This copy is for personal use only. To order printed copies, contact reprints@rsna.org I n P r e s s Abbreviations: AUC = area under the receiver operating characteristic curve CI = confidence interval COVID-19 = coronavirus disease 2019 COVNet = COVID-19 detection neural network CAP = community acquired pneumonia DICOM = digital imaging and communications in medicine Key Results:A deep learning method was able to identify COVID-19 on chest CT exams (area under the receiver operating characteristic curve, 0.96).A deep learning method to identify community acquired pneumonia on chest CT exams (area under the receiver operating characteristic curve, 0.95).There is overlap in the chest CT imaging findings of all viral pneumonias with other chest diseases that encourages a multidisciplinary approach to the final diagnosis used for patient treatment. Summary Statement:Deep learning detects coronavirus disease 2019 (COVID-19) and distinguish it from community acquired pneumonia and other non-pneumonic lung diseases using chest CT. I n P r e s s Abstract:Background: Coronavirus disease has widely spread all over the world since the beginning of 2020. It is desirable to develop automatic and accurate detection of COVID-19 using chest CT.Purpose: To develop a fully automatic framework to detect COVID-19 using chest CT and evaluate its performances. Materials and Methods:In this retrospective and multi-center study, a deep learning model, COVID-19 detection neural network (COVNet), was developed to extract visual features from volumetric chest CT exams for the detection of COVID-19. Community acquired pneumonia (CAP) and other non-pneumonia CT exams were included to test the robustness of the model. The datasets were collected from 6 hospitals between August 2016 and February 2020. Diagnostic performance was assessed by the area under the receiver operating characteristic curve (AUC), sensitivity and specificity. Results:The collected dataset consisted of 4356 chest CT exams from 3,322 patients. The average age is 49±15 years and there were slightly more male patients than female (1838 vs 1484; p-value=0.29). The per-exam sensitivity and specificity for detecting COVID-19 in the independent test set was 114 of 127 (90% [95% CI: 83%, 94%]) and 294 of 307 (96% [95% CI: 93%, 98%]), respectively, with an AUC of 0.96 (p-value<0.001). The per-exam sensitivity and specificity for detecting CAP in the independent test set was 87% (152 of 175) and 92% (239 of 259), respectively, with an AUC of 0.95 (95% CI: 0.93, 0.97). Conclusions:A deep learning model can accurately detect COVID-19 and differentiate it from community acquired pneumonia and other lung diseases.

Trimethlyamine-N-oxide (TMAO) was recently identified as a promoter of atherosclerosis. Patients with CKD exhibit accelerated development of atherosclerosis; however, no studies have explored the relationship between TMAO and atherosclerosis formation in this group. This study measured serum concentrations and urinary excretion of TMAO in a CKD cohort (n=104), identified the effect of renal transplant on serum TMAO concentration in a subset of these patients (n=6), and explored the cross-sectional relationship between serum TMAO and coronary atherosclerosis burden in a separate CKD cohort (n=220) undergoing coronary angiography. Additional exploratory analyses examined the relationship between baseline serum TMAO and long-term survival after coronary angiography. Serum TMAO concentrations demonstrated a strong inverse association with eGFR (r 2 =0.31, P,0.001). TMAO concentrations were markedly higher in patients receiving dialysis (median [interquartile range], 94.4 mM [54.8-133.0 mM] for dialysis-dependent patients versus 3.3 mM [3.1-6.0 mM] for healthy controls; P,0.001); whereas renal transplantation resulted in substantial reductions in TMAO concentrations (median [min-max] 71.2 mM [29.2-189.7 mM] pretransplant versus 11.4 mM [8.9-20.2 mM] posttransplant; P=0.03). TMAO concentration was an independent predictor for coronary atherosclerosis burden (P=0.02) and predicted long-term mortality independent of traditional cardiac risk factors (hazard ratio, 1.26 per 10 mM increment in TMAO concentration; 95% confidence interval, 1.13 to 1.40; P,0.001). In conclusion, serum TMAO concentrations substantially increase with decrements in kidney function, and this effect is reversed by renal transplantation. Increased TMAO concentrations correlate with coronary atherosclerosis burden and may associate with long-term mortality in patients with CKD undergoing coronary angiography. Patients with CKD have a high prevalence of cardiovascular comorbidities, which primarily contributes to the exceedingly high mortality in this group. 1,2 For example, the 5-year survival for ESRD patients receiving dialysis is approximately 35%, with .50% of the mortality in this group resulting directly from cardiovascular causes. 1 It is well established that CKD patients exhibit a disproportionate burden of atherosclerosis as compared with individuals having normal kidney function. [2][3][4][5] Furthermore, a higher prevalence of traditional risk factors for the development of atherosclerosis, such as hypertension, diabetes and hyperlipidemia, only partially accounts for the accelerated atherosclerosis in CKD patients, leading to the hypothesis that unique risk factors must be present in this population. 6,7

