Abstract: Objective: To investigate the role of CS in the recruitment and response of microglia after facial nerve axotomy. Methods: CFDA was slowly injected into the spleen of CS-/- and wild-type mice. 24 h later, the right side facial nerves of these animals were axotomized at the stylomastoid foramen after injection. In some animals, The distal free axotomized end of the facial nerve was filled with DiI as a tracing marker of facial motoneuron. For double staining, sections of the brain stem were incubated with anti-CS,CB,chAT,MMP-9 antibody, then further treated with Iba1 or F4/80 antibody. After14,50days of axotomy, sections were incubated with anti-CD3 antibody, then further treated with Iba1 antibody. The specimens obtained from CS-/- and wild-type mice after a 7-day-axotomy were incubated with anti-CS,anti-CB and anti-MMP-9 for Westernblot analysis. The specimens were also treated with CS and CB RT-PCR analysis. ATP-induced migration/transmigration and GM-CSF-induced proliferation of primary cultured microglia assay were performed. Results: After axotomy, CS and MMP-9 were highly expressed in wild-type but not in CS-/- migroglia.CB was only expressed in wild-type motoneuron. CFDA and CD3 were only detected in wild-type FMN. RT-PCR and Westernblot analysis indicated that CS and MMP-9 increased only in wild-type FMN and CB increased only in CS-/- FMN after axotomy. Migration and transmigration assay indicated that CS deficiency impaired the invasive ability of monicitic cells including micrglia. There was no difference between both groups in microglial proliferation assay. Conclusion: CS deficiency impaired the recruitment and infiltration of monocitic cells and T lymphocytes into FMN after axotomy. The CS deficiency caused microglia to become neurotoxic and phagocytic.

Key words: Cathepsin S deficient mice , Facial nerve axotomy, Micoglia