Metabolic transitions define spermatogonial stem cell maturation

STUDY QUESTION

Do spermatogonia, including spermatogonial stem cells (SSCs), undergo metabolic changes during prepubertal development?

SUMMARY ANSWER

Here, we show that the metabolic phenotype of prepubertal human spermatogonia is distinct from that of adult spermatogonia and that SSC development is characterized by distinct metabolic transitions from oxidative phosphorylation (OXPHOS) to anaerobic metabolism.

WHAT IS KNOWN ALREADY

Maintenance of both mouse and human adult SSCs relies on glycolysis, while embryonic SSC precursors, primordial germ cells (PGCs), exhibit an elevated dependence on OXPHOS. Neonatal porcine SSC precursors reportedly initiate a transition to an adult SSC metabolic phenotype at 2 months of development. However, when and if such a metabolic transition occurs in humans is ambiguous.

STUDY DESIGN, SIZE, DURATION

To address our research questions: (i) we performed a meta-analysis of publicly available and newly generated (current study) single-cell RNA sequencing (scRNA-Seq) datasets in order to establish a roadmap of SSC metabolic development from embryonic stages (embryonic week 6) to adulthood in humans (25 years of age) with a total of ten groups; (ii) in parallel, we analyzed single-cell RNA sequencing datasets of isolated pup (n = 3) and adult (n = 2) murine spermatogonia to determine whether a similar metabolic switch occurs; and (iii) we characterized the mechanisms that regulate these metabolic transitions during SSC maturation by conducting quantitative proteomic analysis using two different ages of prepubertal pig spermatogonia as a model, each with four independently collected cell populations.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single testicular cells collected from 1-year, 2-year and 7-year-old human males and sorted spermatogonia isolated from 6- to 8-day (n = 3) and 4-month (n = 2) old mice were subjected to scRNA-Seq. The human sequences were individually processed and then merged with the publicly available datasets for a meta-analysis using Seurat V4 package. We then performed a pairwise differential gene expression analysis between groups of age, followed by pathways enrichment analysis using gene set enrichment analysis (cutoff of false discovery rate < 0.05). The sequences from mice were subjected to a similar workflow as described for humans. Early (1-week-old) and late (8-week-old) prepubertal pig spermatogonia were analyzed to reveal underlying cellular mechanisms of the metabolic shift using immunohistochemistry, western blot, qRT-PCR, quantitative proteomics, and culture experiments.

MAIN RESULTS AND THE ROLE OF CHANCE

Human PGCs and prepubertal human spermatogonia show an enrichment of OXPHOS-associated genes, which is downregulated at the onset of puberty (P < 0.0001). Furthermore, we demonstrate that similar metabolic changes between pup and adult spermatogonia are detectable in the mouse (P < 0.0001). In humans, the metabolic transition at puberty is also preceded by a drastic change in SSC shape at 11 years of age (P < 0.0001). Using a pig model, we reveal that this metabolic shift could be regulated by an insulin growth factor-1 dependent signaling pathway via mammalian target of rapamycin and proteasome inhibition.

LARGE SCALE DATA

New single-cell RNA sequencing datasets obtained from this study are freely available through NCBI GEO with accession number GSE196819.

LIMITATIONS, REASONS FOR CAUTION

Human prepubertal tissue samples are scarce, which led to the investigation of a low number of samples per age. Gene enrichment analysis gives only an indication about the functional state of the cells. Due to limited numbers of prepubertal human spermatogonia, porcine spermatogonia were used for further proteomic and in vitro analyses.

WIDER IMPLICATIONS OF THE FINDINGS

We show that prepubertal human spermatogonia exhibit high OXHPOS and switch to an adult-like metabolism only after 11 years of age. Prepubescent cancer survivors often suffer from infertility in adulthood. SSC transplantation could provide a powerful tool for the treatment of infertility; however, it requires high cell numbers. This work provides key insight into the dynamic metabolic requirements of human SSCs across development that would be critical in establishing ex vivo systems to support expansion and sustained function of SSCs toward clinical use.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the NIH/NICHD R01 HD091068 and NIH/ORIP R01 OD016575 to I.D. K.E.O. was supported by R01 HD100197. S.K.M. was supported by T32 HD087194 and F31 HD101323. The authors declare no conflict of interest.

