Distribution of the hematopoietic growth factor G-CSF and its receptor in the adult human brain with specific reference to Alzheimer's disease

Abstract

The granulocyte colony-stimulating factor (G-CSF), being a member of the hematopoietic growth factor family, is also critically involved in controlling proliferation and differentiation of neural stem cells. Treatment with G-CSF has been shown to result in substantial neuroprotective and neuroregenerative effects in various experimental models of acute and chronic diseases of the central nervous system. Although G-CSF has been tested in a clinical study for treatment of acute ischemic stroke, there is only fragmentary data on the distribution of this cytokine and its receptor in the human brain. Therefore, the present study was focused on the immunohistochemical analysis of the protein expression of G-CSF and its receptor (G-CSF R) in the adult human brain. Since G-CSF has been shown not only to exert neuroprotective effects in animal models of Alzheimer's disease (AD) but also to be a candidate for clinical treatment, we have also placed an emphasis on the regulation of these molecules in this neurodegenerative disease. One major finding is that both G-CSF and G-CSF R were ubiquitously but not uniformly expressed in neurons throughout the CNS. Protein expression of G-CSF and G-CSF R was not restricted to neurons but was also detectable in astrocytes, ependymal cells, and choroid plexus cells. However, the distribution of G-CSF and G-CSF R did not substantially differ between AD brains and control, even in the hippocampus, where early neurodegenerative changes typically occur.

Keywords: Alzheimer's disease; granulocyte colony-stimulating factor; granulocyte colony-stimulating factor receptor; immunohistochemistry; neurotrophin.

Figure 1

G-CSF and G-CSF R IR in ependymal cells (a and c, respectively) and cells of the choroid plexus (b and d, respectively) of control brains. There is only faint G-CSF IR in ependymal cells (a), whereas staining for the G-CSF R is stronger (c). The choroid plexus reveals faint to moderate labeling for the ligand (b), whereas, again, staining for the receptor is slightly more intense (d). Sections are counterstained with hematoxylin. Scale bar: 50 μm.

Figure 2

Distribution of G-CSF IR in the inferior temporal gyrus (a), the basal nucleus of Meynert (b), the cerebellum (c) and the inferior olivary nucleus (d) of controls. Some scattered cortical neurons of the inferior temporal gyrus display faint immunostaining (a, arrows). By contrast, nearly all neurons of the basal nucleus of Meynert are labeled, although IR is only faint (b). In the cerebellum, G-CSF IR is largely absent (c). In the inferior olivary nucleus, all neurons and the neuropil (arrows) are faintly stained (d). Sections are counterstained with hematoxylin. Scale bars: 50 μm (all insets), 100 μm (a,b), and 400 μm (c,d), respectively.

Figure 3

Distribution of G-CSF R IR in the inferior temporal gyrus (a), the basal nucleus of Meynert (b), the cerebellum (c) and the inferior olivary nucleus (d) of controls. Pyramidal neurons of the inferior temporal gyrus display no immunostaining (a). Scattered neurons of the basal nucleus of Meynert are faintly labeled (b). Within the cerebellar cortex, only weak immunostaining is visible in the granule cell layer (c). In the inferior olivary nucleus, neurons are very weakly labeled, while faint staining is visible in the neuropil (d, arrows). Sections are counterstained with hematoxylin. Scale bar: 50 μm (all insets), 100 μm (a,b) and 400 μm (c,d), respectively.

Figure 4

Hippocampal distribution of G-CSF R IR in the hippocampus of control cases (a,b) and AD brains (c,d). At low magnification, no reliable IR is visible in the hippocampal formation (a). At higher magnification, very weakly stained hilar neurons are detectable (b). In consecutive sections from an AD brain, immunostaining for G-CSF R (c) and AT8 (d) clearly demonstrates that phospho-tau-positive neuronal structures are not labeled by antibodies recognizing G-CSF R. Similarly, amyloid plaques labeled with an anti-β-amyloid antibody (f, arrows) do not stain for G-CSF R (e, arrows). Sections are counterstained with hematoxylin. Scale bar: 50 μm (b), 100 μm (c,d), 200 μm (e,f), 400 μm (a).