Low birth weight is a risk factor for chronic kidney disease (CKD), while adult podocyte depletion is a key event in the pathogenesis of glomerulosclerosis. However, whether low birth weight due to poor maternal nutrition is associated with low podocyte endowment and glomerulosclerosis in later life is not known. Female Sprague-Dawley rats were fed a normal (NPD, 20%) or low (LPD, 8%) protein diet from 3 weeks before mating until postnatal day 21 (PN21), when kidneys from some male offspring were taken for quantitation of podocyte number and density in whole glomeruli using immunolabeling, tissue clearing and confocal microscopy. Remaining offspring were fed a normal or high fat diet until 6 months to induce catch-up growth and excessive weight gain, respectively. At PN21, podocyte number per glomerulus was 15% lower in low birth weight (LPD) than normal birthweight (NPD) offspring, with this deficit greater in outer glomeruli. Surprisingly, podocyte number in LPD offspring increased in outer glomeruli between PN21 and 6 months, although an overall 9% podocyte deficit persisted. Postnatal fat feeding to LPD offspring did not alter podometric indices or result in glomerular pathology at 6 months, whereas fat feeding in NPD offspring was associated with far greater body and fat mass as well as podocyte loss, reduced podocyte density, albuminuria and glomerulosclerosis. This is the first report that maternal diet can influence podocyte endowment. Our findings provide new insights into the impact of low birth weight, podocyte endowment and postnatal weight on podometrics and renal health in adulthood.

Fetal hypoxia is a common complication of pregnancy. We have previously reported that maternal hypoxia in late gestation in mice gives rise to male offspring with reduced nephron number, while females have normal nephron number. Male offspring later develop proteinuria and renal pathology, including glomerular pathology, whereas female offspring are unaffected. Given the central role of podocyte depletion in glomerular and renal pathology, we examined whether maternal hypoxia resulted in low podocyte endowment in offspring. Pregnant CD1 mice were allocated at embryonic day 14.5 to normoxic (21% oxygen) or hypoxic (12% oxygen) conditions. At postnatal day 21, kidneys from mice were immersion fixed, and one mid‐hilar slice per kidney was immunostained with antibodies directed against p57 and synaptopodin for podocyte identification. Slices were cleared and imaged with a multiphoton microscope for podometric analysis. Male hypoxic offspring had significantly lower birth weight, nephron number, and podocyte endowment than normoxic male offspring (podocyte number; normoxic 62.86 ± 2.26 podocytes per glomerulus, hypoxic 53.38 ± 2.25; p < .01, mean ± SEM). In contrast, hypoxic female offspring had low birth weight but their nephron and podocyte endowment was the same as normoxic female offspring (podocyte number; normoxic 62.38 ± 1.86 podocytes per glomerulus, hypoxic 61.81 ± 1.80; p = .88). To the best of our knowledge, this is the first report of developmentally programmed low podocyte endowment. Given the well‐known association between podocyte depletion in adulthood and glomerular pathology, we postulate that podocyte endowment may place offspring at risk of renal disease in adulthood, and explain the greater vulnerability of male offspring.

Progressive podocyte loss is a feature of healthy ageing. While previous studies have reported age-related changes in podocyte number, density and size and associations with proteinuria and glomerulosclerosis, few studies have examined how the response of remaining podocytes to podocyte depletion changes with age. Mild podocyte depletion was induced in PodCreiDTR mice aged 1, 6, 12 and 18 months via intraperitoneal administration of diphtheria toxin. Control mice received intraperitoneal vehicle. Podometrics, proteinuria and glomerular pathology were assessed, together with podocyte expression of p-rp-S6, a phosphorylation target that represents activity of the mammalian target of rapamycin (mTOR). Podocyte number per glomerulus did not change in control mice in the 18-month time period examined. However, control mice at 18 months had the largest podocytes and the lowest podocyte density. Podocyte depletion at 1, 6 and 12 months resulted in mild albuminuria but no glomerulosclerosis, whereas similar levels of podocyte depletion at 18 months resulted in both albuminuria and glomerulosclerosis. Following podocyte depletion at 6 and 12 months, the number of p-rp-S6 positive podocytes increased significantly, and this was associated with an adaptive increase in podocyte volume. However, at 18 months of age, remaining podocytes were unable to further elevate mTOR expression or undergo hypertrophic adaptation in response to mild podocyte depletion, resulting in marked glomerular pathology. These findings demonstrate the importance of mTORC1-mediated podocyte hypertrophy in both physiological (ageing) and adaptive settings, highlighting a functional limit to podocyte hypertrophy reached under physiological conditions.

A range of perturbations to the maternal environment result in low nephron endowment in offspring, which is often linked to increased blood pressure and renal pathology in later life. Given that nephrogenesis in mammals ends shortly before or after birth, this nephron deficit is permanent. To date, very few studies have examined the morphology of nephrons in offspring born with low nephron endowment. Given the link between podocyte loss and glomerulosclerosis in adults, we examined whether maternal perturbations also result in low podocyte endowment in offspring, thereby rendering offspring at increased risk of adult disease. Three models of maternal perturbation were investigated: (1) gestational hypoxia in mice; (2) maternal low protein diet (LPD) in mice followed by postnatal hyperglycaemia; and (3) maternal low protein diet in rats followed by high fat feeding. Podocytes were counted at postnatal day 21 in whole glomeruli contained in tissue slices immunostained for specific podocyte markers, cleared and imaged with confocal microscopy. In all three models, total podocyte number per glomerulus was reduced in settings of maternal perturbation. In male mice exposed to hypoxia, podocyte endowment was 15% lower than controls (p<0.01), but no effect was observed in females; in male and female mouse LPD offspring, podocyte endowment was 15% (p<0.001) and 9% (p<0.05) lower than controls; and in male LPD rats (females were not studied), podocyte endowment was 15% (p<0.0001) lower than controls. This is the first report of developmental programming of low podocyte endowment. We have identified low podocyte endowment in two species, three models and both sexes. We are currently investigating whether this podocyte deficit is permanent, and the effects on renal function in later life.

adolescents who scored positive for disorders of initiating and maintaining sleep reported use of electronic devices in the hour before bed. Conclusions: A high prevalence of sleep disturbances are present in children and adolescents after kidney transplantation which may have an under recognised impact on quality of life. Serum magnesium may be a modifiable risk factor and lifestyle factors may also contribute. We suggest that screening for sleep disturbances should be part of routine post-transplant care to optimise normal growth and development.