N6-Methyladenosine Methyltransferase METTL3 Promotes Angiogenesis and Atherosclerosis by Upregulating the JAK2/STAT3 Pathway via m6A Reader IGF2BP1

Atherosclerosis (AS) is a life-threatening vascular disease. RNA N6-methyladenosine (m6A) modification level is dysregulated in multiple pathophysiologic processes including AS. In this text, the roles and molecular mechanisms of m6A writer METTL3 in AS progression were explored in vitro and in vivo. In the present study, cell proliferative, migratory, and tube formation capacities were assessed through CCK-8, Transwell migration, and tube formation assays, respectively. RNA m6A level was examined through a commercial kit. RNA and protein levels of genes were measured through RT-qPCR and western blot assays, respectively. VEGF secretion level was tested through ELISA assay. JAK2 mRNA stability was detected through actinomycin D assay. The relationship of METTL3, IGF2BP1, and JAK2 was investigated through bioinformatics analysis, MeRIP, RIP, RNA pull-down, and luciferase reporter assays. An AS mouse model was established to examine the effect of METTL3 knockdown on AS development in vivo. The angiogenetic activity was examined through chick chorioallantoic membrane assay in vivo. The results showed that METTL3 was highly expressed in ox-LDL-induced dysregulated HUVECs. METTL3 knockdown inhibited cell proliferation, migration, tube formation, and VEGF expression/secretion in ox-LDL-treated HUVECs, hampered AS process in vivo, and prevented in vivo angiogenesis of developing embryos. METTL3 positively regulated JAK2 expression and JAK2/STAT3 pathway in an m6A dependent manner in HUVECs. IGF2BP1 positively regulated JAK2 expression through directly binding to an m6A site within JAK2 mRNA in HUVECs. METTL3 knockdown weakened the interaction of JAK2 and IGF2BP1. METTL3 exerted its functions through JAK2/STAT3 pathway. In conclusion, METTL3 knockdown prevented AS progression by inhibiting JAK2/STAT3 pathway via IGF2BP1.

Developing a near-infrared spectroscopy and microwave-induced thermoacoustic tomography-based dual-modality imaging system

Near-infrared spectroscopy (NIRS) techniques can provide noninvasive in vivo hemoglobin oxygenation information but suffer from relatively low resolution in biological tissue imaging. Microwave-induced thermoacoustic tomography (TAT) can produce high-resolution images of the biological tissue anatomy but offer limited physiological information of samples because of the single species of the chromophore it maps. To overcome these drawbacks and take advantage of the merits of the two independent techniques, we built a dual-modality system by combining a NIRS system and a TAT system to image biological tissues. A series of phantom trials were carried out to demonstrate the performance of the new system. The spatial resolution is about 1 mm, with a penetration depth of at least 17.5 mm in the human subject. A cohort of five healthy subjects was recruited to conduct real-time forearm venous and arterial cuff occlusion experiments. Numerous results showed that this dual-modality system could measure oxygen metabolism and simultaneously provide anatomical structure changes of biological tissues. We also found that although the hemoglobin concentration varied consistently with many other published papers, the TAT signal intensity of veins showed an opposite variation tendency in the venous occlusion stage compared with other existing work. A detailed explanation is given to account for the discrepancy, thus, providing another possibility for the forearm experiments using TAT. Furthermore, based on the multiple types of information afforded by this dual-modality system, a pilot clinical application for the diagnosis of anemia is discussed.

A survey of a COVID-19 cluster of charter flight importation

OBJECTIVES

Although a number of cases of importation with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection have been reported, there are still no data available concerning the characteristics in the coronavirus disease 2019 (COVID-19) cluster of charter flight importation. Here, we provide an analysis of COVID-19 cases and their close contacts who worked for the same company on a project in Karbala, Iraq, and returned back to Chengdu, China, by a charter flight.