We examined the osteoblast/osteocyte expression and function of polycystin-1 (PC1), a transmembrane protein that is a component of the polycystin-2 (PC2)-ciliary mechano-sensor complex in renal epithelial cells. We found that MC3T3-E1 osteoblasts and MLO-Y4 osteocytes express transcripts for PC1, PC2, and the ciliary proteins Tg737 and Kif3a. Immunohistochemical analysis detected cilia-like structures in MC3T3-E1 osteoblastic and MLO-Y4 osteocyte-like cell lines as well as primary osteocytes and osteoblasts from calvaria. Pkd1 m1Bei mice have inactivating missense mutations of Pkd1 gene that encode PC1. Pkd1 m1Bei homozygous mutant mice demonstrated delayed endochondral and intramembranous bone formation, whereas heterozygous Pkd1 m1Bei mutant mice had osteopenia caused by reduced osteoblastic function. Heterozygous and homozygous Pkd1 m1Bei mutant mice displayed a gene dose-dependent decrease in the expression of Runx2 and osteoblastrelated genes. In addition, overexpression of constitutively active PC1 C-terminal constructs in MC3T3-E1 osteoblasts resulted in an increase in Runx2 P1 promoter activity and endogenous Runx2 expression as well as an increase in osteoblast differentiation markers. Conversely, osteoblasts derived from Pkd1 m1Bei homozygous mutant mice had significant reductions in endogenous Runx2 expression, osteoblastic markers, and differentiation capacity ex vivo. Co-expression of constitutively active PC1 C-terminal construct into Pkd1 m1Bei homozygous osteoblasts was sufficient to normalize Runx2 P1 promoter activity. These findings are consistent with a possible functional role of cilia and PC1 in anabolic signaling in osteoblasts/osteocytes.

PC1 (polycystin-1) is a highly conserved, receptor-like multidomain membrane protein widely expressed in various cell types and tissues (1, 2). Mutations of human PKD1 (polycystic kidney disease gene 1) cause autosomal dominant polycystic kidney disease (ADPKD) 2 (3, 4). The genetics of ADPKD is complex, because it is widely held that inactivation of the normal copy of the PKD1 gene by a second somatic mutation in conjunction with the inherited mutation of the other allele is required for renal cyst formation, which occurs in only a subset of the dually affected tubules (5). Although primarily affecting the kidney, ADPKD is also a multisystem disorder (6, 7). Extrarenal manifestations include intracranial and aortic aneurysms and cystic disease of liver and pancreas (8 -11). The biological functions of PC1 are poorly defined in some tissues that express PKD1 transcripts, such as bone. Indeed, the absence of clinically demonstrable skeletal abnormalities in patients with ADPKD initially delayed the investigation of PKD1 function in bone. The apparent lack of abnormalities in other tissues expressing PC1 may arise because of differences in the frequency of a second hit somatic mutation, the presence of other modifying factors that may compensate for lack of PC1 function in other organs (12), or failure to detect more subtle phenotypes. For example, lung was not thought to be affected by PKD1 mutations until computed tomography scans of lungs of ADPKD patients showed a 3-fold increase in the prevalence of bronchiectasis compared with controls (13).Pkd1 is highly expressed in bone, and several mouse models with inactivating mutations of Pkd1 have skeletal abnormalities in the setting of polycystic kidney disease and embryonic lethality (6, 7, 14 -16). Most recently, however, the heterozygous Pkd1 m1Bei mouse, which has an inactivating mutation of Pkd1 and survives to adulthood without polycystic kidney disease, has been shown to develop osteopenia and impaired osteoblastic differentiation (17,18), suggesting that Pkd1 may function in bone. Because homozygous PKD1/Pkd1 mutations in humans and mice are lethal, and most of the existing models are globally Pkd1-deficient, the significance of inactivation of Pkd1 in osteoblasts remains uncertain, and the bone changes might reflect an indirect effect due to loss of PKD1, in the kidney or other tissues.In the current study, to determine if PKD1 in osteoblasts has a direct function in regulating postnatal skeletal functions, we used mouse genetic approaches to conditionally delete Pkd1 in osteoblasts. We demonstrate that conditional deletion of Pkd1 from osteoblasts using Oc-Cre results defective osteoblast function in vivo and in vitro, and osteopenia, indicating that PKD1 has a direct role to regulate osteoblast function and skeletal homeostasis. EXPERIMENTAL PROCEDURES

