Assessment of Blood-brain Barrier Leakage and Brain Oxygenation in Connexin-32 Knockout Mice with Systemic Neuroinflammation Using Pulse Electron Paramagnetic Resonance Imaging Techniques

Purpose: The determination of blood-brain barrier (BBB) integrity and partial pressure of oxygen (pO) in the brain is of substantial interest in several neurological applications. This study aimed to assess the feasibility of using trityl OX071-based pulse electron paramagnetic resonance imaging (pEPRI) to provide a quantitative estimate of BBB integrity and pO maps in mouse brains as a function of neuroinflammatory disease progression.

Methods: Five Connexin-32 (Cx32)-knockout (KO) mice were injected with lipopolysaccharide to induce neuroinflammation for imaging. Three wild-type mice were also used to optimize the imaging procedure and as control animals. An additional seven Cx32-KO mice were used to establish the BBB leakage of trityl using the colorimetric assay. All pEPRI experiments were performed using a preclinical instrument, JIVA-25 (25 mT/720 MHz), at times t = 0, 4, and 6 h following lipopolysaccharide injection. Two pEPRI imaging techniques were used: (a) single-point imaging for obtaining spatial maps to outline the brain and calculate BBB leakage using the signal amplitude, and (b) inversion-recovery electron spin echo for obtaining pO maps.

Results: A statistically significant change in BBB leakage was found using pEPRI with the progression of inflammation in Cx32 KO animals. However, the change in pO values with the progression of inflammation for these animals was not statistically significant.

Conclusions: For the first time, we show the ability of pEPRI to provide pO maps in mouse brains noninvasively, along with a quantitative assessment of BBB leakage. We expect this study to open new queries from the field to explore the pathology of many neurological diseases and provide a path to new treatments.