Review: Will "cultured meat" transform our food system towards more sustainability?

Our agri-food system today should provide enough healthy food of good quality for the growing human population. However, it should also preserve natural resources and better protect livestock. In this context, some FoodTech companies are developing a disruptive approach: cell culture for in vitro food production of "meat" but this technology is still at the research and development stage. This article will highlight its development, the technologies used and the stakeholders involved (Part 1), its potential environmental impacts (Part 2) but also regulatory, social and ethical issues (Part 3). This article aims to shed light throughout the manuscript on two major controversies related to "cultured meat". The first controversy is related to its ethical aspects, which includes different points: its potential to reduce animal suffering and therefore to improve animal welfare, the future values of our society, and a trend towards food artificialisation. The second controversy includes environmental, health and nutritional issues, in relation to the characteristics and quality of "cultured meat" with an important question: should we call it meat? These two controversies act in interaction in association with related societal, legal and consequently political issues. Answers to the various questions depend on the different visions of the World by stakeholders, consumers and citizens. Some of them argue for a moderate or a strong reduction in livestock farming, or even the abolition of livestock farming perceived as an exploitation of farm animals. Others just want a reduction of the current much criticised intensive/industrial model. Compared with other potential sustainable solutions to be implemented such as reduction of food losses and waste, new food consumption habits with less proteins of animal sources, sustainable intensification, development of agroecological livestock production, or the development of the market for other meat substitutes (proteins from plants, mycoproteins, algae, insects, etc.), "cultured meat" has an uncertain future.

The Potential Role of Epigenetic Modifications on Different Facets in the Periodontal Pathogenesis.

Periodontitis is a chronic inflammatory disease that affects the supporting structures of teeth. In the literature, the association between the pathogenicity of bacteria and environmental factors in this regard have been extensively examined. In the present study, we will shed light on the potential role that epigenetic change can play on different facets of its process, more particularly the modifications concerning the genes involved in inflammation, defense, and immune systems. Since the 1960s, the role of genetic variants in the onset and severity of periodontal disease has been widely demonstrated. These make some people more susceptible to developing it than others. It has been documented that the wide variation in its frequency for various racial and ethnic populations is due primarily to the complex interplay among genetic factors with those affecting the environment and the demography. In molecular biology, epigenetic modifications are defined as any change in the promoter for the CpG islands, in the structure of the histone protein, as well as post-translational regulation by microRNAs (miRNAs), being known to contribute to the alteration in gene expression for complex multifactorial diseases such as periodontitis. The key role of epigenetic modification is to understand the mechanism involved in the gene-environment interaction, and the development of periodontitis is now the subject of more and more studies that attempt to identify which factors are stimulating it, but also affect the reduced response to therapy.

The myocardial and neuronal infectivity of SARS-CoV-2 and detrimental outcomes.

The epidemiological outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), alias COVID-19, began in Wuhan, Hubei, China, in late December and eventually turned into a pandemic that has led to over 3.71 million deaths and over 173 million infected cases worldwide. In addition to respiratory manifestations, COVID-19 patients with neurological and myocardial dysfunctions exhibit a higher risk of in-hospital mortality. The immune function tends to be affected by cardiovascular risk factors and is thus indirectly related to the prognosis of COVID-19 patients. Many neurological symptoms and manifestations have been reported in COVID-19 patients; however, detailed descriptions on the prevalence and characteristic features of these symptoms are restricted due to insufficient data. It is thus advisable for clinicians to be vigilant for both cardiovascular and neurological manifestations to detect them at an early stage to avoid inappropriate management of COVID-19 and to address the manifestations adequately. Patients with severe COVID-19 are notably more susceptible to developing cardiovascular and neurological complications than non-severe COVID-19 patients. This review focuses on the consequential outcomes of COVID-19 on cardiovascular and neuronal functions, including other influencing factors.

