Comparative study of nanocarriers targeted to different transport pathways into and across the endothelium for brain delivery of therapeutic enzymes

Abstract

[eng] The blood-brain barrier (BBB) is a major obstacle for the treatment of neurological diseases such as common Parkinson’s disease or rare lysosomal storage disorders (LSDs). LSDs are characterised by deficiency of lysosomal components, mainly enzymes, resulting in lysosomes accumulation of macromolecules affecting the CNS and peripheral organs. Examples are Niemann-Pick disease (NPD) and Gaucher disease (GD), characterised by deficiency in acid sphingomyelinase (ASM) and glucocerebrosidase (GBA), respectively. Additionally, GBA alterations are involved in Parkinson’s. Currently, enzyme replacement therapy (ERT) fails to treat neuropathic symptoms due to the BBB. Targeting enzymes across the BBB using nanocarriers capable to transcytosis in this interface offers an interesting approach to improve ERT.

This project studied the transport of differently targeted therapeutic nanocarriers across the BBB to identify the most suitable formulations, using polymer nanocarriers targeted to different routes, BBB cell models and in vivo animal models, as well as physicochemical measurements of colloidal properties, radioactive tracing, and confocal fluorescence microscopy. Four aims were addressed. First, biodegradable PLGA nanocarriers and non-degradable polystyrene models were produced, which had similar physicochemical properties, were functionalized for targeting, loaded with a enzyme and increased enzyme delivery in cell cultures, also providing in vivo targeting.

Non degradable nanocarriers were thereafter used to focus on transport solely avoiding degradation artifacts. Second, transport across a cellular BBB was examined for formulations targeting intercellular adhesion molecule 1 (ICAM-1), identifying a dual simultaneous transport to endothelial lysosomes and BBB transcytosis with additional basolateral re-uptake of nanocarriers, intertwined and dependent on the targeting valency of nanocarriers. Third, the effects of NPD on this transport was examined for ICAM-1 targeting nanocarriers along with formulations targeting the transferrin receptor (TfR) or plasmalemma vesicle associated protein 1 (PV1). Disease altered all pathways in different ways, with ICAM-1 targeting nanocarriers being the most efficient formulation for BBB transport in this disease model. Fourth, a similar study was conducted in GD, where different alterations were also found, yet again ICAM-1 targeting nanocarrier were the most suitable candidate for trans BBB delivery. Thus, this study, encompassing multidisciplinary basic and applicable research, found relevant findings for a better understanding of the pathological alterations associated to these neuropathies and the practical design of therapeutic nanocarriers.