LOW-AFFINITY NGF-RECEPTOR AND E-N-CAM EXPRESSION DEFINE 2 TYPES OF OLFACTORY NERVE ENSHEATHING CELLS THAT SHARE A COMMON LINEAGE

Previously, we have shown that the O4 antibody can be used to define a nd purify olfactory nerve ensheathing cells (ONECs) from the rat olfac tory bulb by fluorescence-activated cell sorting. In this study, using a larger panel of neural markers, we demonstrate that this apparently homogeneous population of ONECs possess a heterogeneous antigenic pro file both in vivo and in vitro. The antigenic profile of the sorted ce lls initially correlated with their antigenic profile in vivo, althoug h expression of some of the markers was either lost or gained during t ime in culture. These changes were influenced by the culture condition s, with a greater loss of ''typical'' ONEC markers in serum-containing medium. In serum-free medium, which maintains the cells in a phenotyp e that closely resembles their in vivo counterparts, we were able to r eclassify the ONECs into two cell types based on morphology and antige nic phenotype by using antibodies to polysialic acid (correlating with the embryonic form of N-CAM expression) and the low-affinity nerve gr owth factor receptor. A detailed immunocytochemical study of the devel oping olfactory system showed that these two cell types could also be detected along the entire length of the olfactory nerve and the outer layer of the olfactory bulb from Embryonic Day 14 to adulthood, sugges ting they were not an in vitro artefact. To address the relationship b etween the two cell types we constructed a clonal ONEC cell line by re troviral infection with the temperature-sensitive mutant gene of the l arge T antigen. This clonal cell line contained cells that expressed a ntigenic phenotypes of both classes of ONECs, suggesting that both cel l types are related and share a common lineage. (C) 1996 Academic Pres s, Inc.