Neural Hypertrophy and Hyperplasia in a Case of Chronic Ovine Pancreatitis.

Nerves can be severely reshaped in human pancreatic diseases such as chronic pancreatitis (CP) and pancreatic cancer, in which pancreatic nerves can undergo hypertrophy or hyperplasia. This neural plasticity is associated with neuropathic pain. Although there are several animal models of CP, pancreatic neuropathy is not well-characterized. Thus, the translational value of these in-vivo models cannot be entirely ascertained for the study of neural plasticity. We now describe spontaneous alterations characteristic of pancreatic neural plasticity in a lamb. Microscopic lesions of chronic sclerosing pancreatitis were associated with neuronal hypertrophy and hyperplasia. Although CP and pancreatic tumours are common in many animal species, to the authors' knowledge, spontaneous occurrence of associated pancreatic neural plasticity has not been reported in any non-human species. Sheep might be a suitable animal model for the study of this condition.

Analysis of Scientific and Press Articles Related to Cultured Meat for a Better Understanding of Its Perception.

Cultured meat is presented by its advocates as a good alternative for consumers who want to be more ethically minded but who do not wish to change their diet. This novel food has become an emerging topic in both the scientific field and the press media. From a bibliometric analysis of scientific publications and on a sociometric analysis of the mainstream press, the aim of this study was to identify potential differences between the scientific view and the public perception. This research analyzed the publications indexed by SCI-EXPANDED in the Web of Science Core Collection database owned by Clarivate Analytics, for scientific literature analysis, and indexed by the Factiva database, for the press media. A total of 327 scientific publications were analyzed according to year of publication and country and institution of origin, also including coauthorships, co-citations, and scientific fields' and journals' networks. A knowledge mapping using VOSviewer was used to study the literature in the field. Based on Factiva, 12,900 press articles dealing with artificial meat, mainly in English, have been found through public databases. The main conclusion is that cultured meat is mainly developing in the USA and the UK, with other countries, such as China, observing the trend for potential future applications. Scientific articles seemed initially to focus mainly on technical aspects of artificial meat and more recently on health value, consumer's acceptance, and sustainability. However, the potential environment-friendly effects of this novel food are more and more studied or described in scientific or press articles.

Automating Quality Control for Structured Standardized Radiology Reports Using Text Analysis.

Radiology reports describe the findings of a radiologist in an imaging examination, produced for another clinician in order to answer to a clinical indication. Sometimes, the report does not fully answer the question asked, despite guidelines for the radiologist. In this article, a system that controls the quality of reports automatically is described. It notably maps the free text onto MeSH terms and checks if the anatomy and disease terms match in the indication and conclusion of a report. The agreement between manual checks of experienced radiologists and the system is high with automatic checks requiring only a fraction of time. Being able to quality control all reports has the potential to improve report quality and thus limit misunderstandings, loosing time for requesting more information and possibly avoid medical mistakes.

Local clinical diagnostic reference levels for chest and abdomen CT examinations in adults as a function of body mass index and clinical indication: a prospective multicenter study.

