GFAP immunoreactivity in trigeminal ganglion satellite cells after tooth injury in rats

Glial fibrillary acidic protein (GFAP) is a member of a heterogeneous group of intermediate filaments in glial cells of both the central and peripheral nervous systems. We demonstrate here that satellite cells in the trigeminal ganglion (TG) increase immunoreactivity (IR) for GFAP in response to dental injury. The satellite cell reaction was most often confined to the somatotopic region of the ganglion that corresponded to the zone of damage in the periphery, although in some cases it was seen to spread out from a focal center in the maxillary region to neighboring zones corresponding to cell bodies that innervate other tissues such as the cornea. We used two methods to demonstrate that the increase in satellite cell GFAP-IR was site specific and injury related. First, by altering the site of the pulp exposure from the maxillary molars to the mandibular molars, we could change the site of satellite cell reaction in the TG. Second, we used combined retrograde transport of DiI from the molar pulp and GFAP immunofluorescence to show direct correspondence between neurons that innervate the molars and neurons that are encircled by GFAP-IR satellite cells. The satellite cell GFAP-IR was seen at 3 and 7 days, the longest time point examined here. This GFAP response in satellite cells around injured sensory neurons will be a useful tool in future studies of mechanisms in trigeminal pain and neuron-support cell interactions. We conclude that a GFAP-IR satellite cell reaction is induced in TG by an injury to the molar pulp in a site specific manner at 3-7 days.