PLoS One. 2013;8(3):e58243.

Altered ureteric branching morphogenesis and nephron endowment in offspring of diabetic and insulin-treated pregnancy.

Hokke SN, Armitage JA, Puelles VG, Short KM, Jones L, Smyth IM, Bertram JF, Cullen-McEwen LA.

Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia.


Abstract

There is strong evidence from human and animal models that exposure to maternal hyperglycemia during in utero development can detrimentally affect fetal kidney development. Notwithstanding this knowledge, the precise effects of diabetic pregnancy on the key processes of kidney development are unclear due to a paucity of studies and limitations in previously used methodologies. The purpose of the present study was to elucidate the effects of hyperglycemia on ureteric branching morphogenesis and nephrogenesis using unbiased techniques. Diabetes was induced in pregnant C57Bl/6J mice using multiple doses of streptozotocin (STZ) on embryonic days (E) 6.5-8.5. Branching morphogenesis was quantified ex vivo using Optical Projection Tomography, and nephrons were counted using unbiased stereology. Maternal hyperglycemia was recognised from E12.5. At E14.5, offspring of diabetic mice demonstrated fetal growth restriction and a marked deficit in ureteric tip number (control 283.7 ± 23.3 vs. STZ 153.2 ± 24.6, mean ± SEM, p<0.01) and ureteric tree length (control 33.1 ± 2.6 mm vs. STZ 17.6 ± 2.7 mm, p = 0.001) vs. controls. At E18.5, fetal growth restriction was still present in offspring of STZ dams and a deficit in nephron endowment was observed (control 1246.2 ± 64.9 vs. STZ 822.4 ± 74.0, p<0.001). Kidney malformations in the form of duplex ureter and hydroureter were a common observation (26%) in embryos of diabetic pregnancy compared with controls (0%). Maternal insulin treatment from E13.5 normalised maternal glycaemia but did not normalise fetal weight nor prevent the nephron deficit. The detrimental effect of hyperglycemia on ureteric branching morphogenesis and, in turn, nephron endowment in the growth-restricted fetus highlights the importance of glycemic control in early gestation and during the initial stages of renal development.

PMID: 23516451

 

Luise McEwen

 

Supplementary Figure: A) Duplex collecting duct system at embryonic day 14.5, kidney stained for the ureteric tree and imaged with optical projection tomography. B) Kidney with duplex ureter and hydroureter at embryonic day 18.5 (left) and control kidney (right). C) Histological section of kidney with duplex ureter and hydroureter.

It is well established that a range of perturbations to the feto-maternal environment can increase the risk of chronic disease (such as hypertension, chronic kidney disease (CKD), obesity or type 2 diabetes) in adulthood, a phenomenon known as developmental programming or “developmental origins of health and disease.” The kidney appears to be particularly susceptible to the effects of developmental programming with both genetic and environmental factors contributing to the programming of subsequent risk of CKD.

Both human and animal studies have demonstrated a link between a reduction in the number of nephrons and later renal dysfunction. Nephrogenesis involves reciprocal molecular signalling/interactions between an epithelial ureteric bud and a mass of surrounding mesenchyme (metanephric mesenchyme). The mesenchyme induces the bud to branch into a complex tree-like structure, which ultimately forms the renal collecting duct system. Nephrons are induced only at the tips of the branching ureteric epithelium. The tip induces the mesenchyme directly surrounding the tip (cap mesenchyme) to epithelialize and differentiate. Nephrogenesis is a complex process highly regulated by the extent of branching morphogenesis (number of ureteric tips available for nephron induction). In addition, cells of the metanephric mesenchyme within which the arborisation occurs must be able to commit and differentiate into nephrons as well as maintain a self-renewing pool of undifferentiated cells to enable further induction. Nephrogenesis ceases when this self-renewing pool of progenitor cells is lost.

Previous studies have identified that development of the fetal kidney is susceptible to maternal hyperglycemia and results in a low nephron number. Our paper examines how maternal hyperglycemia affects both nephrogenesis and branching morphogenesis in a mouse model of maternal diabetes and whether treatment with insulin mid to late gestation to restore normoglycemia can prevent the nephron deficit. Our results confirm a nephron deficit with exposure to maternal diabetes and this is associated with reduced ureteric tree development. Interestingly, maternal diabetes was also associated with 25% of offspring showing congenital renal abnormalities such as duplex collecting duct systems and hydroureter (see supplementary Figure), highlighting the susceptibility of the developing kidney to excess glucose levels during development. Our results also indicate that glucose should be tightly controlled during early stages of kidney development to prevent a nephron deficit in the offspring.

 

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