Foreign Body Reactions To Neural Implants In The Brain

Abstract

Neural implants have been used and studied for many decades. They are applied to record neural signals or to locally deliver drugs. Unfortunately, foreign body reaction and accompanied glial scar formation often lead to implant failure. The lack of knowledge about the molecular mechanism governing foreign body reactions in the brain significantly hinders the development of brain implantable devices with improved safety and biocompatibility. To study the immune responses to brain implants, a novel animal model has been developed and used for the following investigation. Our studies have established cell recruitment time courses of astrocytes, microglial cells, lymphocytes, monocytes and mesenchymal stem cells following implantation. The differential cell migration suggests an interesting interaction between these cells leading to glial scar formation. In a parallel studies, the potential role of lymphocytes and fibrin deposition on foreign body reactions in the brain was also tested using Severe Combined Immuno Deficient mice and heparin therapy. Our results clear support that both T lymphocyte accumulation and fibrin deposition surrounding brain implants play a critical role in foreign body reactions to brain implants. It is our belief that the results obtained from this work will help the development of better and safer implantable brain devices.