Expression of GFAP in satellite glial cells after tooth extraction

Objectives: After a peripheral nerve injury in the oral region, the trigeminal ganglion (TG) neurons produce various neuropeptides that are secreted retrogradely and modulate the inflammation. Neurons in the TG are surrounded by an envelope of satellite glial cells (SGCs) that passively support the function of the neurons. However, little is known about the interactions between the SGCs and TG neurons after a peripheral nerve injury. To examine the effect of nerve injury on SGCs, we investigated the relationship between cell injury and satellite cell activation in rat TG neurons and SGCs following upper molar extraction.

Methods: Rats were anesthetized and their upper molars were extracted. Under deep anesthesia with diethyl ether, the animals were perfused transcardially with 4% paraformaldehyde 3 and 7 days after extraction, and the TG was removed. Cryosections were immunostained using antibodies against ATF3, a marker of damaged neurons, and glial fibrillary acidic protein (GFAP), a marker of activated SGCs.

Results: Three days after tooth extraction, ATF3 immunopositive neurons appeared in the maxillary nerve region in the TG and were present through day 7. Both ATF3 and GFAP immunopositive SGCs were initially observed at day 3 and they increased in number at day 7 in the maxillary nerve region, especially around ATF3-IR neurons, whereas in the mandibular nerve region, few SGCs with immunoreactivity for GFAP were seen.

Conclusions: These results suggest that a peripheral nerve injury affects not only the activation of TG neurons but also the activation of SGCs around the injured neurons, which may be involved in the maintenance of neurogenic pain.