Histochemical and immunohistochemical study of the glomerular development in human fetuses.

Few studies exist that establish the normal morphological patterns of glomerular development, though this is one of the organs that continues to evolve morphologically during the postnatal period up to 4 weeks after birth. In our study one kidney from each autopsy of a total of 86 autopsies was analyzed [15 weeks to 40 weeks of gestational age (GA)]. We examined the variation in the nephrogenic zone thickness, the area and diameter of the glomerular tuft, the area and diameter of the glomerular capsule, and the immunohistochemical markers, anti-CD31 and anti-CD34 antibodies, which accompany the development of the glomerular microvasculature. Periodic acid-methenamine silver (PAMS) stain was used for the morphological and morphometrical analyses, and it was particularly useful in fetuses in which autolysis had occurred. The length of the nephrogenic zone (NZ) decreased with the increase of the GA (P < 0.001) according to the formula: GA = 36.5 - (0.05 x length of NZ). The areas of the Bowman capsule (P < 0.0001), the capillary tuft (P < 0.0001), and the capillary tuft diameter (P = 0.00393) of the intermediary glomeruli increased with the advance of GA, with a positive significant correlation. The same parameters of the juxtamedullary and superficial glomeruli had no correlation with the advance of GA. The cells of the primary structures in the "S" shape of the primitive nephrons were negative for CD31 and CD34. Staining for both antibodies was found, for all GAs, in the endothelial cells of the mature glomeruli tuft and in the renal interstitial vessels. The data obtained in this work contribute to the evaluation of renal maturity in autopsied fetuses and are particularly important in fetuses when autolysis has occurred, to which the parameters used in this study can also be applied. The establishment of normal morphometric and immunohistochemical parameters for the evaluation of renal maturity increases the diagnostic precision of renal pathological alterations in aborted material and perinatal autopsy.