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

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).