SCIP/Oct-6, Krox-20, and desert hedgehog mRNA expression during CNS remyelination by transplanted olfactory ensheathing cells

Olfactory ensheathing cells (OECs), although having a separate developmenta l origin to Schwann cells, are able to generate myelin sheaths following tr ansplantation into areas of CNS demyelination that are remarkably similar t o those made by Schwann cells. The transcriptional control of Schwann cell myelination has been well documented, in particular the role of SCIP/Oct-6 and Krox-20. It is not known, however, whether these transcription factors are also expressed when OECs assume a myelinating phenotype. In this study, we addressed this question by using a transplantation approach to generate myelinating OECs and then examined the expression of SCIP/ Oct-6 and Krox- 20 mRNA by in situ hybridization using oligonucleotide probes. We also exam ined the expression of desert hedgehog (Dhh), a Schwann cell-derived signal ing molecule that is responsible for regulating the development of the conn ective tissue elements in peripheral nerve, which bear similarities to the morphologies adopted by nonmyelinating transplanted cells. Our results indi cate that both Krox-20 and Dhh mRNA are strongly expressed by transplanted OECs, with SCIP mRNA present at much lower levels. The expression of Krox-2 0 relative to the expression of PO mRNA by the transplanted OECs is consist ent with its playing a similar role in OEC myelination to that in Schwann c ell myelination, while the expression of Dhh suggests a possible mechanism for the diverse morphologies that cells adopt following OEC transplantation into the damaged CNS. Taken together, our results provide further evidence for the close similarity of OECs and Schwann cells and suggest that, despi te their separate origins, the manner in which they generate a peripheral-t ype myelin sheath involves similar regulatory mechanisms. (C) 2001 Wiley-Li ss, Inc.