METHODS

The data of imported COVID-19 cases and their close contacts were obtained from National Notifiable Disease Report System of Chinese Center for Disease Control and Prevention and field epidemiological investigation reports by Centers for Disease Control and Prevention (CDCs) in Chengdu. The information of general characteristics and laboratory findings of this cluster were collected and summarized.

RESULTS

One hundred and six (66.67%) of 159 charter flight passengers tested positive for COVID-19 before entry. Through treatment, all 159 people tested negative and meet the requirements of taking flights bound for China before boarding. However, there has been still 36 (22.64%) of them tested positive after entry. The median time from entry to confirmation was 1.0 day (Interquartile Range (IQR): 0-4.3). The Cycle threshold value (Ct value) of 36 patients' positive samples are all above 30 and most values are above 35.

CONCLUSIONS

In conclusion, there is still a risk that a number of COVID-19 cases can be imported through charter flight. However, the infectivity of confirmed patients of the charter flight was considered to be low.

Advances on molecular mechanism of hepatitis B virus-induced hepatocellular carcinoma

The pathogenesis of hepatitis B virus （HBV）-associated hepatocellular carcinoma （HCC） is complicated with the crosstalk of multiple factors and the multi-step processes. The main mechanisms underlying the HBV-induced HCC include:①integration of HBV DNA into the host hepatocyte genome to alter gene function at the insertion site，resulting in host genome instability and expression of carcinogenic truncated proteins;②HBV gene mutations at S，C，and X coding regions in the genome;③HBV X gene-encoded HBx protein activates proto-oncogenes and inhibits tumor suppressor genes，leading to the HCC occurrence. In this article，the recent research progress on the molecular mechanism of HBV-induced HCC is comprehensively reviewed，so as to provide insights into the prevention，early prediction and postoperative adjuvant therapy of HCC.

WITHDRAWN: Knocking out c-Jun promotes cardiomyocyte differentiation from embryonic stem cells

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Differential Expression of Integrin β1 in Two Brain Injury Models of Rats

Abstract

Objective To study the characteristics of positive expression of integrin β1 in the rat brain tissue of two kinds of traumatic brain injury models and to explore the feasibility of inferring the mode of traumatic brain injury using the positive expression of integrin β1. Methods The occipital region of rats was hit by hydraulic impact method and pendulum striking method to produce two closed brain injury models of linear and rotation acceleration respectively, then 120 SD rats were randomly divided into linear acceleration injury group, rotation acceleration injury group, sham operation group and normal control group. Immunohistochemistry staining and Western blotting method were used to detect the positive expression of integrin β1 in different parts of the brain tissue at 30 min, 3 h, 6 h, 12 h, 3 d and 7 d after rat injury. The data was processed statistically by SPSS 18.0 software. Results The positive expression of integrin β1 was detected 30 min after brain injury and reached the peak 6 h after brain injury. With the extension of injury time, the expression tended to enhance. At the same time points after injury, the differences in the positive expression of integrin β1 between the linear acceleration injury group and the rotation acceleration injury group in the occipital strike point and thalamus had no statistical significance （ P>0.05）, but the differences in the expression of integrin β1 in the frontal lobe and brain stem had statistical significance （P<0.05）. Conclusion The characteristics of positive expression of integrin β1 in brain tissue can be used to infer the strike point and the manner of injury and has application value for the reconstruction of craniocerebral injury process.

Novel variants and uncommon cases among southern Chinese children with X-linked hypophosphatemia

PURPOSE

X-linked hypophosphatemia (XLH) is the most common inherited renal phosphate wasting disorder and is often misdiagnosed as vitamin D deficiency. This study aims to provide clinical and mutational characteristics of 65 XLH pediatric patients in southern China.

METHODS

In this work, a combination of DNA sequencing and qPCR analysis was used to study the PHEX gene in 80 pediatric patients diagnosed with hypophosphatemia. The clinical and laboratory data of confirmed 65 XLH patients were assessed and analyzed retrospectively.

