Progressive Damage Research Articles

Effects of Hyperbaric Oxygen Therapy in Treatment on Diverse Diseases

INTRODUCTION: Hyperbaric oxygen therapy (HBOT) indeed holds significant therapeutic potential across various medical conditions, primarily by increasing the concentration of oxygen delivered to tissues under pressure. Saturating tissues with oxygen allows for the effective alleviation of underlying hypoxia, facilitating healing, tissue repair and mechanisms of action leads to reducing concentration of pro-inflammatory acute phase proteins, interleukins, and cytokines. Conversely, HBOT while also boosting levels of growth factors and other cytokines that promote angiogenesis. REVIEW METHODS: The article was complied by analyzing data from PubMed and Google Scholar regarding effects of hyperbaric therapy. THE STATE OF KNOWLEDGE: Studies indicate that HBOT provides numerous opportunities in the treatment of extensive diseases acress various systems. Neurodegenerative disorders involve progressive nerve cell damage leading to motor or cognitive decline, exacerbated by oxidative stress and inflammation. HBOT has shown promise in delaying disease onset by improving mitochondrial dysfunction in motor neuron disease. In case of intestinal obstruction HBOT reduces intestinal gas volume, diameter of obstructed loops, and improves intestinal contractility. Significant benefits have been observed in conditions such as Crohn's disease and ulcerative colitis. Hyperbaric therapy presents potential benefits for the infertility, improving the environment for blastocyst implantation and pregnancy. CONCLUSION: There is no doubt that HBOT has a beneficial impact on treatment of many systems such as the nervous, cardiovascular, digestive, and skeletal. This innovative approach of hyperbaric therapy extends to selected disorders such as neurodegenerative diseases, Crohn's disease, ulcerative colitis, and infertility.

Predicting Structural Consequences of Antibody Light Chain N-Glycosylation in AL Amyloidosis

Background/Objectives: Antibody light chains form amyloid fibrils that lead to progressive tissue damage in amyloid light chain (AL) amyloidosis. The properties of each patient’s unique light chain appear to determine its propensity to form amyloid. One factor is N-glycosylation, which is more frequent in amyloid-associated light chains than in light chains from the normal immune repertoire. However, the mechanisms underlying this association are unknown. Here, we investigate the frequency and position within the light chain sequence of the N-glycosylation sequence motif, or sequon. Methods: Monoclonal light chains from AL amyloidosis and multiple myeloma were identified from the AL-Base repository. Polyclonal light chains were obtained from the Observed Antibody Space resource. We compared the fraction of light chains from each group harboring an N-glycosylation sequon, and the positions of these sequons within the sequences. Results: Sequons are enriched among AL-associated light chains derived from a subset of precursor germline genes. Sequons are observed at multiple positions, which differ between the two types of light chains, κ and λ, but are similar between light chains from AL amyloidosis and multiple myeloma. Positions of sequons map to residues with surface-exposed sidechains that are compatible with the folded structures of light chains. Within the known structures of λ AL amyloid fibrils, many residues where sequons are observed are buried, inconsistent with N-glycosylation. Conclusions: There is no clear structural rationale for why N-glycosylation of κ light chains is associated with AL amyloidosis. A better understanding of the roles of N-glycosylation in AL amyloidosis is required before it can be used as a marker for disease risk.

The role of antibiotic-derived mycobacterial vesicles in tuberculosis pathogenesis.

Pulmonary tuberculosis (TB) causes progressive and irreversible damage to lung tissue, a damage that may not fully resolve after treatment. Mycobacterial vesicles (MVs), which are poorly understood, may contribute to TB pathology. This study investigated the effects of stress, such as treatment with conventional TB antibiotics rifampicin, isoniazid, ethambutol, or treatment with an antimycobacterial peptide (NZX), on mycobacterial vesiculation. Stress from minimal inhibitory concentrations of antibiotics, or peptide all increased MV formation. Electron microscopy and lipid profiling revealed that these vesicles, about 40nm in size, were released from the bacterial inner membrane and consisted of apolar lipids. Using mass spectrometry, the study identified key differences in MVs protein cargo dependent on the antibiotic used, especially with ethambutol-induced MVs that contained proteins from several mycobacterial pathways. Additionally, toxicology analysis using different concentrations of MVs on primary human macrophages and the monocytic cells indicated that MVs from the different treatments were not toxic to human cells, however induced specific inflammatory profiles. In conclusion, this study identified mycobacterial vesicles to be a potential contributor to tuberculosis pathology.

