Osteoblastic Transdifferentiation Research Articles

#1293 Endothelial calcification induced by high-phosphate is characterized by mesenchymal and osteoblastic transdifferentiation

Abstract Background and Aims Chronic kidney disease (CKD) is a prevalent condition that affects millions of people. Patients with CKD have an increased cardiovascular risk, mostly due to vascular calcification (VC). By now, it's quite clear how, in vitro and in vivo, vascular smooth muscle cells (VSMCs) actively participate to VC. In contrast to the wide studies on VSMCs, the role of endothelial cells (ECs) has been poorly investigated. It's known that ECs have a dynamic nature and following particular stimuli they can trans-differentiate and acquire several different phenotypes through the endothelial-to-mesenchymal transition (EndMT). Methods Human aortic ECs (HAECs) were challenged, in an in vitro calcification model, with 2, 2.5, 3, 3.5 mM Pi for up to 7 days. Early morphological changes, gene expression and cell migration were evaluated. Afterwards calcium deposition, genes and protein expression and ultrastructural changes were analyzed. Results High-Pi, at a concentration of 3 mM, is able to induce EC calcium deposition. Calcification is dependent on calcium influx without influencing Pit-1 expression. During the first days of high-Pi treatment ECs change their morphology from cobblestone to spindle shape acquiring motility, as demonstrated by the 24% increased closure in the scratch wound test. EndMT master genes such as SNAIL and TWIST resulted up-regulated at day 3 together with an increased protein expression of mesenchymal markers such as N-Cadherin, α-SMA, SM22α, FSP-1 and Fibronectin. Starting from day 5 high-Pi induces osteoblastic differentiation with RUNX2 and BMP2 mRNA up-regulation up to day 7, osteopontin increased protein expression and positive Alcian Blu staining. In calcified ECs mesenchymal and endothelial markers, such as α-SMA, SM22α, FSP-1 and Fibronectin or vWF progressively decrease. Finally, uremic serum is able to exacerbate in vitro calcification, compared to healthy serum characterized by an increase in both mesenchymal and osteoblastic mastergene such as TWIST and RUNX2. Conclusions Our data demonstrate that in vitro high-Pi induces the EndMT process and similar osteoblastic trans-differentiation suggesting a potential role of endothelium in VC. The relevancy of endothelial calcification is suggested by the calcification exacerbation induced by uremic compared to healthy sera.

Pro-osteogenic role of interleukin-22 in calcific aortic valve disease

Background and aimsAlthough calcific aortic valve disease (CAVD) is a common valvular disease among elderly populations and its incidence has markedly increased in recent decades, the pathogenesis of CAVD remains unclear. In this study, we explored the potential role of interleukin (IL)-22 and the underlying molecular mechanism in CAVD. Methods and ResultsOur results showed that IL-22 was upregulated in calcific aortic valves from CAVD patients, and its main sources were CD3+ T cells and CD68+ macrophages. Human aortic valve interstitial cells (VICs) expressed the IL-22–specific receptor IL-22R1, and IL-22R1 expression also was elevated in calcified valves. Treatment of cultured human VICs with recombinant human IL-22 resulted in markedly increased expression of osteogenic proteins Runt-related transcription factor 2 (RUNX2) and alkaline phosphatase (ALP), as well as increased matrix calcium deposition. Moreover, siRNA silencing of IL-22R1 blocked the pro-osteogenic effect of IL-22 in VICs. In IL-22–treated VICs, we also observed increased phosphorylation of JAK3 and STAT3 and nuclear translocation of STAT3. Pretreatment with a specific JAK3 inhibitor, WHIP-154, or siRNA knockout of STAT3 effectively mitigated the IL-22–induced osteoblastic trans-differentiation of human VICs. ConclusionsTogether, these data indicate that IL-22 promotes osteogenic differentiation of VICs by activating JAK3/STAT3 signaling. Based on our results demonstrating a pro-osteogenic role of IL-22 in human aortic valves, pharmacological inhibition of IL-22 signaling may represent a potential strategy for alleviating CAVD.