RESULTS

In 65 XLH patients from 61 families, 51 different variants in the PHEX gene were identified, including 23 previously reported variants and 28 novel variants. In this cohort of XLH patients, the c.1601C>T(p.Pro534Leu) variant appears more frequently. Fourteen uncommon XLH cases were described, including four boys with de novo mosaic variants, eight patients with large deletions and a pair of monozygotic twins. The clinical manifestations in this cohort are very similar to those previously reported.

CONCLUSION

This study extends the mutational spectrum of the PHEX gene, which will contribute to accurate diagnosis. This study also suggests a supplementary qPCR or MLPA assay may be performed along with classical sequencing to confirm the gross insertion/deletion.

PPARγ inhibits breast cancer progression by upregulating PTPRF expression

OBJECTIVE

Peroxisome proliferator-activated receptor γ (PPARγ) regulates fatty acid storage and glucose metabolism. Recently, PPARγ has been reported to be involved in cancer. The present study reported a PPARγ consensus binding site (AGGTCA) in the ptprf promoter and identified a strong association between PPARγ and PTPRF expression, as well as their tumor suppressor roles in a v-Ha-Ras-induced model of breast cancer.

MATERIALS AND METHODS

The prognostic potential of PPARγ was assessed with a KM analysis of raw data from 3,951 breast cancer patients. The expression of PPARγ and PTPRF in the rat breast cancer cell lines was detected by Western blot and qPCR. The impact of PPARγ on cancer cell migration, invasion, and growth was confirmed using cell migration assay, transwell cell invasion assay, tri-dimensional soft agar culture, respectively. The binding of PPARγ with the ptprf promoter was then examined using electrophoretic mobility shift assay. The inhibitory effect of PPARγ on tumor growth was then examined in mouse tumor model in vivo.

RESULTS

It was identified that PPARγ expression is lost in the aggressive v-Ha-Ras-induced breast cancer cell line FE1.2 but highly expressed in less malignant FE1.3 cells. Exogenous expression of PPARγ in FE1.2 cells (FE1.2-PPARγhi) resulted in a marked inhibition of proliferation compared with that in FE1.2-Vector control group. FE1.2-PPARγhi cells also exhibited reduced migration, invasion, and colony formation abilities compared with those of the controls. The PPARγ agonist rosiglitazone also suppressed the malignant properties of FE1.2 cells. Protein tyrosine phosphatase receptor F (PTPRF), a downstream target of PPARγ, was markedly induced in FE1.2-PPARγhi cells. A PPARγ consensus binding site (AGGTCA) was identified in the ptprf promoter, and an electrophoretic mobility shift assay confirmed that PPARγ bind to this promoter. Similar to the effect of vector-mediated overexpression of PPARγ, ectopic overexpression of PTPRF in FE1.2 cells led to reduced proliferation. Furthermore, a PPARγ antagonist (GW9662) and PTP inhibitor (NSC87877) abrogated the suppressive function of PPARγ and PTPRF in FE1.2 cells, respectively. PPARγ overexpression or activation suppressed the progression and distant organ metastasis of breast cancer cells in a NOD/SCID mouse model.

CONCLUSIONS

These results suggest that PPARγ inhibits tumor cell proliferation, at least in part, through direct regulation of the ptprf gene and that PPARγ is a potential target for breast cancer treatment.

