Patient-derived induced pluripotent stem cells with a MERTK mutation exhibit cell junction abnormalities and aberrant cellular differentiation potential.

BACKGROUND: Human induced pluripotent stem cell (hiPSC) technology is a valuable tool for generating patient-specific stem cells, facilitating disease modeling, and investigating disease mechanisms. However, iPSCs carrying specific mutations may limit their clinical applications due to certain inherent characteristics. AIM: To investigate the impact of MERTK mutations on hiPSCs and determine whether hiPSC-derived extracellular vesicles (EVs) influence anomalous cell junction and differentiation potential. METHODS: We employed a non-integrating reprogramming technique to generate peripheral blood-derived hiPSCs with and hiPSCs without a MERTK mutation. Chromosomal karyotype analysis, flow cytometry, and immunofluorescent staining were utilized for hiPSC identification. Transcriptomics and proteomics were employed to elucidate the expression patterns associated with cell junction abnormalities and cellular differentiation potential. Additionally, EVs were isolated from the supernatant, and their RNA and protein cargos were examined to investigate the involvement of hiPSC-derived EVs in stem cell junction and differentiation. RESULTS: The generated hiPSCs, both with and without a MERTK mutation, exhibited normal karyotype and expressed pluripotency markers; however, hiPSCs with a MERTK mutation demonstrated anomalous adhesion capability and differentiation potential, as confirmed by transcriptomic and proteomic profiling. Furthermore, hiPSC-derived EVs were involved in various biological processes, including cell junction and differentiation. CONCLUSION: HiPSCs with a MERTK mutation displayed altered junction characteristics and aberrant differentiation potential. Furthermore, hiPSC-derived EVs played a regulatory role in various biological processes, including cell junction and differentiation.

Transcutaneous auricular vagal nerve stimulation for consciousness recovery in patients with prolonged disorders of consciousness (TAVREC): study protocol for a multicenter, triple-blind, randomized controlled trial in China.

INTRODUCTION: Prolonged disorders of consciousness (pDoC) are a catastrophic condition following brain injury with few therapeutic options. Transcutaneous auricular vagal nerve stimulation (taVNS), a safe, non-invasive intervention modulating thalamo-cortical connectivity and brain function, is a possible treatment option of pDoC. We developed a protocol for a randomised controlled study to evaluate the effectiveness of taVNS on consciousness recovery in patients with pDoC (TAVREC). METHODS AND ANALYSIS: The TAVREC programme is a multicentre, triple-blind, randomised controlled trial with 4 weeks intervention followed by 4 weeks follow-up period. A minimum number of 116 eligible pDoC patients will be recruited and randomly receive either: (1) conventional therapy plus taVNS (30 s monophasic square current of pulse width 300 µs, frequency of 25 Hz and intensity of 1 mA followed by 30 s rest, 60 min, two times per day, for 4 weeks); or (2) conventional therapy plus taVNS placebo. Primary outcome of TAVREC is the rate of improved consciousness level based on the Coma Recovery Scale-Revised (CRS-R) at week 4. Secondary outcomes are CRS-R total and subscale scores, Glasgow Coma Scale score, Full Outline of UnResponsiveness score, ECG parameters, brainstem auditory evoked potential, upper somatosensory evoked potential, neuroimaging parameters from positron emission tomography/functional MRI, serum biomarkers associated with consciousness level and adverse events. ETHICS AND DISSEMINATION: This study was reviewed and approved by the Research Ethics Committee of the First Affiliated Hospital of Nanjing Medical University (Reference number: 2023-SR-392). Findings will be disseminated in a peer-reviewed journal and presented at relevant conferences. TRIAL REGISTRATION NUMBER: ChiCTR2300073950.

m6A epitranscriptomic modification of inflammation in cardiovascular disease.

Cardiovascular disease is currently the number one cause of death endangering human health. There is currently a large body of research showing that the development of cardiovascular disease and its complications is often accompanied by inflammatory processes. In recent years, epitranscriptional modifications have been shown to be involved in regulating the pathophysiological development of inflammation in cardiovascular diseases, with 6-methyladenine being one of the most common RNA transcriptional modifications. In this review, we link different cardiovascular diseases, including atherosclerosis, heart failure, myocardial infarction, and myocardial ischemia-reperfusion, with inflammation and describe the regulatory processes involved in RNA methylation. Advances in RNA methylation research have revealed the close relationship between the regulation of transcriptome modifications and inflammation in cardiovascular diseases and brought potential therapeutic targets for disease diagnosis and treatment. At the same time, we also discussed different cell aspects. In addition, in the article we also describe the different application aspects and clinical pathways of RNA methylation therapy. In summary, this article reviews the mechanism, regulation and disease treatment effects of m6A modification on inflammation and inflammatory cells in cardiovascular diseases in recent years. We will discuss issues facing the field and new opportunities that may be the focus of future research.

