Fig. 4
Integrin expression in arthritic joints. a 68Ga-Aquibeprin (α5β1-integrin) μPET for a DBA mouse from week 4. b MOVAT pentachrome staining of the right knee of the same animal used for μPET imaging (a, f). c–e α5-integrin immunohistochemistry (IHC). f 68Ga-Avebetrin (αvβ3-integrin) μPET for the same animal shown in a. g–i β3-integrin IHC. α5 and β3 IHC, respectively, are shown for consecutive slices of the right knee (c, g; area shown corresponds to the frame in b), left front paw (d, h), and left knee (e, i) of the same mouse used for PET (joints subjected to IHC are marked with arrows in a and f). In many areas, the synovial membrane shows multifocal α5 expression (indicated by pink arrows in c, d, and e) but virtually no presence of β3. Vascular endothelia (indicated by green arrows) show only a slight expression of α5 (e) but a moderate level of β3 (i). Furthermore, β3 is expressed by macrophages (i, blue arrow). In the respective arthritic joints, overall stronger α5 expression gives rise to a more intense signal for 68Ga-Aquibeprin (a) as compared to 68Ga-Avebetrin (f). Unless otherwise noted, all scale bars indicate 100 μm. Color coding of μPET images (a, f) is similar to Fig. 2