K. Mertsch et al., Characterization of microglial cells and their response to stimulation in an organotypic retinal culture system, J COMP NEUR, 431(2), 2001, pp. 217-227
An organotypic culture system of the early postnatal rat retina was develop
ed to study microglial activation within a tissue environment. One day afte
r tissue preparation, microglial cells of the ganglion cell/nerve fiber lay
er revealed features of activation. Cells acquired an ameboid morphology as
revealed by Bandeiraea simplicifolia lectin staining. Proliferation-as rev
ealed by Ki67 immunocytochemistry-resulted in higher cell densities. In the
supernatant, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6)
, and monocyte chemoattractant factor-1 (MCP-1) were detected by using spec
ific enzyme-linked immunosorbent assay systems, activated microglia being t
he most likely source of their release. After 6 days in vitro (div), microg
lial cells regained their resting morphology, and cell counts returned to c
ontrol levels. Concomitantly, the release activity decreased to undetectabl
e levels. When slices were treated at this later stage of cultivation (>6 d
iv) with bacterial lipopolysaccharide (LPS; 100 ng/ml for 24 hours), microg
lial cells became activated, as revealed by a change in morphology. In para
llel, the LPS treatment also resulted in high levels of TNF-alpha, IL-6, an
d MCP-1 in the culture medium. Both the release from the tissue and the mor
phological changes of the microglia were reversible. Seventy-two hours afte
r LPS removal, only microglia with ramified morphology were found, and rele
ase activities returned to baseline. These data suggest that the organotypi
c culture of the retina is a useful model for studying microglial activatio
n from its resting form. J. Comp. Neurol. 431:217-227, 2001. (C) 2001 Wiley
-Liss. Inc.