F JIANG1, MJ DAHL2, K ALBERTINE2, MJ BLACK1, MR SUTHERLAND1
1Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Clayton, Australia, 2Department of Pediatrics, University of Utah, Salt Lake City, USA
Aim: To determine the long-term impact of preterm birth with postnatal ventilation on glomerular capillary morphology in lambs.
Background: Preterm birth (delivery <37 weeks gestation) can affect ongoing kidney development in neonates, resulting in the formation of glomeruli with shrunken capillary tufts. We have also shown, in lambs, that preterm birth and postnatal ventilation lead to substantial reductions in glomerular capillary length and filtration surface area at 3 days after birth. If this persists, it may result in renal dysfunction and nephron loss; indeed, preterm birth is an important risk factor for hypertension and chronic kidney disease.
Methods: Lambs were delivered preterm at 128 days (~0.85) of gestation, ventilated for 3-6 days, and then euthanised at 5 months term-equivalent age. Preterm lambs were compared to unventilated age-matched lambs born at term (n=8/group). Stereological methods were used to determine glomerular volume and glomerular capillary length and surface area in the outer, mid, and inner regions of the renal cortex. Glomerulosclerosis was assessed histologically.
Results: Glomeruli located in the inner cortex were significantly larger than those in the mid and outer cortex, but there was no significant difference in glomerular volume between the Preterm and Term lambs. Similarly, there was no significant effect of preterm birth on mean capillary length per glomerulus (Term: 8.1 ± 0.4 mm, Preterm: 7.6 ± 0.2 mm; p=0.32) or glomerular capillary surface area. Levels of glomerulosclerosis were low in all lambs, with no difference between groups.
Conclusions: Findings suggest that early-life impairments in glomerular capillary growth following preterm birth and ventilation may not persist long-term; the underlying causes of hypertension and renal disease in individuals born preterm remain to be fully elucidated.
Charles (Fan) Jiang is an Honours student at the Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University.