Uptake of cis-4-[18 F]fluoro-L-proline in scar formation: a marker of collagen synthesis?

Excessive scar formation is accompanied by abnormal collagen synthesis. The feasibility of monitoring collagen synthesis in vivo with no-carrier-added cis-4[18F]fluoro-L-proline (cis-FPro) was evaluated in an animal model with scar formation induced by implanted meshes. The abdominal wall of rats was replaced by alloplastic meshes. At days 3, 7, 14, 21 and 90 after implantation, the uptake of cis-FPro at 4 h post-injection was determined for resected samples of the mesh and normal tissues. The highest uptake was found in the kidneys (1.73+/-0.47%ID/g) followed by the liver (0.59+/-0.19%ID/g). The meshes showed the maximum uptake at day 3 (0.20+/-0.07%ID/g) with a decrease to 0.10+/-0.03%ID/g at day 90 (P<0.001). After 3 days no connective tissue was shown by histopathological morphometric analysis. The maximum partial volume (PV%) of connective tissue was 43+/-14 PV% 90 days after implantation. The maximum levels of granulocytes and inflammatory infiltrate were found at day 3 with minimal levels at day 90, paralleling the course of cis-FPro uptake. In conclusion, the uptake of cis-FPro at 4 h post-injection is not related to the content of connective tissue. Cis-FPro radiolabelled with 18F appears not to be a suitable radiopharmaceutical for in vivo monitoring of collagen synthesis in scar formation.