gms | German Medical Science

Introduction: A large body of work supports the proposal that transplantation of OECs into various nerve injuries can promote axonal regeneration and restore functional recovery. Yet, there is an important controversy as to whether the transplanted OECs associate with axons and form peripheral myelin, or if they recruit endogenous SCs that form myelin.

Material and methods: Olfactory bulbs from transgenic mice expressing the enhanced green fluorescent protein (eGFP) under the control of the 2-3-cyclic nucleotide 3-phosphodiesterase (CNPase) promoter were studied. Here, we examined CNPase expression in OECs from adult CNPase transgenic mice both in situ and in vitro in order to determine if OECs express CNPase commensurate with their myelination potential.

Results: eGFP was observed in the nuclei and cytoplasm of glial cells in the outer nerve layer (ONL) of the olfactory bulb where olfactory ensheathing cells (OECs) reside, and in oligodendrocytes in the interior of the olfactory bulb. Immunohistochemical analysis for CNPase in the olfactory bulb demonstrated weak expression of CNPase in the ONL, but intense expression in oligodendrocytes. However, dissociated OECs derived from the olfactory bulb and maintained in culture for 4 days had both intense eGFP expression and CNPase immunostaining. Transplanted eGFP cells survived in peripheral nerve.

Conclusion: These data indicate that CNPase expression of OECs in vivo is present as evidenced by accumulated intracellular eGFP in OECs of the ONL in CNPase transgenic mice. Moreover, in culture the OECs maintain strong eGFP expression, but also increase their expression CNPase. Thus, while OECs do not normally form myelin on the fine calibre olfactory nerve axons, their upregulation of CNPase in culture is commensurate with reports that transplantation of cultured OECs can form myelin when transplanted into injured peripheral nerve.