Infiltrating blood-derived macrophages invade brain areas affected by the pilocarpine-lithium model of TLE

ROSSI A, MURTA V, USACH V, VILLARREAL A, SETTON P, RAMOS AJ

Buenos Aires

Congreso; VIII Congreso Latinoamericano de Epilepsia; 2014

Objectives: The pilocarpine-lithium experimental model reproduces several features of human temporal lobe epilepsy (TLE). We have previously shown that gabapentin treatment drastically reduce reactive gliosis and neuronal loss when administered during 4 days following status epilepticus (SE) (Rossi et al PloS One, 2013). Here we investigated if the affected brain areas hippocampus and pyriform cortex were also invaded by blood derived macrophages that may contribute to the neuroinflammation, reactive gliosis and neuronal death.   Methods: Adult male Wistar rats were injected intraperitoneally (ip) with 3mEq/Kg LiCl and 20h later they received 30 mg/Kg pilocarpine. 15 minutes after the onset of the status epilepticus (SE), seizures were finished by the injection of 20mg/Kg diazepam. A group of animals received either white blood cells or bone marrow cells collected from the femurs and the tibia of eGFP transgenic Wistar rats. Animals were sacrificed at 3, 7 or 15 DPSE (days post-SE).     Results: A profuse gliosis was observed during the latency period with a peak of maximal microgliosis at 7DPSE and astrogliosis at 15DPSE, respectively. At 3DPSE macrophage-like cells accumulated in striatum, hippocampus and pyriform cortex. Many of these cells expressed the macrophage NG2 chondroitin sulfate proteoglycan and bound tomato-lectin. At 7 and 15DPSE macrophages showed a different morphology, indistinguishable from resident reactive microglia.   Conclusions: Blood derived macrophage invasion seems to precede reactive gliosis evaluated by phenotypical parameters, thus challenging the hypothesis that reactive glia recruits infiltrating cells. These initial steps occurring during the latency period are essential for understanding epileptogenesis.