IN-VITRO GENERATION OF ADULT-RAT OLFACTORY SENSORY NEURONS AND REGULATION OF MATURATION BY COCULTURE WITH CNS TISSUES

Olfactory sensory neurons (OSNs) are continually generated throughout life. Although previous studies have examined neurogenesis in olfactor y cell cultures derived from embryonic or newborn rodents, we demonstr ate neurogenesis in cell cultures derived from adult rat tissues. Diss ociated cells taken from adult rat nasal mucosal tissues (ANM cells) w ere plated onto a feeder layer of newborn rat cortical glia (astrocyte s) in serum-free conditions. Immature OSNs (stained for neuron-specifi c tubulin, NST) increased in number between 1 and 5 d in vitro (DIV) a nd in mass thereafter. Mature OSN (stained for olfactory marker protei n, OMP) numbers decreased between I and 5 DIV, then increased over 5 D IV values by 12 and 15 DIV. Pulse labeling with [H-3]thymidine confirm ed in vitro neurogenesis. To determine whether the target cells for OS Ns, olfactory bulb (OB) neurons, provide trophic support, dissociated newborn rat OB cells were cocultured with ANM cells on glia. This resu lted in greater numbers of OMP-positive (OMP+) neurons after 9 DIV tha n ANM-alone cultures. This neurotrophic effect was not OB specific. Ad dition of newborn rat cerebellar and embryonic rat ventral mesencephal ic cells to ANM cells also increased OMP+ neurons, whereas addition of newborn rat cortical cells or controls (purified glia or fibroblasts) did not. Changes in numbers of dopaminergic neurons (stained for tyro sine hydroxylase), present in OB and VM cultures, did not correlate wi th OMP+ neuronal increases. Thus, cultures of adult rat OSNs demonstra te neurogenesis, and trophic/maturation support is variably provided b y CNS neurons (and not glia).