Circulating tumour cells predict recurrences and survival in head and neck squamous cell carcinoma patients.

Patients with head and neck squamous cell carcinoma (HNSCC) are at a high risk of developing recurrence and secondary cancers. This study evaluates the prognostic and surveillance utilities of circulating tumour cells (CTCs) in HNSCC. A total of 154 HNSCC patients were recruited and followed up for 4.5 years. Blood samples were collected at baseline and follow-up. CTCs were isolated using a spiral microfluid device. Recurrence and death due to cancer were assessed during the follow-up period. In patients with HNSCC, the presence of CTCs at baseline was a predictor of recurrence (OR = 8.40, p < 0.0001) and death (OR= ∞, p < 0.0001). Patients with CTCs at baseline had poor survival outcomes (p < 0.0001). Additionally, our study found that patients with CTCs in a follow-up appointment were 2.5 times more likely to experience recurrence or death from HNSCC (p < 0.05) prior to their next clinical visit. Our study highlights the prognostic and monitoring utilities of CTCs' in HNSCC patients. Early identification of CTCs facilitates precise risk assessment, guiding treatment choices and ultimately enhancing patient outcomes.

Redox homeostasis in cardiac fibrosis: Focus on metal ion metabolism.

Cardiac fibrosis is a major public health problem worldwide, with high morbidity and mortality, affecting almost all patients with heart disease worldwide. It is characterized by fibroblast activation, abnormal proliferation, excessive deposition, and abnormal distribution of extracellular matrix (ECM) proteins. The maladaptive process of cardiac fibrosis is complex and often involves multiple mechanisms. With the increasing research on cardiac fibrosis, redox has been recognized as an important part of cardiac remodeling, and an imbalance in redox homeostasis can adversely affect the function and structure of the heart. The metabolism of metal ions is essential for life, and abnormal metabolism of metal ions in cells can impair a variety of biochemical processes, especially redox. However, current research on metal ion metabolism is still very limited. This review comprehensively examines the effects of metal ion (iron, copper, calcium, and zinc) metabolism-mediated redox homeostasis on cardiac fibrosis, outlines possible therapeutic interventions, and addresses ongoing challenges in this rapidly evolving field.

m6A epitranscriptomic and epigenetic crosstalk in cardiac fibrosis.

Cardiac fibrosis, a crucial pathological characteristic of various cardiac diseases, presents a significant treatment challenge. It involves the deposition of the extracellular matrix (ECM) and is influenced by genetic and epigenetic factors. Prior investigations have predominantly centered on delineating the substantial influence of epigenetic and epitranscriptomic mechanisms in driving the progression of fibrosis. Recent studies have illuminated additional avenues for modulating the progression of fibrosis, offering potential solutions to the challenging issues surrounding fibrosis treatment. In the context of cardiac fibrosis, an intricate interplay exists between m6A epitranscriptomic and epigenetics. This interplay governs various pathophysiological processes: mitochondrial dysfunction, mitochondrial fission, oxidative stress, autophagy, apoptosis, pyroptosis, ferroptosis, cell fate switching, and cell differentiation, all of which affect the advancement of cardiac fibrosis. In this comprehensive review, we meticulously analyze pertinent studies, emphasizing the interplay between m6A epitranscriptomics and partial epigenetics (including histone modifications and noncoding RNA), aiming to provide novel insights for cardiac fibrosis treatment.

Charge-density wave mediated quasi-one-dimensional Kondo lattice in stripe-phase monolayer 1T-NbSe2.

