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Exposure to hyperglycemia in utero impairs rat nephrogenesis. The effect of maternal diabetes on insulin-like growth factors and their receptors in the fetal kidney is associated with an increase in both mRNA and protein of the insulin-like growth factor II/mannose 6-phosphate receptor. However, this receptor has never been localized in the fetal kidney. The spatial and temporal distribution of the three insulin-like growth factor receptors (insulin-like growth factor I receptor, insulin-like growth factor II/mannose 6-phosphate receptor and insulin receptor) in rat metanephros during both normal and streptozotocin-induced diabetic renal development was investigated using in situ hybridization and immunohistochemistry. All receptors were found in the fetal kidney from the start of nephrogenesis. Insulin-like growth factor I receptor expression was ubiquitous and continuously present during metanephric development. Insulin receptor expression was developmentally regulated during kidney maturation with an enhanced expression in proximal tubules at the late stages of development. Insulin-like growth factor II/mannose 6-phosphate receptor expression was ubiquitous in the early stages of development and was dramatically decreased at the late stages of normal kidney development. Insulin receptor and insulin-like growth factor I receptor expressions were unchanged in diabetic metanephroi. Although the spatial expression of insulin-like growth factor II/mannose 6-phosphate receptor was unaffected by hyperglycemia, its expression was not downregulated in the mesenchyme of the nephrogenic zone of diabetic fetuses on gestational day 20. This study suggests a crucial role of insulin-like growth factor II/mannose 6-phosphate receptor in the pathogenesis of the impaired nephrogenesis in fetuses of diabetic mothers. [ABSTRACT FROM AUTHOR]

Diabetic glomerulosclerosis is defined by increased glomerular extracellular matrix (ECM) that is mainly synthesized by mesangial cells that underwent an activation mediated by cytokines and growth factors from various cellular origins. In this study, we tested whether macrophages could infiltrate the glomeruli and influence ECM synthesis in experimental diabetes. To test our hypothesis, we initially studied the dynamics of glomerular macrophage recruitment in streptozotocin-induced diabetic rats at days 1, 2, 4, 8, 15, and 30 by using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) on isolated glomeruli and immunohistochemistry and morphometry. We then assessed the role of macrophages on the basis of the pharmacological modulation of their recruitment by insulin or ACE inhibitor treatments and by X-irradiation-induced macrophage depletion at days 8 and 30. Macrophages were recruited within the glomeruli at the very early phase of hyperglycemia by using RT-PCR CD14 detection from day 2 and by using ED1 immunohistochemistry from day 8. This glomerular macrophage infiltration was associated with an increase in alpha1-chain type IV collagen mRNA. In parallel, the diabetic glomeruli became hypertrophic with an increase in the mesangial area. Macrophage recruitment was preceded by or associated with an increased glomerular expression of vascular cell adhesion molecule 1, intracellular adhesion molecule 1, and monocyte chemoattractant protein 1, which contributes to monocyte diapedesis. Glomerular interleukin-1beta mRNA synthesis was also enhanced as early as day 1 and could be involved in the increase in ECM and adhesion molecule gene expressions. Insulin treatment and irradiation-induced macrophage depletion completely prevented the glomerular macrophage recruitment and decreased alpha1-chain type IV collagen mRNA and mesangial area in diabetic rats, whereas ACE inhibitor treatment had an incomplete effect. It can be concluded that in the streptozotocin model, hyperglycemia is followed by an early macrophage recruitment that contributes to the molecular and structural events that could lead to glomerulosclerosis. Therefore, besides direct stimulation of mesangial cells by hyperglycemia, macrophages recruited in the glomeruli during the early phase of hyperglycemia could secondarily act on mesangial cells. [ABSTRACT FROM AUTHOR]