OBJECTIVES: To compare institutional dose levels based on clinical indication and BMI class to anatomy-based national DRLs (NDRLs) in chest and abdomen CT examinations and to assess local clinical diagnostic reference levels (LCDRLs). METHODS: From February 2017 to June 2018, after protocol optimization according to clinical indication and body mass index (BMI) class (< 25; ≥ 25), 5310 abdomen and 1058 chest CT series were collected from 5 CT scanners in a Swiss multicenter group. Clinical indication-based institutional dose levels were compared to the Swiss anatomy-based NDRLs. Statistical significance was assessed (p < 0.05). LCDRLs were calculated as the third quartile of the median dose values for each CT scanner. RESULTS: For chest examinations, dose metrics based on clinical indication were always below P75 NDRL for CTDIvol (range 3.9-6.4 vs. 7.0 mGy) and DLP (164.0-211.2 vs. 250 mGycm) in all BMI classes except for DLP in BMI ≥ 25 (248.8-255.4 vs. 250.0 mGycm). For abdomen examinations, they were significantly lower or not different than P50 NDRLs for all BMI classes (3.8-9.0 vs. 10.0 mGy and 192.9-446.8 vs. 470mGycm). The estimated LCDRLs show a drop in CTDIvol (21% for chest and 32% for abdomen, on average) with respect to current DRLs. When considering BMI stratification, the largest LCDRL difference within the same clinical indication is for renal tumor (4.6 mGy for BMI < 25 vs. 10.0 mGy for BMI ≥ 25; - 117%). CONCLUSION: The results suggest the necessity of estimating clinical indication-based DRLs, especially for abdomen examinations. Stratifying per BMI class allows further optimization of the CT doses. KEY POINTS: • Our data show that clinical indication-based DRLs might be more appropriate than anatomy-based DRLs and might help in reducing large variations in dose levels for the same type of examinations. • Stratifying the data per patient-size subgroups (non-overweight, overweight) allows a better optimization of CT doses and therefore the possibility to set LCDRLs based on BMI class. • Institutions who are fostering continuous dose optimization and LDRLs should consider defining protocols based on clinical indication and BMI group, to achieve ALARA.

Early development of calcific aortic valve disease and left ventricular hypertrophy in a mouse model of combined dyslipidemia and type 2 diabetes mellitus.

OBJECTIVE: This study aimed to determine the potential impact of type 2 diabetes mellitus on left ventricular dysfunction and the development of calcified aortic valve disease using a dyslipidemic mouse model prone to developing type 2 diabetes mellitus. APPROACH AND RESULTS: When compared with nondiabetic LDLr(-/-)/ApoB(100/100), diabetic LDLr(-/-)/ApoB(100/100)/IGF-II mice exhibited similar dyslipidemia and obesity but developed type 2 diabetes mellitus when fed a high-fat/sucrose/cholesterol diet for 6 months. LDLr(-/-)/ApoB(100/100)/IGF-II mice showed left ventricular hypertrophy versus C57BL6 but not LDLr(-/-)/ApoB(100/100) mice. Transthoracic echocardiography revealed significant reductions in both left ventricular systolic fractional shortening and diastolic function in high-fat/sucrose/cholesterol fed LDLr(-/-)/ApoB(100/100)/IGF-II mice when compared with LDLr(-/-)/ApoB(100/100). Importantly, we found that peak aortic jet velocity was significantly increased in LDLr(-/-)/ApoB(100/100)/IGF-II mice versus LDLr(-/-)/ApoB(100/100) animals on the high-fat/sucrose/cholesterol diet. Microtomography scans and Alizarin red staining indicated calcification in the aortic valves, whereas electron microscopy and energy dispersive x-ray spectroscopy further revealed mineralization of the aortic leaflets and the presence of inflammatory infiltrates in diabetic mice. Studies showed upregulation of hypertrophic genes (anp, bnp, b-mhc) in myocardial tissues and of osteogenic genes (spp1, bglap, runx2) in aortic tissues of diabetic mice. CONCLUSIONS: We have established the diabetes mellitus -prone LDLr(-/-)/ApoB(100/100)/IGF-II mouse as a new model of calcified aortic valve disease. Our results are consistent with the growing body of clinical evidence that the dysmetabolic state of type 2 diabetes mellitus contributes to early mineralization of the aortic valve and calcified aortic valve disease pathogenesis.

Circulating levels of matrix gla protein and progression of aortic stenosis: a substudy of the Aortic Stenosis Progression Observation: Measuring Effects of rosuvastatin (ASTRONOMER) trial.