The heavy fermion physics is dictated by subtle competing exchange interactions, posing a challenge to their understanding. One-dimensional (1D) Kondo lattice model has attracted special attention in theory, because of its exact solvability and expected unusual quantum criticality. However, such experimental material systems are extremely rare. Here, we demonstrate the realization of quasi-1D Kondo lattice behavior in a monolayer van der Waals crystal NbSe2, that is driven into a stripe phase via Se-deficient line defects. Spectroscopic imaging scanning tunneling microscopy measurements and first-principles calculations indicate that the stripe-phase NbSe2 undergoes a novel charge-density wave transition, creating a matrix of local magnetic moments. The Kondo lattice behavior is manifested as a Fano resonance at the Fermi energy that prevails the entire film with a high Kondo temperature. Importantly, coherent Kondo screening occurs only in the direction of the stripes. Upon approaching defects, the Fano resonance exhibits prominent spatial 1D oscillations along the stripe direction, reminiscent of Kondo holes in a quasi-1D Kondo lattice. Our findings provide a platform for exploring anisotropic Kondo lattice behavior in the monolayer limit.

Carbon Nanofibers-Based Anodes for Potassium-Ion Battery.

In recent years, with the global warming getting worse and increasing demand for energy, countries around the world are trying to develop new energy storage technologies to solve this problem. Currently, potassium-ion batteries (PIBs) have attracted tremendous attention from researchers as low-cost and high-performance energy storage devices. However, due to the huge ionic radius of K+ , PIBs face significant volume expansion during cycling, which can easily lead to the collapse of electrode structures. In addition, the poor diffusion kinetics of K+ seriously affect the electrochemical performance of the battery. Carbon nanofibers (CNFs)-based materials (including CNFs, metal/CNFs composites, chalcogenide/CNFs composites, and other CNFs-based materials) are widely used as PIBs electrode anode materials due to their three-dimensional conductive network, heteroatom doping and excellent mechanical properties. This review discusses in detail the research progress of CNFs-based materials in PIBs, including material preparation, structural design, and performance optimization. On this basis, this article explores the key issues faced by CNFs-based materials and future development directions, and proposes improvement suggestions for providing new ideas for the development of CNFs-based materials.

Navigating the post-operative nose as a primary care physician.

BACKGROUND: Rhinology procedures represent a wide and diverse category of procedures, which, on the surface, can appear very similar. Thus, it is difficult to navigate postoperative presentations in the general practice setting. OBJECTIVE: This article provides a comprehensive guide to managing acute presentations that might arise in primary care settings following common rhinology surgeries. It outlines common complications, their potential aetiology and first-aid measures that might be employed to temporise patients prior to escalation. It also provides a guide as to potential red flag symptomatology, and when and how to escalate specific presentations. DISCUSSION: Most acute postoperative complications can be effectively managed, or at the very least temporised, in the community setting. When in doubt, discuss with your local otolaryngologist or nearest centre with otolaryngology cover.

Post-viral olfactory loss and parosmia.

The emergence of SARS-CoV-2 has brought olfactory dysfunction to the forefront of public awareness, because up to half of infected individuals could develop olfactory dysfunction. Loss of smell-which can be partial or total-in itself is debilitating, but the distortion of sense of smell (parosmia) that can occur as a consequence of a viral upper respiratory tract infection (either alongside a reduction in sense of smell or as a solo symptom) can be very distressing for patients. Incidence of olfactory loss after SARS-CoV-2 infection has been estimated by meta-analysis to be around 50%, with more than one in three who will subsequently report parosmia. While early loss of sense of smell is thought to be due to infection of the supporting cells of the olfactory epithelium, the underlying mechanisms of persistant loss and parosmia remain less clear. Depletion of olfactory sensory neurones, chronic inflammatory infiltrates, and downregulation of receptor expression are thought to contribute. There are few effective therapeutic options, so support and olfactory training are essential. Further research is required before strong recommendations can be made to support treatment with steroids, supplements, or interventions applied topically or injected into the olfactory epithelium in terms of improving recovery of quantitative olfactory function. It is not yet known whether these treatments will also achieve comparable improvements in parosmia. This article aims to contextualise parosmia in the setting of post-viral olfactory dysfunction, explore some of the putative molecular mechanisms, and review some of the treatment options available.

Post-treatment 18F-fludeoxyglocuse-positron emission tomography in human papillomavirus-associated oropharyngeal cancer.

