Imaging of chemokine receptor CXCR4 expression in culprit and nonculprit coronary atherosclerotic plaque using motion-corrected [68Ga]pentixafor PET/CT

Fig. 1. Expression of CXCR4 in human coronary arteries. a Immunofluorescence staining of healthy artery wall (left) and atherosclerotic artery wall (right) reveals a higher number of CXCR4-expressing mononuclear cells (green; blue reflects DAPI staining of nuclei). b Quantification of CXCR4+ cells relative to all cells (scale bars: 10x = 200 µm, 20x = 100 µm, 40x = 50 µm)

Fig. 2. CXCR4 expression in human atherosclerotic carotid plaques. a Immunofluorescence staining reveals a higher number of CXCR4-expressing mononuclear cells in plaques of symptomatic patients (right) than in plaques of asymptomatic patients (left; green CXCR4, blue DAPI staining of nuclei). b Representative western blot shows stronger CXCR4 protein content in samples from symptomatic patients. c Quantification of CXCR4+ cells relative to all cells on fluorescence microscopy (individual examples shown in a). d Analysis of CXCR4 mRNA expression as determined by qPCR. e Densitometric analysis of western blots in groups (individual blot examples shown in b) (scale bars: 10x = 200 µm, 20x = 100 µm, 40x = 50 µm)

Fig. 3. CXCR4 in atherosclerotic plaques of human coronary arteries is predominantly expressed on leucocytes. Immunofluorescent costaining of CXCR4 (green, bottom left) with the macrophage lineage marker CD68 (red, top right) and DAPI staining of nuclei (blue, top left) reveals that the vast majority of CXCR4+ cells are CD68+ leucocytes (merged image, bottom right, arrows) (scale bars: 40x = 50 µm)

Fig. 4. [68Ga]Pentixafor PET/CT identifies CXCR4 upregulation in culprit coronary lesions after acute myocardial infarction and stent-based reperfusion. a Coronary angiogram prior to reperfusion shows LAD occlusion (arrow lesion). b Coronary angiogram after stent-based LAD reperfusion. c [68Ga]Pentixafor PET/CT after reperfusion showing focal CXCR4 signal at the site of the LAD culprit lesion fusing to the stent location (i.e. CXCR4+ culprit lesion)

Fig. 5. Effect of motion correction on [68Ga]pentixafor uptake and detectability in culprit coronary lesions. a [68Ga]Pentixafor PET/CT images of a culprit LCX lesion. Focal CXCR4 signal (red) is more clearly depicted after cardiac, respiratory motion or dual cardiac/respiratory motion correction (lower row) compared to ungated images (upper row, middle). b Detection rates for CXCR4+ culprit coronary lesions are higher in gated images (P ≤ 0.005). c Signal intensity of CXCR4+ culprit coronary lesions is higher in gated images (P < 0.05). Background subtraction was performed using an individually adjusted threshold in this particular subject for clearer visualization of tracer uptake

Fig. 6. [68Ga]Pentixafor PET/CT identifies CXCR4 upregulation in various types of coronary lesions. a Calcified LAD plaque without visually identified uptake (control). b CXCR4+ LAD plaque, partially calcified on CT and with CXCR4 signal. c Focal CXCR4 upregulation at the site of a stented LCX nonculprit lesion fusing to the stent location. d Signal intensity of CXCR4 expression is highest in stented culprit lesions and lowest in calcified plaques without visually identified uptake (controls) (ANOVA, P < 0.0001). The images were obtained from different patients. Background subtraction was performed using individually adjusted thresholds for clearer visualization of tracer uptake

Fig. 7. Temporal evolution of [68Ga]pentixafor signal. There was a mild but significant correlation between CXCR4 PET signal in culprit lesions and (a) time after symptom onset (R2 = 0.14, P = 0.03, and (b) time after stenting (R2 = 0.15, P = 0.02; dual-gated data)