Analysis of Scores of SCL-90 of Patients with Traumatic Subdural Effusion

Abstract

Objective To investigate the factors affecting changes of Symptom Check List-90 （SCL-90） of patients with traumatic subdural effusion. Methods One hundred and forty-two cases of patients with traumatic subdural effusion from the Center of Forensic Identification, Wannan Medical College collected from 2007-2018 were tested with SCL-90. The differences between SCL-90 results and the national norm and the influences of gender, age, education level, the number of effusion sites and location on SCL-90 results were analyzed. Results The differences between the scores of somatization, interpersonal sensitivity, depression, anxiety, hostility, terror, paranoia and psychosis factors and total mean scores in SCL-90 of traumatic subdural effusion and that of the national norm had statistical significance （P<0.05）. The differences in depression and hostility factor scores between males and females had statistical significance （P<0.05）. The differences in compulsion, anxiety and terror factor scores and total mean scores among different age groups had statistical significance （P<0.05）. The differences in hostility, paranoia and psychosis factors among patients with different degrees of education had statistical significance （P<0.05）. The differences in depression, anxiety, hostility and terror factor scores and total mean scores among single-site group, double-site group and multi-site group had statistical significance （P<0.05）. The differences in somatization, depression and anxiety factor scores and total mean scores between the right cerebral hemisphere group and the left cerebral hemisphere group and bilateral hemisphere group had statistical significance （P<0.05）. Conclusion Traumatic subdural effusion can cause certain psychological changes, which are related to the primary trauma of arachnoid tear as well as the number and location of effusion sites. Attention should be paid to the influence of the above factors during the assessment of psychological symptoms.

SAT0186 DEVELOPING PREDICTORS OF GLOBAL BILAG TREATMENT RESPONSE IN PATIENTS WITH LUPUS NEPHRITIS: MORE LESSONS FROM THE ASPREVA LUPUS MANAGEMENT STUDY GROUP (ALMS) DATA

Background:

Lupus Nephritis (LN) occurs in up to 60% of patients with SLE and is often associated with other organ involvement, morbidity and mortality. Treatment response and clinical improvement rates are limited with conventional therapy. Little is known about clinical predictors of response in SLE overall or in LN.

The ALMS induction trial compared mycophenolate mofetil (MMF) to IV cyclophosphamide (CYC) as induction for LN. MMF was deemed non-superior. The ALMS maintenance trial randomised responders to induction treatment at 6 months to MMF or Azathioprine, with MMF superior during follow-up.

Objectives:

To identify predictors of overall clinical response at 6 and 12 months, in a cohort of SLE patients with LN.

Methods:

Using the ALMS trial cohort, we analysed predictors of response in all the patients as a single cohort. ‘Classic’ BILAG scores were used to assess organ responses over time. Endpoints analysed were:

1) Improvement: defined as reduction in BILAG score to ≤ one BILAG B and no new BILAG organ domains involved, no increase in steroids from baseline and no increase in SLEDAI from baseline.

2) Major Clinical Response (MCR): defined as reduction in BILAG score to BILAG C in all domains, a reduction in steroid dose to ≤ 7.5mg daily and a SLEDAI score ≤ 4.

Potential predictors examined included baseline demographics, medication, disease activity (BILAG, SLEDAI), SLICC/ACR damage index (SDI) and serology. Univariate logistic regressions were used to provide odds ratios of predictors. Multivariate logistic regressions with LASSO and cross-validation in randomly split samples were utilised to build prediction models. Predictors were ranked by the percentage of times they were selected by LASSO.

Results:

370 patients enrolled in the ALMS induction trial. 227 patients were randomised at 6 months to maintenance. 313(84.59%) patients were female. 147(39.72%) patients were Caucasian. The mean age was 31.9 years. 236(63.78%) patients had a disease duration of LN of < 1 year. Baseline mean(± SD) SLEDAI score was 15.28 (±6.78) and mean(± SD) numerical BILAG score was 19.61(±7.67).

Improvement at 6 months was attained by 180 (48.65%). Predictors included older age (OR=1.03 [95% CI: 1.01,1.05] per year) and normal haemoglobin (OR=1.90 [95% CI: 1.19, 3.05] vs low hb). Activity (BILAG A or B) in haematological and mucocutaneous domains predicted less improvement (OR [95% CI] = 0.59 [95% CI: 0.38, 0.94] and 0.50 [95% CI: 0.31,0.82] respectively). Baseline damage (SDI >1) negatively predicted improvement (OR 0.54 [95% CI: 0.31,0.92]).

