Morphology of reactive microglia in the injured cerebral cortex. Fractal analysis and complementary quantitative methods

The present study focuses on application of quantitative methods measuring differences between particular morphological types of microglial cells as w ell as between their proliferating and non-proliferating examples. On the b asis of subjective classification, microglial cells of three morphological types (ramified, hypertrophied and bushy) were selected from the neocortex of injured rat brain. Thereafter, the morphological complexity of each cell was assessed by calculation its fractal dimension as well as its form fact or, convexity, ramification factor and solidity. The fractal dimension seem ed a good parameter for detecting small changes in the space-filing capacit y of cells, for example, it shows differences between ramified cells from c ontrol and injured brains. This measure seemed insensitive to some aspects of cell morphology. To obtain precise quantification of observed changes ot her morphological parameters had to be applied. Proliferating and non-proli ferating microglial cells displayed significant differences in their solidi ty and ramification factors, but not in fractal dimension and convexity. Th e results indicated that proliferating microglia were more massive and less -ramified but they did not reduce their spatial complexity. (C) 2001 Wiley- Liss, Inc.