Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease

The ultimate cause of blindness in glaucoma is the death of retinal ganglion cells, and understanding the mechanism behind retinal ganglion cell loss during glaucoma could lead to the development of novel treatments for glaucoma. Endothelin-1 has been shown to mediate retinal ganglion cell death during glaucoma through impairment of mitochondrial function. Retinal ganglion cells are highly metabolically active, and susceptible to oxidative damage and decreased respiratory capacity. Mitophagy is the process whereby damaged mitochondria are degraded to prevent further propagation of oxidative damage. The current study evaluates the effect of endothelin-1 on mitophagy in retinal ganglion cells. Electron microscopy revealed endothelin-1 administration lead to a decrease in healthy mitochondria in the optic nerve. The MitoQC mouse was used to evalute mitophagy in response to endothelin-1, along with immunohistochemical analysis of mitophagy proteins. Mitophagy follows different trends in the optic nerve and retinal ganglion cell bodies following endothelin-1 administration, mitophagy was increased in the optic nerve but decreased in the retina following endothelin administration. With elevation of intraocular pressure, mitophagy was increased in the retina but decreased in the optic nerve. In retinal ganglion cells, parkin expression and activation was unchanged 24 hours after endothelin-1 administration, but was decreased 72 hours following endothelin-1 administration. Taken together, these results suggest that endothelin-1 impacts mitophagy through parkin-independent mechanisms in retinal ganglion cell bodies, and the ganglion cell bodies and optic nerve appear to have different responses to endothelin-1.

Myotonic Dystrophy type 1 (DM1) is an autosomal multisystem disorder manifested due to unstable CTG nucleotide repeat expansion within the 3'-untranslated region of the dystrophia myotonica protein kinase (DMPK) gene. Although progress towards understanding of molecular pathogenesis in muscle and heart has been made, the pathways that affect the brain in DM1 is fundamentally unknown. In addition, the congenital DM1 manifest even more complicated brain abnormalities. Despite the wealth of existing cellular and animal models, iPSCs based studies are being fostered as they replicate the human model more closely to the disease. In view of this context, we set out to characterize the differentiation potential of congenital DM1 patient derived iPSC lines towards neuronal cells. Using neurogenin2 (NGN2) induced direct reprogramming of iPSCs into neurons and chemically defined media-induced neural induction protocol, we find that congenital DM1 mutant iPSC derived neurons exhibited precocious differentiation, as evidenced by their expression of pan-neuronal markers TUJ1 and Map2, along with increased processes extension and neurite length. Moreover, unbiased RNA sequencing analyses and qPCR validation revealed precocious and enhanced expression of several neurogenic transcription factors including, Ascl1, NeuroG2, and NeuroD1. Furthermore, immunofluorescence imaging of MBNL1 and MBNL2, RNA-splicing factors, displayed enhanced nuclear aggregations, a hallmark of the DM1 disease, in the mutant lines. Moreover, investigation of RNA splicing events identified mis-splicing in many important genes/transcripts including RMST, ANK3 and MBD1 during the neural conversion of congenital DM1 lines. These studies reveal novel paradigms that may contribute to neurological pathogenesis in CDM1 patients. These studies also provide a strong foundation for future mechanistic investigation aimed at understanding CDM1 pathology and may open new avenues for the development of gene therapy approaches for individuals with DM1.