Improvement at 12 months was acheived by 139 (37.57%). Low IgG predicted improvement (OR 4.66 [95% CI: 1.34,16.23]. Black US patients were less likely to improve (OR 0.29 [95% CI: 0.06,0.90] vs Asian patients).

MCR was achieved by 14(3.79%) and 40(10.81%) at 6 and 12 months. We found regional and racial differences in 12-month MCR responses (Figure 1). Baseline normal C4 predicted a decreased likelihood of MCR (OR 0.37 [95% CI: 0.17,0.64] vs normal C4).

Figure 1.

Univariate analysis of Improvement at 6 and 12 months and MCR at 12 months.

Results of multivariate logistic regression with LASSO were consistent with the univariate analyses.

Conclusion:

A number of factors were related to improvement and MCR in conventionally treated LN patients. Those with damage and active non-renal disease were less likely to improve at 6 months. Baseline low C4 increased MCR likelihood at 12 months. These factors may help stratify patients based on likelihood of response and help select patients who may need alternative treatment strategies.

Disclosure of Interests:

Stephen McDonald: None declared, Sean Yiu: None declared, Li Su: None declared, Caroline Gordon Grant/research support from: UCB, Consultant of: UCB, BMS, EMD Serono, Speakers bureau: UCB, Neil Solomons Shareholder of: Aurinia Pharmaceuticals, Inc. stock, Employee of: Employed currently by Aurinia Pharmaceuticals

Previous employee of Aspreva Pharmaceuticals, Ian N. Bruce Grant/research support from: Genzyme Sanofi, GSK, and UCB, Consultant of: Eli Lilly, AstraZeneca, UCB, Iltoo, and Merck Serono, Speakers bureau: UCB

Designing a therapeutic hepatitis B vaccine to circumvent immune tolerance

An effective prophylactic hepatitis B virus (HBV) vaccine has long been available but is ineffective for chronic infection. The primary cause of chronic hepatitis B (CHB) and greatest impediment for a therapeutic vaccine is the direct and indirect effects of immune tolerance to HBV antigens. The resulting defective CD4⁺/CD8⁺ T cell response, poor cytokine production, insufficient neutralizing antibody (nAb) and poor response to HBsAg vaccination characterize CHB infection. The objective of this study was to develop virus-like-particles (VLPs) that elicit nAb to prevent viral spread and prime CD4⁺/CD8⁺ T cells to eradicate intracellular HBV. Eight neutralizing B cell epitopes from the envelope PreS1 region were consolidated onto a species-variant of the HBV core protein, the woodchuck hepatitis core antigen (WHcAg). PreS1-specific B cell epitopes were chosen because of preferential expression on HBV virions. Because WHcAg and HBcAg are not crossreactive at the B cell level and only partially cross-reactive at the CD4⁺/CD8⁺ T cell level, CD4⁺ T cells specific for WHcAg-unique T cell sites can provide cognate T-B cell help for anti-PreS1 Ab production that is not curtailed by immune tolerance. Immunization of immune tolerant HBV transgenic (Tg) mice with PreS1-WHc VLPs elicited levels of high titer anti-PreS1 nAbs equivalent to wildtype mice. Passive transfer of PreS1 nAbs into human-liver chimeric mice prevented acute infection and cleared serum HBV from mice previously infected with HBV in a model of CHB. At the T cell level, PreS1-WHc VLPs and hybrid WHcAg/HBcAg DNA immunogens elicited HBcAg-specific CD4⁺ Th and CD8⁺ CTL responses.

