Process of Metanephric Cap Mesenchyme Cells Developing into the Glomerular Podocytes in Pigs

Objective:To investigate the process of metanephric cap mesenchyme cells developing into the glomerular podocytes in Chinese experimental miniature pigs.Methods:Periodic acid-Schiff staining (PAS) was used to identify the morphological changes of glomerular development in Chinese experimental miniature pig at different time points (from embryonic day 28 to 112, and postnatal days 1, 7, 14 and 21). Immunofluorescence staining was applied to detect the development of glomerular podocytes at different developmental stages: Cap mesenchyme, Renal vesiclee, Comma-shaped body, S-shaped body, Glomeruli of capillary loop stage and mature stage). Results:PAS staining revealed that metanephric development in pigs began at E28d, at which point the typical cap mesenchyme, renal vesicle, comma-shaped body and S-shaped body could be detected; Glomeruli were formed at E35d, including the immature glomeruli, which were located below the nephrogenic zone,and the mature glomeruli, which were located juxtamedullary. Immunofluorescence staining showed that WT1 (podocyte marker) expression was observed in the metanephric cap mesenchyme cells which were Six2-positive, and then in the renal vesicle, the comma-shaped body, the tail of the comma-shaped body, the lower aspect of the S-shaped body and the glomerular podocytes, in succession.Conclusion:The porcine podocytes arise from metanephric cap mesenchyme cells which are Six2-positive, and these cells specialize into the renal vesicle, the comma-shaped body, the S-shaped body and differentiate into mature podocytes.