Spinal Microvascular Expression of PV-1 is Associated with Inflammation, Perivascular Astrocyte Loss, and Diminished EC Glucose Transport Potential in Acute SCI

Abstract

The endothelial-specific expression of plasmalemmal vesicle associated protein-1 (PV-1) is typical of fenestrated endothelium observed in pulmonary capillaries and some endocrine organs. In the central nervous system (CNS) it is expressed during development but disappears concomitant with maturation of the blood-CNS barrier [1]. Consistent with observations made in models of stroke, Alzheimer's disease, and tumorigenesis, we show PV-1 expression in the spinal cord specifically upregulated by pathologically-activated endothelial cells (ECs) in response to traumatic spinal cord injury (SCI). Adult female C57Bl/6 mice received a moderate T9/10 contusive SCI. PV-1 assessed by qRT-PCR and immunohistochemistry 3 hours to 14 days post-injury showed expression as early as 1 day post-SCI, with levels decreasing by 14 days. This expression was associated with microvessels in the injury epicenter and penumbral zone, with the time course and distribution correlated with progressing peripheral inflammatory cell infiltration. PV-1-immunoreactive ECs were angiogenic as demonstrated by intravascular binding of Griffonia simplicifolia isolectin B4 (IB4). ECs expressing high levels of PV-1 were anatomically and physiologically abnormal with altered/absent immunostaining for occludin and zonula occludens-1 (ZO-1), and decreased expression of glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQP4). Glucose transporter type I (Glut-1) expression decreased in affected, PV-1 positive microvessels with little colocalization of PV-1 and Glut-1 apparent by 7 days post-SCI. These data suggest that upregulation of microvascular expression of PV-1 post-SCI may promote major components of secondary injury including extravasation of cellular and acellular mediators of inflammation and may accelerate loss of neuropil and decline in the functional and anatomical integrity of the neurovascular unit (NVU).

Vascular Pathology as a Potential Therapeutic Target in SCI

“…For example, loss of Glut-1 expression in ECs upon astrocytic regression corresponds with increased microvascular permeability [9,165]. While the metabolic implications of this response remain unknown, we have observed an increase of transendothelial transport potential temporally associated with the loss of Glut-1 expression by ECs [98]. Another key consequence of astrocytic regression from the microvessel in response to SCI may be the alteration of AQP4 function.…”

“…For example, leaky neovasculature predominantly within the injury epicenter exhibit altered occludin and claudin-5 expression [9]. More recently we have shown that this subpopulation of reactive microvessels exhibit a fenestrated phenotype with increased pinocytotic potential [98]. Further studies are needed to assess which route predominates and whether normalization of these changes in EC barrier properties represents a novel therapeutic target.…”

Fibrinogen-Induced Increased Pial Venular Permeability in Mice

“…The cranium was opened and the brain was gently dissected and removed for fresh tissue processing. Mouse brain tissue immunohistochemistry was done according to the method described earlier (Mozer et al, 2010). The brain was mounted in protective matrix (Polyscience, Inc., Warrington, PA, USA) and cryosectioned using a Leica CM 1850 Cryocut (Bannockburn, IL, USA).…”

“…Plasmalemmal vesicle-associated protein-1 (PV-1) is an integral membrane-associated protein of caveolae found in fenestral and stomatal diaphragms in fenestrated endothelial and transendothelial channels (Hnasko et al, 2002). It is considered a functional biomarker for altered vascular permeability following central nervous system trauma (Mozer et al, 2010) and disruption of blood-brain barrier (BBB) (Shue et al, 2008). Thus, the combination and the functional balance of these two pathways govern the net transport of substances in microcirculation.…”

Intravenous Infusion of Magnesium Chloride Improves Epicenter Blood Flow during the Acute Stage of Contusive Spinal Cord Injury in Rats

“…24 We and others identify perfused microvessels by intravenous injection of the lectin, Lycopersicon esculentum (tomato) agglutinin (LEA), which binds to glucosamines on endothelial cells. [25][26][27][28] Microscopic histological analyses of LEA + microvessels provide a measure of the perfusion status of microvessels that are lined with endothelial cells at the injury epicenter and penumbra, two areas where therapeutic intervention is needed during the acute stage of injury. 20,21,29 Here, we determined the temporal changes in the number of perfused and endothelial-lined microvasculature over 2 days following contusive SCI in adult rats.…”