A macrophage hippocampal slice co-culture system: application to the study of HIV-induced brain damage.

We have developed an in vitro system that allows the study of the effects of factors released from macrophages on neuronal and glial survival in cultured hippocampal slices. Organotypic hippocampal slice cultures are grown on semi-permeable membranes in stationary co-culture with a murine macrophage cell line (RAW 264.7). The two culture systems are separated by a semi-permeable membrane specifically allowing the study of diffusable factors between the two culture systems. The use of the fluorescent exclusion dye propidium iodide as an in vitro marker of cell viability allows the study of progressive toxicity as it evolves in the slice cultures. We demonstrate that the HIV-1 derived nuclear regulatory protein Tat induces toxicity in slice cultures via the production of soluble mediators. The advantages of organotypic cultures over other in vitro systems is discussed as well as the general applicability of this method to the study of other brain pathologies, where macrophage derived factors are thought to play a role in neuronal survival.