Beneficial effects of bone marrow mononuclear cells on the demyelinated sciatic nerve of the rat

USACH V; LOPEZ MARGARITA; LAVALLE LUCIA; MARTINEZ VIVOT ROCíO; BRUSCO ALICIA; SETTON, CLARA P

Washington

Congreso; 41 Annual Meeting of the Society for Neuroscience; 2011

Society for Neuroscience

Demyelination is known to be one of the distinctive features of Wallerian degeneration. In the context of such a process -induced by the crush of the sciatic nerve- we have described the reorganization of major myelin proteins (P0 and MBPs) and the axonal protein PGP 9.5 in the demyelinated area, as well as the recovery of nerve fiber structure as from day 28 post-lesion. We have also demonstrated fresh CD34+ bone marrow mononuclear cells (BMMC) migration exclusively to the ipsilateral nerve. Once there, some BMMC have been observed to conserve their phenotype (CD34+), while others have changed it (S100â+, MBP+ and PGP9.5+). The aim of the present work is to evaluate the effect of BMMC on remyelination and the biological signals involved in their recruitment. Adult rats were submitted to sciatic nerve crush and sacrificed 7 and 14 days post injury. The ipsilateral nerve was dissected in proximal, crush and distal areas. BMMC were isolated from rat bone marrow and injected intravenously immediately after crush. Electronic microscopy was performed in order to analyze ultrastructural changes, and immunohistochemical analysis was done to evaluate myelin and nerve fiber integrity. All experiments were done comparing BMMC-transplanted animals with non transplanted animals. The participation of prostaglandins (PGs) in cell recruitment was evaluated through Western blot analysis of their biosynthetic enzymes -Cox1 and Cox2- within 24 hours after sciatic nerve crush. All studies were done comparing ipsilateral to contralateral nerve. Our results demonstrate a reduction in MBP and P0 clusters, as well as the presence of more myelinated axons in the crush and distal area in BMMC-transplanted rats. However, their myelin structure is still different from control axons. No significant differences were observed in the proximal area of animals transplanted with BMMC. As regards PGs analysis, the expression of the constitutive enzyme Cox-1 shows an increase 4 hours after lesion, while the expression of inducible Cox-2 is observed 6 hours after nerve injury and continues until 24 hours, suggesting the participation of PGs in BMMC recruitment. These data suggest a beneficial effect of BMMC on myelination either by preventing demyelination or stimulating remyelination through the elimination of myelin debris, transdifferentiation to Schwann cells or the release of factors that help the process. Nevertheless, further experiments will be necessary to elucidate the mechanisms involved in BMMC migration.