Iba1 expressing microglia in the dorsal root ganglia become activated following peripheral nerve injury in rats.

The presence of microglia in dorsal root ganglia (DRG) has not been reported earlier. The dorsal root ganglia contain satellite glial cells (SGCs) and macrophages, which are considered to have infiltrated from the systemic blood. An attempt was made to investigate whether microglia as found in the central nervous system are also present in the dorsal root ganglia of untreated rats and following experimental peripheral nerve injury. Female adult Wistar rats were subjected to sciatic nerve transection injury on the right hand side. The DRGs of the right side were studied with the contralateral DRGs of the left side serving as controls. The tissues, harvested at different time points after injury, following intracardial perfusion fixation, and frozen sections were immunolabeled with anti-GFAP as a marker for SGCs and anti-Iba1 and OX-6 as markers for microglia and activated macrophagic microglia, respectively. These antibodies were also used in combination to ascertain if Iba1+ cells are the SGCs or otherwise and also if macrophagic OX-6+ cells are Iba1 positive microglia. The results indicate that Iba1 positive microglial cells are different from the SGCs in the DRGs. The Iba1 positive microglial cells respond to the sciatic nerve injury becoming activated and macrophagic and express MHCII molecules. Such activated microglia apparently may serve as neurosupportive cells, providing neuroprotection and scavenging cellular debris in response to the injury.