The development of metanephros is a complex and gradual process. The number, size and distribution of nephrons provide important information about the organization of the kidney. Stereology is the current gold-standard technique for the morphometrical evaluation of kidney structures. This study describes morphometric features of the kidney development in sheep using design-based stereological techniques aimed to introduce the sheep as a translational model in human nephrogenesis. Left kidneys of 16 sheep fetuses in four groups at 9–11, 12–14, 15–17, and 18–20 weeks of gestation were used in the present study. Systematic uniform random sections were obtained. The kidney volume, volume fraction of nephrogenic zone, cortex and medulla, and glomerular volume were estimated using point counting and Cavalieri's estimator. The total glomerular number was estimated using a physical disector/fractionator technique. The kidney and its compartments presented gradual changes with aging, with differences found in the last fetal ages. The kidney volume increased from 0.94 ± 0.22 cm³ to 8.6 ± 0.88 cm³ during development. The volume of cortex increased from 406 ± 85 mm³ to 5,151 ± 309 mm³ and the volume of medulla showed increase from 301 ± 91 mm³ to 3,426 ± 599 mm³. The total glomerular volume increased from 13.8 ± 1.6 mm³ to 235 ± 44 mm³. The total glomerular number increased from 4,683 ± 757 to 639 × 10³ ± 11.6 × 10³. Our data might contribute to the knowledge of embryological urology and promote future experimental investigations in this field.

中文翻译：

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羊产前发育期肾脏的体视学研究

后肾的发育是一个复杂而渐进的过程。肾单位的数量、大小和分布提供了有关肾脏组织的重要信息。体视学是目前用于肾脏结构形态测量评估的金标准技术。本研究使用基于设计的体视技术描述了绵羊肾脏发育的形态特征，旨在将绵羊作为人类肾发生的转化模型。本研究使用了妊娠 9-11、12-14、15-17 和 18-20 周的四组 16 只羊胎儿的左肾。获得了系统的均匀随机切片。使用点计数和 Cavalieri 估计器估计肾脏体积、肾源区、皮质和髓质的体积分数以及肾小球体积。使用物理解剖器/分离器技术估计总肾小球数目。肾脏及其隔室随着年龄的增长呈现出逐渐变化，在最后一个胎儿年龄中发现了差异。肾脏体积从 0.94 ± 0.22 cm 增加³至 8.6 ± 0.88 cm ³显影过程中。皮质体积从 406 ± 85 mm ³增加到 5,151 ± 309 mm ³，髓质体积从 301 ± 91 mm ³增加到 3,426 ± 599 mm ³。总肾小球体积从 13.8 ± 1.6 mm ³增加到 235 ± 44 mm ³。总肾小球数目从 4,683 ± 757 增加到 639 × 10 ³  ± 11.6 × 10 ³。我们的数据可能有助于了解胚胎泌尿学，并促进该领域未来的实验研究。