Evaluation of lentiviral vectors in Morquio syndrome type A patients' fibroblasts

Mucopolysaccharidosis IVA (Morquio syndrome type A) is a lysosomal storage disease produced by deficiency in the N-acetylgalactosamine-6-sulfate sulfatase (GALNS) enzyme, leading to lysosomal accumulation of keratan sulfate and chondroitin-6-sulfate. Although enzyme replacement therapy has shown impact in some disease manifestations, it has limited impact in bone and cardiac problems and requires a weekly infusion of the recombinant enzyme. The use of gene therapy represents an alternative that can help to overcome some of these current therapies limitations. In this work, we evaluated the use of lentiviral vectors to mediate the transduction of GALNS (lenti-GALNS) and SUMF1 (lenti-SUMF1) cDNAs to fibroblasts derived from three Morquio syndrome type A patients. Vector transduction was monitored by intra and extracellular GALNS activity, lysosomal mass by LysoTracker staining, and autophagy evaluation by monitoring p62 and LC3B. The results showed an increase in GALNS activity after lenti-GALNS transduction and, in some cases, a higher increase after lenti-SUMF1 co-transduction. We observed a wide cell-to-cell variation in GALNS activity, with fibroblasts with severe mutations showing a higher increase in enzyme activity. In addition, we observed that high vector titers and co-transduction with lenti-SUMF1 showed a deleterious effect in GALNS activity in some treated fibroblasts. Noteworthy, it was observed that the treatment with the lentiviral vectors allowed a reduction in lysosomal mass, as observed by changes in the LysoTracker staining, and a change in the autophagy biomarkers p62 and LC3B. Overall, this study offers valuable data towards the use of lentiviral vectors as tools for the design of a gene therapy strategy for Morquio syndrome type A patients, and shows the first evidence of the autophagy impairment in Morquio syndrome type A fibroblasts.