BACKGROUND: Matrix γ-carboxyglutamate protein is an inhibitor of cardiovascular calcification. The objective of this substudy of the Aortic Stenosis Progression Observation: Measuring Effects of Rosuvastatin (ASTRONOMER) trial was to examine the relationship between total (ie, carboxylated [active] form + uncarboxylated [inactive] form) circulating desphosphorylated matrix γ-carboxyglutamate protein (dpMGP) level and the progression rate of aortic stenosis (AS). METHODS: Among the patients included in the ASTRONOMER trial, 215 patients had measures of baseline circulating total dpMGP level and an echocardiographic follow-up (mean follow-up: 3.5 ± 1.3 years). Progression of AS was assessed according to the measurement of the annualized increase in peak aortic jet velocity. RESULTS: In the whole cohort, baseline dpMGP level was associated with faster progression rate of peak aortic jet velocity (r = 0.16; P = 0.02) in individual analysis but not in multivariable analysis (P = 0.40). However, there was a significant interaction (P = 0.03) between dpMGP level and age, with respect to the effect on AS progression. After dichotomization according to median value of age (ie, 57 years old), total dpMGP level was associated with faster AS progression rate (r = 0.24; P = 0.008) in the younger patients, and this association remained significant in multivariable analysis (P = 0.04), but not in the older ones. The independent correlates of dpMGP level were fasting glucose (P = 0.009) and oxidized low-density lipoprotein (P = 0.01). CONCLUSIONS: This is the first prospective study to demonstrate a relationship between increased circulating levels of total dpMGP and faster progression rate of AS in younger individuals. Future studies are needed to determine if dpMGP is simply a marker or a contributing factor to ectopic mineralization of aortic valve.

Paradoxical low-flow, low-gradient aortic stenosis despite preserved left ventricular ejection fraction: new insights from weights of operatively excised aortic valves.

AIMS: We reported that patients with small aortic valve area (AVA) and low flow despite preserved left ventricular ejection fraction (LVEF), i.e. 'paradoxical' low flow (PLF), have worse outcomes compared with patients with normal flow (NF), although they generally have a lower mean gradient (MG). The aortic valve weight (AVW) excised at the time of valve replacement is a flow-independent marker of stenosis severity. The objective of this study was to compare the AVW of patients with PLF and MG<40 mmHg with the AVW of patients with NF and MG≥40 mmHg. METHODS AND RESULTS: We recruited 250 consecutive patients undergoing valve replacement (Cohort A) for severe stenosis. Among them, 33 (13%) were in PLF [LVEF > 50% but stroke volume index (SVi) ≤ 35 mL/m(2)] with MG < 40 mmHg (PLF-LG group) and 105 (42%) were in NF (LVEF > 50% and SVi > 35 mL/m(2)) with MG ≥ 40 mmHg (NF-HG group). Despite a much lower MG (29 ± 7 vs. 53 ± 10 mmHg; P < 0.0001), patients in the PLF-LG group had a similar AVA (0.73 ± 0.12 vs. 0.69 ± 0.13; P = 0.19) compared with those in the NF-HG group. The AVW [median (interquartile): 1.90 (1.63-2.50) vs. 2.60 (1.66-3.32)] and prevalence of bicuspid phenotype (15 vs. 42%) were lower in the PLF-LG group than in the NF-HG group. However, AVWs analysed separately in the tricuspid and bicuspid valves were similar in both groups [tricuspid valves: 1.80 (1.63-2.50) vs. 2.30 (1.58-3.00) g; P = 0.26 and bicuspid valves: 2.72 (1.73-3.61) vs. 2.60 (2.10-3.55) g; P = 0.93]. When using cut-point values of AVW established in another series of non-consecutive patients (n = 150, Cohort B) with NF and concordant Doppler-echocardiographic findings, we found that the percentage of patients with evidence of severe stenosis in Cohort A was 70% in patients with PLF-LG and 86% in patients with NF-HG. CONCLUSION: The aortic valve weight data reported in this study provide evidence that a large proportion of patients with PLF and low-gradient have a severe stenosis and that the gradient may substantially underestimate stenosis severity in these patients. A multi-parametric approach including all Doppler-echocardiographic parameters of valve function as well as other complementary diagnostic tests may help correctly identify these patients.

