Olfactory ensheathing cells and Schwann cells differ in their in vitro interactions with astrocytes

Transplanted olfactory ensheathing cells (OECs) are able to remyelinate dem yelinated axons and support regrowth of transected axons after transplantat ion into the adult CNS, Transplanted Schwann cells (SCs) share these repair properties but have limitations imposed on their behavior by the presence of astrocytes (ACs). Because OECs exist alongside astrocytes in the olfacto ry bulb, we have hypothesized that they have advantages over SCs in transpl ant-mediated CNS repair due to an increased ability to integrate and migrat e within an astrocytic environment. In this study, we have tested this hypo thesis by comparing the interactions between astrocytes and either SCs or O ECs, using a range of in vitro assays. We have shown that (1) astrocytes an d SCs segregate into defined non-overlapping domains in co-culture, whereas astrocytes and OECs freely intermingle; (2) both SCs and OECs will migrate across astrocyte monolayers, but only OECs will migrate into an area conta ining astrocytes; (3) SCs spend less time in contact with astrocytes than d o OECs; and (4) astrocytes undergo hypertrophy when in contact with SCs, bu t not with OECs. Expression of N-cadherin has been implicated as a key medi ator of the failure of SCs to integrate with astrocytes. However, we found no differences in the intensity of N-cadherin immunoreactivity between SCs and OECs, suggesting that it is not the adhesion molecule that accounts for the observed differences. In addition, the number of astrocytes expressing chondroitin sulfate proteoglycans (CSPG) is increased when astrocytes are co-cultured with Schwann cells compared with the number when astrocytes are grown alone or with OECs. Taken together, these data support the hypothesi s that OECs will integrate more extensively than Schwann cells in astrocyti c environments and are therefore better candidates for transplant-mediated repair of the damaged (C) 2000 Wiley-Liss, Inc.