engleski

Development of microglia in the rhesus monkey during midgestation

In this study we examined microglial development in telencephalon of cynomolgus monkey between embryonic day (E) 68 and E90 using the rabbit IgG and two monoclonal antibodies against the CD11b (OX42) and CD68 epitop, as a specific marker of primate microglia. Aggregates of closely packed oval to amoeba like or polymorph cells with patchy cytoplasmic staining (resembling the macrophage morphology) were through analyzed period regularly seen: (a) bellow the corpus callosum, (b) in the ventricular/subventricular zone of the temporal cortex, (c) in the capsula interna, (d) in the capsula externa, and (e) in the ganglionic eminence. Smaller and not so densely packed aggregates were seen in the cingular bundle, rest of ventricular/subventricular telencephalic zone, fimbrial borders, as in the pia and plexus chorioideus. Numerous individual cells were seen in the intermediate zone and subplate.. In addition, solitary cells with processes were also found around the regions of microglia aggregations. These cells were stained by CD11b and CD68 antibody but not by rabbit IgG. Majority of this dendritic cells resemble morphology of ramified microglia ; most of them have one thick process bifurcating in brush like manner. On some of them few thinner processes could be distinguished and in many of them there was a patchy cytoplasmatic staining. The processes do not extend for distance longer than 50 microns with some varicosities. It is interesting that in addition to this dendritic like processes, on some of those cells one thin and longer, axon-like process is present. In addition to this two population, resembling morphology of amoeboid and ramified microglia, lightly labeled cells that have uni-bipolar morphology, typical for tangentionally migrating cells, and more differentiated, subplate neurons like cells were stained, too. Their density was highest around regions of microglia aggregates and decreased progressively in more distant positions, so that inside the cortical plate they were not observed. Thus, the highest density of the microglial cells is found on position of growing axon bundles and tantgentionaly migrating cell routes. Therefore, we suggest that in the monkey brain during midgestation microglial cells might be involved in axon guidance and tangentional migration. Our descriptive data also showed that these cells are at different stages of microglia differentiation, and that there might be interaction between microglia and immature/early born neurons. It seems that under influence of developing monkey brain environment, microglia can differentiate in to the cells that resemble closely neuron morphology.

microglia; monkey; fetus; brain; development

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