Pathogenic mutations in the ABCA4 gene cause several inherited retinal diseases, particularly Stargardt disease (STGD1). However, many missense variants remain classified as variants of uncertain significance (VUS) due to inconclusive evidence regarding their pathogenic impact. The missense VUS span across all the domains of ABCA4, with the majority found in the larger extracellular domains (ECDs). The largest uncharacterized region of ABCA4 is located in ECD1, where limited structural information and inconsistent computational predictions hinder clinical interpretation of missense VUS in this region. Here, we integrated in silico analysis with in vitro functional assays to evaluate the pathogenicity of VUS in this region and improve their diagnostic classification. Missense VUS in the ECD1 uncharacterized region were curated from ClinVar. Six multiallelic sites were identified in the uncharacterized region and 13 missense VUS on these multiallelic sites were characterized using the integrated analysis. In the in silico platform, the pathogenicity of the VUS were predicted using multiple algorithms, and the structural effects of the variants were analyzed compared to the wild type. Recombinant variants were expressed in virus-like particles (VLPs), and protein expression, membrane localization, and ATPase activity were quantified relative to wild type to identify potential disease-causing variants. From the integrated analysis, variants with pronounced structural destabilization, impaired membrane trafficking, and reduced or absent N-retinylidene-phosphatidylethanolamine (NRPE) substrate stimulated ATPase activities were identified as potentially deleterious. Notably, VUS at p.H193P and p.I214N showed loss of function, with p.I214N reflecting selectively impaired membrane targeting and p.H193P reflecting combined expression and trafficking defects. Additionally, NRPE-stimulated ATPase activities were impaired in VUS, p.V195L, p.V195I, p.D197H, p.I214F and p.N269S. Overall structural destabilization interfered with the NRPE-stimulated ATPase activities of p.N269S, while the lack of NRPE-stimulated ATPase activities of p.D197H, p.V195L, p.V195I and p.I214F are thought to be due to impaired NRPE interactions with ABCA4. All the VUS at p.R140, p.H193Y, p.D197N and p.N269H showed both the basal and NRPE-stimulated ATPase activities but less than that of the wild type, displaying a mild functional deficit. Together, these findings demonstrated that certain VUS within the unresolved ECD1 region disrupt ABCA4 stability and function, supporting their contribution to disease pathogenesis. This integrative approach highlights key residues likely to be pathogenic and advances the interpretation of VUS in inherited retinal disorders.

Phenylketonuria (PKU) is a genetic metabolic disorder caused by the lack of functional phenylalanine hydroxylase (PAH). Elevated levels of phenylalanine (Phe) are known to be neurotoxic; however, the molecular mechanisms underlying Phe's effects remain elusive. This study investigates the impact of PKU on proteostasis, redox balance, and metabolism in BTBR PAHenu2 mice, a severe disease animal model. Combined proteomics and metabolomics revealed impaired redox homeostasis in the brain and disrupted mitochondrial energy metabolism (ATP and TCA intermediates). The dysregulation was further supported by decreased levels of ATP, reduced glutathione (GSH), cysteine, and reduced catalase activity. Western blot analyses revealed substantial remodeling of protein degradation systems: the 19S regulatory (Rpt1) subunit and 26S proteasome content and activity were significantly increased, and ubiquitinated protein levels were elevated, indicating protein turnover and activation of the ubiquitin-proteasome system. Autophagy was also activated, as evidenced by a reduced LC3-II/LC3-I ratio, decreased p62 levels, unchanged ATG5 levels, and increased HSPA8 protein expression. By contrast, UPR markers remained stable despite an increase in the oxidized-to-reduced PDI ratio, suggesting a localized shift without activation of a full ER stress response. In parallel, systemic alterations were assessed in whole blood. Indeed, GSH, cysteine, ATP and ADP were decreased in PKU, whereas NADPH increased. These changes were accompanied by reduced activities of GSH reductase and GSH peroxidase, thereby confirming metabolic and redox disruption. Collectively, these findings indicate that PKU is associated with activation of protein degradation pathways as an adaptive response to cellular stress combined with redox imbalance and energy dysregulation.

Objectives; The role of nuclear receptor subfamily 4, group A, member 3 (NR4A3) in hepatic steatosis, inflammation, and insulin resistance (IR) within the context of metabolic dysfunction-associated steatotic liver disease (MASLD) remains largely underexplored. Consequently, this study aimed to examine NR4A3's impact on MASLD and the potential underlying mechanisms. Methods; We aimed to elucidate the functional role of NR4A3 in MASLD through its knockdown in cell culture and animal models. To establish the cell culture model of MASLD, LO2 cells were treated with free fatty acids (FFAs), while male C57BL/6 mice were fed a high-fat diet (HFD) to create the animal model. NR4A3 knockdown was achieved using specific short hairpin RNA (NR4A3-shRNA) in the mice model and three small interfering RNAs (NR4A3-siRNAs) in the cell culture model. The lipids content, fatty acid synthesis, inflammatory factors, and IR were then assessed with and without NR4A3 knockdown. Furthermore, the underlying mechanism through which NR4A3 exerts its influence was explored by analyzing the interaction between NR4A3 and activating transcription factor 3 (ATF3). Results: In the cell culture experiments, the knockdown of NR4A3 significantly decreased the lipids content, fatty acid synthesis, and inflammatory factors in the LO2 cells treated with FFAs in the NR4A3-shRNA group compared with those in the NC-shRNA control group. In the animal model experiments, NR4A3 knockdown in the HFD male C57BL/6 mice significantly ameliorated HFD-induced hepatic steatosis, inflammation, and IR. Mechanistically, the knockdown of NR4A3 downregulated the expression and transcriptional activity of ATF3, resulting in an impaired ATF3 function. ATF3 overexpression significantly reversed lipid accumulation decline and reduced inflammation after NR4A3 knockdown. Conclusion: The downregulation of NR4A3 alleviates MASLD by modulating ATF3, suggesting this may be a promising therapeutic target.

