Biophysical properties, morphology and gap junction coupling of olfactory ensheathing cells

LORENA RELA; ANGELIQUE BORDEY; CHARLES A. GREER

San Francisco, CA, Estados Unidos

Simposio; International Symposium on Olfaction and Taste; 2008

International Symposium on Olfaction and Taste

Olfactory ensheathing cells (OECs) wrap axons of olfactory sensory neurons (OSNs) and promote axon growth in cell culture, and when transplanted, in animal models of spinal cord injury. We hypothesize that OECs communicate among themselves and with OSNs to regulate OSN axon growth and incorporation into olfactory circuits. With this hypothesis as guide, we began studying the biophysical and communication properties of OECs using whole-cell voltage-clamp in acute mouse olfactory bulb slices, and with immunohistochemistry. We found both linear current profiles and voltage- and time-dependent currents in OECs, showing that they are a heterogeneous population. Hyperpolarization-activated inward currents were blocked by 100 mM barium, identifying them as inwardrectifier potassium (K+) channels. Outward currents were partially blocked by 20 mM tetraethylammonium and 100 mM aminopyridine, K+ channel blockers. Dye-fills of OECs revealed a complex morphology with fine interdigitations and long lamellae surrounding axon bundles. Approximately 15 % of OECs were dye-coupled to 1- 9 other OECs, suggesting that coupling is regulated and may have a functional role. OEC markers colocalized with connexin43, a known mediator of glial gap junction coupling which likely mediates coupling among OECs. OECs seem to better promote axon growth in the olfactory nerve than when transplanted to sites of injury; studying them in their normal environment will help understand the mechanisms accounting for this difference. We present a characterization in normal conditions that establishes a foundation for studying OEC phenotypes in conditions of synchronized OSN regeneration after a lesion to the olfactory epithelium, in order to find candidate mechanisms involved in the role of OECs as regulators of circuit formation.