Targeted ED-B fibronectin SPECT in vivo imaging in experimental atherosclerosis

AIM

The extracellular matrix protein ED-B fibronectin (ED-B) is upregulated in inflammatory atherosclerotic lesions. However, functional in vivo imaging of ED-B-containing plaques has not been explored. This study evaluated whether [(99m)Tc]-conjugated AP39 ([(99m)Tc]-AP39), a single-chain antibody specific to ED-B, can be used for in vivo detection of atherosclerotic plaques in Western diet (WD)-fed, apolipoprotein E-deficient (apoE-/-) mice as compared to wildtype (WT) control mice.

METHODS

Using SPECT, 12-month-old WD-fed apoE-/- and WT mice were studied 4 hours after injecting [(99m)Tc]-AP39 (148 MBq). Subsequently, mice were sacrificed, thoracic aortas measured in a g-counter, and plaques analyzed using histology, immuno-histochemistry, autoradiography, and morphometry.

RESULTS

In vivo [(99m)Tc]-AP39-SPECT imaging of apoE-/- mice demonstrated a significant signal activity in the plaque-ridden thoracic aorta (52.236 ± 40.646 cpm/cm³) that co-localized with the aortic arch and the supra-aortic arteries in MRI scans. Low signal activity (9.468 ± 4.976 cpm/cm³) was observed in WT mice. In apoE-/- mice, the strongest signals were detected in the aortic root, aortic arch and along the abdominal aorta. Autoradiography analysis of aortas from apoE-/- mice confirmed the in vivo observation by demonstrating signal localization in atherosclerotic plaques. The size of autoradiography-positive plaque areas correlated significantly with the size of ED-B-positive (r=0.645, P=0.044) or macrophage-infiltrated (r=0.84, P<0.002) plaques. A significant correlation was found between the sizes of ED-B-positive and macrophage-infiltrated plaque areas (r=0.93, P<0.01).

CONCLUSION

[(99m)Tc]-AP39-SPECT in vivo imaging detects inflammatory plaque lesions in WD-fed apoE-/- mice.

Induction of carbon monoxide in the donor reduces graft immunogenicity and chronic graft deterioration

Chronic allograft dysfunction remains the major obstacle for long-term successful transplantation. To date there is no effective treatment. Overexpression of protective genes has provided increased graft function and survival. This mechanism has been implicated in the process of graft accommodation. One of these genes that has been shown to mediate protective effects decodes the enzyme heme oxygenase-1 (HO-1), and an HO-1 downstream product, carbon monoxide (CO). Using an established model of kidney chronic allograft rejection in the rat, we investigated the impact of methylene chloride (MC), a CO donor, as a therapeutic tool to reduce chronic graft deterioration. We showed that donor and long-term recipient treatment with MC improved graft function and reduced histological signs of chronic rejection. Carbon monoxide may be a promising agent to improve graft quality and long-term graft function.