Audiometric Outcomes in Chronic Otitis Media with Mastoid Involvement: A Five-Year Clinical Overview

Background/Objectives. Otomastoiditis, an inflammatory condition affecting the middle ear and mastoid cells, poses significant risks for hearing impairment. This study aimed to analyze the clinical presentations, anatomical variations, and audiometric outcomes associated with acute and chronic otomastoiditis over a five-year period at the ENT Clinic of the Clinical County Emergency Hospital of Craiova. Methods. A retrospective clinical–statistical analysis was conducted on 145 patients aged 2 to 78 years, who were treated for otomastoiditis. The study involved a comprehensive review of clinical and audiometric data, with a focus on the type of hearing loss (conductive or mixed), audiometric thresholds, and the relationship between the anatomical form of the disease and the severity of hearing loss. Results. The majority of cases (93.83%) were chronic otomastoiditis, with 66.89% of patients presenting with mixed hearing loss and 33.10% with conductive hearing loss. Audiometric assessments revealed significant air conduction deficits, particularly at low and mid-range frequencies, with losses averaging 50–55 dB in cases of conductive hearing loss. Chronic cases demonstrated notable bone conduction impairments, indicating progressive cochlear damage. Statistical analysis identified a moderate correlation between the anatomical form of the disease and the severity of hearing loss, particularly in patients with cholesteatomatous-suppurative forms. Conclusions. This study underlines the critical need for the early and precise diagnosis of otomastoiditis, supported by audiometric evaluations. Our findings emphasize the substantial risk of progressive cochlear damage in chronic cases, underscoring the necessity for timely intervention to mitigate long-term hearing loss. These results offer valuable insights for clinicians, potentially guiding improved therapeutic approaches and contributing to enhanced patient outcomes in managing chronic otomastoiditis.

Peak width of skeletonized mean diffusivity: a novel biomarker for white matter damage in spinocerebellar ataxia type 2.

Peak width of skeletonized mean diffusivity (PSMD) is a robust and fully automated imaging marker employed to detect microstructural damage in white matter. This study aimed to evaluate whether PSMD reflects the severity of white matter damage and tracks disease progression in patients with spinocerebellar ataxia type 2 (SCA2). Nine patients with SCA2 and sixteen age- and gender-matched healthy controls were enrolled. Clinical and imaging data were collected at baseline and after 3.5years. Each participant underwent MRI scans twice to obtain diffusion tensor imaging data, from which PSMD were automatically calculated. Differences in PSMD between SCA2 patients and healthy controls were analyzed using a linear mixed model. Additionally, Spearman's rank correlations were employed to assess associations between PSMD values and clinical variables. Patients with SCA2 exhibited higher PSMD values at baseline and follow-up compared to HCs, indicating more severe white matter damage. Longitudinal data revealed a continual increase in PSMD values in SCA2 patients over time. The mixed-effects model confirmed significant differences in PSMD values between the two groups, as well as an interaction effect suggesting different progression rates. These findings suggest that SCA2 associates with progressive deterioration of white matter. No significant correlations were observed between PSMD values and clinical variables in this study. This study underscores the potential of PSMD as a neuroimaging biomarker for detecting microstructural white matter damage and monitoring disease progression in patients with SCA2.

Mechanistic Insights Into Redox Damage of the Podocyte in Hypertension.

Podocytes are specialized cells within the glomerular filtration barrier, which are crucial for maintaining glomerular structural integrity and convective ultrafiltration. Podocytes exhibit a unique arborized morphology with foot processes interfacing by slit diaphragms, ladder-like, multimolecular sieves, which provide size and charge selectivity for ultrafiltration and transmembrane signaling. Podocyte dysfunction, resulting from oxidative stress, dysregulated prosurvival signaling, or structural damage, can drive the development of proteinuria and glomerulosclerosis in hypertensive nephropathy. Functionally, podocyte injury leads to actin cytoskeleton rearrangement, foot process effacement, dysregulated slit diaphragm protein expression, and impaired ultrafiltration. Notably, the renin-angiotensin system plays a pivotal role in podocyte function, with beneficial AT2R (angiotensin receptor 2)-mediated nitric oxide (NO) signaling to counteract AT1R (angiotensin receptor 1)-driven calcium (Ca2+) influx and oxidative stress. Disruption of this balance contributes significantly to podocyte dysfunction and drives albuminuria, a marker of kidney damage and overall disease progression. Oxidative stress can also lead to sustained ion channel-mediated Ca2+ influx and precipitate cytoskeletal disorganization. The complex interplay between GPCR signaling, ion channel activation, and redox injury pathways underscores the need for additional research aimed at identifying targeted therapies to protect podocytes and preserve glomerular function. Earlier detection of albuminuria and podocyte injury through routine noninvasive diagnostics will also be critical in populations at the highest risk for the development of hypertensive kidney disease. In this review, we highlight the established mechanisms of oxidative stress-mediated podocyte damage in proteinuric kidney diseases, with an emphasis on a hypertensive renal injury. We will also consider emerging therapies that have the potential to selectively protect podocytes from redox-related injury.