BACKGROUND: Human papillomavirus association has changed the landscape of treatment for oropharyngeal squamous cell carcinoma; it remains to be seen whether current post-treatment surveillance schedules are effective. OBJECTIVE: Evaluate whether post-treatment surveillance of oropharyngeal cancer through FDG-PET imaging is modified by human papillomavirus association. METHODS: A prospective cohort analysis of retrospective data was conducted for patients undergoing treatment of oropharyngeal cancer between 2016 and 2018. This study was conducted at a single large tertiary referral center in Brisbane, Australia. RESULTS: Two-hundred and twenty-four patients were recruited for the purposes of the study, 193 (86%) with HPV-associated disease. In this cohort FDG-PET had a sensitivity of 48.3%, specificity of 72.6%, positive predictive value of 23.7%, and negative predictive value of 88.8% in detecting disease recurrence. CONCLUSIONS: FDG-PET in HPV-associated oropharyngeal cancer has significantly lower positive predictive value when compared to non-HPV-associated oropharyngeal cancer. Caution should be used when interpreting positive post-treatment FDG-PET.

What benefit can be obtained from magnetic resonance imaging diagnosis with artificial intelligence in prostate cancer compared with clinical assessments?

The present study aimed to explore the potential of artificial intelligence (AI) methodology based on magnetic resonance (MR) images to aid in the management of prostate cancer (PCa). To this end, we reviewed and summarized the studies comparing the diagnostic and predictive performance for PCa between AI and common clinical assessment methods based on MR images and/or clinical characteristics, thereby investigating whether AI methods are generally superior to common clinical assessment methods for the diagnosis and prediction fields of PCa. First, we found that, in the included studies of the present study, AI methods were generally equal to or better than the clinical assessment methods for the risk assessment of PCa, such as risk stratification of prostate lesions and the prediction of therapeutic outcomes or PCa progression. In particular, for the diagnosis of clinically significant PCa, the AI methods achieved a higher summary receiver operator characteristic curve (SROC-AUC) than that of the clinical assessment methods (0.87 vs. 0.82). For the prediction of adverse pathology, the AI methods also achieved a higher SROC-AUC than that of the clinical assessment methods (0.86 vs. 0.75). Second, as revealed by the radiomics quality score (RQS), the studies included in the present study presented a relatively high total average RQS of 15.2 (11.0-20.0). Further, the scores of the individual RQS elements implied that the AI models in these studies were constructed with relatively perfect and standard radiomics processes, but the exact generalizability and clinical practicality of the AI models should be further validated using higher levels of evidence, such as prospective studies and open-testing datasets.

Manipulating single excess electrons in monolayer transition metal dihalide.

Polarons are entities of excess electrons dressed with local response of lattices, whose atomic-scale characterization is essential for understanding the many body physics arising from the electron-lattice entanglement, yet difficult to achieve. Here, using scanning tunneling microscopy and spectroscopy (STM/STS), we show the visualization and manipulation of single polarons in monolayer CoCl2, that are grown on HOPG substrate via molecular beam epitaxy. Two types of polarons are identified, both inducing upward local band bending, but exhibiting distinct appearances, lattice occupations and polaronic states. First principles calculations unveil origin of polarons that are stabilized by cooperative electron-electron and electron-phonon interactions. Both types of polarons can be created, moved, erased, and moreover interconverted individually by the STM tip, as driven by tip electric field and inelastic electron tunneling effect. This finding identifies the rich category of polarons in CoCl2 and their feasibility of precise control unprecedently, which can be generalized to other transition metal halides.

[Acupuncture for treatment of tobacco withdrawal syndrome: systematic review and Meta-analysis].

OBJECTIVE: To systematically review the efficacy of acupuncture for the treatment of tobacco withdrawal syndrome. METHODS: The randomized controlled trials (RCTs) regarding acupuncture for treatment of tobacco withdrawal syndrome were searched in CNKI, Wanfang, VIP, SinoMed, PubMed, Cochrane, Medline and EMbase databases. The search period was from January 1st of 2011 to December 31st of 2021. After data extraction and bias risk assessment of the included literature, the Meta-analysis was performed using RevMan5.4.1 software. RESULTS: Totally 23 RCTs were included, including 2 120 patients. The Meta-analysis results showed that compared with medication, acupuncture showed no significant difference at improving Fagerström test for nicotine dependence (FTND) score (MD=0.16, 95%CI: -0.08, 0.41), heaviness of smoking index (HSI) score (MD=0.11, 95%CI: -0.13, 0.36), Minnesota nicotine withdrawal scale (MNWS) score (MD=0.12, 95%CI: -0.11, 1.35), questionnaire of smoking urges (QSU) score (MD=-0.30, 95%CI: -2.78, 2.18), Hamilton depression scale (HAMD) score (MD=0.76, 95%CI: -1.54, 3.06), abstinence rate (RR=0.95, 95% CI: 0.82, 1.10) and effective rate (RR=1.01, 95%CI: 0.95, 1.07). Acupuncture was superior to sham acupuncture in reducing MNWS score (MD=-4.88, 95%CI: -5.21, -4.55, P<0.000 01). Acupuncture was superior to cognitive behavioral therapy in reducing FTND score (MD=-1.41, 95%CI: -1.74, -1.08), MNWS score (MD=-4.28, 95%CI: -5.31, -3.25) and increasing abstinence rate (RR=2.19, 95%CI: 1.39, 3.45, P<0.000 01, P<0.001). CONCLUSION: Acupuncture could effectively improve tobacco withdrawal syndrome, increase abstinence rate and effective rate. Limited by the quantity and quality of the included studies, this conclusion needs to be verified by more studies.

