High field MRI image showing labelled macrophages as T2* hypointense spots (indicated by arrowheads). Some of the spots were motile cells, and crawled in the in-vivo mouse brain (link to the movie below).

Immune cells constantly survey the brain microvasculature for irregularities in levels of factors that signal homeostasis. Immune responses are initiated when necessary, resulting in the mobilisation of the microglial cells residing in the central nervous system (CNS) and/or of infiltrating peripheral cells. However, little is known about the kinetics of immune cells in healthy and diseased CNS, because it is difficult to perform long-term visualization of cell motility in intravital tissues, especially the brain, with minimal invasion.

In this research, Yuki Mori (CiNet/IFReC) and colleagues report a highly sensitive in-vivo MRI technique for sequential monitoring of cell migration in the CNS at the single-cell level. Furthermore, they demonstrate the technique by successfully tracking the migration of cells in live animal brains using time-lapse MRI videos (see link below). This novel MRI technique can reveal critical insights into cell behaviors that can not be obtained by optical microscopy. Applications of this technique may further advance our understanding of the interaction between the nervous and the immune systems, and reveal the mechanisms of immune cell dynamics in the normal CNS as well as in situations of CNS injury, inflammation and disease.

Link to the movie:
http://www.nature.com/srep/2014/141111/srep06997/extref/srep06997-s2.mov

This paper appeared in the journal Scientific Reports on November 11 2014.

Full Reference:
“From cartoon to real time MRI: in vivo monitoring of phagocyte migration in mouse brain”
Yuki Mori, Ting Chen, Tetsuya Fujisawa, Syoji Kobashi, Kohji Ohno, Shinichi Yoshida, Yoshiyuki Tago, Yutaka Komai, Yutaka Hata & Yoshichika Yoshioka
Scientific Reports, 4, Article number: 6997
http://www.nature.com/srep/2014/141111/srep06997/full/srep06997.html