Defects in lysosomal lipid handling provoke fatal disorders presenting neurovisceral symptoms with variable onset and life spans. A prime example is Niemann-Pick type C disease (NPCD), where export of cholesterol and other lipids from the endosomal-lysosomal system is impaired due to variants of either NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2). Therapeutic options for NPCD are limited to palliative care and disease-modifying drugs, and there is an unmet need for new treatments. Based on positive effects in patient-derived fibroblasts in vitro, we explored how inhibition of bromodomain and extra-terminal domain (BET) proteins affects a well-established mouse model bearing the frequent I1061T variant of NPC1. Treatment with JQ1, a hydrophobic prototype BET protein inhibitor, induced beneficial but sex-dependent molecular and behavioral changes in mice. Our results indicate bromodomain proteins as therapeutic drug target for NPCD and reveal sex-dependent BET protein signaling in mice.

Laminin-2 (gene: LAMA2) is a key protein in the basement membrane of muscle and Schwann cells. A complete lack of this protein results in LAMA2-related congenital muscular dystrophy (LAMA2-RD), a severe muscle disease characterized by progressive muscle weakness, respiratory insufficiency, failure to thrive and shortened life span. One key signature of this disease is early onset of fibrosis coupled with poor muscle growth. We previously showed that TGF-{beta} and its activator, integrin-V, are elevated in dystrophic fibers of DyW mice, a mouse model of LAMA2- RD. Other than activating TGF-{beta}, integrin-V is also known to facilitate the transdifferentiation of various cell types to myofibroblasts. In this study we present evidence for transcriptional dysregulation of genes driving myofibroblast transdifferentiation and extracellular matrix (ECM) remodelling during the early development of DyW mice that is also reflected in muscle biopsies from young LAMA2-RD patients. We hypothesize that the early ECM remodelling, seen in both DyW mice and LAMA2-RD children, may explain the congenital onset of fibrosis with poor muscle growth seen in the disease.

Pigment epithelial-derived factor (PEDF) is a multifunctional protein produced predominantly by the retinal pigment epithelium and expressed in many tissues, including the brain, highlighting its participation in crucial processes, such as neuroprotection and angiogenesis. Some neurodevelopmental disorders, such as ASD, are characterized by neurodevelopmental abnormalities, including altered neurite formation, spine formation, and neuronal activities. Many efforts have been made to resolve NDDs, but until now, some symptoms remain untargeted. PEDF is involved in many steps of neurodevelopment. The treatment of PEDF peptide might improve the outcome of NDD symptoms by altering neuronal morphologies. We used PEDF peptides that contain different functional domains to study the effect of administering PEDF peptides on neuronal morphology in a prenatal valproic acid (VPA)-exposed mouse model. We identified that the treatment with PEDF peptides rectified the abnormalities in neurite formation and spine formation in VPA-exposed cortical neurons. In vitro calcium imaging showed abnormalities in the spontaneous activity in VPA-exposed cortical neurons. Treatment of a short PEDF peptide normalized intracellular calcium response to the control level. Accordingly, PEDF peptides have the prospect of serving as potential treatments for patients with neurodevelopmental disorders, such as ASD.

