瘦素通过其受体刺激小鼠血管平滑肌细胞增殖而促进动脉内膜增生

Leptin promotes neointimal formation by stimulating vascular smooth muscle cell proliferation through leptin receptor

目的探讨瘦素是否影响动脉内膜的增生及其发生机制。方法利用野生型（Wt）、瘦素基因缺陷（Lep^-/-）、瘦素受体基因缺陷（LepR^-/-）小鼠，通过股动脉内膜损伤及瘦素疗法，结合组织学特性，分析瘦素影响动脉内膜增生情况及其机制。结果动脉内膜损伤后4周，Lep^-/-和LepR^-/-小鼠的内膜面积与中层面积比值（I／M）均小于Wt小鼠，差异均有统计学意义（Lep^-/-小鼠比Wt小鼠为0．80±0．14比1．50±0．22，P〈0．01；LepR^-/-小鼠比Wt小鼠为0．55±0．20比1．50±0．22，P〈0．05）。Lep^-/-和LepR^-/-小鼠经动脉内膜损伤并同时给予瘦素治疗后，前者的I／M显著增加，而后者的I/M无明显变化。α-肌动蛋白和5-溴-2-脱氧尿嘧啶染色显示，二者在各组动脉增生内膜的阳性率分布趋势与内膜增厚程度一致。结论瘦素缺乏或瘦素受体缺乏防止动脉内膜增生，外源性瘦素恢复Lep^-/-小鼠动脉内膜增生，但对LepR^-/-小鼠内膜无影响。本研究从动物模型上证明，高瘦素血症是动脉内膜增生的高危因素，并说明瘦素通过瘦素受体刺激血管平滑肌细胞增殖而促进动脉内膜增生。

Objective To evaluate the role of leptin in neointimal formation and related mechanisms. Methods Femoral arterial injury was induced in wild-type （Wt, n = 10）, leptin-deficient （Lep^-/- , n = 12）, and leptin receptor-deficient （ LepR^-/- , n = 10） mice. Leptin treatment studies （ tail vein injection of adenovirus expressing murine leptin on the RSV promoter, ad-leptin） were performed on Lep^-/- （n =5） and LepR^-/- （n =4） mice. Intimal （I） and medial （M） areas were measured and the ratio of I/M was calculated. Smooth muscle cells were detected by smooth muscle α-actin staining using an α-actin monoclonal antibody. Cellular proliferation was analyzed with BrdU Staining Kit and the number of BrdU-positive cells was counted manually. Plasma leptin level was measured by ELISA. Results The I/M ratio of Lep^-/- and LepR^-/- mice was significantly lower than that in Wt separately （ Lep^-/- vs. Wt = 0.80±0.14 vs. 1.50±0.22, P〈0.01; LepR^-/- vs. Wt=0.55±0.20 vs. 1.50 ±0.22, P〈0.05）. Plasma leptin level was significantly increased in Lep^-/- and LepR^-/- mice post leptin treatment. I/M was significantly increased in Lep^-/- mice receiving ad-leptin compared with untreated Lep^-/- mice （P 〈 0.05） , while I/M was similar between LepR^-/- mice with and without ad-leptin treatment （P 〉 0.05 ）. The changes on number of positive α-actin and BrdU stained smooth muscle cells were consistent with the neointimal formation findings in various groups. Conclusions Mice lacking leptin or the leptin receptor were protected from neointimal formation following vascular injury. Leptin treatment increased neointimal formation in Lep^-/- but not in LepR^-/- mice, suggesting leptin receptor activation and vascular smooth muscle cell proliferation played a pivotal role on neointimal formation post-injury in this model, giving an evidence that high plasma leptin level is a risk factor for neointimal formation.