| Renal hypertrophy in the early stage and glomerulosclerosis in the end stage are the characteristics of diabetic nephropathy (DN). Both proliferation and hypertrophy of renal cells are thought to be involved in the pathogenesis of renal enlargement. Cell growth is ultimately controlled by cell cycle regulatory proteins such as cyclins (cyclin A, cyclin D, cyclin E et al), cyclin-dependent kinases (CDKs, such as CDK2, CDK) and cyclin-kinase inhibitors (CKIs, such as P21, P27 and P16). With the progress of diabetic nephropathy, a complex of pathological changes, including accumulation of extracellular matrical components, glomerulosclerosis, tubular atrophy and interstitial fibrosis, is followed, but the detailed events of these changes and its regulating mechanism are still unclear. It was found that apoptotic cells were more in number and the expression of apoptosis-related genes was higher in the diabetic kidneys. Proliferation, hypertrophy and apoptosis of renal cells may play important roles in pathogenesis of diabetic nephropathy. Experimental and clinical investigations indicate that antagonists of renin-angiotensin system, such as angiotensin converting enzyme inhibitors(ACEI) and angiotensin II receptor I antagonisms(ATlRa), have renal protective effects. In this study Sprague-Dawlay (SD) rats were used to induce experimental diabetes and rat glomerular mesangial cells were cultured in high glucose medium to investigate the effects of proliferation, hypertrophy and apoptosis of renal cells to the development of diabetic nephropathy and effects of antagonism of renin-angiotensin system.1 Renal hypertrophy and expression of cell cycle related genes in the early stage of experimental diabetesExperimental diabetic rats and mesangial cells exposed to high glucose were used to observe proliferation and hypertrophy of renal cells in the early stage of diabetes, and gene chip was used to screen responsible genes for renal hypertrophy from cell cycle related genesMethods: Male SD rats were divided into two groups: control group and diabetic group. The diabetic group received a single intraperitioneal injection of STZ (sigma) dissolved in 0.1 mol/L sodium citrate (pH 4.5) at a dose of 65mg/kg body weight. The rats were respectively sacrificed at day 3,5,9,14,30 after STZ injection. Urine samples were collected before sacrifice and 24-h urinary protein excretion was measured. Apart of the animals received a single intraperitioneal injection of lOOug BrdU/g body weight two hours prior to sacrifice to observe BrdU incorporation by immunohistochemistry. The expressions of cyclin E, CDK2, P27 were measured by flow cytometry. Light microscopy and TD2000 image pattern analysis system were used to detect cell numbers and diameters of each glomerular and tubular cross section.Six rats from each group were respectively sacrificed at day 10 after STZ injection, renal cortices (Ig from each rat) were mixed. Total RNA was abstracted with one-step method and mRNA was purified with Oligo-dt cellulose, cDNA probes labeled with cy3 and cy5 were obtained by reverse transcription-polymerase chain reaction (RT-PCR). Hybridization of cDNA probe and gene chip was carried out, gene chip was scanned with Scan Array 3000, and results were analyzed with ImaGene 3.0.Glomerular mesangial cells were separated from SD rats and cultured separately in normal or high glucose medium. [3H]-thymidine and [3H]-leucine incorporation into the measngial cells were measured. Flow cytometry and immunohistochemistry were used to evaluate cell proliferation or hypertrophy, and to detect expressions of CyclinE, CDK2 and P27.In vivo results: Image pattern analysis and kidney/body weight ratio: Compared with the control group, cell numbers of each glomerular crosssection increased at day 5 in DM group, peaked at day 9, remained at this level to day 14, and a slight decrease was observed at day 30. Cell numbers of each tubular cross section increased at day 3, then changed as those of glomeruli. Diameters of proximal tubules increased at...
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