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Kidney Week

Abstract: PO2271

Morphologic Evidence of Excretory Function in Human Mesonephros

Session Information

Category: Pediatric Nephrology

  • 1700 Pediatric Nephrology

Authors

  • Zhang, Ping L., Beaumont Health, Royal Oak, Michigan, United States
  • Bonventre, Joseph V., Brigham and Women's Hospital, Boston, Massachusetts, United States
Background

Human mesonephros develops at 4 weeks of gestation and regresses at approximately 16 weeks of gestation. It is not clear if the human mesonephros has excretory function. Our goal was to assess morphologic evidence of primordial glomeruli, and renal tubules suggestive of excretory function using special staining and immunohistochemical staining methods.

Methods

Five mesonephric kidneys from human embryos found in miscarriage (missed abortion) or ectopic pregnancy specimens were studied. They were obtained from 4 weeks to 10 weeks gestation. In addition, 8 early metanephric kidneys from 10 weeks to 21 weeks of gestation were identified from our surgical pathology and autopsy cases for comparison with mesonephric specimens. Beside routine hematoxylin and eosin staining, the sections were stained for Periodic Acid Schiff (PAS) to detect proximal tubules (PT) brush borders and glomerular basement membranes (GBM). Furthermore, mesonephros and metanephros sections were immunohistochemically stained for CD133 for progenitor cells, GATA3 for mesangial cells and distal tubules, P504S for proximal tubules, and kidney injury molecule-1 (KIM-1) for PT injury.

Results

CD133 was positive in mesonephric glomerular and tubular structures at 4 weeks but this expression disappeared in the mesonephros from 5 weeks to 10 weeks, implying gradual maturation. GATA3 staining was positive in Wolffian duct, mesangial cells of primordial glomeruli (at 7 weeks the GBM was PAS+) and distal tubules, but not in PT. PT were positively stained for P504S. PT of mesonephric kidneys revealed brush borders on PAS stained sections from 7 to 10 weeks suggestive of reabsorption capacity. The PT of mesonephros at 7 weeks stained positively for KIM-1, suggestive of acute tubular injury during abortion processes. The metanephros showed expression of markers in respective renal compartments, similar to those in mesonephros.

Conclusion

Human mesonephros can have GATA3+ mesangial cells in the glomeruli. Although structures are simplified (no loop of Henle and collecting ducts), the human mesonephric nephrons include primitive glomeruli, PT showing brush borders and distal tubules, having morphological features similar to those of advanced metanephric stages with excretory function. They have react to injury, at least during 7 to 10 weeks of gestation based on identification of brush borders and KIM-1 expression in PT.