Mouse model for ablation of proliferating microglia in acute CNS injuries

Activation of microglia, the primary immune effectors of the CNS and proinflammatory signaling, is a hallmark of brain damage. However, it remains controversial whether microglial cells have beneficial or detrimental functions in various neuropathological conditions. We report the generation of transgenic mice that express a mutant form of herpes simplex virus type 1 thymidine kinase (HSV-1 TKmt-30) driven by the myeloid-specific CD11b promoter. Using two paradigms of nervous system damage, hypoglossal nerve axotomy, and cortical stab injury, we show that specific ablation of proliferating microglia in CD11b-TKmt-30 mice can be achieved by administration of ganciclovir. For example, after hypoglossal nerve injury, a 75% reduction in proliferating microglial cells was observed at the site of injury. The CD11b-TKmt-30 transgenic mouse should provide a valuable tool for studying the role of microglia in CNS damage and repair. (C) 2005 Wiley-Liss, Inc.