Damage evaluation in plain-woven CFRP plate with circular hole under cyclic tensile loading using electrical impedance tomography

Understanding and predicting damage progression within thin plain-woven carbon fiber-reinforced polymer (CFRP) components is an essential issue for scheduling maintenance intervals and structural inspections and typically requires extensive test series. However, uncertainties always remain and result in conservative design and unnecessary downtimes due to the repeated inspections of a healthy structure. Structural health monitoring (SHM) can be used to reduce these uncertainties, as it allows one to evaluate the condition of a mechanical structure during operation. Numerous SHM methods have been developed, which achieve different levels of damage identification but are often investigated at small coupons with nonrealistic structural damages and loading conditions on both structure and sensor. The present research investigates electrical impedance tomography (EIT) featuring an elastoresistive thin-film sensor to evaluate damage that propagates from a circular hole in a large plate under cyclic tensile–tensile multiblock loading. Applied fatigue loads were increased multiple times up to a total number of two million cycles. During the loading, damage initiated at the hole and continuously propagated into the plate. Repeated EIT evaluations of the applied sensor and validating evaluations by means of digital image correlation clearly revealed the robustness of the hardware and the potential of the SHM method for damage evaluation of plain-woven CFRP components.

Prolonged Photobiomodulation with Deep Red Light Mitigates Incipient Retinal Deterioration in a Mouse Model of Type 2 Diabetes

Diabetic retinopathy is a prevalent complication of type 2 diabetes mellitus, characterized by progressive damage to the retinal structure and function. Photobiomodulation therapy, using red or near-infrared light, has been proposed as a non-invasive intervention to mitigate retinal damage, but has been tested generally with short-term stimuli. This study aimed to evaluate the effects of prolonged photobiomodulation with deep red light on retinal structure and function in a type 2 diabetes mouse model. Transgenic LepRdb/J (db/db) mice were exposed to photobiomodulation therapy via LED devices emitting 654 nm light for 12 h daily over ten weeks and compared to untreated mice. Retinal function was evaluated by flash electroretinography, while structural changes were assessed through histology and immunohistochemistry to detect astro- and microgliosis. At 33 weeks of age, db/db mice were obese and severely diabetic, but exhibited only incipient indicators of retinal deterioration. Electroretinogram b-wave peak latencies were prolonged at intermediate flash intensities, while the outer plexiform layer displayed significantly elevated IBA1 expression. Photobiomodulation therapy prevented these two markers of early retinal deterioration but had no effect on other morphological and functional parameters. Photobiomodulation is well-tolerated and maintains potential as a complementary treatment option for diabetic retinopathy but requires further optimization of therapeutic settings and combinatory treatment approaches.

Unraveling the Nexus: The Role of Collapsin Response Mediator Protein 2 Phosphorylation in Neurodegeneration and Neuroregeneration.

Neurodegenerative disease characterized by the progressive damage of the nervous system, and neuropathies caused by the neuronal injury are both led to substantial impairments in neural function and quality of life among geriatric populations. Recovery from nerve damage and neurodegenerative diseases present a significant challenge, as the central nervous system (CNS) has limited capacity for self-repair. Investigating mechanism of neurodegeneration and regeneration is essential for advancing our understanding and development of effective therapies for nerve damage and degenerative conditions, which can significantly enhance patient outcomes. Collapsin response mediator protein 2 (CRMP2) was first identified as a key mediator of axonal growth and guidance is essential for neurogenesis and neuroregeneration. Phosphorylation as a primary modification approach of CRMP2 facilitates its involvement in numerous physiological processes, including axonal guidance, neuroplasticity, and cytoskeleton dynamics. Prior research on CRMP2 phosphorylation has elucidated its involvement in the mechanisms of neurodegenerative diseases and nerve damage. Pharmacological and genetic interventions that alter CRMP2 phosphorylation have shown the potential to influence neurodegenerative diseases and promote nerve regeneration. Even with decades of research delving into the intricacies of CRMP2 phosphorylation, there remains a scarcity of comprehensive literature reviews addressing this topic. This absence of synthesis and integration of findings hampers the field's progress by preventing a holistic understanding of CRMP2's implications in neurobiology, thereby impeding potential advancements in clinical treatments and interventions. This review intends to compile investigations focused on the role of CRMP2 phosphorylation in both neurodegenerative disease models and injury models to summarizing impacts and offer novel insight for clinical therapies.

