Molecular Imaging of Fibrosis Figure 3. Histochemical analysis of peptide binding to tissue collagen. A: Frozen sections of rat aorta were incubated with B-collagelin or control peptide (200 mg/mL) and detected using HRP-coupled streptavidin. Sections were counter-stained with hematoxylin. Contiguous serial sections were stained with picrosirius red. In a competition experiment, the peptide was mixed with anti-GPVI IgG 9O121.2 (300 mg/mL). B: Paraffin embedded sections of rat tail tendon were treated as above. doi:10.1371/journal.pone.0005585.g003 Figure 4. In- vivo scintigraphy, ex vivo myocardial autoradiography and histology using 99mTc-streptavidin-B-collagelin. A: Planar thoracic scintigraphy of a control rat (sham). B: Planar and tomographic (frontal and sagittal views) thoracic images of a rat with a fibrotic myocardial infarction: a hot-spot (arrows) can be seen in the left ventricular myocardial area. C: Corresponding myocardial autoradiography and histology (collagen-specific picrosirius red staining,), confirming tracer uptake in the thin, fibrotic (red) myocardial scar (arrows). D: Control experiment: no activity can be seen in the myocardial scar of a rat injected with irrelevant 99mTc-streptavidin-B-Pc. doi:10.1371/journal.pone.0005585.g004 PLoS ONE | www.plosone.org 6 May 2009 | Volume 4 | Issue 5 | e5585