New myelinating oligodendrocytes during CNS remyelination are derived from proliferating oligodendrocyte precursor cells (OPC). Using cre/lox technology for OPC fate mapping we have previously demonstrated that these cells give rise not only to oligodendrocytes but also astrocytes and Schwann cells in response to demyelination. We have demonstrated that Schwann cells, derived form OPC, occupied almost exclusively the tissue around blood vessels in astrocyte-deficient areas. It suggests that the peri-vascular microenvironmental niche is the critical determinant of this alternative fate choice phenomenon. The aim of present study was to identify and characterise the microenviromental factors and their downstream cellular effectors determining the fate of adult CNS precursor cells which could be modulated in order to control the remyelination process. We used a well-defined demyelination model that involves bilateral stereotaxic injection of ethidium bromide into the brain white matter of adult rats. At 6 and 10 days after lesion animals were sacrificed and the fresh frozen sections were subjected to immunohistochemical detection of endothelial cell markers, to establish the area of vascular and non-vascular niches. Tissue was then microdissected from pre-defined niches by using infrared and ultraviolet laser capture microdissection system. The microdissected cells represent the in vivo state of the cells at the time of cells recruitment and early differentiation. The tissue was collected as a separate niche pools and RNA was extracted for global gene expression analysis. The major outcome of present work is identification of microenviromental factors and quantitative spatial and temporal profile of their expression in the specific niche. Our data serves as a starting point to explore in details the molecular pathways involved in multipotentiality of precursor cells induced by mixed extrinsic microeviromental signals.
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