Two-photon laser scanning microscopy imaging of intact spinal cord and cerebral cortex reveals requirement for CXCR6 and neuroinflammation in immune cell infiltration of cortical injury sites

The mouse spinal cord is an important site for autoimmune and injury models. Skull thinning surgery provides a minimally invasive window for microscopy of the mouse cerebral cortex, but there are no parallel methods for the spinal cord. We introduce a novel, facile and inexpensive method for two-photon laser scanning microscopy of the intact spinal cord in the mouse by taking advantage of the naturally accessible intervertebral space. These are powerful methods when combined with gene-targeted mice in which endogenous immune cells are labeled with green fluorescent protein (GFP). We first demonstrate that generation of the intervertebral window does not elicit a reaction of GFP+ microglial cells in CX3CR1gfp/+ mice. We next demonstrate a distinct rostrocaudal migration of GFP+ immune cells in the spinal cord of CXCR6gfp/+ mice during active experimental autoimmune encephalomyelitis (EAE). Interestingly, infiltration of the cerebral cortex by GFP+ cells in these mice required three conditions: EAE induction, cortical injury and expression of CXCR6 on immune cells.