Surgical Techniques for Catheter Placement and 5/6 Nephrectomy in Murine Models of Peritoneal Dialysis

STAT3 signaling mediates peritoneal fibrosis by activating hyperglycolysis

BACKGROUND

Long term peritoneal dialysis leads to peritoneal epithelial-mesenchymal transformation (EMT), angiogenesis, and ultrafiltration failure. Although recent evidence suggests that inhibiting STAT3 (signal transducer and activator of transcription 3) can prevent kidney fibrosis, and that STAT3 can enhance glucose metabolism, the effect of STAT3 in peritoneal fibrosis (PF) has not been clarified.

METHODS

Our study determined the effects of STAT3 on EMT and key glycolysis enzymes in mesothelial HMrSV5 cells by knockdown and overexpression of STAT3. In addition, we established a rat PF model to examine the role of pharmacologic inhibition of STAT3 or 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 3 (PFKFB3) in this process.

RESULTS

High glucose (HG) caused the upregulation of α-smooth muscle actin and transforming growth factor beta 1 and the downregulation of E-cadherin, and induced STAT3 activation in HMrSV5 cells. In addition, HMrSV5 cells cultured in high glucose showed high expression of key glycolysis enzymes, which could be inhibited by STAT3 siRNA. Furthermore, treating mesothelial cells with 3PO, the PFKFB3 inhibitor, could attenuate high glucose-induced EMT. Moreover, daily administration of dialysis fluid could induce peritoneal fibrosis. The peritoneal fibrosis was accompanied by enhanced phosphorylation of STAT3 and the upregulation of PFKFB3. The administration of BP-1-102 or 3PO prevented fibrosis and inhibited angiogenesis in PF rats.

CONCLUSIONS

si-STAT3 attenuated the HG-induced EMT and hyperglycolysis, and the overexpression of STAT3 could induce EMT in HMrSV5 cells. 3PO could markedly attenuate HG-induced EMT by decreasing PFKEB3 in HMrSV5 cells. In addition, we demonstrated that inhibiting STAT3 signaling or peritoneal hyperglycolysis could attenuate peritoneal fibrosis and angiogenesis in vivo. Our findings linked the STAT3/PFKFB3 signaling to the development of PF. HG/STAT3/PFKFB3 might promote the progression of PF through regulating profibrosis and angiogenesis.

Steviol glycosides as an alternative osmotic agent for peritoneal dialysis fluid

Background: Peritoneal dialysis (PD) is a renal replacement technique that requires repeated exposure of the peritoneum to hyperosmolar PD fluids (PDFs). Unfortunately, it promotes alterations of the peritoneal membrane (PM) that affects its functionality, including mesothelial-mesenchymal transition (MMT) of mesothelial cells (MCs), inflammation, angiogenesis, and fibrosis. Glucose is the most used osmotic agent, but it is known to be at least partially responsible, together with its degradation products (GDP), for those changes. Therefore, there is a need for more biocompatible osmotic agents to better maintain the PM. Herein we evaluated the biocompatibility of Steviol glycosides (SG)-based fluids.

Methods: The ultrafiltration and transport capacities of SG-containing and glucose-based fluids were analyzed using artificial membranes and an in vivo mouse model, respectively. To investigate the biocompatibility of the fluids, Met-5A and human omental peritoneal MCs (HOMCs) were exposed in vitro to different types of glucose-based PDFs (conventional 4.25% glucose solution with high-GDP level and biocompatible 2.3% glucose solution with low-GDP level), SG-based fluids or treated with TGF-β1. Mice submitted to surgery of intraperitoneal catheter insertion were treated for 40 days with SG- or glucose-based fluids. Peritoneal tissues were collected to determine thickness, MMT, angiogenesis, as well as peritoneal washings to analyze inflammation.

Results: Dialysis membrane experiments demonstrated that SG-based fluids at 1.5%, 1%, and 0.75% had a similar trend in weight gain, based on curve slope, as glucose-based fluids. Analyzing transport capacity in vivo, 1% and 0.75% SG-based fluid-exposed nephrectomized mice extracted a similar amount of urea as the glucose 2.3% group. In vitro, PDF with high-glucose (4.25%) and high-GDP content induced mesenchymal markers and angiogenic factors (Snail1, Fibronectin, VEGF-A, FGF-2) and downregulates the epithelial marker E-Cadherin. In contrast, exposition to low-glucose-based fluids with low-GDP content or SG-based fluids showed higher viability and had less MMT. In vivo, SG-based fluids preserved MC monolayer, induced less PM thickness, angiogenesis, leukocyte infiltration, inflammatory cytokines release, and MMT compared with glucose-based fluids.

Conclusion: SG showed better biocompatibility as an osmotic agent than glucose in vitro and in vivo, therefore, it could alternatively substitute glucose in PDF.