MJ. FGF23 directly impairs endothelium-dependent vasorelaxation by increasing superoxide levels and reducing nitric oxide bioavailability. Am J Physiol Endocrinol Metab 307: E426 -E436, 2014. First published July 15, 2014 doi:10.1152/ajpendo.00264.2014.-Fibroblast growth factor 23 (FGF23) is secreted primarily by osteocytes and regulates phosphate and vitamin D metabolism. Elevated levels of FGF23 are clinically associated with endothelial dysfunction and arterial stiffness in chronic kidney disease (CKD) patients; however, the direct effects of FGF23 on endothelial function are unknown. We hypothesized that FGF23 directly impairs endothelial vasorelaxation by hindering nitric oxide (NO) bioavailability. We detected expression of all four subtypes of FGF receptors (Fgfr1-4) in male mouse aortas. Exogenous FGF23 (90 -9,000 pg/ml) did not induce contraction of aortic rings and did not relax rings precontracted with PGF 2␣. However, preincubation with FGF23 (9,000 pg/ml) caused a ϳ36% inhibition of endothelium-dependent relaxation elicited by acetylcholine (ACh) in precontracted aortic rings, which was prevented by the FGFR antagonist PD166866 (50 nM). Furthermore, in FGF23-pretreated (9,000 pg/ml) aortic rings, we found reductions in NO levels. We also investigated an animal model of CKD (Col4a3 Ϫ/Ϫ mice) that displays highly elevated serum FGF23 levels and found they had impaired endothelium-dependent vascular relaxation and reduced nitrate production compared with age-matched wild types. To elucidate a mechanism for the FGF23-induced impairment, we measured superoxide levels in endothelial cells and aortic rings and found that they were increased following FGF23 treatment. Crucially, treatment with the superoxide scavenger tiron reduced superoxide levels and also restored aortic relaxation to ACh. Therefore, our data suggest that FGF23 increases superoxide, inhibits NO bioavailability, and causes endothelial dysfunction in mouse aorta. Together, these data provide evidence that high levels of FGF23 contribute to cardiovascular dysfunction. fibroblast growth factor 23; chronic kidney disease; nitric oxide; superoxide; and cardiovascular disease IT IS WELL KNOWN THAT PATIENTS with chronic kidney disease (CKD) have an increased risk of cardiovascular disease (CVD). Modification of the traditional risk factors for CVD (e.g., dyslipidemia, hypertension, anemia, and hyperhomocysteinemia) does not improve cardiovascular function in patients with CKD (32), suggesting that other factors may be responsible. Fibroblast growth factor 23 (FGF23) is a hormone secreted by osteocytes that serves as an important regulator of serum phosphate and vitamin D via direct actions on the kidney and parathyroid (6,8). Recently, high circulating levels of FGF23 have been clinically associated with the development of CVD (3,9,33,47,55,72) especially during CKD where serum FGF23 is substantially increased 10-to 1,000-fold (30, 37). Nevertheless, despite these clinical associations, there have been relatively few studies to determine whethe...