Abstract 13571: Endothelial Jagged1 in Vascular Calcification Induced by Chronic Kidney Disease

Introduction: Chronic kidney disease (CKD)-induced vascular calcification (VC) is a dire complication with high incidence, while its pathogenesis has not been fully elucidated. Hypothesis: We hypothesized that endothelial Jagged1 prevents vascular smooth muscle cell from osteoblast trans-differentiation thus alleviates CKD induced vascular calcification. Methods: We have generated a CKD mouse model by 5/6 nephrectomy followed by high phosphate diet (HPiD). CKD-induced VC were determined in Jagged1 EC specific KO and Notch3 KO mice. Co-culture of EC with vascular muscle cells (VSMCs) was performed to study the mechanism. Results: Endothelial Jagged1 expression was decreased in calcified arteries from CKD patients vs . normal arteries. Knockout of EC Jagged1 significantly induced artery calcification and decreased the mice survival rate vs. WT CKD mice. There was decreased expression of VSMC contractile markers and Notch3, and increased expression of ossification markers in calcified arteries from endothelial Jagged1 KO CKD mice. Furthermore, overexpression of EC Jagged1 significantly prevented artery calcification. In EC Jag1 OE /Notch3 KO CKD mice, KO Notch3 partially blocked the protective effects on VC by Jag1 OE. In co-culture experiments, KO of Jagged1 in ECs enhanced transdifferentiation of VSMCs into osteoblast cells after high-phosphate (HPi) treatment, while overexpression of Notch3 alleviated calcium deposition induced by HPi. Silencing Hes1 in VSMC led to remarkably increased Runx2 expression and more severe calcification in response to HPi treatment. Conclusions: Jagged1 expression in ECs controls CKD-induced VC. Down-regulation of EC Jagged1 impairs VSMC Notch3 activation, thus induces VSMC transdifferentiation and VC through Notch target Hes1.

Effects of advanced glycation end-products, diabetes and metformin on the osteoblastic transdifferentiation capacity of vascular smooth muscle cells: In vivo and in vitro studies

AimsOur objective was to study the vascular smooth muscle cells (VSMC) osteoblastic transdifferentiation in AGE exposed cells or those from diabetic animals, and its response to metformin treatment. MethodsVSMC were obtained from non-diabetic rats, grown with or without AGE; while VSMC of in vivo-ex vivo studies were obtained from non-diabetic control animals (C), diabetic (D), C treated with metformin (M) and D treated with metformin (D-M). We studied the osteoblastic differentiation by evaluating alkaline phosphatase (ALP), type I collagen (Col) and mineral deposit. ResultsIn vitro, AGE increased proliferation, migration, and osteoblastic differentiation of VSMC. Metformin cotreatment prevented the AGE induced proliferation and migration. Both AGE and metformin stimulated the expression of ALP and Col. AGE induced mineralization was prevented by metformin. VSMC from D expressed a higher production of Col and ALP. Those from D-M showed an ALP increase vs C and M, and a partial decrease vs D. Cultured in osteogenic medium, ALP, Col and mineralization increased in D vs C, remained unchanged in M, and were prevented in D-M animals. ConclusionBoth AGE and DM favor VSMC differentiation towards the osteogenic phenotype and this effect can be prevented by metformin.

Updates in the chronic kidney disease-mineral bone disorder show the role of osteocytic proteins, a potential mechanism of the bone-Vascular paradox, a therapeutic target, and a biomarker.

The chronic kidney disease-mineral bone disorder (CKD-MBD) is a complex multi-component syndrome occurring during kidney disease and its progression. Here, we update progress in the components of the syndrome, and synthesize recent investigations, which suggest a potential mechanism of the bone-vascular paradox. The discovery that calcified arteries in chronic kidney disease inhibit bone remodeling lead to the identification of factors produced by the vasculature that inhibit the skeleton, thus providing a potential explanation for the bone-vascular paradox. Among the factors produced by calcifying arteries, sclerostin secretion is especially enlightening. Sclerostin is a potent inhibitor of bone remodeling and an osteocyte specific protein. Its production by the vasculature in chronic kidney disease identifies the key role of vascular cell osteoblastic/osteocytic transdifferentiation in vascular calcification and renal osteodystrophy. Subsequent studies showing that inhibition of sclerostin activity by a monoclonal antibody improved bone remodeling as expected, but stimulated vascular calcification, demonstrate that vascular sclerostin functions to brake the Wnt stimulation of the calcification milieu. Thus, the target of therapy in the chronic kidney disease-mineral bone disorder is not inhibition of sclerostin function, which would intensify vascular calcification. Rather, decreasing sclerostin production by decreasing the vascular osteoblastic/osteocytic transdifferentiation is the goal. This might decrease vascular calcification, decrease vascular stiffness, decrease cardiac hypertrophy, decrease sclerostin production, reduce serum sclerostin and improve skeletal remodeling. Thus, the therapeutic target of the chronic kidney disease-mineral bone disorder may be vascular osteoblastic transdifferentiation, and sclerostin levels may be a useful biomarker for the diagnosis of the chronic kidney disease-mineral bone disorder and the progress of its therapy.

