Blood–spinal cord barrier breakdown and pericyte reductions in amyotrophic lateral sclerosis

Ethan A Winkler,Berislav V Zlokovic,John S Sullivan,Stanley H Appel,Jenny S Henkel,Jesse D Sengillo

doi:10.1007/s00401-012-1039-8

Ethan A Winkler, Berislav V Zlokovic + Show 4 more

Open Access

https://doi.org/10.1007/s00401-012-1039-8

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Abstract

The blood–brain barrier and blood–spinal cord barrier (BSCB) limit the entry of plasma components and erythrocytes into the central nervous system (CNS). Pericytes play a key role in maintaining blood–CNS barriers. The BSCB is damaged in patients with amyotrophic lateral sclerosis (ALS). Moreover, transgenic ALS rodents and pericyte-deficient mice develop BSCB disruption with erythrocyte extravasation preceding motor neuron dysfunction. Here, we studied whether BSCB disruption with erythrocyte extravasation and pericyte loss are present in human ALS. We show that 11 of 11 cervical cords from ALS patients, but 0 of 5 non-neurodegenerative disorders controls, possess perivascular deposits of erythrocyte-derived hemoglobin and hemosiderin typically 10–50 μm in diameter suggestive of erythrocyte extravasation. Immunostaining for CD235a, a specific marker for erythrocytes, confirmed sporadic erythrocyte extravasation in ALS, but not controls. Quantitative analysis revealed a 3.1-fold increase in perivascular hemoglobin deposits in ALS compared to controls showing hemoglobin confined within the vascular lumen, which correlated with 2.5-fold increase in hemosiderin deposits (r = 0.82, p < 0.01). Spinal cord parenchymal accumulation of plasma-derived immunoglobulin G, fibrin and thrombin was demonstrated in ALS, but not controls. Immunostaining for platelet-derived growth factor receptor-β, a specific marker for CNS pericytes, indicated a 54 % (p < 0.01) reduction in pericyte number in ALS patients compared to controls. Pericyte reduction correlated negatively with the magnitude of BSCB damage as determined by hemoglobin abundance (r = −0.75, p < 0.01). Thus, the BSCB disruption with erythrocyte extravasation and pericyte reductions is present in ALS. Whether similar findings occur in motor cortex and affected brainstem motor nuclei remain to be seen.

Highlights

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disorder with an incidence of approximately 2–3 cases annually per 100,000 people [18, 37, 43, 69]
Our postmortem tissue analysis suggests that blood–spinal cord barrier (BSCB) disruption in amyotrophic lateral sclerosis (ALS) patients leads to extravasation of erythrocytes in the spinal cord and subsequent accumulation of erythrocyte-derived hemoglobin and iron-containing hemosiderin, as well as extravasation of multiple plasmaderived proteins
We show that BSCB breakdown in ALS subjects is associated with pericyte loss in motor neuron dense regions of the spinal cord, i.e., the cervical spinal cord anterior horn gray matter

Summary

Introduction

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disorder with an incidence of approximately 2–3 cases annually per 100,000 people [18, 37, 43, 69]. Mice with deficient platelet-derived growth factor receptor-b (Pdgfrb) signaling in pericytes resulting in pericyte loss develop chronic BBB and/or BSCB disruption with accumulation of plasma proteins and erythrocyte extravasation preceding neuronal injury [6, 63]. We show that capillary leakage of erythrocytes and plasma proteins is present in ALS, and that vascular rupture coincides with reductions in capillary pericyte populations in human ALS spinal cord tissue specimens. These findings raise a number of questions regarding the significance and/or contributory role of vascular dysfunction in ALS pathogenesis

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