SUBSTRATE-DEPENDENT INTERACTIONS OF LEECH MICROGLIAL CELLS AND NEURONS IN CULTURE

The principal aim of the present experiments hits been to analyze the properties of microglial cells :and their role in nerve regeneration. In the leech, damage to the CNS has been shown to be followed by accum ulation of laminin and microglial cells at the site of injury( Masuda- Nakagawa et at, 1990. Proc. R. Soc. Lond. B. 241:201-206; and 1993. Pr oc. Natl. Acad. Sci. USA 90:4966-4970). Procedures were devised for is olating these small, wandering cells from the CNS of the leech. In cul ture, they were reliably identified by their sizes, shapes, and phagoc ytotic activity. Their morphology, motility, and interactions with neu rons were influenced by the substrate molecules on which they were pla ted. On the plant lectin concanavalin A (Con A) microglia had a rounde d shape and remained stationary. By contrast on extracts of leech extr acellular matrix (ECM) enriched with laminin the cells were mobile and spindle-shaped with long processes. On Con A, neuronal growth cones a voided microglial cells, whereas on ECM extract the presence of a micr oglial cell did not influence neurite grow th. Microglial cells showed immunoreactivity on both substrates when stained with a monoclonal an tibody against leech laminin. Together these results suggest that micr oglial cells are influenced in their properties by molecules in the en vironment and that they could contribute to neuronal outgrowth at the site of an injury. (C) 1994 John Wiley and Sons, Inc.