Posttraumatic checkrein deformity following isolated Lauge-Hansen pronation external rotation stage IV malleolar fracture-a case report and literature review.

The checkrein deformity is characterized by flexion contracture of the interphalangeal joint and extension contracture of the metatarsophalangeal joint. It is a rare condition occurring after lower extremity trauma, especially a malleolar fracture. Little is known about the possible cause and therapeutic strategy. This unique case presents a 20-year-old male patient with a diagnosis of the checkrein deformity secondary to open reduction and internal fixation of a Lauge-Hansen pronation external rotation stage IV malleolar fracture. After performing a detailed physical examination, radiographic evaluation, and ultrasonography, open exploration was performed to remove the hardware and correct the deformity with sole tenolysis of the flexor hallucis longus (FHL). In the 4-month follow-up, no recurrence of the checkrein deformity was observed. This deformity was caused by FHL adhesion. Interosseous membrane injury and fibular fracture together with local hematomas increases the risk of FHL adhesion. Open exploration and tenolysis of the FHL are feasible options to correct the checkrein deformity.

[Auricular point sticking combined with transcutaneous electrical acupoint stimulation for smoking cessation：a randomized controlled trial].

OBJECTIVE: To compare the clinical efficacy between auricular point sticking combined with transcutaneous electrical acupoint stimulation (TEAS) and nicotine patch for smoking cessation. METHODS: Two hundred patients who voluntarily quit smoking were randomly divided into a combination group and a nicotine patch group, 100 cases in each group. In the combination group, auricular point sticking (Shenmen [TF4], Neifenmi [CO18], Pizhixia [AT4], Jiaogan [AH6a], etc., once every other day) combined with TEAS（Lieque [LU 7] and Zusanli [ST 36], with continuous wave, 20 Hz in frequency, 1 mA in current intensity, 30 min each time, once a day) were applied. In the nicotine patch group, nicotine patch was applied. Both groups were treated for 8 weeks. The immediate withdrawal rate and persistent withdrawal rate 8 weeks into treatment and in follow-up of 16 weeks after treatment in the two groups were compared; before treatment, 8 weeks into treatment and in follow-up of 16 weeks after treatment, the degree of nicotine dependence was evaluated by using Fagerström test for nicotine dependence (FTND); 1 week into treatment, 8 weeks into treatment and in follow-up of 16 weeks after treatment, the withdrawal symptoms and smoking craving were evaluated by using Minnesota nicotine withdrawal scale (MNWS); the safety and compliance (dropped off rate and treatment completeness) were evaluated in the two groups. RESULTS: There was no statistical significance of the differences in the immediate withdrawal rate and persistent withdrawal rate 8 weeks into treatment and during follow-up between the two groups (P>0.05). The FTND scores were decreased 8 weeks into treatment and during follow-up in the two groups compared with those before treatment (P<0.01); the FTND score during follow-up in the combination group was lower than the nicotine patch group (P<0.05). The MNWS scores were decreased 8 weeks into treatment and during follow-up in the two groups compared with those 1 week into treatment (P<0.05); the changes of MNWS scores 8 weeks into treatment and during follow-up in the combination group were greater than the nicotine patch group (P<0.05, P<0.01). There were no serious adverse reactions in either group. Eight weeks into treatment and during follow-up, the dropped off rates were all 16.0% (16/100) in the combination group, which were 20.0% (20/100) and 23.0% (23/100) in the nicotine patch group, there was no statistical significance of the differences in the two groups (P>0.05). There was no significant difference in treatment completeness between the two groups (P>0.05). CONCLUSION: Auricular point sticking combined with TEAS could effective decrease the degree of nicotine dependence, improve withdrawal symptoms in smokers, its effect is superior to nicotine patch.