Novel Peptides Derived from Sea Cucumber Intestine Promotes Osteogenesis by Upregulating Integrin-Mediated Transdifferentiation of Growth Plate Chondrocytes to Osteoblasts.

The sea cucumber intestine is a major by-product of sea cucumber processing and contains high levels of protein. In this study, we isolated and identified 28 novel osteogenic peptides from sea cucumber intestinal hydrolysis by the activity-tracking method for the first time. In vitro experimental results showed that compared with high molecular weight, the peptides from sea cucumber intestine (SCIP) with molecular weight <3 kDa more significantly promoted the proliferation and mineralized nodules of MC3T3-E1 cell and exhibited potential integrin binding capacity. In vivo experimental results showed that the SCIP supplement significantly increased the longitudinal bone length and elevated the height of the growth plate (especially the hypertrophic zone, 37.2%, p < 0.01) in adolescent mice. Further, immunofluorescence labeling results indicated that the SCIP supplement increased chondrocyte transdifferentiate to osteoblast in the growth plate close to the diaphysis. Mechanistically, transcriptome analysis revealed that the SCIP supplement induced the dedifferentiation of chondrocyte to osteoprogenitor cell via integrin-mediated histone acetylation and then redifferentiated to osteoblast via integrin-mediated Wnt/β-catenin signaling. These results reported for the first time that sea cucumber intestine had the potential to develop into a dietary supplement for promoting osteogenic, and provide new evidence for the mechanism of dietary promotes chondrocyte to osteoblast transdifferentiation.

An integrative bioinformatics approach to decipher adipocyte-induced transdifferentiation of osteoblast

In human, bone loss is associated with increased marrow adipose tissue and recent data suggest that medullary adipocytes could play a role in osteoporosis by acting on neighboring bone-forming osteoblasts. Supporting this hypothesis, we previously showed, in a coculture model based on human bone marrow stromal cells, that factors secreted by adipocytes induced the conversion of osteoblasts towards an adipocyte-like phenotype. In this work, we employed an original integrative bioinformatics approach connecting proteomic and transcriptomic data from adipocytes and osteoblasts, respectively, to investigate the mechanisms underlying their crosstalk. Our analysis identified a total of 271 predicted physical interactions between adipocyte-secreted proteins and osteoblast membrane protein coding genes and proposed three pathways for their potential contribution to osteoblast transdifferentiation, the PI3K-AKT, the JAK2-STAT3 and the SMAD pathways. Our findings demonstrated the effectiveness of our integrative omics strategy to decipher cell-cell communication events.

The ATF3-OPG Axis Contributes to Bone Formation by Regulating the Differentiation of Osteoclasts, Osteoblasts, and Adipocytes.

Activating transcription factor 3 (ATF3) has been identified as a negative regulator of osteoblast differentiation in in vitro study. However, it was not associated with osteoblast differentiation in in vivo study. To provide an understanding of the discrepancy between the in vivo and in vitro findings regarding the function of ATF3 in osteoblasts, we investigated the unidentified roles of ATF3 in osteoblast biology. ATF3 enhanced osteoprotegerin (OPG) production, not only in osteoblast precursor cells, but also during osteoblast differentiation and osteoblastic adipocyte differentiation. In addition, ATF3 increased nodule formation in immature osteoblasts and decreased osteoblast-dependent osteoclast formation, as well as the transdifferentiation of osteoblasts to adipocytes. However, all these effects were reversed by the OPG neutralizing antibody. Taken together, these results suggest that ATF3 contributes to bone homeostasis by regulating the differentiation of various cell types in the bone microenvironment, including osteoblasts, osteoclasts, and adipocytes via inducing OPG production.

Adipocyte-induced transdifferentiation of osteoblasts and its potential role in age-related bone loss.

