Indagini strutturali e quantitative durante lo sviluppo del rene mediante l’utilizzo di elaborazione immagini

The attention of the scientific community about human intrauterine life is constantly growing. A very relevant aspect is the development of the kidney. Nephron number at birth has a relevant clinical importance with implications for long-term renal health. In recent years, the podocyte depletion hypothesis has emerged as an important concept in kidney pathology. Moreover, a variety of renal and urological abnormalities have been reported in subjects with chromosomal aberrations, such as Down syndrome and Beta Thalassemia. This study was aimed at verifying how human kidney structures, in particular glomerular shape and podocyte number, change during intrauterine life. Moreover, we evaluated if glomerular and tubular changes observed previously in adult subjects with Down syndrome and Beta Thalassemia might be related to changes in renal development in the early phases of embryogenesis. With these aims, fetal kidney sections were stained with H&E and digitally scanned; dimensional and quantitative analyses were performed using an algorithm developed in Matlab (Mathworks©). We first examined sixty-two normal subjects with gestational age ranging from 20 up to 41 weeks; subjects were subdivided into: fetuses (gestational age ≤ 24 weeks, n=5), preterms (gestational age ≥25 and ≤ 36 weeks, n=39), and at term (gestational age ≥ 37 weeks, n=18) infants. we found an average podocyte number of 1908 ± 645, 1394 ± 498 and 1126 ± 256 was respectively observed in fetuses, preterms and at term infants. A significant main effect (P=0.0051) of gestational age on podocyte number was observed with a significantly lower number in at term infants than in fetuses (P<0.001). An intra-group variability was also observed. To evaluate renal differences between Down syndrome fetuses and normal fetuses twenty-five subjects were examined. Subjects were subdivided into two groups: fetuses with Down syndrome (DS-fetuses, n=11) with a gestational age ranging from 13 up to 21 weeks, and healthy fetuses (N-fetuses, n=14) with a gestational age ranging from 9 up to 22 weeks. DS-fetuses showed slightly larger glomeruli as compared to N-fetuses. Moreover, glomeruli in DS-fetuses group were characterized by an enlarged Bowman’s space as compared to glomeruli in N-fetuses (p=0.0028 ). Differences in the nephrogenic zone width were also observed; DS-fetuses showed a greater width of this zone as compared with N-fetuses. Finally, with the end of evaluate differences in Beta Thalassemia, four beta-thalassemic fetuses and four normal fetuses at 13-15 weeks of gestational age were examined. The presence of enlarged glomeruli in the deep cortex, with the enlargement of the urinary space, has been observed in beta-thalassemic fetuses. Moreover, the presence of podocytes in urinary space, and of clusters of mesangial cells at the periphery of the glomerulus, was observed. An average podocyte number of 2494 ± 317 and 1546 ± 372 was observed in normal fetuses and beta-thalassemic fetuses (P=0.0082) respectively. In conclusion, a decreasing trend in podocyte number during gestation in normal condition was observed; this decreasing trend of podocyte number suggests that podocytes might undergo a programmed cell death (apoptosis) or alternatively transdifferentiation during the glomerular growth; the high cell number in the first step of kidney development being correlated to the presence of both podocytes and podocyte precursors. In fetuses with Down Syndrome relevant morphological differences, such as glomerular abnormalities and expanded nephrogenic zone, have been found. Moreover, in fetuses with Beta Thalassemia relevant differences in architecture, in particular a deficiency in podocyte number, have been observed. These harmful changes in the glomerular structure may result in a nephron deficit, which may be associated with development of renal diseases and hypertension later in life. We hypothesize that the observed morphological anomalies could have significant implications for both the short- and long-term renal health of subjects with Down Syndrome and with Beta Thalassemia.