P2Y2 receptor represses IL-6 expression by valve interstitial cells through Akt: implication for calcific aortic valve disease.

Calcific aortic valve disease (CAVD) is a disorder characterized by an abnormal mineralization, which may have intricate links with inflammation. Interleukin-6 (IL-6) and its cognate cytokines are widely expressed and exert pleiotropic effects on different tissues. In this study, we examined the expression of the IL-6 family of cytokines in human CAVD by using a transcriptomic approach and we performed in-depth functional assays with valve interstitial cells (VICs) to unravel the process regulating IL-6 expression and its role during the mineralization of the aortic valve. We documented by both microarray and q-PCR analyses an elevated expression of IL-6 in human CAVD, which was correlated with the remodeling process. IL-6 was highly expressed by VICs. We found that following treatment with a phosphate-containing medium the level of IL-6 expressed by VICs increased by several-fold. Phosphate-induced expression of IL-6 relied on reduced PI3K/Akt signaling downstream of the P2Y2 receptor (P2Y2R). In this regard, we found by using transfection experiments that Akt-1 is a negative regulator of the NF-κB pathway. In addition, by using a siRNA targeting IL-6 we found that phosphate-induced mineralization was largely dependent on IL-6 expression. A transfection of Akt-1 rescued the hypermineralizing phenotype of P2Y2R(-/-) mouse VICS (MVICs). Hence, we documented a novel mechanism whereby P2Y2R and Akt modulate the NF-κB pathway and its downstream target IL-6, which is a strong promoter of the mineralization of VICs.

Angiotensin receptor blockers are associated with reduced fibrosis and interleukin-6 expression in calcific aortic valve disease.

BACKGROUND: Calcific aortic valve disease (CAVD) is a chronic disorder characterized by the mineralization of the aortic valve and involving fibrosis. OBJECTIVES: In this work we sought to determine if the fibrotic component of the remodeling process of CAVD was related to the use of angiotensin-converting enzyme inhibitors (ACEi) and/or angiotensin receptor blockers (ARBs). METHODS: In 477 patients with CAVD, the aortic valve was examined by histology. A semiquantitative score of fibrosis was generated and associations with clinical/cardiometabolic variables examined. In a subset of 103 patients the aortic valve was available to study the infiltration by inflammatory cells and expression of interleukin-6 (IL-6) by quantitative real-time PCR. RESULTS: The fibrosis score of the aortic valve was independently related to the hemodynamic severity of CAVD measured by echocardiography. The fibrotic score of the aortic valve was also related to the expression of IL-6. The use of ARBs but not of ACEi was associated with a lower fibrosis score of the aortic valve even after correction for covariates. In addition, patients under ARBs had lower aortic valve inflammation and expression of IL-6. CONCLUSIONS: These findings suggest that ARBs may alter the fibrotic process of the aortic valve in CAVD, possibly by lowering tissue inflammation.

Lp-PLA2 is associated with structural valve degeneration of bioprostheses.

