Radiolabeled GPVI-Fc for PET Imaging of Multiple Extracellular Matrix Fibers: A New Look into Pulmonary Fibrosis Progression.

Invariably fatal and with a particularly fast progression, pulmonary fibrosis (PF) is currently devoid of curative treatment options. Routine clinical diagnosis relies on breathing tests and visualizing the changes in lung structure by CT, but anatomic information is often not sufficient to identify early signs of progressive PF. For more efficient diagnosis, additional imaging techniques were investigated in combination with CT, such as F-FDG PET, although with limited success because of lack of disease specificity. Therefore, novel molecular targets enabling specific diagnosis are investigated, in particular for molecular imaging techniques. In this study, we used a Cu-radiolabeled platelet glycoprotein VI fusion protein (Cu-GPVI-Fc) targeting extracellular matrix (ECM) fibers as a PET tracer to observe longitudinal ECM remodeling in a bleomycin-induced PF mouse model. Cu-GPVI-Fc showed significant uptake in fibrotic lungs, matching histology results. Contrary to F-FDG PET measurements, Cu-GPVI-Fc uptake was linked entirely to the fibrotic activity of tissue and not was susceptible to inflammation. Our study highlights Cu-GPVI-Fc as a specific tracer for ECM remodeling in PF, with clear therapy-monitoring and clinical translation potential.