Rasmussen Encephalitis: Clinical Features, Pathophysiology, and Management Strategies—A Comprehensive Literature Review

Rasmussen encephalitis (RE) is a rare and progressive form of chronic encephalitis that typically affects one hemisphere of the brain and primarily occurs in pediatric individuals. The current study aims to narratively review the literature about RE, including historical information, pathophysiology, and management of this condition. RE often occurs in individuals with normal development, and it is estimated that only a few new cases are identified each year in epilepsy centers. Approximately 10% of cases also occur in adolescents and adults. The hallmark feature of RE is drug-resistant focal seizures that can manifest as epilepsia partialis continua. Also, patients with RE usually develop motor and cognitive impairment throughout the years. Neuroimaging studies show progressive damage to the affected hemisphere, while histopathological examination reveals T-cell-dominated encephalitis with activated microglial cells and reactive astrogliosis. The current therapy guidelines suggest cerebral hemispherotomy is the most recommended treatment for seizures in RE, although significant neurological dysfunction can occur. Another option is pharmacological management with antiseizure medications and immunomodulatory agents. No significant progress has been made in understanding the pathophysiology of this condition in the last decades, especially regarding genetics. Notably, RE diagnosis still depends on the criteria established by Bien et al., and the accuracy can be limited and include genetically different individuals, leading to unexpected responses to management.

An evaluation of progressive damage analysis methods for modeling low velocity impact of thermoplastic composites

State-of-the-art progressive damage and failure analysis (PDFA) tools for composites were developed for thermoset materials because of the prevalence of the material system within the aerospace industry and the need to address damage growth behavior of composites analytically. As the presence of thermoplastic materials has started to grow in the industry, it is necessary to be able to predict their behavior as well. However, it is unclear whether existing tools based on linear elastic fracture mechanics (LEFM) can be used to represent thermoplastics. One application area for PDFA tools is low velocity impact (LVI). This work presents two PDFA modeling methods originally validated for predicting damage of thermoset composites in low-velocity impact and evaluates their ability to model a thermoplastic material system in the same scenario. Both methods use MAT299, a continuum damage mechanics material model, to represent interlaminar damage and a cohesive tiebreak definition within LS-DYNA to represent delamination within a laminate. The results reveal that the cohesive tiebreak modeling method, while successful in modeling thermoset materials, is not currently capable of predicting the delamination response of thermoplastics. The larger strain energy release rates for the thermoplastic material in combination with a deficiency in the modeling method are believed to be the cause of the reduced delamination in the simulations. Potential routes for improving the delamination prediction in the simulations include adjusting the mode-mixity behavior, using a different cohesive approach for delamination, developing new best practices for cohesive behavior, and incorporating further non-linearity into the material model.

The impact of different forms of exercise on intraocular pressure, blood flow, and the risk for primary open angle glaucoma.

Primary open angle glaucoma (POAG) is a chronic disease characterized by progressive optic nerve damage and irreversible loss of vision, often diagnosed at late stages. Elevated intraocular pressure (IOP) is the major risk factor for its onset and progression while older age, myopia, genetic factors, blood pressure (BP), and reduced ocular blood flow (OBF) have also been linked to the disease. Different forms of exercise are known to have significant, but variable, effects on IOP, BP, ocular perfusion pressure (OPP), OBF and oxygen metabolism, and ultimately the risk for development and progression of POAG. While population-based studies lack agreement regarding the relationship between exercise and POAG status, data suggests that resistance training causes a short-term increase in IOP, BP, and OPP. Conversely, aerobic exercise has been shown to cause a short-term decrease in IOP and increase in BP and OPP. Research also suggests that following an exercise program over an extended period may lead to a long-term decrease in IOP, however its cessation results in a prompt return to baseline levels. Data suggests normal vascular autoregulation ensures minimal change in OBF following extended exercise unless OPP rises ∼70% above baseline. Although exercise may alter IOP, BP, and OBF, both acutely and chronically, it is currently uncertain if physical activity significantly alters risk for the onset and progression of POAG.

