Molecular Genetics and Metabolism 86 (2005) 141–149 www.elsevier.com/locate/ymgme 1096-7192/$ - see front matter  2005 Elsevier Inc. All rights reserved. doi:10.1016/j.ymgme.2005.04.013 Penetration, diVusion, and uptake of recombinant human -L-iduronidase after intraventricular injection into the rat brain P.V. Belichenko a , P.I. Dickson b , M. Passage b , S. Jungles c , W.C. Mobley a , E.D. Kakkis b,c,¤ a Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA b Division of Medical Genetics, Department of Pediatrics, Harbor-UCLA Medical Center and Los Angeles Biomedical Research Institute, Torrance, CA, USA c BioMarin Pharmaceutical Inc., Novato, CA, USA Received 28 February 2005; received in revised form 26 April 2005; accepted 29 April 2005 Available online 11 July 2005 Abstract Central nervous system disease can have devastating consequences in the severe or Hurler form of mucopolysaccharisosis I (MPS I). Intravenously administered recombinant human -L-iduronidase (rhIDU) is not expected to reach and treat the brain disease due to the blood–brain barrier. To determine whether administration of rhIDU into the cerebrospinal Xuid could successfully treat the brain, we studied intraventricular administration of rhIDU in rats. RhIDU was stereotactically administered directly to the lateral ventricle of the intact rat brain and the brain tissues assessed by enzyme assays, immunoXuorescence and confocal microscopy 30 min, 24 h, or 7 days later. Quantitation of activity revealed that rhIDU was widely distributed throughout the brain following injection into the lateral ventricle, with activities increased by a factor of 3.3 higher than control in most samples 30 min–24 h after injection and highest levels on the side of injection. The enzyme crossed the ependymal lining of the ventricle and entered neurons into lysosomal-like vesicles. The enzyme was able to diVuse through brain tissue as demonstrated by a decreasing signal gradient from 0.2 to 4.8 mm from the ventricle surface. The largest amount of rhIDU, as detected by immunostaining, was observed 24 h after injection and decreased approximately 50% during the Wrst 7 days. Although the immunostaining decreased with time, speciWc vesic- ular staining was still detectable 28 days after injection. The data suggest that rhIDU given into the ventricle can diVuse, penetrate at least several millimeters of brain tissue and be taken up into neurons and glial cells.  2005 Elsevier Inc. All rights reserved. Keywords: Lysosomal storage disease; Hurler; Scheie; -L-Iduronidase; Mucopolysaccharidosis; Brain; Rat Introduction Mucopolysaccharidosis I (MPS I) is an inherited dis- order of glycosaminoglycan (GAG) metabolism. AVected individuals lack or are deWcient in the enzyme -L-iduronidase necessary for stepwise breakdown of GAG. Without suYcient enzyme, GAG progressively accumulates in lysosomes in a wide variety of tissues throughout the body, including the brain [1]. The disease results in catastrophic disability and eventual death without treatment. Enzyme replacement therapy with recombinant human -L-iduronidase (Aldurazyme, laronidase, rhIDU, EC 3.2.1.76) has been approved for intravenous use in the US and EU since 2003 [2]. The treatment reduces lysosomal GAG storage in animal models and results in clinical improvement in functional vital capac- ity and walk endurance in treated individuals [2–5]. Intravenous rhIDU, however, is not likely to cross the blood–brain barrier in patients and therefore may not * Corresponding author. Fax: +1 415 382 7889. E-mail address: ekakkis@bmrn.com (E.D. Kakkis).