OBJECTIVES: In this study, we sought to determine the metabolic markers associated with structural valve degeneration (SVD). BACKGROUND: Structural valve degeneration (SVD) is the major cause of bioprosthetic valve failure leading to bioprostheses (BPs) stenosis or regurgitation. We hypothesized that lipoprotein-associated phospholipase A2 (Lp-PLA2) is involved in the SVD of BPs. METHODS: We included 197 patients who underwent aortic valve replacement with a bioprosthetic valve and had echocardiographic follow-up to evaluate valve function. Moreover, explanted BPs (n = 39) were analysed by immunohistochemistry for the expression of Lp-PLA2. RESULTS: After a mean follow-up of 7·9 ±0·2 years, forty-one patients (21%) were identified as developing SVD. Patients with SVD had significantly higher plasma level of Lp-PLA2 mass (151·8 ± 9·2 ng/mL vs. 133·2 ± 3·4 ng/mL, P = 0·03) and activity (27·6 ± 0·9 nmol/min/mL vs. 25·0 ± 0·4 nmol/min/mL, P = 0·005). Multivariate analysis revealed that Lp-PLA2 activity (OR: 1·09, 95% CI: 1·01-1·18; P = 0·03) was the strongest independent predictor of SVD. Immunohistochemistry studies of explanted BP showed that 77% of explanted BPs had the expression of Lp-PLA2, which correlated with the density of macrophages (CD68), and ox-LDL levels in bioprosthetic tissues. CONCLUSIONS: Increased blood plasma activity of Lp-PLA2 is associated with higher prevalence of SVD. These findings open new avenues for the identification of patients at risk for SVD and for the development of pharmacotherapy aiming at the prevention of SVD.

Mechanical strain induces the production of spheroid mineralized microparticles in the aortic valve through a RhoA/ROCK-dependent mechanism.

Calcific aortic valve disease (CAVD) is a chronic disorder characterized by an abnormal mineralization of the leaflets, which is accelerated in bicuspid aortic valve (BAV). It is suspected that mechanical strain may promote/enhance mineralization of the aortic valve. However, the effect of mechanical strain and the involved pathways during mineralization of the aortic valve remains largely unknown. Valve interstitial cells (VICs) were isolated and studied under strain conditions. Human bicuspid aortic valves were examined as a model relevant to increase mechanical strain. Cyclic strain increased mineralization of VICs by several-fold. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analyses revealed that mechanical strain promoted the formation of mineralized spheroid microparticles, which coalesced into larger structure at the surface of apoptotic VICs. Apoptosis and mineralization were closely associated with expression of ENPP1. Inhibition of ENPP1 greatly reduced mineralization of VIC cultures. Through several lines of evidence we showed that mechanical strain promoted the export of ENPP1-containing vesicles to the plasma membrane through a RhoA/ROCK pathway. Studies conducted in human BAV revealed the presence of spheroid mineralized structures along with the expression of ENPP1 in areas of high mechanical strain. Mechanical strain promotes the production and accumulation of spheroid mineralized microparticles by VICs, which may represent one important underlying mechanism involved in aortic valve mineralization. RhoA/ROCK-mediated export of ENPP1 to the plasma membrane promotes strain-induced mineralization of VICs.

Elevated expression of lipoprotein-associated phospholipase A2 in calcific aortic valve disease: implications for valve mineralization.

OBJECTIVES: This study sought to document the presence and role of lipoprotein-associated phospholipase A2 (Lp-PLA2) in calcific aortic valve disease (CAVD). BACKGROUND: CAVD is a chronic disorder characterized by pathological mineralization and remodeling. Studies have indicated that human CAVD tissues are infiltrated by lipids and that inflammation may play a role in the pathobiology. We hypothesized that Lp-PLA2 (encoded by the PLA2G7 gene) is expressed in CAVD and may play a role in the mineralization of valve interstitial cells. METHODS: We have documented the expression of the phospholipase A2 family of genes in aortic valves by using a transcriptomic assay. Messenger ribonucleic acid and protein expression were confirmed in aortic valves explanted from 60 patients by quantitative polymerase chain reaction and immunohistochemistry, respectively. The effect of lysophosphatidylcholine, the product of Lp-PLA2 activity, was documented on the mineralization of valve interstitial cell cultures. RESULTS: Transcriptomic analyses of CAVD and control nonmineralized aortic valves revealed that Lp-PLA2 was increased by 4.2-fold in mineralized aortic valves. Higher expression of Lp-PLA2 in stenotic aortic valves was confirmed by quantitative polymerase chain reaction, immunohistochemistry, and enzymatic Lp-PLA2 activity. The number of Lp-PLA2 transcripts correlated with several indexes of tissue remodeling. In vitro, lysophosphatidylcholine increased the expression of alkaline phosphatase, the ectonucleotide pyrophosphatase/phosphodiesterase 1 enzyme, sodium-dependent phosphate cotransporter 1 (encoded by the SLC20A1 gene), and osteopontin. We then showed that lysophosphatidylcholine-induced mineralization involved ectonucleotidase enzyme as well as apoptosis through a protein-kinase-A-dependent pathway. CONCLUSIONS: Together, these results demonstrated that Lp-PLA2 is highly expressed in CAVD, and it plays a role in the mineralization of valve interstitial cells. Further work is necessary to document whether Lp-PLA2 could be considered as a novel target in CAVD.