Performance Assessment of an Electrostatic Filter-Diverter Stent Cerebrovascular Protection Device: Evaluation of a Range of Potential Electrostatic Fields Focusing on Small Particles

Silent Brain Infarction (SBI) is increasingly recognized in patients with cardiac conditions, particularly Atrial Fibrillation (AF) in elderly patients and those undergoing Transcatheter Aortic Valve Implantation (TAVI). While these infarcts often go unnoticed due to a lack of acute symptoms, they are associated with a threefold increase in stroke risk and are considered a precursor to ischemic stroke. Moreover, accumulating evidence suggests that SBI may contribute to the development of dementia, depression, and cognitive decline, particularly in the elderly population. The burden of SBI is substantial, with studies showing that up to 11 million Americans may experience a silent stroke annually. In AF patients, silent brain infarcts are common and can lead to progressive brain damage, even in those receiving anticoagulation therapy. The use of cerebral embolic protection devices (CEPDs) during TAVI has been explored to mitigate the risk of stroke; however, their efficacy remains under debate. Despite advancements in TAVI technology, cerebrovascular events, including silent brain lesions, continue to pose significant challenges, underscoring the need for improved preventive strategies and therapeutic approaches. We propose a device consisting of a strut structure placed at the base of the treated artery to model the potential risk of cerebral embolisms caused by atrial fibrillation, thromboembolism, or dislodged debris of varying potential TAVI patients. The study has been carried out in two stages. Both are based on computational fluid dynamics (CFD) coupled with the Lagrangian particle tracking method. The first stage of the work evaluates a variety of strut thicknesses and inter-strut spacings, contrasting with the device-free baseline geometry. The analysis is carried out by imposing flow rate waveforms characteristic of healthy and AF patients. Boundary conditions are calibrated to reproduce physiological flow rates and pressures in a patient’s aortic arch. In the second stage, the optimal geometric design from the first stage was employed, with the addition of lateral struts to prevent the filtration of particles and electronegatively charged strut surfaces, studying the effect of electrical forces on the clots if they are considered charged. Flowrate boundary conditions were used to emulate both healthy and AF conditions. Results from numerical simulations coming from the first stage indicate that the device blocks particles of sizes larger than the inter-strut spacing. It was found that lateral strut space had the highest impact on efficacy. Based on the results of the second stage, deploying the electronegatively charged device in all three aortic arch arteries, the number of particles entering these arteries was reduced on average by 62.6% and 51.2%, for the healthy and diseased models respectively, matching or surpassing current oral anticoagulant efficacy. In conclusion, the device demonstrated a two-fold mechanism for filtering emboli: (1) while the smallest particles are deflected by electrostatic repulsion, avoiding micro embolisms, which could lead to cognitive impairment, the largest ones are mechanically filtered since they cannot fit in between the struts, effectively blocking the full range of particle sizes analyzed in this study. The device presented in this manuscript offers an anticoagulant-free method to prevent stroke and SBIs, imperative given the growing population of AF and elderly patients.

Proteinuria and Progression of Renal Damage: The Main Pathogenetic Mechanisms and Pharmacological Approach

The integrity of the glomerular filtration barrier maintains protein excretion below 150 mg/day. When urinary proteins increase, this indicates damage to the filtration barrier. However, proteinuria is not only a marker of kidney damage but also exacerbates it through various mechanisms involving the glomerular and tubulointerstitial compartments. Therefore, it is essential to intervene with renoprotective action that reduces the proteinuria. In this context, Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are cornerstone treatments. Recent advancements include sodium–glucose cotransporter 2 inhibitors, initially used for glycemic control, now recognized for their renoprotective properties in both diabetic and non-diabetic populations. Another drug, Finerenone, a selective non-steroidal mineralocorticoid receptor antagonist, has emerged as a promising agent, offering anti-inflammatory and antifibrotic benefits with fewer side effects than traditional steroidal options. Finally, dual inhibition of angiotensin II and endothelin-1 receptors through agents like Sparsentan presents a novel approach with significant antiproteinuric effects in IgA nephropathy and focal segmental glomerulosclerosis. This brief review summarizes the mechanisms by which proteinuria promotes kidney damage and the renoprotective therapeutic approaches available, which can be combined with lifestyle modifications and specific treatments for underlying diseases to mitigate the progression of chronic kidney disease.

