Characterization of ion channels involved in the proliferative response of femoral artery smooth muscle cells.

OBJECTIVE: Vascular smooth muscle cells (VSMCs) contribute significantly to occlusive vascular diseases by virtue of their ability to switch to a noncontractile, migratory, and proliferating phenotype. Although the participation of ion channels in this phenotypic modulation (PM) has been described previously, changes in their expression are poorly defined because of their large molecular diversity. We obtained a global portrait of ion channel expression in contractile versus proliferating mouse femoral artery VSMCs, and explored the functional contribution to the PM of the most relevant changes that we observed. METHODS AND RESULTS: High-throughput real-time polymerase chain reaction of 87 ion channel genes was performed in 2 experimental paradigms: an in vivo model of endoluminal lesion and an in vitro model of cultured VSMCs obtained from explants. mRNA expression changes showed a good correlation between the 2 proliferative models, with only 2 genes, Kv1.3 and Kvbeta2, increasing their expression on proliferation. The functional characterization demonstrates that Kv1.3 currents increased in proliferating VSMC and that their selective blockade inhibits migration and proliferation. CONCLUSIONS: These findings establish the involvement of Kv1.3 channels in the PM of VSMCs, providing a new therapeutical target for the treatment of intimal hyperplasia.

Increased p53 gene dosage reduces neointimal thickening induced by mechanical injury but has no effect on native atherosclerosis.

OBJECTIVE: The tumor suppressor p53 regulates cell proliferation and apoptosis, two key processes in the pathogenesis of occlusive vascular disease. Here, we examined the consequences of heightening p53 function on neointimal lesion formation in the setting of atherosclerosis and mechanical injury. METHODS: For this study we employed immunohistopathological characterization of neointimal lesions in atherosclerosis-prone apolipoprotein E-null mice with normal p53 gene dosage (apoE-KO) and carrying a p53 transgene (Super-p53/apoE-KO). We also carried out molecular studies in macrophages and smooth muscle cells (SMCs) obtained from these mice. RESULTS: The p53 transgene conferred p53 gain-of-function in cultured cells and mice. In vitro, survival of irradiated Super-p53 macrophages and femoral SMCs was reduced, but only Super-p53 SMCs exhibited attenuated proliferation. In vivo, whereas the size of spontaneously formed and diet-induced aortic atheromas was indistinguishable in apoE-KO and Super-p53/apoE-KO mice, the latter exhibited attenuated neointimal thickening in mechanically injured femoral artery. In both models, neither apoptosis nor cell proliferation were affected by additional p53 gene dosage when examined in established neointimal lesions. However, at 2 days after mechanical injury when neointimal lesions were not yet formed, cell proliferation was significantly attenuated within medial SMCs of Super-p53/apoE-KO mice. CONCLUSION: Heightening p53 function has differential effects on in vitro proliferation of macrophages (unaffected) versus SMCs (reduced), and on native atherosclerosis (unaffected) versus mechanically induced neointimal thickening (reduced) in apoE-KO mice. The protective effect of p53 in mechanically injured femoral artery coincided with limited medial SMC proliferation at early time points preceding neointima formation, but neither medial nor neointimal cell proliferation was affected in vessels with established occlusive lesions. These findings corroborate p53 gain-of-function as a promising therapeutic strategy to limit post-angioplasty restenosis but not native atherosclerosis.

Effects of cyclosporine, tacrolimus and sirolimus on vascular changes related to immune response.

BACKGROUND: Despite the use of newer immunosuppressors such as sirolimus (SRL) and tacrolimus (TRL) in heart transplantation, the rate of humoral rejection has remained unchanged. The aim of this study was to analyze the immunologic and histologic effects of cyclosporine (CsA), SRL, and TRL in a porcine model of arterial transplantation. METHODS: Each transplant recipient animal (n = 49) received an autograft and an allograft and was then allocated to one of four treatment groups and a 7- or 30-day follow-up period, as follows: a WOT group (without immunosuppressor treatment), 7 days (n = 6) and 30 days (n = 5); a CsA group, 7 days (n = 5) and 30 days (n = 6); an SRL group, 7 days (n = 7) and 30 days (n = 8); and a TRL group, 7 days (n = 6) and 30 days (n = 6). The presence of donor-specific antibodies (DSA) was tested at the end of the follow-up period. Morphometric parameters and inflammatory infiltration were analyzed in the explanted grafts. RESULTS: At 30-day follow-up, SRL was the only treatment capable of suppressing DSA formation (0 of 7 vs 4 of 5 in the WOT group; p < 0.05). SRL completely prevented aneurismal dilation and reduced the number of macrophages in the allografts. TRL treatment achieved a greater reduction of T lymphocytes. CsA did not prevent the reduction in total vascular area at 7 days that was achieved with the SRL and TRL groups. Animals treated with CsA had the largest number of T lymphocytes and macrophages in both follow-up periods. CONCLUSIONS: SRL prevented DSA formation and reduced the number of macrophages as compared with TRL and CsA.