Lipoprotein lipase in aortic valve stenosis is associated with lipid retention and remodelling.

BACKGROUND: Calcific aortic valve disease (CAVD) is a chronic disorder characterized by a fibrocalcific remodelling. It is suspected that lipid retention within the aortic valve may be one important mechanism participating to aortic valve remodelling. Lipoprotein lipase (LPL) is implicated in lipid metabolism and may play a role in lipid retention within the aortic valve. METHODS: In 57 patients, CAVD were analysed for the expression of LPL by q-PCR and immunohistochemistry. Expression of oxidized-LDL (ox-LDL) and decorin was also documented. In addition, a complete blood profile, including the size of LDL and high-density lipoprotein (HDL) particles, were performed to find associations between the blood lipid profile and expression of ox-LDL and LPL within CAVD. RESULTS: Immunohistochemistry studies revealed that LPL was expressed in stenotic aortic valves as a diffuse staining and also in dense cellular areas where macrophages were abundant. Expression of LPL co-localized with decorin and ox-LDL. In turn, valves with higher amount of ox-LDL had elevated number of LPL transcripts. In addition, we documented that the small, dense HDL phenotype was associated with an elevated amount of ox-LDL and LPL transcripts within CAVD. Furthermore, expression of LPL was associated with several indices of fibrocalcific remodelling of the aortic valve. CONCLUSION: Expression of LPL within CAVD is related to the amount of ox-LDL, which is, in turn, associated with the small, dense HDL phenotype. Lipid retention associated with smaller HDL particles may participate in the expression of LPL, whereby a fibrocalcific remodelling of the aortic valve is promoted.

High expression of the Pi-transporter SLC20A1/Pit1 in calcific aortic valve disease promotes mineralization through regulation of Akt-1.

The regulation of phosphate (Pi) handling is crucial during calcification of the aortic valve. Gene profiling of Pi transporters revealed that VIC culture expresses SLC201A1/Pit1 and SLC20A2/Pit2. On exposure to a mineralizing medium (2 mM Pi), the expression of Pi transporters in VIC culture is increased several folds, with the highest magnitude for SLC20A1. By using siRNAs, we established that silencing SLC20A1 significantly reduced Pi-induced mineralization of VICs. In human pathological specimens, we found that the expression of SCL20A1 was increased in CAVD tissues compared to control non-mineralized aortic valves. Treatment of VIC culture with Pi promoted the loss of mitochondrial membrane potential (ΔΨm) and cytochrome c release within the cytosol, leading to apoptosis. Inhibition of Pi transporters with phosphonoformic acid (PFA) prevented Pi-mediated apoptosis of VICs. Moreover, we discovered that the level of the Akt-1 transcript is diminished in CAVD tissues compared with control valves. Accordingly, treatment with Pi caused a reduction of the Akt-1 transcript in VIC culture, and treatment with PFA or siRNA against SLC20A1 restored the level of Akt-1. Overexpression of Akt-1 (pCMVAkt-1) prevented both Pi-induced apoptosis and mineralization of VIC culture. These results strongly suggest that overexpression of SLC20A1 promotes apoptosis and mineralization by altering the level of Akt-1.