Phagocytosis of bacteria by olfactory ensheathing cells and Schwann cells

Abstract

Opportunistic bacterial infections of the nasal cavity could potentially lead to infection of the brain if the olfactory or trigeminal nerves are colonised. The olfactory nerve may be a more susceptible route because primary olfactory neurons are in direct contact with the external environment. Peripheral glia are known to be able to phagocytose some species of bacteria and may therefore provide a defence mechanism against bacterial infection. As the nasal cavity is frequently exposed to bacterial infections, we hypothesised that the olfactory and trigeminal nerves within the nasal cavity could be subjected to bacterial colonisation and that the olfactory ensheathing cells and Schwann cells may be involved in responding to the bacterial invasion. We have examined the ability of mouse OECs and Schwann cells from the trigeminal nerve and dorsal root ganglia to phagocytose Escherichia coli and Burkholderia thailandensis in vitro. We found that all three sources of glia were equally able to phagocytose E. coli with 75-85% of glia having phagocytosed bacteria within 24h. We also show that human OECs phagocytosed E. coli. In contrast, the mouse OECs and Schwann cells had little capacity to phagocytose B. thailandensis. Thus subtypes of peripheral glia have similar capacities for phagocytosis of bacteria but show selective capacity for the two different species of bacteria that were examined. These results have implications for the understanding of the mechanisms of bacterial infections as well as for the use of glia for neural repair therapies.

Burkholderia pseudomallei Capsule Exacerbates Respiratory Melioidosis but Does Not Afford Protection against Antimicrobial Signaling or Bacterial Killing in Human Olfactory Ensheathing Cells

“…In the primary olfactory nerve, OECs are the principal phagocytic cells and macrophages are largely excluded even after injury (53). OECs can phagocytose bacteria in vitro (54)(55)(56). We did not investigate invasion of the central nervous system in the present study, but our data demonstrate a tropism of B. pseudomallei for the OM and a defensive reaction by OECs to the bacteria, which supports these previous findings.…”

Burkholderia pseudomallei Rapidly Infects the Brain Stem and Spinal Cord via the Trigeminal Nerve after Intranasal Inoculation

“…We and others have shown that olfactory glia, olfactory ensheathing cells (OECs), play an essential role in preventing microbial invasion of the olfactory nerve by phagocytosing microorganisms (2,3). The glia of the trigeminal nerve are Schwann cells, which are also phagocytic and remove debris after peripheral nerve injury as well as at least some types of bacteria (3,4).…”

“…The glia of the trigeminal nerve are Schwann cells, which are also phagocytic and remove debris after peripheral nerve injury as well as at least some types of bacteria (3,4). Thus, glial cells in the nerves that innervate the nasal cavity constitute potentially critical defenses against microbial invasion of the brain.…”

The role of olfactory ensheating cells in regenerative medicine: review of the literature

“…Glial cells of the peripheral nervous system have phagocytic properties, being involved in protection from infection with different bacterial species. The nose is usually exposed to infections with different pathogen germs, which may affect also the fibers of the trigeminal and olfactory nerves found in the nasal cavity 14 . The olfactory nerve may be a more susceptible route because primary olfactory neurons are in direct contact with the external environment.…”

“…The olfactory nerve may be a more susceptible route because primary olfactory neurons are in direct contact with the external environment. It was shown that olfactory ensheathing cells and Schwann cells are involved in responding to the bacterial invasion, human OECs being able to phagocyte E. coli 14 .…”