Our preliminary findings have lead us to propose bone marrow adipocyte secretions as new contributors to bone loss. Indeed, using a coculture model based on human bone marrow stromal cells, we previously showed that soluble factors secreted by adipocytes induced the conversion of osteoblasts towards an adipocyte-like phenotype. In this study, microarray gene expression profiling showed profound transcriptomic changes in osteoblasts following coculture and confirmed the enrichment of the adipocyte gene signature. Double immunofluorescence microscopic analyses demonstrated the coexpression of adipogenic and osteoblastic specific markers in individual cells, providing evidence for a transdifferentiation event. At the molecular level, this conversion was associated with upregulated expression levels of reprogramming genes and a decrease in the DNA methylation level. In line with these in vitro results, preliminary immunohistochemical analysis of bone sections revealed adipogenic marker expression in osteoblasts from elderly subjects. Altogether, these data suggest that osteoblast transdifferentiation could contribute to decreased bone mass upon ageing.

Carnosine attenuates vascular smooth muscle cells calcification through mTOR signaling pathway.

ObjectiveVascular calcification is prevalent in the aging population, as we know that arterial calcification is associated with aging. Recent studies have demonstrated that carnosine, a naturally occurring dipeptide, performs the treatment of aging‐related diseases, such as atherosclerosis and type 2 diabetes. Here, we investigated the role of carnosine in a calcification model of vascular smooth muscle cells (VSMCs).MethodsIn this research, we used an in vitro model of VSMC calcification to investigate the role of carnosine in the progression of rat VSMC calcification.ResultsCarnosine treatment attenuated calcium deposition in a dose‐dependent manner, detected by Alizarin Red S staining and calcium content assay. Carnosine also reduced the protein level of Runx2, bone morphogenetic protein 2 (BMP‐2), and cellular reactive oxygen species (ROS) production. Further, carnosine inhibited the activation of the mammalian target of rapamycin (mTOR) pathway.ConclusionCarnosine attenuated the VSMC calcification via inhibition of osteoblastic transdifferentiation and the mTOR signaling pathway.

Evidence of vasculature and chondrocyte to osteoblast transdifferentiation in craniofacial synovial joints: Implications for osteoarthritis diagnosis and therapy.

Temporomandibular joint osteoarthritis (TMJ OA) leads to permanent cartilage destruction, jaw dysfunction, and compromises the quality of life. However, the pathological mechanisms governing TMJ OA are poorly understood. Unlike appendicular articular cartilage, the TMJ has two distinct functions as the synovial joint of the craniofacial complex and also as the site for endochondral jaw bone growth. The established dogma of endochondral bone ossification is that hypertrophic chondrocytes undergo apoptosis, while invading vasculature with osteoprogenitors replace cartilage with bone. However, contemporary murine genetic studies support the direct differentiation of chondrocytes into osteoblasts and osteocytes in the TMJ. Here we sought to characterize putative vasculature and cartilage to bone transdifferentiation using healthy and diseased TMJ tissues from miniature pigs and humans. During endochondral ossification, the presence of fully formed vasculature expressing CD31+ endothelial cells and α-SMA+ vascular smooth muscle cells were detected within all cellular zones in growing miniature pigs. Arterial, endothelial, venous, angiogenic, and mural cell markers were significantly upregulated in miniature pig TMJ tissues relative to donor matched knee meniscus fibrocartilage tissue. Upon surgically creating TMJ OA in miniature pigs, we discovered increased vasculature and putative chondrocyte to osteoblast transformation dually marked by COL2 and BSP or RUNX2 within the vascular bundles. Pathological human TMJ tissues also exhibited increased vasculature, while isolated diseased human TMJ cells exhibited marked increased in vasculature markers relative to control 293T cells. Our studyprovides evidence to suggest that the TMJ in higher order species are in fact vascularized. There have been no reports of cartilage to bone transdifferentiation or vasculature in human-relevant TMJ OA large animal models or in human TMJ tissues and cells. Therefore, these findings may potentially alter the clinical management of TMJ OA by defining new drugs that target angiogenesis or block the cartilage to bone transformation.

IL-21 promotes osteoblastic differentiation of human valvular interstitial cells through the JAK3/STAT3 pathway.