Polycystin-1 (PC1) may play an important role in skeletogenesis through regulation of the bone-specific transcription factor Runx2-II. In the current study we found that PC1 co-localizes with the calcium channel polycystin-2 (PC2) in primary cilia of MC3T3-E1 osteoblasts. To establish the role of Runx2-II in mediating PC1 effects on bone, we crossed heterozygous Pkd1 m1Bei and Runx2-II mice to create double heterozygous mice (Pkd1 ؉/m1Bei /Runx2-II ؉/؊ ) deficient in both PC1 and Runx2-II. Pkd1؉/m1Bei /Runx2-II ؉/؊ mice exhibited additive reductions in Runx2-II expression that was associated with impaired endochondral bone development, defective osteoblast-mediated bone formation, and osteopenia. In addition, we found that basal intracellular calcium levels were reduced in homozygous Pkd1 m1Bei osteoblasts. In contrast, overexpression of a PC1 C-tail construct increased intracellular calcium and selectively stimulated Runx2-II P1 promoter activity in osteoblasts through a calcium-dependent mechanism. Site-directed mutagenesis of critical amino acids in the coiled-coil domain of PC1 required for coupling to PC2 abolished PC1-mediated Runx2-II P1 promoter activity. Additional promoter analysis mapped the PC1-responsive region to the "osteoblast-specific" enhancer element between ؊420 and ؊350 bp that contains NFI and AP-1 binding sites. Chromatin immunoprecipitation assays confirmed the calcium-dependent binding of NFI to this region. These findings indicate that PC1 regulates osteoblast function through intracellular calcium-dependent control of Runx2-II expression. The overall function of the primary cilium-polycystin complex may be to sense and transduce environmental clues into signals regulating osteoblast differentiation and bone development.Embryonic bone is formed from mesenchymal stem cells by either direct differentiation of these cells into mineralized matrix-generating osteoblasts (intramembranous bone) or by their condensation and subsequent formation of a cartilage template that is replaced by osteoblast-mediated bone formation (endochondral bone formation) (1-3). Runx2 is a master transcription factor controlling skeletogenesis that regulates the differentiation of mesenchymal precursors into osteoblasts and hypertrophic chondrocytes (4 -10). The total loss of Runx2 in the mouse results in the complete absence of intramembranous and endochondral bone formation. Expression of Runx2 is initiated from the distal P1 and the proximal P2 promoters that, respectively, give rise to N-terminal distinct Runx2-type II (Runx2-II) and Runx2-type I (Runx2-I) isoforms. Selective deletion of the P1 promoter and Runx2-II in mice results in impaired terminal osteoblastic maturation and endochondral bone formation (5, 7, 11). The P2 promoter regulation of Runx2-I is sufficient for early osteoblastogenesis and intramembranous bone formation (11-13). The presence of regulatory sequences in the P1 promoter required for osteoblast-specific expression of Runx2-II have been identified (14), but the developmentally relevant ...

Runx2 transcribes Runx2-II and Runx2-I isoforms with distinct N-termini. Deletion of both isoforms results in complete arrest of bone development, whereas selective loss of Runx2-II is sufficient to form a grossly intact skeleton with impaired endochondral bone development. To elucidate the role of Runx2-II in osteoblast function in adult mice, we examined heterozygous Runx2-II (Runx2-II(+/-)) and homozygous Runx2-II (Runx2-II(-/-))-deficient mice, which, respectively, lack one or both copies of Runx2-II but intact Runx2-I expression. Compared to wild-type mice, 6-week-old Runx2-II(+/-) had reduced trabecular bone volume (BV/TV%), cortical thickness (Ct.Th), and bone mineral density (BMD), decreased osteoblastic and osteoclastic markers, lower bone formation rates, impaired osteoblast maturation of BMSCs in vitro, and significant reductions in mechanical properties. Homozygous Runx2-II(-/-) mice had a more severe reduction in BMD, BV/TV%, and Ct.Th, and greater suppression of osteoblastic and osteoclastic markers than Runx2-II(+/-) mice. Non-selective Runx2(+/-) mice, which have an equivalent reduction in Runx2 expression due to the lack one copy of Runx2-I and II, however, had an intermediate reduction in BMD. Thus, selective Runx2-II mutation causes diminished osteoblastic function in an adult mouse leading to low-turnover osteopenia and suggest that Runx2-I and II have distinct functions imparted by their different N-termini.

Runx2 controls the commitment of mesenchymal cells to the osteoblastic lineage. Distinct promoters, designated P1 and P2, give rise to functionally similar Runx2-II and Runx2-I isoforms. We postulate that this dual promoter gene structure permits temporal and spatial adjustments in the amount of Runx2 isoforms necessary for optimal bone development. To evaluate the gene dose-dependent effect of Runx2 isoforms on bone development, we intercrossed selective Runx2-II +/2 with nonselective Runx2-II +/2 / Runx2-I +/2 mice to create compound mutant mice: Runx2-II +/2 , Runx2-II. Analysis of the different Runx2-deficient genotypes showed gene dose-dependent differences in the level of expression of the Runx2 isoforms. In addition, we found that Runx2-I is predominately expressed in the perichondrium and proliferating chondrocytes, whereas Runx2-II is expressed in hypertrophic chondrocytes and metaphyseal osteoblasts. Newborn mice showed impaired development of a mineralized skeleton, bone length, and widening of the hypertrophic zone that were proportionate to the reduction in total Runx2 protein expression. Osteoblast differentiation ex vivo was also proportionate to total amount of Runx2 expression that correlated with reduced Runx2 binding to the osteocalcin promoter by quantitative chromatin immunoprecipitation analysis. Functional analysis of P1 and P2 promoters showed differential regulation of the two promoters in osteoblastic cell lines. These findings support the possibility that the total amount of Runx2 derived from two isoforms and the P1 and P2 promoters, by regulating the time, place, and amount of Runx2 in response to changing environmental cues, impacts on bone development.