOD1 gene. AAV-miR(SOD1) was injected in the tongue and intrapleural space of SOD1(G93A) mice, and repetitive respiratory and behavioral measurements were performed until the end stage. Robust silencing of SOD1 was observed in the diaphragm and tongue as well as systemically. Silencing of SOD1 prolonged survival by approximately 50 days, and it delayed weight loss and limb weakness in treated animals compared to untreated controls. Histologically, there was preservation of the neuromuscular junctions in the diaphragm as well as the number of axons in the phrenic and hypoglossal nerves. Although SOD1 suppression improved breathing and prolonged survival, it did not ameliorate the restrictive lung phenotype. Suppression of SOD1 expression in motor neurons that underlie respiratory function prolongs survival and enhances breathing until the end stage in SOD1(G93A) ALS mice

Hypoglossal Neuropathology and Respiratory Activity in Pompe Mice

Pompe disease is a lysosomal storage disorder associated with systemic deficiency of acid α-glucosidase (GAA). Respiratory-related problems in Pompe disease include hypoventilation and upper airway dysfunction. Although these problems have generally been attributed to muscular pathology, recent work has highlighted the potential role of central nervous system (CNS) neuropathology in Pompe motor deficiencies. We used a murine model of Pompe disease to test the hypothesis that systemic GAA deficiency is associated with hypoglossal (XII) motoneuron pathology and altered XII motor output during breathing. Brainstem tissue was harvested from adult Gaa−/− mice and the periodic acid Schiff method was used to examine neuronal glycogen accumulation. Semi-thin (2 μm) plastic sections showed widespread medullary neuropathology with extensive cytoplasmic glycogen accumulation in XII motoneuron soma. We next recorded efferent XII bursting in anesthetized and ventilated Gaa−/− and B6/129 mice both before and after bilateral vagotomy. The coefficient of variation of respiratory cycle duration was greater in Gaa−/− compared to B6/129 mice (p < 0.01). Vagotomy caused a robust increase in XII inspiratory burst amplitude in B6/129 mice (239 ± 44% baseline; p < 0.01) but had little impact on burst amplitude in Gaa−/− mice (130 ± 23% baseline; p > 0.05). We conclude that CNS GAA deficiency results in substantial glycogen accumulation in XII motoneuron cell bodies and altered XII motor output. Therapeutic strategies targeting the CNS may be required to fully correct respiratory-related deficits in Pompe disease

Therapeutic rAAVrh10 Mediated SOD1 Silencing in Adult SOD1(G93A) Mice and Nonhuman Primates

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease; survival in ALS is typically 3-5 years. No treatment extends patient survival by more than three months. Approximately 20% of familial ALS and 1-3% of sporadic ALS patients carry a mutation in the gene encoding superoxide dismutase 1 (SOD1). In a transgenic ALS mouse model expressing the mutant SOD1(G93A) protein, silencing the SOD1 gene prolongs survival. One study reports a therapeutic effect of silencing the SOD1 gene in systemically treated adult ALS mice; this was achieved with a short hairpin RNA, a silencing molecule that has raised multiple safety concerns, and recombinant adeno-associated virus (rAAV) 9. We report here a silencing method based on an artificial microRNA termed miR-SOD1 systemically delivered using adeno-associated virus rAAVrh10, a serotype with a demonstrated safety profile in CNS clinical trials. Silencing of SOD1 in adult SOD1(G93A) transgenic mice with this construct profoundly delayed both disease onset and death in the SOD1(G93A) mice, and significantly preserved muscle strength and motor and respiratory functions. We also document that intrathecal delivery of the same rAAVrh10-miR-SOD1 in nonhuman primates significantly and safely silences SOD1 in lower motor neurons. This study supports the view that rAAVrh10-miR-SOD1 merits further development for the treatment of SOD1-linked ALS in humans

Editing out five Serpina1 paralogs to create a mouse model of genetic emphysema

Chronic obstructive pulmonary disease affects 10% of the worldwide population, and the leading genetic cause is alpha-1 antitrypsin (AAT) deficiency. Due to the complexity of the murine locus, which includes up to six Serpina1 paralogs, no genetic animal model of the disease has been successfully generated until now. Here we create a quintuple Serpina1a-e knockout using CRISPR/Cas9-mediated genome editing. The phenotype recapitulates the human disease phenotype, i.e., absence of hepatic and circulating AAT translates functionally to a reduced capacity to inhibit neutrophil elastase. With age, Serpina1 null mice develop emphysema spontaneously, which can be induced in younger mice by a lipopolysaccharide challenge. This mouse models not only AAT deficiency but also emphysema and is a relevant genetic model and not one based on developmental impairment of alveolarization or elastase administration. We anticipate that this unique model will be highly relevant not only to the preclinical development of therapeutics for AAT deficiency, but also to emphysema and smoking research

Macroglossia, Motor Neuron Pathology, and Airway Malacia Contribute to Respiratory Insufficiency in Pompe Disease: A Commentary on Molecular Pathways and Respiratory Involvement in Lysosomal Storage Diseases

The authors of the recently published, &#8220;Molecular Pathways and Respiratory Involvement in Lysosomal Storage Diseases&#8222;, provide an important review of the various mechanisms of lysosomal storage diseases (LSD) and how they culminate in similar clinical pathologies [...

Hereditary mucoepithelial dysplasia and severe respiratory distress

Hereditary mucoepithelial dysplasia (HMD) is a rare autosomal dominant disorder characterized by mucoepithelial disruption of the skin, hair and mucous membranes. It results from defective gap junction formation and leads to non-scarring alopecia, mucosal erythema, perineal erythematous intertrigo, involvement of the conjunctival mucosa, and pulmonary disease. We present a case of severe respiratory distress in an initially healthy full term infant born to a mother with HMD. This infant later developed signs and symptoms of HMD. A high index of suspicion for pulmonary infection with atypical organism is essential in infants with a family history of HMD who present with respiratory distress

Development of rAAV2-CFTR: History of the First rAAV Vector Product to be Used in Humans

The first human gene therapy trials using recombinant adeno-associated virus (rAAV) vectors were performed in cystic fibrosis (CF) patients. Over 100 CF patients were enrolled in 5 separate trials of rAAV2-CFTR administration via nasal, endobronchial, maxillary sinus, and aerosol delivery. Recombinant AAV vectors were designed to deliver the CF transmembrane regulator (CFTR) gene and correct the basic CFTR defect by restoring chloride transport and reverting the upregulation of proinflammatory cytokines. However, vector DNA expression was limited in duration because of the low incidence of integration and natural airway epithelium turnover. In addition, repeated administration of AAV-CFTR vector resulted in a humoral immune response that prevented effective gene transfer from subsequent doses of vector. AAV serotype 2 was used in human trials before the comparison with other serotypes and determination that serotypes 1 and 5 not only possess higher tropism for the airway epithelium, but also are capable of bypassing the binding and trafficking processes-both were important hindrances to the effectiveness of rAAV2. Although rAAV-CFTR gene therapy does not appear likely to supplant newer small-molecule CFTR modulators in the near future, early work with rAAV-CFTR provided an important foundation for later use of rAAV in humans