ABSTRACT
The whole world has been affected by a dramatically increasing prevalence of diabetes. Today, the etiology of both type 1 and type 2 diabetes is thought to revolve around the dysfunction of ß-cells, the insulin producing cells of the body. Within the pharmaceutical industry, the evaluation of new drugs for diabetes treatment is mostly done using cell lines or rodent islets and depends solely on the assessment of static insulin secretion. However, the use of cell lines or rodent islets is limiting lack of similarity of the human islet cells, leading to a constrain of the predictive value regarding the clinical potential of newly developed drugs. To overcome this issue, we developed an Engineered Micro-Pancreas as a unique platform for drug discovery. The Engineered Micro Pancreas is composed of (i) an organ-derived micro-scaffold, specifically a decellularized porcine lung-derived micro-scaffold and (ii) cadaveric islets seeded thereon. The Engineered Micro Pancreas remained viable and maintained insulin secretion in vitro for up to three months. The quantities of insulin were comparable to those secreted by freshly isolated human islets and therefore hold the potential for real-time and metabolic physiology mimicking drug screening.
Subject(s)
Insulin-Secreting Cells/metabolism , Lung/chemistry , Pancreas/metabolism , Tissue Engineering/methods , Tissue Scaffolds/chemistry , Animals , Cell Survival , Drug Discovery , Extracellular Matrix/chemistry , Humans , Insulin/metabolism , Insulin-Secreting Cells/cytology , Mass Spectrometry , Pancreas/growth & development , Swine , Tissue Engineering/instrumentationABSTRACT
Serum FGF23 is markedly elevated in chronic kidney disease and has been associated with poor long-term outcomes. FGF23 expression is increased by activation of the FGF receptor 1 (FGFR1) in rats with normal renal function and in vitro in bone-derived osteoblast-like cells. We studied the regulation of FGF23 by FGFR1 in vivo in acute and chronic uremia in mice and rats. Folic acid-induced acute kidney injury increased calvaria FGF23 mRNA and serum FGF23 and parathyroid hormone (PTH) levels at 6 h. The FGFR1 receptor inhibitor PD173074 prevented the folic acid-induced increase in both FGF23 mRNA and serum levels but had no effect on serum PTH levels. A more prolonged uremia due to an adenine high-phosphorus diet for 14 days resulted in high levels of FGF23 mRNA and serum FGF23 and PTH. PD173074 decreased serum FGF23 and mRNA levels with no effect on PTH in the adenine high phosphorus-induced uremic rats. Therefore, a derangement in FGF23 regulation starts early in the course of acute kidney injury, is in part independent of the increase in serum PTH, and involves activation of FGFR1. It is possible that FGFR1 in the osteocyte is activated by locally produced canonical FGFs, which are increased in uremia. This is the first demonstration that activation of FGFR1 is essential for the high levels of FGF23 in acute and chronic experimental uremia.
Subject(s)
Acute Kidney Injury/metabolism , Fibroblast Growth Factors/blood , Osteocytes/metabolism , Receptor, Fibroblast Growth Factor, Type 1/metabolism , Skull/metabolism , Uremia/metabolism , Acute Kidney Injury/blood , Acute Kidney Injury/chemically induced , Acute Kidney Injury/genetics , Adenine , Animals , Chronic Disease , Disease Models, Animal , Fibroblast Growth Factor-23 , Fibroblast Growth Factors/genetics , Folic Acid , Male , Mice, Inbred C57BL , Osteocytes/drug effects , Parathyroid Hormone/blood , Phosphorus, Dietary , Pyrimidines/pharmacology , RNA, Messenger/metabolism , Rats, Sprague-Dawley , Receptor, Fibroblast Growth Factor, Type 1/antagonists & inhibitors , Receptor, Fibroblast Growth Factor, Type 1/genetics , Skull/drug effects , Up-Regulation , Uremia/blood , Uremia/chemically induced , Uremia/geneticsABSTRACT
Parathyroid hormone (PTH) increases FGF23 mRNA and protein levels in vivo and in vitro. Here we tested whether the increased FGF23 expression by PTH is mediated by the orphan nuclear receptor Nurr1. PTH increased Nurr1 mRNA levels prior to elevation of FGF23 mRNA levels in UMR-106 rat osteoblast-like cells. Activation of PKA increased both FGF23 and Nurr1 mRNA levels. Modification of Nurr1 expression showed that Nurr1 is essential for the PTH-mediated increase in FGF23 and luciferase reporter gene experiments identified a functional promoter region containing several potential Nurr1 binding sites. Chromatin immunoprecipitation assays confirmed the binding of Nurr1 to these regions in the FGF23 promoter. In vivo, Nurr1 mRNA and protein levels were increased in calvaria from rats with experimental CKD together with high PTH and FGF23 expression. Calcimimetics decrease PTH and FGF23 levels in CKD patients. Importantly, in rats with experimental CKD, the calcimimetic R568 decreased PTH expression, calvaria Nurr1 mRNA and protein levels, and FGF23 mRNA. Immunohistochemistry for Nurr1 showed an increase in the number of Nurr1 expressing osteocytes in the femurs of rats with CKD and this was decreased by R568. Thus, the effect of PTH to increase FGF23 transcription is mediated by Nurr1 in vitro and in vivo. In CKD, calcimimetics decrease PTH, which in turn decreases Nurr1 and consequently FGF23.
