The aim of this research was to investigate the expression of proliferation marker Ki-67 and apoptosis-related markers Bcl-2 and Bax during nephrogenesis by immunohistochemistry. Also, developmental characteristics of kidney tissue in different periods of gestation were quantified using morphometric analysis methods. Kidney samples of 38 human fetuses with gestational age (GA) ranging from 13-40 weeks were analyzed. The study showed that Ki-67 was expressed in numerous cells of the metanephric mesenchyme, the pretubular aggregate, the renal vesicles, the comma-shaped body, and the early S-shaped body. During subsequent development and the spatial expansion of nephrons toward the matured zone, the expression Ki-67 was markedly reduced from corpuscular towar tubular portion of nephron. Similarly, Bcl-2 was strongly expressed in the induced nephrogenic progenitor cells, the pretubular aggregates, the renal vesicles and the comma-shaped body. As the vascularization and matu-ration of the n...ephron proceeded, Bcl-2 staining became less intense and limited to the parietal layer of Bowman's capsule and renal tubules. Weak Bax expression is observed in individual scattered cells within segments of developing nephrons at all developmental stages. In the matured zone, more intense Bax staining was observed in the renal tubules. As nephrogenesis progresses, the width of the nephrogenic zone decreased, showing a strong negative correlati-on with GS. In contrast, the number of glomerular generations and the thickness of the cortex increased, showing a strong positive correlation with GS. The average area, perimeter, and Feret's diameter of the glomeruli decreased up to a period of 29-32 weeks of gestation and subsequently increased until a period of 37-40 weeks. There was a weak negative correlation with GA. In contrast, the areal density of glomeruli increased up to a period of 21-24 weeks and then decreased until a period of 37-40 weeks, showing a moderate negative correlation with GA. The average area of renal tubules slightly decreased until a period of 21-24 weeks of gestation and then increased until a period of 36-40 weeks, showing a moderate positive correlation with GA. The average areal density of renal tubules increased until a period of 21-24 weeks of gestation, remained relatively constant until a period of 33-36 weeks, and then increased at 36-40 weeks. There was a strong positive correlation with GA.
