Hypomethylation of the LncRNA H19 promoter accelerates osteogenic differentiation of vascular smooth muscle cells by activating the Erk1/2 pathways.

OBJECTIVE: Vascular calcification is a common chronic kidney disease complication. This study aimed to investigate the function of long non-coding RNA (LncRNA) H19 in vascular calcification to explore new therapeutic strategies. METHODS: We induced osteogenic differentiation and calcification of vascular smooth muscle cells (VSMCs) using ß-glycerophosphate. Then, we detected the LncRNA H19 promoter methylation status and Erk1/2 pathways using methylation-specific polymerase chain reaction and western blotting, respectively. RESULTS: Compared with the control group, high phosphorus levels induced VSMC calcification, accompanied by increases in LncRNA H19 and the osteogenic marker Runx2 and reduction of the contractile phenotype marker SM22a. LncRNA H19 knockdown inhibited osteogenic differentiation and calcification of VSMCs. However, the suppressed role of VSMC calcification caused by shRNA H19 was partially reversed by simultaneous activation of the Erk1/2 pathways. Mechanically, we found that the methylation rate of CpG islands in the LncRNA H19 promoter region was significantly lower in the high-phosphorus group, and the hypomethylation state elevated LncRNA H19 levels, which in turn regulated phosphorylated Erk1/2 expression. CONCLUSIONS: LncRNA H19 promoted osteogenic differentiation and calcification of VSMCs by regulating the Erk1/2 pathways. Additionally, hypomethylation of LncRNA H19 promoter CpG islands upregulated LncRNA H19 levels and subsequently activated Erk1/2 phosphorylation.

LncRNA H19 sponges miR-103-3p to promote the high phosphorus-induced osteoblast phenotypic transition of vascular smooth muscle cells by upregulating Runx2.

Elucidating the mechanism of the osteogenic phenotypic transdifferentiation of vascular smooth muscle cells (VSMCs) is the key to determining the diagnosis and treatment of arterial medial calcification (AMC). Long noncoding RNAs (lncRNAs) have been reported to participate in the regulation of vascular physiology and pathology. Here, we investigated the effect and mechanism of the lncRNA H19 on the osteoblastic differentiation of VSMCs induced by high phosphorus. H19 was expressed at high levels in high phosphorus-induced primary rat VSMCs. Further experiments indicated that H19 played a positive role in the osteoblast phenotypic transition by suppressing miR-103-3p expression and subsequently promoting osteoblast-specific marker expression, including bone morphogenetic protein 2 (BMP-2) and osteopontin (OPN). Mechanistically, we recognized RUNX family transcription factor 2 (Runx2) as a direct target of miR-103-3p. Moreover, H19 directly interacted with miR-103-3p, and overexpression of miR-103-3p reversed the upregulation of Runx2 induced by H19. Therefore, H19 positively regulated Runx2 expression by sponging miR-103-3p and promoted the osteoblast phenotypic transition in VSMC calcification. Collectively, the lncRNA H19 promoted osteogenic differentiation by modulating the miR-103-3p/Runx2 axis in the process of VSMC calcification induced by a high phosphorus concentration. The current study provided new insights into an important role for the lncRNA H19 as a miRNA sponge in VSMCs and supplied novel insights into lncRNA-directed diagnostics and therapeutics for vascular calcification.

Extracellular acidosis suppresses calcification of vascular smooth muscle cells by inhibiting calcium influx via L-type calcium channels.

