Morphological Study On The Origin And Development Of Renal Corpuscles In Mouse

ObjectiveTo observe the origin time of the renal corpuscle, the unvarying of the corpuscle ' s number and study the morphological changes, the cellular proliferation and apoptosis of developing renal corpuscles in mouse.MethodsLight and transmission electron microscope, stereological methods, meta-nephric culture and graft were used to assess the renal corpuscles of embryonic and postnatal mouse kidneys. Also cell proliferation and apoptosis were evaluated by PCNA immunohistochemistrical method, TUNEL staining method and morphometrical criteria.ResultsThe observations confirmed the existence of four developmental phases (five stages) of the renal corpuscles, that is comma - like body ( I ) , S body ( II ) , capillary tuft stage ( M ) , immature ( IV ) and mature stage ( V ) ? Comma -shaped bodies and S - shaped bodies emerged at embryonic day 14 (E14) , The volume of renal corpuscles increased approximately 70 - fold from E16 to N40 (neonatal day 40) , and the number of the corpuscles did not change anymore since N7.The renal corpuscles were developed in cultured and transplanted E13d metanephroses that had no appearances of renal corpuscles before. The glomeru-lar basement membrane (BM) was originated dually from both epithelial and en-dothelial BM. Hie BM of epithelium appeared earlier than the BM of endotheli-um. The endothelial cell was developed from continuous to fenestrated. Hie basal projects of the podocytes attached to the endothelial cell could be seen in developing glomeniles. Two types, light and dark of podocytes were observed in the early stage of development.Nearly all cells in I and II stage had nuclear PCNA immunolabeling. The number of PCNA immunolabeling cells during HI and IV stage was changed from high to low, and to less in V stage. TUNEL positive cells could be easily identified in III and IV stage. Electron microscope revealed that the mitotic activity was observed in all cells of I and H stage renal corpuscles. The mitotic phases of endothelial cells and podocytes could be seen in HI stage, but only endothelial mitotic activities in IV stage of renal corpuscle. Apoptotic activities of endothelial cell and Bowman' s parietal cell were noted, predominantly in Iff and IV stages.ConclusionsMouse renal corpuscles originated at E14, nearly matured at N7, and at N40, had the same structures as those of adult mice. Endogenous metanephros origin of glomerular endothelial cells was determined. The structural contact between podocytes and endothelial cells could be discerned during the glomerular development. Epithelial BM appeared first during the glomerular BM development. Two types of podocyte appeared during the development of corpuscle. The highest cellular proliferation was noted in early stages of developing renal corpuscles , and decreased during developing into mature. Cellular proliferation and apoptosis were necessary for development of renal corpuscles. Among the corpuscle cells the endothelium had the highest activities of both proliferation and apoptosis. Less apoptotic activity was noted in podocytes.