Author + information
- Received August 21, 2015
- Revision received September 9, 2015
- Accepted September 17, 2015
- Published online December 1, 2015.
- James T. Thackeray, PhD∗,
- Thorsten Derlin, MD∗,
- Arash Haghikia, MD†,
- L. Christian Napp, MD†,
- Yong Wang, MD†,
- Tobias L. Ross, PhD∗,
- Andreas Schäfer, MD†,
- Jochen Tillmanns, MD†,
- Hans J. Wester, PhD‡,
- Kai C. Wollert, MD†,
- Johann Bauersachs, MD† and
- Frank M. Bengel, MD∗∗ ()
- ∗Department of Nuclear Medicine, Hannover Medical School, Hannover, Germany
- †Department of Cardiology and Angiology, Hannover Medical School, Hannover, Germany
- ‡Pharmaceutical Radiochemistry, Technical University of Munich, Munich, Germany
- ↵∗Reprint requests and correspondence:
Dr. Frank M. Bengel, Department of Nuclear Medicine, Hannover Medical School, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany.
Objectives An assay for molecular imaging of myocardial CXCR4 expression was evaluated, in order to obtain mechanistic insights noninvasively based on quantitative positron emission tomography (PET).
Background The chemokine receptor CXCR4 has emerged as a therapeutic target after acute myocardial infarction (AMI), because of its role in inflammatory and progenitor cell recruitment.
Methods PET with the specific CXCR4 ligand, gallium-68 (68Ga)-pentixafor, was performed in mice (n = 53) and compared with ex vivo autoradiography, immunohistochemistry, and left ventricular flow cytometry. In addition, 12 patients were imaged at 2 to 8 days after AMI.
Results In mice, 68Ga-pentixafor identified regional CXCR4 upregulation in the infarct region, peaking at 3 days (infarct/remote [I/R] ratio 1.5 ± 0.2 at 3 days vs. 1.2 ± 0.3 at 7 days; p = 0.03), corresponding to a flow cytometry-based peak of CD45+ leukocytes and immunohistochemical detection of CD68+ macrophages and Ly6G+ granulocytes. Blockade with the CXCR4 antagonist AMD3100 abolished the signal. No specific uptake was found in sham-operated or control animals. Long-term treatment with oral enalapril attenuated the CXCR4 signal (I/R 1.2 ± 0.2 at 3 days and 1.0 ± 0.0.1 at 7 days; p = 0.01 vs. untreated). Patients showed variable degrees of CXCR4 upregulation in the infarct region. No single clinical parameter allowed for prediction of CXCR4 signal strength. At multivariate analysis, a combination of infarct size and time after reperfusion predicted the CXCR4 infarct signal (rmultiple = 0.73; p = 0.03). Infarct signal in the myocardium was paralleled by elevated pentixafor uptake in bone marrow (r = 0.61; p = 0.04), which highlighted systemic interactions.
Conclusions Targeted PET imaging with 68Ga-pentixafor identifies the global and regional CXCR4 expression pattern in myocardium and systemic organs. CXCR4 upregulation after AMI coincides with inflammatory cell infiltration, but shows interindividual variability in patients. This may have implications for the response to CXCR4- or other inflammation-targeted therapy, and for subsequent ventricular remodeling.
This study was supported by the German Research Foundation (Excellence Cluster REBIRTH-2) and by EU FP7 grant PIRG08-GA-2010-276889 (FMB). Dr. Thackeray is supported by a fellowship of the Canadian Institutes of Health Research. Dr. Haghikia is supported by the “Junge Akademie” program of Hannover Medical School.
Dr. Wester is a shareholder of Scintomics GmbH, Fürstenfeldbruck, Germany. The other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Received August 21, 2015.
- Revision received September 9, 2015.
- Accepted September 17, 2015.
- 2015 American College of Cardiology Foundation