Vascular calcification such as arteriosclerosis, which is characterized by a calcification of the tunica media, is a severe complication of chronic kidney disease (CKD), contributing to the high prevalence of cardiovascular morbidity and mortality in patients with CKD. An essential step during the development of arteriosclerosis is the transdifferentiation/calcification of vascular smooth muscle cells (VSMCs), resembling osteogenesis. Metabolic acidosis, a common clinical manifestation in CKD, is known to decrease vascular calcification. To understand the underlying regulatory mechanisms of acidosis, we investigated whether the acidosis-decreased VSMC calcification involves altered signaling of the LTCC/Ca2+/Runx2 pathway. Vascular calcifications, calcium content, runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), L-type calcium channel (LTCC) ß3 subunits, and calcium influx were measured in vivo or in vitro. Calcified nodules and calcium content increased either in aorta sections of vascular calcified rats or in VSMCs induced by ß-GP. The expression of Runx2 and ALP activity markedly rose, accompanied by the increasing expression of LTCC ß3 subunits and calcium influx. However, acidosis supplementation successfully attenuated VC and VSMC calcification and inhibited Runx2, ALP, LTCC ß3 subunits, and calcium influx. In conclusion, acidosis significantly attenuated vascular calcification in association with downregulation of the LTCC/Ca2+/Runx2 pathway.

[Risk factors for coronary artery calcification in patients with end-stage renal disease].

OBJECTIVE: To explore risk factors for coronary artery calcification (CAC) inpatients with end-stage renal disease (ESRD). METHODS: A total of 53 ESRD patients undergoing regular hemodialysis (3 times a week) from August 2014 to March 2015 in the Fourth Hospital of Hebei Medical University were enrolled in the study. The patients were divided into the negative control group (13 cases) and three positive groups (11 mild calcification cases, 12 moderate calcification cases and 17 severe calcification cases) based on coronary artery calcification score (CACs). Clinical data of all patients at study entry were collected. Arterial blood samples were also collected at the start of the first hemodialysis (HD) session of the week to measure the levels of serum albumin, uric acid, calcium (Ca), phosphorus (P), magnesium, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), C reactive protein (CRP), beta-2 microglobulin (ß2-MG), free parathyroid hormone (iPTH), alkaline phosphatase, fibrinogen, hemoglobin (HGB) and ferritin. Meanwhile, levels of blood pH were detected after collecting pre- and post-HD blood samples to calculate ΔpH (post-HD pH subtracted pre-HD pH). Logistic regression analysis was performed to analyze the correlation of CACs with clinical data and previously-reported blood biochemical indicators, followed by analysis of the incidence of CAC and influential factors in ESRD patients. RESULTS: Severity of CAC was positively correlated with age (r=0.269), HD duration (r=0.341), serum calcium (r=0.358), serum phosphorus (r=0.186) and pre-HD pH (r=0.275), but negatively correlated with serum albumin (r=-0.192) and ΔpH (r=-0.302), all P<0.05. Logistic regression analysis revealed that age, HD duration, serum phosphorus level and ΔpH were independent risk factors for CAC in ESRD patients (P<0.05). In CAC positive groups, CAC was predominantly involved in the left anterior descending artery (P<0.05, P<0.01 and P<0.01 in mild, moderate and severe calcification group, respectively). CONCLUSIONS: CAC in ESRD patients seems to be affected by multiple factors, such as age, HD duration, serum phosphorus level and ΔpH. Moreover, ΔpH affects CAC mainly by pre-HD pH. Furthermore, left anterior descending artery is predominantly affected by CAC in ESRD patients.

Analysis of a single hemodialysis on phosphate removal of the internal fistula patients by mathematical and statistical methods.

Chronic kidney disease related mineral and bone disease (CKD-MBD) is a worldwide challenge in hemodialysis patients. In china, the number of dialysis patients is growing but few data are available about their bone disorders. In the current study, we aimed to evaluate the effect of clinical factors on the serum phosphorus clearance in the 80 maintenance hemodialysis (MHD) patients. Six clinical factors were identified for their association with the serum phosphorus clearance using the analysis of Spearman's single linear correlation, including predialysis serum phosphate level, CRR, membrane surface area of the dialyzer, effective blood flow rate, the blood chamber volume, and hematocrit. In an overall multivariate analysis, pre-P, CRR, membrane SA, and Qb were identified as independent risk factors associated with the serum phosphorus clearance. In conclusion, HD could effectively clear serum phosphorus. The analysis of CRR might help to estimate serum phosphorus reduction ratio.