Post-capillary venules are the key locus for transcytosis-mediated brain delivery of therapeutic nanoparticles

Krzysztof Kucharz,Kasper Bendix Johnsen,Thomas Lars Andresen,Torben Moos,Martin Johannes Lauritzen,Mette Aagaard Lund,Kasper Kristensen,Micael Lønstrup

doi:10.1038/s41467-021-24323-1

Abstract

Effective treatments of neurodegenerative diseases require drugs to be actively transported across the blood-brain barrier (BBB). However, nanoparticle drug carriers explored for this purpose show negligible brain uptake, and the lack of basic understanding of nanoparticle-BBB interactions underlies many translational failures. Here, using two-photon microscopy in mice, we characterize the receptor-mediated transcytosis of nanoparticles at all steps of delivery to the brain in vivo. We show that transferrin receptor-targeted liposome nanoparticles are sequestered by the endothelium at capillaries and venules, but not at arterioles. The nanoparticles move unobstructed within endothelium, but transcytosis-mediated brain entry occurs mainly at post-capillary venules, and is negligible in capillaries. The vascular location of nanoparticle brain entry corresponds to the presence of perivascular space, which facilitates nanoparticle movement after transcytosis. Thus, post-capillary venules are the point-of-least resistance at the BBB, and compared to capillaries, provide a more feasible route for nanoparticle drug carriers into the brain.

Highlights

Effective treatments of neurodegenerative diseases require drugs to be actively transported across the blood-brain barrier (BBB)
We report that transferrin receptor (TfR)-targeted nanoparticles bind to brain endothelial cells (BEC) at venules and capillaries but not at arterioles
Targeting of the transcytosis pathway in BECs was enabled by coupling high-affinity anti-TfR antibodies to the nanoparticle surface20 —a targeting moiety that mediates a high level of nanoparticle binding to the brain endothelium[21,22]

Summary

Introduction

Effective treatments of neurodegenerative diseases require drugs to be actively transported across the blood-brain barrier (BBB). Post-capillary venules are the point-of-least resistance at the BBB, and compared to capillaries, provide a more feasible route for nanoparticle drug carriers into the brain. We characterized the pharmacokinetics of nanoparticles targeted toward the TfR at the BBB, their intracellular trafficking patterns in vascular BECs, and transcytosismediated entry and transit in the brain parenchyma. The vascular locus of nanoparticle transport was consistent with the presence of perivascular space around post-capillary venules, which facilitates the movement of nanoparticle-sized elements in the CNS. These observations provide insight into therapeutic nanoparticle trafficking and delivery to the brain and challenge the assumed view that capillaries are the hub for effective brain transport of nanoparticle drug carriers. Our findings prompt reconsideration of nanoparticle targeting strategies for improved drug delivery to the brain

Methods

Results

Conclusion