Blood-filled cerebrospinal fluid-enhanced pericyte microvasculature contraction in rat retina: A novel in vitro study of subarachnoid hemorrhage

Abstract

Previously, it was widely accepted that the delayed ischemic injury and poor clinical outcome following subarachnoid hemorrhage (SAH) was caused by cerebral vasospasm. This classical theory was challenged by a clazosentan clinical trial, which failed to improve patient outcome, despite reversing angiographic vasospasm. One possible explanation for the results of this trial is the changes in microcirculation following SAH, particularly in pericytes, which are the primary cell type controlling microcirculation in the brain parenchyma. However, as a result of technical limitations and the lack of suitable models, there was no direct evidence of microvessel dysfunction following SAH. In the present study, whole-mount retinal microvasculature has been introduced to study microcirculation in the brain following experimental SAH in vitro. Artificial blood-filled cerebrospinal fluid (BSCF) was applied to the retinal microvasculature to test the hypothesis that the presence of subarachnoid blood affects the contractile properties of the pericytes containing cerebral microcirculation during the early phase of SAH. It was observed that BCSF induced retina microvessel contraction and that this contraction could be resolved by BCSF wash-out. Furthermore, BCSF application accelerated pericyte-populated collagen gel contraction and increased the expression of α-smooth muscle actin. In addition, BCSF induced an influx of calcium in cultured retinal pericytes. In conclusion, the present study demonstrates increased contractility of retinal microvessels and pericytes in the presence of BCSF in vitro. These findings suggest that pericyte contraction and microvascular dysfunction is induced following SAH, which could lead to greater susceptibility to SAH-induced ischemia.

Non-invasive Assessment of Neurovascular Coupling After Aneurysmal Subarachnoid Hemorrhage: A Prospective Observational Trial Using Retinal Vessel Analysis

“…In any case, the observed microvascular changes resemble aSAH-induced changes in large caliber vessels, namely early cerebral artery vasoconstriction and an associated reduction in cerebral perfusion which may contribute to DCI in some patients ( 33 – 35 ). Considering that increased intracranial pressure during the acute phase of aSAH forces subarachnoid blood into the preretinal space, a significant reduction in retinal vessel diameters observed during the early phase after aSAH is in line with previous in vitro and in vivo animal studies showing that blood-filled cerebrospinal fluid enhances constriction of both, the retinal ( 36 ) and cerebral ( 37 ) microvasculature. Interestingly and in contrast to angiographic vasospasm, which usually dissolves by week 2 after the ictus ( 34 ), however, there was almost no return of arterial and venous diameters toward the control level during the first 3 weeks after aSAH and only a partial, non-significant recovery at follow-up more than 6 weeks later.…”

The expression of cerebrospinal fluid exosomal miR-630 plays an important role in the dysfunction of endothelial cells after subarachnoid hemorrhage

“…Normal cerebrospinal fluid were purchased from United States BIOLOGical (Catalog: 3052). BCSF was prepared following Foley’s and u’sds 15,16 . Briefly, donor patient arterial blood and normal cerebrospinal fluid under aseptic condition were mixed with 1:1 ratio and incubated in a 37 °C water bath for 24 h. Then, the mixed samples were centrifuged at 10,000 × g for 20 min at room temperature.…”

Cyclophilin a signaling induces pericyte-associated blood-brain barrier disruption after subarachnoid hemorrhage

“…A previous study indicated that pericytes bidirectionally control microvessel diameters and regulate cerebral blood flow [4]. Our previous study further demonstrated that pericyte α-SMA phenotype transformation caused acute microvessel/pearl-like constriction and neurological deficits in the setting of SAH [5,6]. However, a recent study suggested that pericytes might have a negative influence on neurovascular integrity and cause neuronal degeneration in apolipoprotein E-deficient mice [7].…”