猪肾小球内皮细胞与系膜细胞的发育过程及相互关系

目的:明确中国实验用小型猪肾小球内皮细胞与系膜细胞的发育过程及相互关系。方法:采集不同时间点(胚胎28～112d及出生后1d、7d、14d、21d)中国实验用小型猪肾组织,应用免疫荧光技术检测胚肾发育不同阶段(帽状间充质、肾小囊体、逗号形体、"S"形体、毛细血管袢期肾小球及成熟肾小球)内皮细胞标志物CD31与系膜细胞标志物α-SMA的表达情况。结果:内皮细胞标志物CD31在胚肾早期呈散在性分布,继而围绕肾小囊体和逗号形体呈"环抱"状分布,然后进入"S"形体下端的血管裂隙内聚集形成无管腔的"前毛细血管束",最后表达于成熟肾小球毛细血管内皮细胞。系膜细胞标志物α-SMA在早期胚肾、肾小囊体和逗号形体阶段均无表达;"S"形体早期分布于"S"形体周围,后期进入"S"形体下端的血管裂隙;毛细血管袢期聚集在肾小球血管极根部;随着肾小球发育逐渐向肾小球内延伸,最终表达于成熟肾小球系膜区。CD31与α-SMA双重染色的结果显示,在毛细血管袢期CD31阳性的内皮细胞聚集形成无管腔的前毛细血管束,而α-SMA阳性的系膜细胞聚集在肾小球血管极的根部;随着肾小球发育,α-SMA阳性的系膜细胞逐渐由血管极根部向肾小球内迁移,同时CD31阳性的内皮细胞逐渐形成带有管腔的毛细血管丛。结论:中国实验用小型猪肾小球内皮细胞的发育开始于后肾间充质阶段,系膜细胞的发育开始于"S"形体阶段,即肾小球系膜细胞发育在内皮细胞之后;在肾小球血管丛形成过程中,内皮细胞与系膜细胞间可能存在重要的相互作用。

Development of Glomerular Endothelial Cells and Mesangial Cells and Their Interaction in Pigs

Objective：To clarify the development process of glomerular endothelial cells and mesangial cells as well as the interaction between them in Chinese experimental miniature pigs. Methods：We collected embryonic kidney tissues of 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 expression of the markers for glomerular endothelial cells （CD31） and mesangial cells （α-SMA） at different developmental stages：Renal vesicle stage, Comma-shaped body stage, S-shaped body stage, Capillary loop stage and Mature stage glomerulus. Results：CD31, a marker for endothelial cells, was scattered throughout the pig fetal kidneys and then ＂hugged＂ the developing renal vesicle and comma-shaped body. At the S-shaped stage, CD31- positive cells migrated into the vascular cleft to form precapillary cords, and finally localized in the endothelium of mature glomeruli. The changes in α-SMA （a marker for mesangial cells） staining were as follows： no expressed in early fetal kidneys, renal vesicle or comma-shaped body; appeared near the periphery of the S-shaped body at the early stage of the S-shaped body; streamed into the vascular cleft by the late S-shaped stage; aggregated at the root of developing glomerulus, migrated to the periphery of the glomerular tuft at the capillary loop stage; and finally localized to the mesangium of the mature glomeruli. The results of dual immunofluorescence of CD31 and α-SMA indicate that at the capillary loop stage, glomerular precapillary cords were formed by the aggregation of CD31-positive cells, accompanied by the distribution of α-SMA-positive cells at the root of the developing nephron. During glomerular development, these α-SMA-positive cells migrated gradually to the interior of the glomerulus while the glomerular capillaries looped, forming the capillary tuft. Eventually, CD31 and α-SMA were located in the endothelial cells and mesangial cells of the mature glomerulus, respectively. Conclusion：The results indicate that the development of endothelial cells in pigs begins as early as the metanephric mesenchyme stage, and the development of mesangial cells begins at the S-shaped stage. Temporally, the development of endothelial cells in pigs precedes the mesangial cells during the metanephric development. There may be an essential role for molecular cross-talk between the endothelial cells and mesangial cells during the development of the porcine tuft.