Isolation and identification of SiCOL5, which is involved in photoperiod response, based on the quantitative trait locus mapping of Setaria italica.

Foxtail millet (Setaria italica) is a versatile grain and fodder crop grown in arid and semi-arid regions. It is an especially important crop for combating malnutrition in certain poverty-stricken areas of the world. Photoperiod sensitivity is a major constraint to the distribution and utilization of foxtail millet germplasm resources. Foxtail millet may be suitable as a model species for studying the photoperiod sensitivity of C4 crops. However, the genetic basis of the photoperiod response of foxtail millet remains poorly studied. To detect the genetic basis of photoperiod sensitivity-related traits, a recombinant inbred line (RIL) population consisting of 313 lines derived from a cross between the spring-sown cultivar "Longgu 3" and the summer-sown cultivar "Canggu 3" was established. The RIL population was genotyped using whole-genome re-sequencing and was phenotyped in four environments. A high-density genetic linkage map was constructed with an average distance between adjacent markers of 0.69 cM. A total of 21 quantitative trait loci (QTLs) were identified by composite interval mapping, and 116 candidate genes were predicted according to gene annotations and variations between parents, among which three genes were considered important candidate genes by the integration and overall consideration of the results from gene annotation, SNP and indel analysis, cis-element analysis, and the expression pattern of different genes in different varieties, which have different photoperiod sensitivities. A putative candidate gene, SiCOL5, was isolated based on QTL mapping analysis. The expression of SiCOL5 was sensitive to photoperiod and was regulated by biological rhythm-related genes. Function analysis suggested that SiCOL5 positively regulated flowering time. Yeast two-hybrid and bimolecular fluorescence complementation assays showed that SiCOL5 was capable of interacting with SiNF-YA1 in the nucleus.

Spin-orbital Yu-Shiba-Rusinov states in single Kondo molecular magnet.

Studies of single-spin objects are essential for designing emergent quantum states. We investigate a molecular magnet Tb2Pc3 interacting with a superconducting Pb(111) substrate, which hosts unprecedented Yu-Shiba-Rusinov (YSR) subgap states, dubbed spin-orbital YSR states. Upon adsorption of the molecule on Pb, the degeneracy of its lowest unoccupied molecular orbitals (LUMO) is lifted, and the lower LUMO forms a radical spin via charge transfer. This leads to Kondo screening and subgap states. Intriguingly, the YSR states display two pairs of resonances with clearly distinct behavior. The energy of the inner pair exhibits prominent inter and intra molecular variation, and it strongly depends on the tip height. The outer pair, however, shifts only slightly. As is unveiled through theoretical calculations, the two pairs of YSR states originate from the ligand spin and charge-fluctuating higher LUMO, coexisting in a single molecule, but only weakly coupled presumably due to different spatial distribution. Our work paves the way for understanding complex many-body excitations and constructing molecule-based topological superconductivity.

Correction: First-principles insights into hydrogen trapping in interstitial-vacancy complexes in vanadium carbide.

Correction for 'First-principles insights into hydrogen trapping in interstitial-vacancy complexes in vanadium carbide' by Shuai Tang et al., Phys. Chem. Chem. Phys., 2022, DOI: https://doi.org/10.1039/d2cp02425j.

First-principles insights into hydrogen trapping in interstitial-vacancy complexes in vanadium carbide.

Hydrogen trapping is a key factor in designing advanced vanadium alloys and steels, where the influence of carbon vacancies is still elusive. Herein we have investigated the effect of carbon vacancies on the hydrogen trapping of defect-complexes in vanadium carbide using first-principles calculations. When a carbon vacancy is present, the second nearest neighboring trigonal interstitial is a stable hydrogen trapping site. A C vacancy enhances the hydrogen trapping ability by reducing the chemical and mechanical effects on H atom solution energy. Electronic structure analysis shows that C vacancies increase the charge density and the Bader atomic volume, leading to a lower H atom solution energy. The strength of the V-H bond is predominant in determining the hydrogen trapping ability in the presence of a C vacancy, in contrast to that of a C-H bond when the C vacancy is absent.