Early Detection Of Chronic Kidney Disease In Children And Biocompatibility Of Peritoneal Dialysis Fluids

Chronic kidney disease (CKD) is a worldwide health and life threatening disease. With high morbidity and mortality, CKD has become a severe public health issue, bringing heavy burden to the patients and their families, and meanwhile, resulting in large expenditure of social health resource. Epidemic studies show that more and more young people develop CKD and some uremic patients are only at their twenties or thirties, thus it can be expected that CKD in children is not only a cause of end stage renal disease (ESRD) in childhood, but may also a major cause of CKD and ESRD in adults. Therefore, great attention should also be paid to CKD in children.Facing severe challenge of CKD, early detection of people at high risk and effective therapies are of great significance in slowing progression of CKD and reducing the incidence of ESRD. Simultaneously, it's also very important to safely and effectively treat the children with ESRD, improve the survival rate and their quality of life. Therefore, this study on one hand focuses on the strategy of early detection of CKD in children and on the other hand, on biocompatibility of peritoneal dialysis (PD) fluids used for PD, the major renal replacement therapy (RRT) modality for children with ESRD.To study the strategy on early detection of CKD in children, we performed school urine screening with various screening methods in four districts of Shanghai. We analyzed the positive rate of urine abnormality, in terms of hematuria and/or proteinura, compared various screening methods and investigated appropriate age for screening. Then based on the follow-up data and retrospective case analysis, we evaluated the significance of school urine screening in early detection of CKD, especially IgA nephropathy in children.Data showed positive rate over 5% at the first screening and 1% at second screening. Two times of dipstick screening was found to be a superior method due to its low direct cost and appropriate sensitivity and specificity, whereas the appropriate age for urine screening required further study with larger samples.Although the follow-up rate was rather low, only 24%,3 cases of IgA nephropathy were diagnosed among 67 children within 3 years of follow-up. Of note, one case was with minor clinical symptoms but severe renal pathologic lesion, and after appropriate treatment, satisfied outcome was achieved with normal urinalysis and renal function. Further study was based on a retrospective case analysis of 158 cases of primary IgA nephropathy in children diagnosed in our hospital between the year 1979 and 2009. Data showed that about one-fifth of patients had the disease onset without obvious clinical symptoms and were not aware of kidney disease until a random urine test. Among them, nearly half only had minor histological lesion manifested by renal biopsy, however,-10% showed severe renal lesion, and the ratio of severe case in these asymptomatic children was similar as that in symptomatic children. All these suggested that school urine screening was of great significance in early detection of CKD in children, especially children who presented minor in clinical symptoms but severe in renal pathology.Even with early detection and careful treatment, a few of patients with CKD still inevitably progress to ESRD. It's of no doubt nephrologists' duty to make great efforts on treating these patients as well. Because of lacking kidney allografts, PD is the first choice of RRT modality for children with ESRD. However, long-term exposure of peritoneum in the traditional bioincompatible PD fluids leads to damage and denudation of human peritoneal mesothelial cells (HPMC) and peritoneal fibrosis and neoangiogenesis, which finally results in loss of ultrafiltration and technical failure of PD. Therefore, new generation of PD fluids have been introduced and these pH neutral, low glucose degradation products (GDP) PD fluids are considered to be more biocompatible, as manifested by protected bioactivity and function of HPMC, preserved stability of peritoneum, improved ultrafiltration, and prolonged survival of ESRD patients. In this study, we focused on the regulation of expression and relevant function of aquaporin-1 (AQP1), a key protein in the peritoneum during PD, by two new PD fluids with different buffer, bicarbonate (B-PDF) or lactate (L-PDF). To study the regulation of AQP1 by different PD fluids, realtime RT-PCR and western blot were carried out and results showed that B-PDF time-dependently up-regulated expression of AQP1 in HPMC, while L-PDF time-and dose-dependently down-regulated expression of AQP1. Immunofluorence further confirmed stronger signals of AQP1 on cell membrane and in cell plasma with respect to HPMC treated with B-PDF. To further study the pH effect on regulation of expression of AQP1, pH of PD fluids was adjusted by NaOH or HC1 to various value as 6,7, and 8. Data showed that by increasing pH value, B-PDF up-regulated mRNA expression of AQP1 in HPMC, while no regulatory effect on expression of AQP1 with respect to L-PDF, suggesting pH only had partial effect on regulation of expression of AQP1.To study the migration capacity of cells treated with different PD fluids, Transwell migration assay, wound healing assay and time-laps microscopy were performed and data showed that B-PDF significantly increased cell migration and wound healing compared to L-PDF. Further siRNA experiments demonstrated that AQP1, not AQP3, participated in HPMC migration and wound healing, and B-PDF increased cell migration in an AQP1-dependent manner.Furthermore, to study the regulation of peritoneal sodium sieving with various PD fluids,2h peritoneal equilibrium test (PET) in a rat model was performed and data showed that B-PDF increased peritoneal sodium sieving compared to L-PDF, suggested that B-PDF might better preserve the ultrafiltration capacity of peritoneum.In conclusion, based on the school urine screening, we reported the positive rate of urine abnormality in well-children in Shanghai, and recommended two times dipstick screening for further big scale screening. The follow-up cases and retrospective case analysis showed the importance of urine screening in early detection of CKD in children. Further in vitro and in vivo studies on two new PD fluids showed B-PDF up-regulated expression of AQP1 in HPMC and in an AQP1-dependent manner increase HPMC migration and wound healing capacity, and as well increased peritoneal sodium sieving. By comparison of two new PD fluids, B-PDF might better protect peritoneal cell function and preserve peritoneal stability and ultrafiltration, thus with better biocompatibility. More studies on new PD fluids will extend our understanding of biocompatibility and will provide experimental and theoretical evidence for clinical option of new PD fluids for patients.