Expression of CD137 in the cerebral artery after experimental subarachnoid hemorrhage in rats: A pilot study

Inflammation and immunity play a crucial role in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). CD137 is recognized as an independent costimulatory molecule of T cells and activator of monocytes. A growing body of evidence indicates that CD137 is vital for inflammation and immunity. Therefore, this study aimed to investigate the expression of CD137 in the basilar artery in a rat SAH model and to clarify the potential role of CD137 in cerebral vasospasm. A total of 107 rats were randomly divided into four groups: control group; day 3, day 5, and day 7 groups. Day 3, day 5, and day 7 groups were all SAH groups. The animals in SAH groups were subjected to injection of autologous blood into cisterna magna twice on day 0 and day 2 and were sacrificed on days 3, 5, and 7, respectively. Cross-sectional area of basilar artery was measured and the CD137 expression was assessed by quantitative real-time PCR, Western blot and immunohistochemistry. The cross-sectional area of basilar artery was found to be 57,944 ± 5581 μm2 in control group, 26,100 ± 2639 μm2 in day 3, 19,723 ± 2412 μm2 in day 5, and 28,800 ± 2980 μm2 in day 7 group, respectively. The basilar artery exhibited vasospasm after SAH and became more severe on day 5. The elevated mRNA and protein of CD137 were detected after SAH and peaked on day 5. CD137 is increasingly expressed in a parallel time course to the development of cerebral vasospasm in a rat experimental model of SAH. These findings indicate the possible role of CD137 in the pathogenesis of cerebral vasospasm after SAH.

Research highlights
► Demonstrate that CD137 was upregulated in the basilar arterial wall during cerebral vasospasm after experimental SAH in rats for the first time.
► The enhanced expression of CD137 could be detected on day 3, peaked on day 5, and recovered on day 7.
► Indicate the possible role of CD137 in the pathogenesis of cerebral vasospasm after SAH.