Objectives: This study amied to whether IL-21 promotes osteoblast transdifferentiation of cultured human Valvular interstitial cells (VICs).Methods: We first confirmed that IL-21 alters gene expression between CAVD aortic valve tissue and normal samples by immunohistochemistry, qPCR, and western blotting. VICs were cultured and treated with IL-21. Gene and protein expression levels of the osteoblastic markers ALP and Runx2, which can be blocked by specific JAK3 inhibitors and/or siRNA of STAT3, were measured.Results: IL-21 expression was upregulated in calcified aortic valves and promotes osteogenic differentiation of human VICs. IL-21 accelerated VIC calcification through the JAK3/STAT3 pathway.Conclusion: Our data suggest that IL-21 is a key factor in valve calcification and a promising candidate for targeted therapeutics for CAVD.

Vitamin D-regulated osteocytic sclerostin and BMP2 modulate uremic extraskeletal calcification.

We induced chronic kidney disease (CKD) with adenine in WT mice, mice with osteocyte-specific deletion of Cyp27b1, encoding the 25-hydroxyvitamin D 1(OH)ase [Oct-1(OH)ase-/-], and mice with global deletion of Cyp27b1 [global-1α(OH)ase-/-]; we then compared extraskeletal calcification. After adenine treatment, mice displayed increased blood urea nitrogen, decreased serum 1,25(OH)2D, and severe hyperparathyroidism. Skeletal expression of Cyp27b1 and of sclerostin and serum sclerostin all increased in WT mice but not in Oct-1α(OH)ase-/- mice or global-1α(OH)ase-/- mice. In contrast, skeletal expression of BMP2 and serum BMP2 rose in the Oct-1α(OH)ase-/- mice and in the global-1α(OH)ase-/- mice. Extraskeletal calcification occurred in muscle and blood vessels of mice with CKD and was highest in Oct-1α(OH)ase-/-mice. In vitro, recombinant sclerostin (100 ng/mL) significantly suppressed BMP2-induced osteoblastic transdifferentiation of vascular smooth muscle A7r5 cells and diminished BMP2-induced mineralization. Our study provides evidence that local osteocytic production of 1,25(OH)2D stimulates sclerostin and inhibits BMP2 production in murine CKD, thus mitigating osteoblastic transdifferentiation and mineralization of soft tissues. Increased osteocytic 1,25(OH)2D production, triggered by renal malfunction, may represent a "primary defensive response" to protect the organism from ectopic calcification by increasing sclerostin and suppressing BMP2 production.

Hydrogen sulfide inhibits calcification of heart valves; implications for calcific aortic valve disease.

Background and PurposeCalcification of heart valves is a frequent pathological finding in chronic kidney disease and in elderly patients. Hydrogen sulfide (H2S) may exert anti‐calcific actions. Here we investigated H2S as an inhibitor of valvular calcification and to identify its targets in the pathogenesis.Experimental ApproachEffects of H2S on osteoblastic transdifferentiation of valvular interstitial cells (VIC) isolated from samples of human aortic valves were studied using immunohistochemistry and western blots. We also assessed H2S on valvular calcification in apolipoprotein E‐deficient (ApoE−/−) mice.Key ResultsIn human VIC, H2S from donor compounds (NaSH, Na2S, GYY4137, AP67, and AP72) inhibited mineralization/osteoblastic transdifferentiation, dose‐dependently in response to phosphate. Accumulation of calcium in the extracellular matrix and expression of osteocalcin and alkaline phosphatase was also inhibited. RUNX2 was not translocated to the nucleus and phosphate uptake was decreased. Pyrophosphate generation was increased via up‐regulating ENPP2 and ANK1. Lowering endogenous production of H2S by concomitant silencing of cystathionine γ‐lyase (CSE) and cystathionine β‐synthase (CBS) favoured VIC calcification. analysis of human specimens revealed higher Expression of CSE in aorta stenosis valves with calcification (AS) was higher than in valves of aortic insufficiency (AI). In contrast, tissue H2S generation was lower in AS valves compared to AI valves. Valvular calcification in ApoE−/− mice on a high‐fat diet was inhibited by H2S.Conclusions and ImplicationsThe endogenous CSE‐CBS/H2S system exerts anti‐calcification effects in heart valves providing a novel therapeutic approach to prevent hardening of valves.Linked ArticlesThis article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc

