Oligodendroglial-derived stress signals recruit microglia in vitro.

Rat oligodendrocytes cultured without the essential survival factors serum and insulin die over a 48 h period. Analysis of supernatants from these dying cultures reveals a microglial chemokine released in advance of significant cell death. The observed microglial chemotactic effect is dose-dependent and not due to release of cellular debris. Interferon (IFN)-gamma activated microglia are more sensitive to the microglial chemokine. We show in co-culture that recruited non-activated microglia can enhance oligodendroglial survival whereas IFN-gamma activation of microglia induces contact-dependent oligodendroglial death. Thus, whilst the initial recruitment of microglia by stressed oligodendroglia may represent part of a survival process engaged by injured cells, this does not necessarily ensure survival.