Anti-migratory effect of rapamycin impairs allograft imaging by 18F-fluorodeoxyglucose-labeled splenocytes

Abstract

Tracking lymphocyte migration is an emerging strategy for non‑invasive nuclear imaging of allografts; however, its clinical application remains to be fully demonstrated. In the present study, the feasibility of using rapamycin‑treated 18F‑fluorodeoxyglucose (18F‑FDG)‑labeled splenocytes for the in vivo imaging of allografts was evaluated. C57BL/6 skin was heterotopically transplanted onto non‑obese diabetic/severe combined immunodeficient recipient mice. BALB/c 18F‑FDG‑labeled splenocytes with or without rapamycin pretreatment (designated as FR and FC cells, respectively) were transferred into recipient mice 30 days later. Imaging of radiolabeled cells in the skin grafts was conducted through in vivo dynamic whole‑body phosphor‑autoradiography and histological analysis. Notably, rapamycin impaired the migration of 18F‑FDG‑labeled splenocytes to the graft. At all time points, the radioactivity of allografts (digital light units/mm2) was significantly lower in the group that received FR cells, compared with the group that received FC cells (P<0.01). Furthermore, the peak allograft to native skin ratio was 1.29±0.02 at 60 min for the FR group and 3.29±0.17 at 30 min for the FC group (P<0.001). In addition, the in vivo radioactivity of the allografts was observed to be correlated with the transferred cells, which were observed histologically (r2=0.887; P<0.0001). Although 18F‑FDG‑labeled splenocytes migrated to the allograft, imaging of these cells may not be possible in the presence of rapamycin.

CD93 in macrophages: A novel target for atherosclerotic plaque imaging?

“…30 18 F-FDG-labelled splenocytes have been used in vivo to track cell aggregation in skin allograft. 31 Since both CD93 and MΦ play a pivotal role in AS, we hypothesize that CD93 in MΦ may be a novel biomarker for AS plaque. Adoptivetransferred MΦ in mouse requires 72 h for complete distribution into different organs.…”

“…Donor spleen cell infusion induced a stable immune tolerance in a miniature pig lung transplantation model 30 . 18 F‐FDG‐labelled splenocytes have been used in vivo to track cell aggregation in skin allograft 31 . Since both CD93 and MΦ play a pivotal role in AS, we hypothesize that CD93 in MΦ may be a novel biomarker for AS plaque.…”