Vascular Calcification in Patients with Chronic Kidney Disease

Cardiovascular morbidity and mortality are very common in patients with chronic kidney disease, which may result in part from vascular calcification. Vascular calcification requires osteoblastic trans-differentiation of vascular smooth muscle cells through an active and highly regulated process that is morphologically and functionally similar to bone formation in a number of ways. Multiple studies have been published on this topic, but the precise mechanism of vascular calcification remains unclear. This review presents recent insights into the mechanism of vascular calcification, as well as therapies that modulate mineral metabolism. (Korean J Med 2019;94:159-169)

Osteogenic transdifferentiation of vascular smooth muscle cells isolated from spontaneously hypertensive rats and potential menaquinone-4 inhibiting effect.

Vascular calcification (VC) is an active and cell-mediated process that shares many common features with osteogenesis. Knowledge demonstrates that in the presence of risk factors, such as hypertension, vascular smooth muscle cells (vSMCs) lose their contractile phenotype and transdifferentiate into osteoblastic-like cells, contributing to VC development. Recently, menaquinones (MKs), also known as Vitamin K2 family, has been revealed to play an important role in cardiovascular health by decreasing VC. However, the MKs' effects and mechanisms potentially involved in vSMCs osteoblastic transdifferentiation are still unknown. The aim of this study was to investigate the possible role of menaquinone-4 (MK-4), an isoform of MKs family, in the modulation of the vSMCs phenotype. To achieve this, vascular cells from spontaneously hypertensive rats (SHR) were used as an in vitro model of cell vascular dysfunction. vSMCs from Wistar Kyoto normotensive rats were used as control condition. The results showed that MK-4 preserves the contractile phenotype both in control and SHR-vSMCs through a γ-glutamyl carboxylase-dependent pathway, highlighting its capability to inhibit one of the mechanisms underlying VC process. Therefore, MK-4 may have an important role in the prevention of vascular dysfunction and atherosclerosis, encouraging further in-depth studies to confirm its use as a natural food supplement.

In times of tobacco-free nicotine consumption: The influence of nicotine on vascular calcification.

Smoking remains the most important avoidable cause of global mortality. Even though the number of cigarette smokers declines in first world countries, the uses of alternative nicotine delivery products increase and may even surpass the sells of cigarettes. In this light, the explicit role of nicotine in the development of cardiovascular diseases should be elucidated. This narrative review attempts to connect current literature about possible effects of nicotine on the environment of the vasculature to the pathogenesis of vascular calcification, focusing on the tunica media of the vessel wall. For this review, papers found on Pubmed and Medline until December 2018 by searching for the keywords nicotine, vascular calcification, oxidative stress, osteoblastic transdifferentiation and matrix degradation were considered. Nicotine creates an environment that probably facilitates and maybe even induces osteogenic transdifferentiation of VSMC by inflammation, endothelial dysfunction and reactive oxygen species. This process is believed to be a key event in calcification of the tunica media of the vessel wall. Furthermore, nicotine could lead to the formation of nucleation sites for hydroxyapatite by facilitating matrix vesicles and extracellular matrix degradation. There is a growing body of evidence implicating that nicotine alone could impair vascular function and lead to vascular calcification. Further research is necessary to elucidate the explicit influence of nicotine on arteriosclerosis.

Uremic Patients with Increased Vascular Calcification Score Have Serum with High Calcific Potential: Role of Vascular Smooth Muscle Cell Osteoblastic Differentiation and Apoptosis

