Identification of podocytes in the primary culture of rat decapsulated glomeruli

肾小球细胞培养中鹅卵石样多角形细胞的起源仍然存在争议，即它们是去分化足细胞还是来自鲍曼囊的壁上皮细胞（PECs）。没有鲍曼囊的肾小球（脱囊肾小球）几乎没有增生使培养细胞的鉴定复杂化。基于传统筛分法分离肾小球过程中足细胞受损的假设，我们尝试采用改良的筛分法，在没有机械力的情况下，用刮刀按压分离肾小球。结果，脱囊肾小球的细胞生长率明显提高。细胞形态与鹅卵石样多边形明显不同。它们延伸了很长的细胞质过程，这些过程经常跨越相邻的细胞。多角形细胞很少从被包膜的肾小球中生长出来，但在被包膜的肾小球中生长较多。从脱囊肾小球中生长出来的细胞显示足细胞特异性标记物（podocalyxin和synaptopodin）染色强烈，但系膜细胞（ty -1）、内皮细胞（von Willebrand factor, RECA-1）或PECs （pan cadheas）特异性标记物未染色，表明这些细胞来自足细胞。另一方面，从被包膜的肾小球中生长出来的纤毛多边形细胞沿细胞间接触呈泛钙粘蛋白阳性，支持多边形细胞起源于PECs的观点。此外，在培养的PECs和小管上皮细胞中也表达了体内足细胞特有的一些表型。这些发现表明，体内所有足细胞特异性标记不一定针对培养的足细胞。

The origin of cobblestone-like polygonal cells in glomerular cell culture remains controversial about whether they are dedifferentiated podocytes or derived from parietal epithelial cells (PECs) of Bowman's capsule. Almost no outgrowths from glomeruli devoid of Bowman's capsule (decapsulated glomeruli) complicate the identification of cells in culture. Based on the assumption that podocytes are damaged during the isolation of glomeruli by the conventional sieving method, we tried to isolate glomeruli by the modified sieving method without the mechanical force by pressing with a spatula. As a result, the rates of cell outgrowths from decapsulated glomeruli were conspicuously improved. The morphology of the cells was distinctly different from cobblestone-like polygonal appearance. They extended long cytoplasmic processes, which often crossed over adjacent cells. Polygonal cells rarely grew out from decapsulated glomeruli, but did more frequently from encapsulated glomeruli. Cells growing out from decapsulated glomeruli showed intense staining for podocyte-specific markers (podocalyxin and synaptopodin), but no staining for markers specific to mesangial cells (Thy-1), endothelial cells (von Willebrand factor, RECA-1) or PECs (pan cadherein), indicating that these cells were of podocyte origin. On the other hand, ciliated polygonal cells growing out from encapsulated glomeruli were positive for pan cadherin along cell-cell contact, supporting the idea that polygonal cells originate from PECs. In addition, some of phenotypes specific to podocytes in vivo were expressed in cultured PECs and tubular epithelial cells. These findings indicate that all podocyte-specific markers in vivo are not necessarily specific to podocytes in culture.