Microglial Ablation Model in Glioma

A model of local microglial ablation using CD11b-HSVTK transgenic mice expressing the herpes simplex thymidine kinase (HSVTK) protein in microglia and macrophages [9 (link), 36 (link)] was employed. When these animals are exposed to ganciclovir (GCV), the cells that express HSVTK are eliminated. CD11b-HSVTK (+/-) male mice (gift of Dr. Tsirka, Stonybrook University) were bred with C57BL/6 males. Offspring were genotyped by PCR using primers 5′ -GACTTCCGTGGCTTCTTGCTGC-3′ and 5′ -GTGCTGGCATTACAGGCGTGAG-3′. GL261 glioma cells were implanted into the right cerebral hemisphere of 12–16 week old CD11b-HSVTK (+/-) mice. C57BL/6 mice were used as controls. Tumors were allowed to grow for ten days and then mini-osmotic pumps (Alzet, DURECT, model 2004) were installed for local administration of GCV (Calbiochem, Billerica, MA, USA) to the tumor. Animals were anesthetized and a 3mm brain infusion cannula connected to pump was set up at the previous tumor implantation site using brain infusion kit (Alzet, DURECT). The pumps were placed subcutaneously on the mouse back. The drug was infused at 0.25 μL/h, 1 mg/mL over 7 days. Pumps with normal saline solution were used as a control.