High Morphologic Plasticity of Microglia/Macrophages Following Experimental Intracerebral Hemorrhage in Rats

Abstract

As current efforts have limited effects on the clinical outcome of intracerebral hemorrhage (ICH), the mechanisms including microglia/macrophages that involved inflammation need further investigation. Here, 0.4 units of collagenase VII were injected into the left caudate putamen (CPu) to duplicate ICH rat models. In the brains of ICH rats, microglia/macrophages, the nearest cells to the hemorrhagic center, were observed as ameboid and Prussian-blue positive. Furthermore, the ameboid microglia/macrophages were differentiation (CD) 68 and interleukin-1β (IL-1β) positive, and neither CD206 nor chitinase3-like 3 (Ym1) positive, suggesting their strong abilities of phagocytosis and secretion of IL-1β. According to the distance to the hemorrhagic center, we selected four areas—I, II, III, and IV—to analyze the morphology of microglia/macrophages. The processes decreased successively from region I to region IV. Microglia/macrophages in region IV had no processes. The processes in region I were radially distributed, however, they showed obvious directivity towards the hemorrhagic center in regions II and III. Region III had the largest density of compactly arrayed microglia/macrophages. All these in vivo results present the high morphologic plasticity of microglia/macrophages and their functions in the pathogenesis of ICHs.

Modulators of microglial activation and polarization after intracerebral haemorrhage

“…In rodents, secretion of proinflammatory cytokines IL-1β, IL-6 and TNF increased in the first 3 days 56 , and then returned to within the normal range on day 7 in both colla-genase-induced 37 and blood-induced 37,54 models of ICH. Interestingly, IL-1β, but not TNF, macrophage mannose receptor 1 (CD206) or chitinase-like protein 3 (also known as Ym1), colocalized with amoeboid microglia in rats with collagenase-induced ICH 57 . This colocalization pattern suggests a phagocytic and secretory phenotype that might be associated with dynamic changes in microglial morphology 57 .…”

“…Interestingly, IL-1β, but not TNF, macrophage mannose receptor 1 (CD206) or chitinase-like protein 3 (also known as Ym1), colocalized with amoeboid microglia in rats with collagenase-induced ICH 57 . This colocalization pattern suggests a phagocytic and secretory phenotype that might be associated with dynamic changes in microglial morphology 57 . Moreover, treatment with the TNF receptor antagonist R-7050 attenuated neurovascular injury and improved functional outcomes in mice with collagenase-induced ICH 58 .…”

Functions of lactate in the brain of rat with intracerebral hemorrhage evaluated with MRI/MRS and in vitro approaches

“…The stereotactic injections were completed in a stereotactic injection system. The detailed steps of ICH animal model generation were described in our pervious study 14 ; thus, only brief steps were provided here. 2 μL (0.4 U) collagenase VII was stereotaxically injected into CPu of the rat brain for the generation of the ICH model, and the vehicle solution 0.9% NaCl (2 μL) was also injected into the same location in sham group.…”

“…And the 1st, 3rd, 7th, 14th, and 28th days, animal behavioral studies were applied, including the balance beam 15 and elevated body swing 16 tests. The procedures of these two studies were exactly the same as in our previous study 14 ; thus, their detailed descriptions are omitted here.…”

“…The brain was collected and sunk with 20% and 30% sucrose gradient. Then, the fixed brain was cut into sections (20 μm) with a freezing microtome (Cryostat 1720, Leitz, Wetzler, Germany) for staining—immunohistochemistry and Prussian blue staining 14 …”