Introduction: Secondary injury due to neuroinflammation poses a target in ICH research. We have demonstrated elevated serum IL-12 levels in rodents with cardiometabolic syndrome with hypertension compared with normotensive rodents. As hypertension is a risk factor in ICH, it is critical to understand whether there are also local cerebral changes in pro-inflammatory cytokines to explore targets for therapeutics. Methods: A pilot study of autologous-injection ICH was induced in (mREN2)27 (n=7) and control Hanover Sprague-Dawley (SD) (n=7) rats. Animals underwent tail-cuff blood pressure measurement, pre- and post-ICH neurobehavioral testing, and serum cytokine measurements. Sacrifice with brain harvest was performed at 24h and 7h post-ICH. Homogenization of the brain with quantitative measurement of hemoglobin and IL-12 concentrations was performed. Results: IL-12 peaked in the ipsilateral hemisphere in both SD and mREN rats at 24h post-ICH. There was a significant difference in local IL-12 levels between the ipsilateral and contralateral hemispheres at 72h, with minimal IL-12 elevation in the contralateral hemisphere (p=0.05) (Figure 1). Additionally, there was high correlation between hematoma size and IL-12 local expression. While there was no difference in cerebral IL-12 levels between strains, there was a significant elevation in baseline IL-12 serum levels in mREN compared to SD rats, and a trend towards serum elevation at 72h post-ICH. Conclusions: Cerebral IL-12 levels ipsilateral to ICH are significantly elevated compared to contralateral levels and peak 24h post-ICH. While serum IL-12 levels are elevated in rats with cardiometabolic syndrome, this is not seen in brain tissue following ICH. With the high correlation between hematoma size and IL-12 expression, these findings implicate macrophage recruitment from the hematoma as a driver of neuroinflammation and potential therapeutic target to augment surgical interventions for ICH.

Introduction: About 500,000 people worldwide die annually from ruptured intracranial aneurysms (IA). The pathophysiology of aneurysm formation is largely unknown. Piezo1 mechanoreceptors are expressed in endothelial and smooth muscle cells of developing blood vessels. In addition to hemodynamic forces, Piezo1 has been shown to play an inflammatory role, as stiffness-sensing macrophages lacking Piezo1 exhibit reduced inflammation and enhanced wound healing responses. Malfunction of Piezo1 mechanoreceptors has been implicated in abdominal aortic aneurysm (AAA) development. With the increasing evidence of relationship between AAA and IAs, it is important to study Piezo1 dysregulation as a potential cause of IA development and/or rupture. Methods: During craniotomy for aneurysm clipping of ruptured and unruptured IAs, we excised and collected the aneurysm dome in four patients. Immunohistochemistry (IHC) was performed for Piezo1 and with CD31 to co-localize Piezo1 in the endothelial cells, and a-SMA to co-localize in smooth muscle cells on all aneurysm domes. Additional specimen was saved for genomic analyses. Results: Piezo1 mechanoreceptor overexpression was found in the smooth muscle layer of IAs, but not in superficial temporal artery (STA) controls, in all four human cerebral aneurysm domes. Additionally, there was significant dysregulation of Piezo1 mechanoreceptors in the IA compared with the regular appearance seen in the control human STA (Figure 1). Overexpression was not seen in human arteriovenous malformation specimens. Conclusions: Our data is the first demonstration of overexpression of Piezo1 mechanoreceptors in a disorganized manner in the walls of human IAs, which may represent a therapeutic target. We hypothesize that vascular shear stress leads to Piezo1-mediated disorganization in arterial smooth muscle cells and pro-inflammatory activation, which may lead to IA development and rupture.

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In the past 20 years, no drug therapies have been successfully translated into human use for intracerebral hemorrhage (ICH), the most devastating stroke subset. One likely factor is lack of effective animal models of human disease including common comorbidities, such as hypertension and diabetes. We evaluated the cardiometabolic rodent model, (mRen2)27, where overexpression of Ren2 results in extreme hypertension, glucose intolerance and obesity, as an appropriate ICH model. Methods: Sprague Dawley (SD) and (mRen2)27 rats were sacrificed at 14‐, 32‐, and 52‐weeks. Brains were sectioned sagittally at 5 μm. Whole‐brain sections were stained using Hematoxylin & Eosin (H&E) and Van Geison (VG) collagen staining to visualize the pial blood vessels. Wall‐to‐lumen ratios for vessels were calculated and compared using a student t‐test to determine significance. Results: There was no significant difference in arteriolar morphology at 14‐weeks between male SD and mRen animals (SD, n=16 and mRen, n=16). At 32‐weeks, there was a significant difference in mRen male rats (SD, n=13 and mRen, n=17; p<0.0001), with significantly increased wall thickness and decreased Lumen size in the mRen animals (increased W:L ratio). However, at this timeframe, there was no significant difference between the female SD and mRen cohorts (SD, n=6 and mRen, n=8). At 52‐weeks, there was a significant increase in W:L ratios in both male (SD, n=4 and mRen, n=7; p<0.01) and female (SD, n=9 and mRen, n=8; p<0.05) mRen animals compared to control. Conclusion: The (mRen2)27 cardiometabolic animal model demonstrates age‐related sex changes in the wall:lumen ratio of cerebral vasculature consistent with cerebrovascular disease seen in ischemic and hemorrhagic stroke patients. Males develop these vascular changes earlier than females, but both sexes in this model develop cerebral vascular changes by 1 year of age. The (mRen2)27 model appears to recapitulate human disease and sex differences, and may serve as an appropriate translational model of ICH.