[Preliminary study on the elimination of artifacts of five kinds of dental prosthetic materials by energy spectrum CT multi-material artifact reduction technology]

Objective: To investigate the effect of the multi-material artifact reduction (MMAR) algorithm of spectral CT in reducing the beam hardening artifacts in dental restoration material. Methods: Three-unit fixed bridge restorations were fabricated on the first to third molars in pig jaw. Gold alloy, zirconia, cobalt chromium alloy, nickel chromium alloy and pure titanium were used as materials for these fixed bridges. After restoration delivery, the pig jaw was scaned using energy spectrum CT machines. Images in regular 120 kVp scan mode were used as conventional group, and reconstructed single-energy horizontal images of 80, 90, 100, 110, 120, 130 and 140 keV in energy spectrum scanning mode were used as energy spectrum group, and reconstructed images applied MMAR technology in energy spectrum scanning mode were used as energy spectrum MMAR group. Each group was scanned 10 times to measure CT value and noise of muscles around dental prosthetic materials and adjacent non-artifact layers. Artifact index was calculated. Two radiologists scored the image quality of each group subjectively. Kruskal Wallis rank sum test was used to compare the difference of image noise, artifact index and subjective score among the control group and the best keV condition in the energy spectrum group and the energy spectrum MMAR group. Results: The image noise of energy spectrum group and energy spectrum MMAR group decreased gradually with the increase of single energy level. The artifact index of pure titanium restorations in conventional group, energy spectrum group and energy spectrum MMAR group were 71.0±8.0, 21.4±2.7 and 14.7±2.7 respectively, and these values were significantly lower than those of other materials in the same group (P<0.05). The subjective image quality scores in energy spectrum MMAR group were as follows: 3.0±0.2 for gold alloy, 4.3±0.5 for zirconia, 3.0±0.4 for cobalt chromium alloy, 3.1±0.4 for cobalt chromium alloy, and 4.6±0.5 for pure titanium. These scores were significantly smaller than those in the conventional group (P<0.05). There was no significant difference in noise between energy spectrum group and energy spectrum MMAR group (P>0.05), and the noise values in energy spectrum group and energy spectrum MMAR group were significantly lower than that in the conventional group (P<0.05). Conclusions: Artifacts of pure titanium is minimal. Energy spectrum CT combined with MMAR technology can effectively reduce the artifacts of gold, zirconia, cobalt-chromium alloy, nickel-titanium alloy and pure titanium. This technique can be used as an effective method to remove artifacts of dental prosthesis.

P4528Feasibility and safety of left bundle branch area pacing by transvenous approach through the interventricular septum in patients with left bundle branch block

Background

His bundle pacing (HBP) has been shown to correct left bundle branch block (LBBB), however it often requires high pacing output and the success rate is variable.

Objective

To assess the feasibility and safety of left bundle branch area pacing (LBBAP) in patients with LBBB.

Methods

From Apr 2014 to Aug 2018, patients with LBBB from multicenters indicated for CRT or pacing therapy were included. LBBAP was performed by advancing the MDT 3830 lead deep into the septum about 1 cm distal to the His bundle region (Figure 1F). Pacing characteristics, success rate, threshold and R-wave amplitude were assessed.

Results

A total of 94 patients aged 68.3±10.7 y with the native QRS duration of 167.2±17.2 ms were included. In 92 patients, LBBAP was successfully achieved and demonstrated RBBB pattern during unipolar tip pacing (UTP), with the paced QRS duration of 116.4±12.6ms (Figure 1C). Fusion of LBBAP and native conduction via the RBB eliminated RBBB and resulted in an average QRS duration of 103.2±10.1 ms (Figure 1D). LBB potential could be recorded from the LBB lead during correction of LBBB by HBP in 21 patients who used two leads method (His lead and LBB lead, Figure 1B). Output dependent selective and non-selective LBBAP were demonstrated in 48 patients (Figure 1C, D). The LBB capture threshold by UTP was 0.53±0.18V/0.5ms at acute and 0.62±0.17V/0.5ms at 6 months and 0.65±0.2V/0.5ms at 1 year. The R-wave amplitude were 11.4±5.2mV, 12.4±5.8mV and 12.0±5.8mV at acute, 6 month and 1 year. During follow-up, only one patient had an increase in LBB capture threshold to 2.5V/0.5ms at 3 months and there were no other complications such as dislodgment, infections, embolism or stroke associated with the implantation.

Conclusion

Permanent LBBAP is feasible and safe in patients with LBBB.