Figure 2

Upregulated cell cycle proteins are associated with GFAP ⁺ reactive astrocytes at 4 weeks after SCI. (A-D) Immunohistochemistry for qualitative assessment of CDK4 expression at 4 weeks after SCI. Coronal section in intact spinal cord showed that CDK4 was mostly expressed in the gray matter (A). CDK4 immunoreactivity was increased in the spared tissues surrounding the central lesion at 1 mm caudal to the epicenter (B), which co-labeled with GFAP⁺ astrocytes (C and insert in D). Note that CDK4⁺ cells also appeared in the central lesion area where GFAP⁺ astrocytes are absent. (E-H) Double-labeling immunohistochemistry revealed increased expression of cyclin D1 (F) and GFAP (G), and their co-localization (insert in H) in the injured tissue at 4 weeks post-injury. (I-L) Cyclin E⁺/GFAP⁺ cells were broadly observed in the spared tissue (insert in L). (M-P) E2F5 is not only expressed by GFAP⁺ hypertrophic astrocytes (insert in P) in the lesion scar border, but also in the central lesion area where GFAP⁺ astrocytes are absent. Scale bars = 500 μm.