Abstract 17034: The Novel Extracellular Matrix Protein Podocan Shows a Distinct Expression Pattern in Human Primary versus Restenotic Atherosclerotic Coronary Lesions and its Lack of Extra-Cellular Expression in Restenotic Tissue is Associated with Increased Wnt-Pathway Activation

Abstract

Background: Vascular smooth muscle cell (VSMC) migration and proliferation are associated with restenosis post percutaneous intervention. Podocan is a novel member of the small leucin rich repeat protein family. We recently have described podocan as an inhbitor of VSMC migration and proliferation via the Wnt-pathway. Now we are reporting the expression of podocan and Wnt-pathway related molecules in human primary stable coronary atherosclerosis compared to restenosis. Methods and Results: The expression of podocan and non-phospho-beta catenin (NPBC) an indicator of Wnt-pathway activation was evaluated by immunohistochemistry in coronary atherectomy samples (n=32) (data presented as mean % cells positive for NPBC, ± SEM). The antibody against the human form of podocan was generated in our lab whereas antibodies for NPBC, Wnt 1 and LRP-6 were obtained commercially. In atherectomy samples from patients with primary stable atherosclerosis (n=20) podocan expression was abundant in extra-cellular as well as intra-cellular location. Podocan deposits were seen especially in plaque areas surrounding neovessels. Out of 20 coronary primary lesions 16 showed podocan expression. In contrast, restenotic lesions showed a paucity of podocan with only 5 out of 12 lesions staining positive for podocan. Of note, extra-cellular podocan deposition was completely absent in all restenosis samples and podocan present was restricted to an intra-cellular/cytoplasmic staining pattern. The expression of NPBC was strongly increased in restenotic compared to primary lesions (35 ± 6 % vs. 4 ± 2 %, P<0.05). Importantly, nuclear staining of NPBC indicative of nuclear translocation of beta catenin was observed only in restenotic lesions. Immuno-fluorescence double labeling showed a strong co-localization of Wnt-1 and LRP-6 on VSMC in areas of hyperplasia in restenotic lesions. Conclusions: We are reporting for the first time the expression of podocan in human coronary atheroma. The paucity of podocan and the absence of extra-cellular podocan in restenotic tissue were associated with a strong increase in NPBC expression in VSMC indicating increased Wnt-pathway activation. This points to podocan and the Wnt-pathway as possible key regulators of VSMC in human atherosclerosis.