Speaker
Description
Introduction:
Time-lapse MRI enables imaging of slowly moving individual immune cells in the intact brain in vivo. Applying this method to naïve mice and mice suffering from experimental autoimmune encephalomyelitis (EAE) has previously shown altered immune cell dynamics. The aim of this study is to evaluate time-lapse MRI of the brain under non-CNS associated inflammatory conditions.
Methods:
In a first animal model, C57BL/6 mice were injected subcutaneously with 100µl of a polyacrylamide-gel (pellet) containing lipopolysaccharide (LPS, 10, 20, 40µg LPS/100µl PAG) to induce a sterile local inflammation (n=6 each). After 24h mice were i.v. injected with iron oxide nano particles (Resovist, Ferucarbotran, 1.9ml/kg BW). 24h later time-lapse MRI of the whole brain with 20 time-frames (scan time: 8min 12s for a single time-frame) was performed.
In a second model C57BL/6 mice (n=3) were i.v. injected with 1x105 CFU of S. aureus, followed by the same time-lapse MRI protocol.
Healthy C57BL/6 mice (n=8) injected only with Resovist were used as control.
Data was analyzed manually by counting labelled cells in the brain, detected as hypointense spots (events).
Results:
Time-lapse MRI enables early detection of non-CNS associated inflammation. In control mice (269±29) events were observed, a similar number as reported previously (Masthoff et al 2018). In the local inflammation model, the number of events was significantly reduced to (173±16). In the systemic sepsis model with (19±2) events this reduction was even more pronounced.
Discussion:
As shown previously time-lapse MRI enables detection and quantification of altered immune cell dynamics between health and disease. Not only EAE as CNS autoinflammation but also local peripheral inflammation as well as systemic sepsis has altered immune cell dynamics in the brain, as detected and quantified by time-lapse MRI. Immune cell dynamics are dependent on the quality and intensity of the inflammatory stimulus.
