Mucopolysaccharidoses are heritable lysosomal storage diseases caused by deficiencies in acid hydrolases involved in the sequential degradation of complex glycosaminoglycans (GAGs). In many mucopolysaccharidoses, GAGs accumulate in the retinal pigment epithelial (RPE) cells of the eye resulting in pronounced lysosomal distension. It is not clear how the progressive accumulation of GAGs affects retinal function. Bone marrow transplantation (BMT) is a relatively effective therapy for many lysosomal storage diseases and can result in a dramatic reduction in lysosomal distention in the RPE. Although effective at reducing lysosomal storage, it is not clear how effective syngeneic BMT is at treating retinal dysfunction. Here we show that there is a progressive decrease in the amplitudes of both the dark-adapted (rod-cone) and light-adapted (cone-dominated) flash electroretinograms (ERG) between 8 and 20 weeks of age in a murine model of mucopolysaccharidosis type VII (MPS VII). By 20 weeks, the average dark-adapted b-wave amplitude was 118 microV in MPS VII mice as compared to 469 microV in normal mice of the same strain. MPS VII mice receiving syngeneic BMT at 4 weeks of age have reduced lysosomal storage in retinal pigment epithelial cells and normal ERG amplitudes at 20 weeks of age. Retinal function is impaired in untreated 8 week old MPS VII mice. Following BMT at 8 weeks, rod-cone- and cone-dominated responses recovered to within the normal range by 20 weeks of age. These data demonstrate the temporal pattern of retinal dysfunction in the MPS VII mouse and indicate that BMT can reduce the lysosomal storage and improve retinal function.
Copyright 2000 Academic Press.