Expression of collagen type IV in human kidney during prenatal development

Background / Aim. Type IV collagen belongs to the group of non-fibrillar collagens and is an important component of the basement membranes where it accounts for approximately 50% of its structural elements. The aim of the paper was to describe the expression and distribution of collagen type IV in embryonic and fetal metanephric kidney, and to determine the volume density of collagen type IV in kidney tissue in each trimester of development. Methods. The material consisted of 19 human embryos/fetuses, in the gestational age from 8th to 37th week. Kidney tissue specimens were routinely processed to paraffin molds and stained with hematoxylin and eosin and immunohistochemically using polyclonal anti-collagen IV antibody. Stained slides were examined using light microscope and images of the selected areas, under different lens magnification were captured with digital camera. Volume density of collagen type IV was determined by using ImageJ 1.48v and a plugin of the software which inserted a grid system with 336 points. For the data comparison One-Way Analysis of Variance was used. Results. Strong collagen IV immunopositivity was seen in all specimens, with a distribution in the basement membranes of urinary bud, parietal leaf of Bowman’s capsule, glomerular basement membrane, basement membrane of interstitial blood vessels, and basement membranes of nephron tubules and collecting ducts. No statistically significant difference in the volume density of type IV collagen was found between the different trimesters of development. Conclusion. The synthesis and secretion of collagen type IV simultaneously follows the development of nephron structures, collecting system and blood vessels. The volume density of collagen type IV remains constant throughout all the trimesters of metanephric kidney development, indicating that it plays a crucial role in normal development of nephron and collecting system structures, as well as in maintaining the normal kidney function.