The role of bone marrow mononuclear and mesenchymal stem cells in the demyelination-remyelination process.

VANINA USACH, ; LUCíA LAVALLE; ROCíO MARTINEZ VIVOT ; PATRICIA SETTON

San Diego, Estados Unidos de Norteamérica

Congreso; 40th annual meeting of the Society for Neuroscience's,; 2010

Society for Neuroscience

We have previously described, in a model of crushed sciatic nerve, the reorganization of major myelin proteins (P0 and MBPs) as well as the axonal protein PGP 9.5 in the ipsilateral nerve during the demyelination period. Nerve fiber structure recovery began 28 days after the lesion, reaching control levels 60 days post injury. Using the same experimental model, we have also demonstrated fresh CD34+ bone marrow mononuclear cells (BMMC) migration exclusively to the ipsilateral nerve, either spontaneously or after intravascular injection, 5 days after the lesion. In the present work, according to our previous results, we have characterised BMMCs as well as mesenchymal stem cells (MSC) in order to evaluate changes in their phenotype after reaching the demyelinated area. For this purpose we have studied the colocalization of BMMC/MSC with Schwann cell (SC) markers. We have also analysed MSCs capacity to acquire a SC-phenotype (SC-MSC) in vitro. Adult female Wistar rats were submitted to right sciatic nerve crush and were sacrificed 5 days post injury. BMMC were isolated from male rat bone marrow. A group of cells were immediately processed and the rest were seeded. The cultured adherent cells were grown to confluence (MSC). BMMC and MSC were dyed with a fluorescent probe and injected intravenously without delay after crushing the sciatic nerve in order to evaluate the migration of these cells to the injured area. Immunohistochemycal analysis was done to evaluate the phenotype of BMMC/MSC once they have reached the nerve. Western Blot, immunocytochemistry and flow cytometry analysis were performed to characterise BMMC, MSC and SC-MSC.  The results show that CD34+ cells represent approximately 5% of the BMMCs and 35-40 % of the MSC. MSC also express CD90, p75NTR, CD68 and nestin. When MSC were incubated in a prodifferentiating medium, although some cells expressed SC’ markers, the in vitro differentiation was not complete. Though the precise role of BMMC migration remains uncertain, we can suggest that BMMC/MSC might help to remove myelin debris during the demyelination period or stimulate remyelination by transdifferentiating to SC. Our results demonstrate that, once the cells reach the injured nerve, they co-localize with S100â and CD34 but not with CD68. This might suggest the participation of the transdifferentiated cells in the remyelination process. Further experiments will be necessary to elucidate the mechanism involved in BMMC/MSC migration in order to promote remyelination of the ipsilateral nerve and to decide which cell population (SC-MSC or BMMC/MSC) would be best for future cellular therapies.