Fig. 4. Proliferating cells in the injured spinal cord include microglia, macrophages, and astrocytes. Double-label immunohistochemistry for OX42 (microglia and macrophages;gray) and BrdU (brown;A–D), and GFAP (astrocytes; gray) and BrdU (brown; E, F).A, Epicenter cross-section at 7 d after injury. Most BrdU+ cells and OX42+ cells are located in the central region of the section in an overlapping manner. B, High-power view of the box in A. Several macrophages double-labeled with OX42 and BrdU are visible (arrows).Arrowheads indicate two macrophages without BrdU+ nuclei. Scale bar: B, F, 10 μm.C, Section 1 cm rostral to epicenter at 7 d after injury. Many activated microglia were visible, especially within the fasciculus gracilis (asterisk) and gray matter. Central canal is indicated by the arrow. Scale bar, 100 μm.D, High-power view of the box inC showing a ramified microglial cell double-labeled with BrdU, indicating that microglial cells relatively long distances from the impact site respond rapidly to SCI. Scale bar, 5 μm.E, Epicenter cross-section at 7 d after injury. Most GFAP+ cells are located within the spared rim of tissue, whereas most BrdU+ cells are found centrally. F, High-power view of the box in E. One astrocyte double-labeled with GFAP (gray) and BrdU (brown) is denoted by the arrow.