Background/Aims: Uremic patients experience premature vascular ageing that causes cardiovascular morbidity. In this study, we investigated the relationship between uremic serum calcific potential induced by high phosphate (Pi) and vascular calcification score (VCS). Methods: Vascular smooth muscle cells (VSMCs) were cultured with 3.5 mM Na₃PO₄ (Pi) with 10% uremic serum and calcium deposition, markers of osteoblastic transformation, and apoptosis were evaluated. Results: Culture with uremic serum and high-Pi significantly induced calcification (0.21 ± 0.03 vs. 8.05 ± 0.6; ctr vs. Pi; OD/mg protein; p < 0.01). We next stratified patients with respect of the degree of VCS in 2 groups: absence of vascular calcification (VC) “no VC group” and presence of VC “VC group”. We found that there was a significant correlation between VCS and uremic serum calcific potential induced by high Pi in vitro (p < 0.01). Interestingly, uremic sera of the “VC group” were more effective than sera from the “no VC group”, in downregulating α-actin and SM22α, after treatment with high-Pi (41.3 ± 4.7 vs. 23.3 ± 2.9 and 25.6 ± 6.8 vs. 8.14 ± 2.3; VC vs. no VC group, α-actin and SM22α respectively; Δ intensity area; p < 0.01). Similarly, sera from “VC group” were more effective than sera from “no VC group” in adjuvanting the high-Pi effect of increasing osteoblastic markers, such as bone morphogenic protein 2 (BMP2), osteocalcin (OC), and runt-related transcription factor 2 (RUNX2; 39.1 ± 11.3 vs. 5.0 ± 2.6 BMP2; 12.2 ± 4.2 vs. 1.7 ± 0.3 OC; 2.9 ± 0.4 vs. 1.2 ± 0.2 RUNX2; VC vs. no VC group respectively; p < 0.05). We found a similar pattern with significantly higher apoptosis and necrosis induction by sera from the “VC group” compared to the “no VC group” (2.05 ± 0.33 vs. 1.29 ± 0.13 and 54.1 ± 19.5 vs. 27.4 ± 10.6; Pi; VC group vs. no VC group; enrichment factor of apoptotic or necrotic fragments, respectively; p < 0.05). Conclusions: We conclude that VCS of end-stage renal disease patients significantly correlates with serum-calcific potential induced by high Pi. In addition, uremic patients with higher VCS have sera with a higher potential to induce VSMC osteoblastic trans-differentiation, apoptosis, and necrosis.

Meis2 represses the osteoblastic transdifferentiation of aortic valve interstitial cells through the Notch1/Twist1 pathway

AimCalcific aortic valve disease (CAVD) is the most common valvular disease worldwide. The osteoblastic transdifferentiation of aortic valve interstitial cells (VICs) is the essential process of CAVD, but the underlying mechanisms are poorly understood. Aortic VICs are generated from epithelial-to-mesenchymal transition (EMT) and migration of neural crest cells (NCCs).Meis2 has been associated with EMT and NCCs migration during development, but its role in CAVD is unknown. This study aims to elucidate the specific functions of Meis2 and its downstream targets in aortic valve calcification. Material and methodsLevels of Meis2 were examined in calcified (n = 30) and normal (n = 30) human aortic valve tissues, respectively. Meis2 was inhibited in porcine aortic VICs in vitro, and the effect on osteoblastic transdifferentiation and its downstream pathway were studied. ResultsMeis2 gene and protein expression decreased significantly in calcified human aortic valve tissue compared with the normal ones. Inhibiting Meis2 by siRNAs reduced the gene and protein expression of Notch1 and Twist1, and induced the osteoblastic transdifferentiation of the porcine aortic VICs in vitro. ConclusionsThe present study indicated that Meis2 repress the osteoblastic transdifferentiation of aortic VICs through the Notch1/Twist1 signaling pathway. The Results identify Meis2 as a potential intervention target for the prevention of CAVD.

SHP2 regulates intramembranous ossification by modifying the TGFβ and BMP2 signaling pathway.

SHP2 is a ubiquitously expressed protein tyrosine phosphatase, which is involved in many signaling pathways to regulate the skeletal development. In endochondral ossification, SHP2 is known to modify the osteogenic fate of osteochondroprogenitors and to impair the osteoblastic transdifferentiation of hypertrophic chondrocytes. However, how SHP2 regulates osteoblast differentiation in intramembranous ossification remains incompletely understood. To address this question, we generated a mouse model to ablate SHP2 in the Prrx1-expressing mesenchymal progenitors by using "Cre-loxP"-mediated gene excision and examined the development of calvarial bone, in which the main process of bone formation is intramembranous ossification. Phenotypic characterization showed that SHP2 mutants have severe defects in calvarial bone formation. Cell lineage tracing and in situ hybridization data showed less osteoblast differentiation of mesenchymal cells and reduced osteogenic genes expression, respectively. Further mechanistic studies revealed enhanced TGFβ and suppressed BMP2 signaling in SHP2 ablated mesenchymal progenitors and their derivatives. Our study uncovered the critical role of SHP2 in osteoblast differentiation through intramembranous ossification and might provide a potential target to treat craniofacial skeleton disorders.