OLMALINC/OCT4/BMP2 axis enhances osteogenic-like phenotype of renal interstitial fibroblasts to participate in Randall's plaque formation.

BACKGROUND: Randall's plaques (RP) are identified as anchored sites for kidney calcium oxalate stones, but the mechanism remains unclear. Given the importance of osteogenic-like cells in RP formation and OCT4 in reprogramming differentiated cells to osteoblasts, the current study explored the potential role of OCT4 in RP formation. METHODS: OCT4 and biomineralization were evaluated in RP, and immunofluorescence co-staining was performed to identify these cells with alteration of OCT4 and osteogenic markers. Based on the analysis of tissue, we further investigated the mechanism of OCT4 in regulating osteogenic-like differentiation of primary human renal interstitial fibroblasts (hRIFs) in vitro and vivo. RESULTS: We identified the upregulated OCT4 in RP, with a positive correlation to osteogenic markers. Interestingly, fibroblast marker Vimentin was partially co-localized with upregulated OCT4 and osteogenic markers in RP. Further investigations revealed that OCT4 significantly enhanced the osteogenic-like phenotype of hRIFs in vitro and in vivo. Mechanically, OCT4 directly bound to BMP2 promoter and facilitated its CpG island demethylation to transcriptionally promote BMP2 expression. Furthermore, combination of RIP and RNA profiling uncovered that lncRNA OLMALINC physically interacted with OCT4 to promote its stabilization via disrupting the ubiquitination. Additionally, OLMALINC was upregulated in fibroblasts in RP visualized by FISH, and a positive correlation was revealed between OLMALINC and OCT4 in RP. CONCLUSIONS: The upregulation of OCT4 in hRIFs was a pathological feature of RP formation, and OLMALINC/OCT4/BMP2 axis facilitated hRIFs to acquire osteogenic-like phenotype under osteogenic conditions, through which the pathway might participate in RP formation. Our findings opened up a new avenue to better understand RP formation in which osteogenic-like process was partially triggered by lncRNAs and pluripotency maintenance related genes.

α-Klotho released from HK-2 cells inhibits osteogenic differentiation of renal interstitial fibroblasts by inactivating the Wnt-ß-catenin pathway.

Randall's plaques (RP) are well established as precursor lesions of idiopathic calcium oxalate (CaOx) stones, and the process of biomineralization driven by osteogenic-like cells has been highlighted in RP formation, but the mechanism is poorly understood. Given the inhibitory role of α-Klotho (KL), an aging suppressor protein with high expression in kidneys, in ectopic calcification and the close association between KL gene polymorphisms and urolithiasis susceptibility, we determined the potential role of KL in RP formation. This study found that both soluble KL (s-KL) and transmembrane KL (m-KL) were downregulated, and that s-KL but not m-KL was inversely correlated with upregulation of osteogenic markers in RP tissues. Additionally, s-KL expression was markedly suppressed in human renal interstitial fibroblasts (hRIFs) and slightly suppressed in HK-2 cells after osteogenic induction, intriguingly, which was echoed to the greater osteogenic capability of hRIFs than HK-2 cells. Further investigations showed the inhibitory effect of s-KL on hRIF osteogenic differentiation in vitro and in vivo. Moreover, coculture with recombinant human KL (r-KL) or HK-2 cells suppressed osteogenic differentiation of hRIFs, and this effect was abolished by coculture with KL-silenced HK-2 cells or the ß-catenin agonist SKL2001. Mechanistically, s-KL inactivated the Wnt-ß-catenin pathway by directly binding to Wnt2 and upregulating SFRP1. Further investigations identified activation of the Wnt-ß-catenin pathway and downregulation of SFRP1 and DKK1 in RP tissues. In summary, this study identified s-KL deficiency as a pathological feature of RP and revealed that s-KL released from HK-2 cells inhibited osteogenic differentiation of hRIFs by inactivating the Wnt-ß-catenin pathway, not only providing in-depth insight into the role of s-KL in renal interstitial biomineralization but also shedding new light on the interaction of renal tubular epithelial cells with interstitial cells to clarify RP formation.

NEAT1 functions as a key mediator of BMP2 to promote osteogenic differentiation of renal interstitial fibroblasts.

Aim: To clarify the mechanism of NEAT1, an aberrantly upregulated lncRNA in Randall's plaques (RP) similar to biomineralization, in mediating osteogenic differentiation of human renal interstitial fibroblasts. Materials & methods: A comprehensive strategy of bioinformatic analysis and experimental verification was performed. Results:BMP2 silence abolished the osteogenic differentiation of human renal interstitial fibroblasts promoted by NEAT1. Mechanically, NEAT1 not only induced the nucleolar translocation of EGR1 binding to BMP2 promotor, but also functioned as a sponge of miR-129-5p in the cytoplasm to promote BMP2 expression. Moreover, there was a positive correlation between NEAT1 and BMP2 expression in RP instead of normal renal papilla. Conclusion:NEAT1 acted as a key mediator of BMP2 to promote human renal interstitial fibroblast osteogenic differentiation, through which NEAT1 might be involved in RP formation.

Lay abstract Kidney stones affect one in ten people in the world, and calcium oxalate (CaOx) stones account for 80% of kidney stones. Calcium and oxalate originate from Randall's plaques (RP) which was identified as an anchor for CaOx in renal papilla (parts of the kidney where collecting ducts open to allow urine to flow to the ureter). RP formation shares similarities with bone formation and blood vessel calcification (hardening caused by calcium salt accumulation). Our findings revealed that long non-coding RNA (long nucleotide sequence not made into protein) NEAT1 controlled genes relating to bone formation in kidney cells known as human renal interstitial fibroblasts which are involved in kidney repair processes. This finding implies human renal interstitial fibroblasts might contribute to kidney calcium phosphate deposits prior to RP formation. Collectively, our study provided a new understanding of how NEAT1 might be involved in RP formation by changing the function of osteogenic-like cells in the kidney.

Value of preoperative urine white blood cell and nitrite in predicting postoperative infection following percutaneous nephrolithotomy: a meta-analysis.

BACKGROUND: To evaluate to what degree preoperative urine white blood cell (WBC) and urine nitrite (NIT) values are predictive of postoperative infections following percutaneous nephrolithotomy (PCNL). METHODS: A systematic literature search was performed of the PubMed, Embase, Cochrane Library, Wanfang Data, National Knowledge Infrastructure (CNKI), and China Science and Technology Journal Database (CSTJ or VIP) online databases to identify relevant studies that examined the predictive value of urine WBC or NIT as risk factors for post-PCNL infection, and the search was finished on February 28, 2020. Two independent reviewers screened the relevant studies, extracted necessary data from the eligible case-control studies (CCS), and assessed the quality of included studies through the Newcastle-Ottawa scale (NOS). RevMan 5.3 software and the Stata 16.0 software were used to complete the statistical analysis of data. Results are expressed as odds ratio (OR) with 95% confidence intervals (CIs). RESULTS: According to the statistical analysis of 12 eligible studies involving 6113 patients, positive urine WBC (WBC+: OR =3.86, 95% CI: 3.03-4.91, P<0.001) and positive NIT (NIT+: OR =7.81, 95% CI: 5.44-11.21, P<0.001) in preoperative tests were identified as independent risk factors for postoperative infections following PCNL. CONCLUSIONS: In summary, as risk factors for postoperative infections, the presence of preoperative urine WBC+ and NIT+ should be evaluated as part of clinical procedure, in order to reduce infections of PCNL.