SDF-1/CXCR7 Chemokine Signaling is Induced in the Peri-Infarct Regions in Patients with Ischemic Stroke
Zhang Yu1, Zhang Hongxia2, Lin Siyang3, Chen Xudong3, Yao Yu4, Mao XiaoOu5, Shao Bei3, Zhuge Qichuan1,3,*, Jin Kunlin2,3,*
1Department of Neurosurgery, the First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang 325000, China. 2Department of Pharmacology and Neuroscience, University of North Texas Health Science Center at Fort Worth, Texas 76107, USA. 3Zhejiang Provincial Key Laboratory of Aging and Neurological Disorder Research, the First Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang 325000, China. 4Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai 200040, China. 5Buck Institute for Age Research, Novato, California 94945, USA
Stromal-derived factor-1 (SDF-1, also known as CXCL12) and its receptors CXCR4 and CXCR7 play important roles in brain repair after ischemic stroke, as SDF-1/ CXCR4/CXCR7 chemokine signaling is critical for recruiting stem cells to sites of ischemic injury. Upregulation of SDF-1/CXCR4/CXCR7 chemokine signaling in the ischemic regions has been well-documented in the animal models of ischemic stroke, but not in human ischemic brain. Here, we found that protein expression of SDF-1 and CXCR7, but not CXCR4, were significantly increased in the cortical peri-infarct regions (penumbra) after ischemic stroke in human, compared with adjacent normal tissues and control subjects. Double-label fluorescence immunohistochemistry shows that SDF-1 and CXCR4 proteins were expressed in neuronal cells and astrocytes in the normal brain tissue and peri-infarct regions. CXCR7 protein was also observed in neuronal cells and astrocytes in the normal cortical regions, but predominantly in astrocytes in the penumbra of ischemic brain. Our data suggest that ischemic stroke in human leads to an increase in the expression of SDF-1 and CXCR7, but not CXCR4, in the peri-infarct cerebral cortex. Our findings suggest that chemokine SFD-1 is expressed not only in animal models of stroke, but also in the human brain after an ischemic injury. In addition, unlike animals, CXCR7 may be the primary receptor of SDF-1 in human stroke brain.
Figure 1. Expression pattern of SDF-1/CXCR4/CXCR7 in post-stroke human brain. A) Representative images show that SDF-1 expression in cerebral cortex of infarcted brain. Top panel: low magnification; Bottom panel: high magnification. B) CXCR7 immunocytochemistry in the peri-infarct region (penumbra) and adjacent normal tissue. C) CXCR4 immunocytochemistry in the cortical penumbra and adjacent normal tissue.
Figure 2. Phenotypes of SDF-1-positive cells in the human ischemic brain. A-B) Confocal image of representative immunofluorescent staining for NeuN (A) or GFAP (B) (Alexa Fluor 594, red), SDF-1 (Alexa Fluor 488, green), nuclei (DAPI, blue), and merged image from adjacent normal regions of human ischemic stroke brain. C) Merged confocal images of double-label immunohistochemistry in the peri-infarct region (penumbra) of the human ischemic brain section using anti-GFAP (green) and anti-SDF-1 (red). D) Merged confocal images of double-label immunohistochemistry in the penumbra on the human ischemic brain using anti-NeuN (red) and anti-SDF-1 (green). DAPI (blue) was used for nuclei counterstains.
Figure 3. Phenotypes of CXCR7-positive cells in the human ischemic brain. A) Merged confocal image of double-label immunohistochemistry on the normal region of the human ischemic brain section using anti-NeuN (red) and anti- CXCR7 (green). B) Merged confocal image of double-label immunohistochemistry on the normal region of the human ischemic brain section using anti-GFAP (red) and anti- CXCR7 (green). C) Double immunocytochemistry was performed on the ischemic brain sections in the penumbra using anti-GFAP (red) and anti-CXCR7 (green). The images were recorded using a 2-photon confocal microscope. D) Higher magnification view of merged confocal image in panel C. DAPI (blue) was used for nuclei counterstains.
Figure 4. Phenotypes of CXCR4-expressed cells in the human ischemic brain. Double immunocytochemistry was performed on the ischemic brain sections and the images were recorded using a 2-photon confocal microscope. Representative images show that CXCR4 (green) was expressed in GFAP-positive astrocytes (red) in the normal region (A) and penumbra (C), and NeuN-positive neuronal cells (red) in the normal region (B) and penumbra (D) of human ischemic brain. DAPI (blue) was used for nuclei counterstains.
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