Masuda Yukinari, Mii Akiko, Shimizu Akira, Fujita Emiko, Aki Kaoru, Ishikawa Kahori, Ishizaki Masamichi, Sato Shigeru, Hayama Naoaki, Iino Yasuhiko, Katayama Yasuo, Fukuda Yuh
Department of Analytic Human Pathology, Nippon Medical School, 1-15 Sendagi, Bunkyo-ku, Tokyo, 113-8602, Japan.
Clin Exp Nephrol. 2008 Dec;12(6):440-9. doi: 10.1007/s10157-008-0100-3. Epub 2008 Nov 8.
The ultrastructural findings of membranous nephropathy (MN) are well described. Recently, podocyte infolding in the glomerular basement membrane (GBM) has been observed to be a unique ultrastructural finding formed from diffuse spherical microparticles and microtubules in the GBM. However, these alterations of glomerular epithelial cells have not been well characterized in MN.
We selected 126 renal biopsies of primary MN that were diagnosed by light microscopy and immunofluorescence. In these biopsies, we investigated the ultrastructural alterations of GBM and podocytes, especially the presence of podocyte invagination, podocyte infolding, and spherical microparticles in the GBM.
In 98 cases (77.8%) we ultrastructurally detected occasional invagination of podocytes in the GBM within or around electron-dense or lucent deposits in mainly stage II-III of MN. In 40 cases (31.7%), we found spherical microparticles in addition to the podocyte invaginations in the GBM. In our cases, spherical microparticles were divided into three types; podocyte infolding, cell debris and virus-like particle types. Only one case displayed numerous spherical microparticles (microspheres) that were probably caused by infolding of podocytes. These microspheres, about 80 nm in diameter, were covered by unit membrane, and were accompanied by similar-sized microtubules and protrusions of podocytes. The spherical microparticles in the other cases were associated with cell debris (n = 23) or virus-like particles (n = 16) and were not connected with podocytes.
Podocyte invagination associated with subepithelial deposits was a common pathological finding of primary MN, especially stage II-III of MN. The spherical microparticles in GBM in the case of MN may be associated with not only podocyte infolding but also cell debris and virus-like particles. The spherical microparticles in GBM due to diffuse podocyte infolding was considered as a new pathology finding of the GBM and may appear to be a new glomerular disease entity termed podocytic infolding glomerulopathy.
膜性肾病（MN）的超微结构特征已有详尽描述。近来，观察到肾小球基底膜（GBM）中的足细胞内陷是一种独特的超微结构表现，由GBM中弥漫性球形微粒和微管形成。然而，MN中肾小球上皮细胞的这些改变尚未得到充分表征。
我们选取了126例经光镜和免疫荧光诊断的原发性MN肾活检标本。在这些活检标本中，我们研究了GBM和足细胞的超微结构改变，尤其是足细胞内陷、足细胞折叠以及GBM中球形微粒的存在情况。
在98例（77.8%）中，我们通过超微结构检测到，在MN主要的II - III期，电子致密或透亮沉积物内或其周围的GBM中偶尔存在足细胞内陷。在40例（31.7%）中，除了GBM中的足细胞内陷外，我们还发现了球形微粒。在我们的病例中，球形微粒分为三种类型；足细胞折叠型、细胞碎片型和病毒样颗粒型。仅1例显示大量球形微粒（微球），可能是由足细胞折叠引起。这些微球直径约80 nm，被单位膜覆盖，并伴有大小相似的微管和足细胞突起。其他病例中的球形微粒与细胞碎片（n = 23）或病毒样颗粒（n = 16）相关，且与足细胞无连接。
与上皮下沉积物相关的足细胞内陷是原发性MN的常见病理表现，尤其是MN的II - III期。MN病例中GBM中的球形微粒可能不仅与足细胞折叠有关，还与细胞碎片和病毒样颗粒有关。GBM中因弥漫性足细胞折叠导致的球形微粒被认为是GBM的一种新的病理表现，可能似乎是一种新的肾小球疾病实体，称为足细胞折叠性肾小球病。