Exploring the Role of Gut Vascular Barrier Proteins in HIV-Induced Mucosal Damage: A Comparative Study.

This study aims to compare intestinal mucosal damage and the expression levels of occludin, zonula occludens-1 (ZO-1), vascular endothelial (VE)-cadherin, β-catenin, and plasmalemma vesicle-associated protein (PLVAP) in the gut vascular barrier (GVB) among people living with HIV (PLWH), asymptomatic PLWH, and healthy volunteers (non-PLWH). Three groups were selected for the study: PLWH, asymptomatic PLWH, and healthy volunteers. Colonic mucosal tissue samples were collected via colonoscopy from all participants. Histological examination of the colonic mucosa was conducted using hematoxylin and eosin staining. The expression levels of occludin, ZO-1, VE-cadherin, β-catenin, and PLVAP were assessed using RT-qPCR, immunohistochemistry, and western blot analyses. Pathological scores of colonic mucosa in PLWH and asymptomatic PLWH were significantly higher than those in non-PLWH (p < .001 and p = .0056, respectively). CD4+ T cell counts in asymptomatic PLWH and non-PLWH were significantly higher than in PLWH (p < 0.05). The CD4+/CD8+ T cell ratio in non-PLWH significantly exceeded those in PLWH and asymptomatic PLWH (p < .05). Analysis of protein and mRNA expression revealed: (1) no statistically significant differences in PLVAP-mRNA expression across all groups (p > .05); (2) higher PLVAP protein levels in PLWH compared with asymptomatic PLWH and non-PLWH (p < .05), with no significant differences between asymptomatic PLWH and non-PLWH (p = .632); (3) significantly higher PLVAP expression in the colonic mucosa of PLWH and asymptomatic PLWH compared with non-PLWH (p = .034 and p = .011, respectively), with no significant differences between PLWH and asymptomatic PLWH (p > .999). ZO-1 expression was significantly lower in PLWH than in non-PLWH (p = .012), with no notable differences between asymptomatic PLWH and other groups. PLWH, compared with healthy controls, exhibit significant inflammatory changes in the intestinal mucosa. PLVAP expression serves as a potential indicator to assess the extent of GVB damage and disease progression in PLWH.

Progress in the Study of Diabetic Nephropathy Markers

Diabetic nephropathy (DN) is the principal consideration of end-stage diabetic nephropathy in China, second only to chronic glomerulonephritis. It is the most common complication of diabetes and the cause of death in diabetic patients. The clinical manifestations of DN are proteinuria, edema, hypertension, and progressive renal damage, and its continuous development can turn into nephrotic syndrome and uremia. It has been reported that urinary microalbumin, cystatin C and homocysteine are related to the diagnosis of renal diseases. In addition, pathological examination of renal biopsy, as the golden standard, plays a vital role in clinical diagnosis of DN. In the meantime, with the rise of biomarkers research, such as Genetic Markers, miRNAs and AGEs, we can evaluate the renal function of diabetic patients by detecting these markers as early as possible. Taking into account the above information, we focus on research advances in the association of microalbuminuria, urinary inhibitory C, serum homocysteine, renal biopsy and biomarkers with DN.

O-GlcNAcylation of RPA2 at S4/S8 antagonizes phosphorylation and regulates checkpoint activation during replication stress

O-linked N-acetylglucosamine (O-GlcNAc) is the most abundant mono-saccharide modification occurring in the cytoplasm, nucleus and mitochondria. Recent advent of the mass spectrometry technology has enabled identification of abundant O-GlcNAc transferase (OGT) substrates in diverse biological processes, such as cell cycle progression, replication and DNA damage response. Herein we report the O-GlcNAcylation of Replication Protein A2 (RPA2), a component of the heterotrimeric RPA complex pivotal for DNA metabolism. We found that RPA2 interacts with OGT, and a topoisomerase II inhibitor, etoposide, diminishes the association. Using higher-energy collisional dissociation mass spectrometry, we mapped RPA2 O-GlcNAc sites to be Ser-4/Ser-8, which are well-known PIKK-dependent RPA2 phosphorylation sites involved in checkpoint activation upon replication stress. We further demonstrated that Ser-4/Ser-8 O-GlcNAcylation antagonizes phosphorylation and impairs downstream Chk1 activation. Moreover, RPA2 O-GlcNAcylation sustains H2AX phosphorylation upon etoposide treatment, and promotes inappropriate cell cycle progression, indicative of checkpoint defects. Our work not only unveils a new OGT substrate, but also underscores the distinct roles of OGT in replication versus replication stress.

