Blood-Brain Barrier crossing of high molecular weight molecules mediated by nanoparticles: a potential approach to treat neurological Lysosomal Storage Disorders

Enzyme Replacement Therapy (ERT) is the most common therapeutic strategy applied to several Lysosomal Storage Disorders (LSDs) including Mucopolysaccharidoses (MPSs), as MPS type I (MPS I, Hurler Disease) and type II (MPS II, Hunter Disease). Both diseases are characterized by a totally or partially defective activity of lysosomal enzymes involved in the catabolism of the mucopolysaccharides (or glycosaminoglycans, GAGs) heparan- and dermatan-sulfate which therefore heavily accumulate within cellular compartment and in the extracellular matrix. Although presenting several forms of clinical severity and disease progression, both pathologies affect most of the organ systems, are mostly life-threatening and about two-thirds of the patients also present neurological and cognitive impairment. Enzyme Replacement Therapy, applied to both diseases in the last few years, has shown to determine some clinical improvements, but it has also shown some limitations. In addition to the elevated costs of intervention, ERT presents the need of weekly administrations in a day-hospital regimen, this reducing patients’compliance, and the inefficacy of the recombinant enzymes in treating the CNS impairment due to their inability in blood-brain barrier (BBB) crossing. Thus, we combined the experience of clinical-based skills with pharmaceutical nanotechnology-based skills in order to create nanocarriers, biodegradable and biocompatible, able to deliver the recombinant enzymes across the BBB and to both assure a prolonged drug circulation and release, and a protection from metabolic drug inactivation. With this aim, we produced polymeric nanoparticles (PLGA-NPs) modified with 7-aminoacid glycopeptides (g7), yet demonstrated to be able to drive the NPs across the BBB after administration in rodents. Before going into functional and efficacy study, we developed several preliminary experiments in order to explore the ability of PLGA-NPs in transferring across the BBB a model drug (FITC-albumin), with a high molecular weight, comparable to that of the enzymes to be delivered across the BBB. In vivo experiments on both WT and knock-out (KO) mouse models for MPS I and MPS II were performed by i.v.-injecting g7-NPs loaded with FICT-albumin together with a plethora of control samples (i.e-. un-modified NPs, FITC-albumin solution) in order to have a broad preliminary view. The results clearly showed that g7-NPs are able to cross the BBB in all treated mice (WT and KO models) and to deliver FITC-albumin to the brain; interestingly, we found qualitative and semi-quantitative evidences of a higher grade of brain accumulation of g7-NPs loaded with Albumin in the KO -brains with respect to WT ones. Taken together, these results pave the way to a possible successful set of pilot experiments on the ability of enzyme-loaded g7-NPs to deliver sufficient amount of the drug to the brain district, hopefully exerting a corrective effect on the pathological cellular GAG deposits.