Abstract Number: Esoc2026a1294 Role of Tissue Kallikrein in the Fluid Exchange and Water Homeostasis in the Paraventricular Region of Mice

Abstract Background and aims The drainage role of the lateral ventricles for the contrast agent in the cisterna magna, which yielded a notable delay in permanent middle cerebral artery occlusion (pMCAO) mice, was assessed in our previous experiment, indicating benign ventricular inflow pathways under physiological conditions and impaired paraventricular brain fluid exchange after stroke. Herein, we hypothesized that cerebrospinal fluid (CSF) and interstitial fluid (ISF) may exchange across the ependyma that covers the ventricular system and thereby enter or exit the parenchyma to maintain water homeostasis. Tissue kallikrein (TK) treatment provides cerebral infarction patients with vasodilatory activity, which may enhance the dynamics of fluid transport in brain tissue by boosting perivascular pumping of CSF/ISF. Methods In this study, we evaluated the effects of TK on CSF/ISF exchange in the paraventricular region. The diffusion tensor imaging along the perivascular space (DTI-ALPS) index was calculated to explore the altered CSF/ISF exchange in the paraventricular region in both sham and TK-treated mice. Results Our results indicated that TK facilitates CSF/ISF exchange in the paraventricular region of mice, which might further rescue the stagnated fluid transport in ischemic brain parenchyma. Conclusions In conclusion, these data suggest the existence of pathway content in the paraventricular region that governs CSF/ISF exchange and dynamics. Improving fluid exchange provides an alternative approach for alleviating unstable water homeostasis in cerebral ischemic edema. Conflict of interest Jianying Zhang, Wenjie Cao and Qiang Dong.nothing to disclose Figure 1 - belongs to Conclusions