A p38 MAPK-ROS axis fuels proliferation stress and DNA damage during CRISPR-Cas9 gene editing in hematopoietic stem and progenitor cells.

Exvivo activation is a prerequisite to reaching adequate levels of gene editing by homology-directed repair (HDR) for hematopoietic stem and progenitor cell (HSPC)-based clinical applications. Here, we show that shortening culture time mitigates the p53-mediated DNA damage response to CRISPR-Cas9-induced DNA double-strand breaks, enhancing the reconstitution capacity of edited HSPCs. However, this results in lower HDR efficiency, rendering exvivo culture necessary yet detrimental. Mechanistically, exvivo activation triggers a multi-step process initiated by p38 mitogen-activated protein kinase (MAPK) phosphorylation, which generates mitogenic reactive oxygen species (ROS), promoting fast cell-cycle progression and subsequent proliferation-induced DNA damage. Thus, p38 inhibition before gene editing delays G1/S transition and expands transcriptionally defined HSCs, ultimately endowing edited cells with superior multi-lineage differentiation, persistence throughout serial transplantation, enhanced polyclonal repertoire, and better-preserved genome integrity. Our data identify proliferative stress as a driver of HSPC dysfunction with fundamental implications for designing more effective and safer gene correction strategies for clinical applications.

Experimental and numerical investigation on the failure behaviors of laminates with various shaped cutouts under tensile loading

Composite structures in aircraft often contain many cutouts, and failure of these structures is prone to occur near the edge of cutouts. Therefore, the failure behaviors of laminates with various shaped cutouts should be carefully investigated. To this end, experiments and numerical simulations are employed to investigate this issue. The tensile tests of composite laminates with circular, elliptical, square, and rectangular cutouts were carried out. Digital image correlation was utilized to capture the strain fields around the cutout. Combining the strain failure criterion and the modified exponential damage variables a three-dimensional progressive damage model was established, which can accurately predict the peak loads of composite laminates with diverse cutouts. All errors between the experimental and numerical results are less than 10 %. The experimental and numerical results indicate that the shape of the cutout has a great influence on the peak loads. As the ratio of major axis to minor axis (a/b) is increased from 1 to 5, peak loads obviously increase for the laminates with elliptical cutouts. Experimental results show that the average peak load of the laminates with elliptical cutout (a/b = 4) is 20.0 % higher than that of the laminates with circular cutout (a/b = 1). The dispersed distribution of high strains near the edge of the cutout results in an improvement of bearing capacity. As the ratio of length to width (l/w) in rectangular cutouts is increased from 0.5 to 3, peak loads are also improved obviously, because experimental results show that the average peak load of the laminates with rectangular cutout (l/w = 0.5) is 12.3 % lower than that of the laminates with square cutout (l/w = 1). Therefore, to improve the peak loads, it is very necessary to select the proper ratios of a/b and l/w. The above conclusions can serve as a reference for the design of composite structures.

Quantifying sandstone crack extension and expansion via deep learning methods

This study investigates the damage evolution of sandstone under loading stresses, which can lead to irreversible plastic deformation and reduced project stability service life. To achieve this objective, we identify and quantify the emergence and expansion process of sandstone cracks using deep learning methods. Specifically, our approach employs a crack segmentation model enhanced by an attention mechanism, achieving a remarkable effective crack detection MIoU of 93.38. Through the application of connectivity domain analysis, skeleton extraction, and orthogonal projection techniques, we extract crucial crack parameters, which are subsequently formulated into equations to determine their actual dimensions. These evolving parameter variations serve as the foundation for predicting the sandstone's entire damage progression, encompassing both microscopic crack growth and eventual catastrophic failure preceding macroscopic manifestation of damage. Validation of our method through uniaxial compression tests on sandstone specimens confirm its efficacy and practical applicability. In conclusion, this study presents a novel framework for quantifying sandstone crack evolution, providing invaluable insights into the intricate mechanisms governing damage fracture progression in rocks.