Growth hormone causes up regulation of Mannose-6-Phosphate receptors and Gb3 mobilization in cultured ERT-treated fabry fibroblasts

Background Fabry disease is an X-linked lysosomal storage disorder in which cardiac involvement is the leading cause of morbidity and mortality. Enzyme replacement therapy (ERT) is effective in early Fabry cardiomyopathy but shows limited efficacy in advanced stages, largely owing to impaired intracellular uptake of α-galactosidase A (α-Gal A) due to deficiency of the cation-independent mannose-6-phosphate receptor (CI-M6PR). Purpose The purpose of this study is to evaluate the mechanisms underlying the limited efficacy of enzyme replacement therapy (ERT) in advanced Fabry cardiomyopathy. Material and Methods Primary fibroblasts from patients with FD and controls were used to investigate CI-M6PR regulation and ERT uptake. Cells were treated with growth hormone (GH) alone or combined with recombinant α-galactosidase A. CI-M6PR expression, localization, and endosomal recycling were assessed by confocal microscopy, Western blot and FACS analysis. Intracellular α-Gal A activity and globotriaosylceramide (Gb3) content were quantified using enzymatic assays and image analysis. Results GH treatment significantly increased CI-M6PR availability in Fabry fibroblasts, GH pre-treatment enhanced intracellular uptake and activity of recombinant α-Gal A compared with ERT alone, resulting in a significant reduction of intracellular Gb3 accumulation. GH alone did not substantially affect Gb3 storage. These findings indicate that GH selectively improves CI-M6PR–mediated enzyme delivery, overcoming a key cellular mechanism of ERT resistance. Conclusions GH increases CI-M6PR–dependent expression and enhances uptake of α-Gal A improving Gb3 clearance in Fabry fibroblasts. Modulating receptor trafficking may represent a novel adjunctive strategy to increase ERT efficacy in Fabry disease.