Effect of sitagliptin on tubulointerstitial Wnt/ß-catenin signalling in diabetic nephropathy.

AIM: To investigate the effect of sitagliptin on Wnt/ß-catenin signalling in the tubulointerstitium of diabetic nephropathy. METHODS: Forty male Wistar rats were divided into normal control (NC), diabetic model (DM), low and high-dose sitagliptin intervention groups (ST1 and ST2, respectively). Changes in the biochemical parameters and tubulointerstitial fibrosis index were observed. The levels of protein and gene expression of different indicators were detected via immunohistochemistry and real-time polymerase chain reaction. NRK-52E cells were divided into the normal control group, mannitol control group, high glucose group (HG), high glucose plus sitagliptin intervention group (HG + ST) and high glucose plus Wnt/ß-catenin inhibitor group (HG + XAV939). The relevant indicators were examined by Western blot or enzyme-linked immunosorbent assay. RESULTS: Compared with the NC group, the blood glucose, glycosylated haemoglobin, 24 h urinary albumin, creatinine clearance and tubulointerstitial fibrosis index were significantly increased in the DM group. These parameters were decreased in the ST1 and ST2 groups compared to the DM group. Compared with the NC group, the levels of Wnt4, ß-catenin, dipeptidyl peptidase-4 and α-smooth muscle actin were higher and E-cadherin was lower in the DM group. Sitagliptin treatment reversed these changes. In the high glucose-stimulated NRK-52E cells, sitagliptin and XAV939 inhibited the elevated expression of Wnt4, ß-catenin, dipeptidyl peptidase-4, α-smooth muscle actin, transforming growth factor-ß and fibronectin and restored E-cadherin activity. CONCLUSION: Sitagliptin may inhibit the tubulointerstitial Wnt/ß-catenin signalling pathway in diabetic nephropathy and provide renal protection by alleviatinge renal tubulointerstitial transdifferentiation and fibrosis.

Wnt4 is overexpressed in human pituitary adenomas and is associated with tumor invasion.

The Wnt4 molecule is a secretory glycoprotein implicated in proliferation and differentiation of both normal and malignant cells. Despite extensive investigation of Wnt4 expression in various cancers, little is known about its expression pattern in different types of pituitary tumors. In this study, we examined the expression of Wnt4 and its downstream molecule ß-catenin in pituitary adenoma specimens. Pituitary adenoma tissues were collected from 43 patients and four normal pituitary tissue samples were obtained at autopsy. Quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry and western blot were performed to detect the expression of Wnt4 and ß-catenin mRNA and protein, respectively. Tumor invasion grade (Knosp grade) was determined on MRI images and was correlated to ß-catenin expression. Immunohistochemistry demonstrated elevated Wnt4 expression in follicle-stimulating hormone-producing adenomas, growth hormone-producing adenomas, prolactin-producing adenomas, thyroid-stimulating hormone-producing adenomas and non-functioning adenomas, while adrenocorticotropic hormone-producing adenomas showed a low level of Wnt4 expression that was comparable to normal pituitary tissue. These results were confirmed by real-time RT-PCR and western blot analyses. The expression pattern of ß-catenin was similar to that of Wnt4 and was inversely correlated to the Knosp grade of tumor invasion. These data indicate that Wnt4 signaling is deregulated in most pituitary adenomas and its excessive activation may inhibit pituitary tumor invasion.

Fibroblast growth factor 2 involved in the pathogenesis of synovial chondromatosis of temporomandibular joint.

BACKGROUND: Synovial chondromatosis (SC) of temporomandibular joint (TMJ) is a rare proliferative disorder characterized by the formation of cartilaginous or osteocartilaginous nodules in synovium and joint space. Fibroblast growth factor 2 (FGF-2) is frequently applied in chondrogenic differentiation assays. Therefore, we hypothesized that FGF-2 might involved in the pathogenesis of SC. METHODS: SC synovium and loose bodies (LBs) specimens were observed by histological and immunohistochemical methods. Real-time PCR was conducted for comparing genes expressions in SC and normal synovium. SC synoviocytes were stimulated by FGF-2 in the presence or absence of its antagonist long pentraxin-3 (PTX3) for 6 days. Real-time PCR and alkaline phosphatase (ALP) activity were performed to examine the effects exerted by FGF-2 and PTX3. RESULTS: SC synovium, no matter facing the articular cavity or covering LB, was characterized by increased quantity of synoviocytes and blood vessels. FGF-2 was expressed in chondrocytes and fibroblast-like cells of LBs, and the wall of blood vessels. Expressions of chondrogenic genes (Sox9 and Wnt-4), osteogenic genes (Foxc2), FGF-2, and VEGF-A mRNA were significantly higher in SC synovium than that of the control group. The stimulation of FGF-2 on SC synoviocytes increased ALP activity and expressions of chondrogenic genes (Sox9, Col2α1, and Aggrecan), osteogenic genes (Foxc2, osteocalcin, and Col1α1), and VEGF-A, but PTX3 inhibited these effects. CONCLUSION: FGF-2 was responsible for the formation of cartilaginous loose bodies and involved in the pathogenesis of SC.

Fluocinolone acetonide promotes the proliferation and mineralization of dental pulp cells.

INTRODUCTION: The aim of this study was to investigate the role of the steroid fluocinolone acetonide on the proliferation and mineralization of human dental pulp cells (DPCs). The potential effect of fluocinolone acetonide on reparative dentin formation and the recovery of injured dental pulp were evaluated. METHODS: The proliferative effect of fluocinolone acetonide on DPCs was analyzed by cholecystokinin octapeptide assay and flow cytometry. The mineralized effect of fluocinolone acetonide was investigated by the detection of mineralization-related biomarkers including alkaline phosphatase (ALP), bone sialoprotein, and osteocalcin by using ALP histochemical staining, ALP activity, immunostaining, alizarin red staining, and reverse-transcriptase polymerase chain reaction. The molecules, including dentin sialophosphoprotein and Wnt4, involved in the process of mineralization were detected by real-time polymerase chain reaction and Western blot analysis. RESULTS: Low concentrations of fluocinolone acetonide (0.1-40 µmol/L) promoted the proliferation of DPCs. The flow cytometry results showed that the CD146-positive subpopulation of DPCs was significantly increased after treatment with fluocinolone acetonide at 1 and 10 µmol/L for 48 hours, respectively. The messenger RNA expression and activity of the early-stage mineralization marker ALP were evidently increased in fluocinolone acetonide-treated DPCs compared with the untreated control group, so did the middle-stage mineralization marker bone sialoprotein and the late-stage mineralization marker osteocalcin. Meanwhile, Wnt4 and the dentin-specific marker dentin sialophosphoprotein were obviously up-regulated by fluocinolone acetonide compared with the untreated controls. CONCLUSIONS: Fluocinolone acetonide can promote the proliferation of DPCs, especially for the CD146+ subpopulation. Fluocinolone acetonide can initiate the mineralization of DPCs and has the potential role in repairing injured pulp tissues.