Immune Responses in Mice after Blast-Mediated Traumatic Brain Injury TBI Autonomously Contribute to Retinal Ganglion Cell Dysfunction and Death

Purpose: The purpose of this study was to examine the role of the immune system and its influence on chronic retinal ganglion cell (RGC) dysfunction following blast -mediated traumatic brain injury (bTBI). Methods: C57BL/6J and B6.129S7-Rag1(tm1Mom)/J (Rag-( /-)) mice were exposed to one blast injury of 140 kPa. A separate cohort of C57BL/6J mice was exposed to sham-blast. Four weeks following bTBI mice were euthanized, and splenocytes were collected. Adoptive transfer (AT) of splenocytes into naive C57BL/6J recipient mice was accomplished via tail vein injection. Three groups of mice were analyzed: those receiving AT of splenocytes from C57BL/6J mice exposed to blast (AT-TBI), those receiving AT of splenocytes from C57BL/6J mice exposed to sham (AT-Sham), and those receiving AT of splenocytes from Rag(-/-)mice exposed to blast (AT-Rag(-/-)). The visual function of recipient mice was analyzed with the pattern electroretinogram (PERG), and the optomotor response (OMR). The structure of the retina was evaluated using optical coherence tomography (OCT), and histologically using BRN3A-antibody staining. Results: Analysis of the PERG showed a decreased amplitude two months post-AT that persisted for the duration of the study in AT-TBI mice. We also observed a significant decrease in the retinal thickness of AT-TBI mice two months post-AT compared to sham, but not at four or six months post-AT. The OMR response was significantly decreased in AT-TBI mice 5-and 6-months post-AT. BRN3A staining showed a loss of RGCs in AT-TBI and AT -Rag(-/-)mice. Conclusion: These results suggest that the immune system contributes to chronic RGC dysfunction following bTBI.