Microvascular Research Laboratories, School of Physiology and Pharmacology, Univ. of Bristol, Preclinical Veterinary School, Southwell St., Bristol, United Kingdom. BS2 8EJ.
Am J Physiol Renal Physiol. 2012 Oct;303(7):F1026-36. doi: 10.1152/ajprenal.00410.2011. Epub 2012 Jul 18.
Vascular endothelial growth factor (VEGF)-A, a family of differentially spliced proteins produced by glomerular podocytes, maintains glomerular filtration barrier function. The expression of VEGF molecules is altered in human nephropathy. We aimed to determine the roles of the angiogenic VEGF(164) isoform, and the antiangiogenic VEGF(165)b isoform in mature, adult glomeruli in vivo using conditional, inducible transgenic overexpression systems in mice. Podocyte-specific VEGF(164) overexpression (up to 100 days) was induced by oral administration of doxycycline to adult podocin-rtTA/TetO-VEGF(164) double transgenic mice. The consequences of simultaneous overexpression of VEGF(164) and VEGF(165)b were assessed in triple-transgenic podocin-rtTA/TetO-VEGF(164)/nephrin-VEGF(165)b mice. Persistent VEGF(164) overexpression did not cause proteinuria but did increase glomerular ultrafiltration coefficient between days 3 and 7. Despite persistently increased VEGF(164) levels, glomerular ultrafiltration coefficient normalized by day 14 and remained normal up to 100 days. Decreased subpodocyte space (SPS) coverage of the glomerular capillary wall accompanied increased glomerular hydraulic conductivity in VEGF(164)-overexpressing mice. The changes in glomerular ultrafiltration coefficient and SPS coverage induced by 7 days of overexpression of VEGF(164) were not present in triple transgenic VEGF(164) and VEGF(165)b overexpressing mice. These results indicate that 1) the adult mouse glomerulus is relatively resistant to induced VEGF(164) overexpression. VEGF(164) overexpression altered glomerular permeability but did not cause proteinuria in these mature, adult animals; 2) the SPS is a dynamic VEGF-responsive modulator of glomerular function; and 3) the balance of VEGF isoforms plays a critical role in the regulation of glomerular permeability. VEGF(165)b is capable of preventing VEGF(164)-induced changes in glomerular permeability and ultrastructure in vivo.
血管内皮生长因子 (VEGF)-A 是一种由肾小球足细胞产生的差异剪接蛋白家族，可维持肾小球滤过屏障功能。VEGF 分子的表达在人类肾病中发生改变。我们旨在使用条件性、诱导型转基因过表达系统在小鼠体内确定血管生成 VEGF(164) 同种型和抗血管生成 VEGF(165)b 同种型在成熟的成年肾小球中的作用。通过给予成年足细胞-rtTA/TetO-VEGF(164)双转基因小鼠强力霉素口服诱导足细胞特异性 VEGF(164)过表达（长达 100 天）。在三重转基因足细胞-rtTA/TetO-VEGF(164)/nephrin-VEGF(165)b 小鼠中评估了同时过表达 VEGF(164)和 VEGF(165)b 的后果。持续的 VEGF(164)过表达不会导致蛋白尿，但会在第 3 天至第 7 天增加肾小球超滤系数。尽管 VEGF(164)水平持续升高，但肾小球超滤系数在第 14 天正常化，并持续正常直至 100 天。过表达 VEGF(164)的小鼠肾小球毛细血管壁下足细胞空间 (SPS) 覆盖率降低，同时肾小球水力传导率增加。在过表达 VEGF(164)7 天诱导的肾小球超滤系数和 SPS 覆盖率的变化在三重转基因 VEGF(164)和 VEGF(165)b 过表达小鼠中不存在。这些结果表明：1）成年小鼠肾小球对诱导的 VEGF(164)过表达相对具有抵抗力。VEGF(164)过表达改变了肾小球通透性，但在这些成熟的成年动物中没有导致蛋白尿；2）SPS 是肾小球功能的动态 VEGF 反应调节剂；3）VEGF 同工型的平衡在调节肾小球通透性方面起着关键作用。VEGF(165)b 能够防止体内 VEGF(164)诱导的肾小球通透性和超微结构变化。
