Label-Free Identification and Analysis of Myelin in Dys and Demyelination Murine Models using Spatial Light Interference Microscopy (SLIM)

Multiple Sclerosis (MS) is believed to cause demyelination across the central nervous system (CNS) because of a mistaken target choice for an over activated destructive immune system -one’s own myelin. The process eventually leads to denuded axons and infiltration of inflammatory cells in to the brain parenchyma. MS is still an elusive disease without a clear description of how this degeneration is orchestrated. Empirical and systematic investigations are needed to evaluate potential mechanisms of MS disease onset and progression in animal models. Spatial light interference microscopy (SLIM) is a label-free imaging technique that allows detailed visualization of cyto- and myeloarchitecture on thin brain samples. In our protocol, we use SLIM microscopy to compare 6-µm brain sections from control mice to comparable sections from demyelination and dysmyelination mice brains from Cuprizone and Shiverer mice, respectively. We use SLIM microscopy to assess differences in cell morphology, cell count, dry mass, and tissue topography. White matter tract structural analysis was done using in-house software for fiber extraction and quantification. Our goal is to establish a platform on SLIM using angle orientation and segmentation of white matter tract fibers to quantify the extension of myelinated fiber damage in the corpus callosum (CC) that can be used across the whole brain and across varied applications.  Our results show an increase in cellularity, presence of vacuoles and indicate possible edema. In addition, quantification of dry mass suggests that demyelination might be triggering the infiltration of inflammatory, immune or glial cells as a repair response to the damaged fibers, therefore increasing dry mass in the region. These results provide a simple protocol on SLIM to investigate patterns in demyelination of thin tissue sections in order to have a better understanding of MS and other demyelinating diseases.