Changes in Kolmer Cells in SHR Rats after Cerebral Ischemia

Kolmer cells (epiplexus macrophages) constitute the least studied population among the phagocytosing cells in the mammalian brain. We report here studies of the reactions of these cells to ischemic brain injury induced by brief termination of the blood supply in the basin of the middle cerebral artery. These studies used rats of spontaneously hypertensive strain SHR and normotensive WKY rats. Kolmer cells in normotensive WKY animals had small volumes of perinuclear cytoplasm with concentration of Iba-1 protein in the cortical layer and typical fine and sometimes tortuous processes. Moderate activation induced by increased arterial pressure in control SHR rats was accompanied by an increase in the volume of perinuclear cytoplasm and the appearance of numerous straight fine processes. Further activation induced by ischemia led to loss of processes, cells taking up a round shape. These structural rearrangements were accompanied by disappearance of the Iba-1 protein concentration gradient in the cytoplasm. This study also provided the first observation of the intranuclear accumulation of cytoplasmic Iba-1 protein in Kolmer cells, regardless of their activation, indicating that this protein is multifunctional within the cells. These results provide evidence that Kolmer cells are involve in the responses of the cerebral brain to injury.