The multiligand endocytic receptor, megalin (LRP2), is expressed in the retinal pigment epithelium (RPE) and patients lacking the receptor develop high myopia. Despite its established role in retinal development, the contribution of megalin to retinal homeostasis in the normally developed/mature eye remains poorly understood. Here, we investigated megalin function using an inducible knockout mouse (KO) model and human iPSC-derived RPE with megalin knockdown (KD) to distinguish post-developmental homeostatic functions from developmental effects. In vivo, megalin ablation caused progressive retinal degeneration and visual impairment, with morphological abnormalities in the RPE but no changes in myopia-associated ocular phenotypes including axial length and intraocular pressure. Proteomic profiling of megalin-KO RPE revealed reduction of autophagy-related proteins. In line with this, megalin deficiency was associated with accumulation of pro-cathepsin D, and perturbed rhodopsin turnover. This was supported in vitro, where trafficking of photoreceptor outer segment (POS) containing phagosomes to lysosomes was reduced, suggesting disturbed phagosome maturation. Megalin KD did not measurably impair initial uptake of POS discs, but delayed rhodopsin degradation, indicating defective post-ingestion processing. Together, these findings establish megalin as a key regulator of retinal homeostasis in the mature eye by controlling phagosome-lysosome fusion in the RPE and suggest that megalin dysfunction contributes to slowly progressive retinal degeneration. This positions megalin as a potential therapeutic target in lysosomal degenerative diseases in the retina.

BACKGROUNDTAR DNA binding protein - 43 (TDP-43) nuclear loss is a pathological hallmark of amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and related neurodegenerative disorders. While the consequences of TDP-43 dysfunction have been well-characterized, the mechanisms driving TDP-43 mislocalization remain poorly understood. Previous observations of altered localization and function of the adenosine-to-inosine (A-to-I) RNA editing enzyme adenosine deaminase acting on RNA 2 (ADAR2) in ALS/FTD tissue prompted us to investigate whether dysregulated RNA editing contributes to pathological TDP-43 nucleocytoplasmic trafficking. METHODSTDP-43 cytoplasmic mislocalization was assessed following ADAR2 and TDP-43 co-overexpression in HEK293T cells and a Drosophila model co-overexpressing human TDP-43 and dADAR in motor neurons. We further evaluated TDP-43 mislocalization through both HeLa cell assays and interspecies heterokaryon assays. Next, we assessed TDP-43 binding to A-to-I edited RNA oligomers through electrophoretic mobility shift assays (EMSAs), and investigated inosine-containing RNAs in vivo via TDP-43 RNA immunoprecipitation followed by sequencing (RIP-seq) datasets from human TDP-43-expressing Drosophila. Finally, RNAseq and enhanced cross-linking and immunoprecipitation (eCLIP-seq) were performed in SH-SY5Y cells overexpressing three ADAR2 variants with differing editing activity to identify editing-related transcriptional alterations and RNAs differentially bound to TDP-43. RESULTSADAR2 overexpression reduced the nucleocytoplasmic (N:C) ratio of TDP-43 in HEK293T cells in a ADAR2 catalytic activity- and TDP-43 RNA-binding capacity-dependent manner. Drosophila motor neurons overexpressing dADAR also exhibited decreased nuclear TDP-43. Interspecies heterokaryons and permeabilized HeLa cell assays demonstrated that catalytically active ADAR2 and synthetic inosine-containing RNA oligomers, respectively, enhance nuclear export of endogenous TDP-43. EMSAs revealed preferential binding of TDP-43 to inosine-containing RNAs relative to unedited RNAs, and analysis of Drosophila RIP-seq datasets demonstrated enrichment of edited transcripts within TDP-43-bound RNAs. Finally, RNAseq and eCLIP-seq analyses identified editing-dependent alterations in gene expression and TDP-43 RNA-binding profiles in SH-SY5Y cells overexpressing active ADAR2 variants. CONCLUSIONSTogether, our findings identify A-to-I RNA editing as a previously unrecognized regulator of TDP-43 localization and RNA interactions. These results support a model where altered RNA editing modifies TDP-43-RNA interactions, promoting increased nuclear export of TDP-43. Broadly, our work highlights RNA editing dysregulation as a potential contributor to early pathogenic mechanisms underlying TDP-43 proteinopathies.

Neurodegenerative diseases are complex disorders characterised by progressive neuronal loss and widespread transcriptomic dysregulation; however, the coordinated interactions among coding and non-coding RNAs that contribute to disease progression remain incompletely understood. In this study, RNA-seq datasets from disease-relevant neuronal populations and brain regions representing Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS) were analysed using an integrative network-based framework. Differential expression analysis coupled with weighted gene co-expression network analysis identified modules significantly correlated with disease and prioritised highly connected hub genes. Integration of these hub genes with curated RNA interaction database enabled the construction of candidate lncRNA-miRNA-mRNA regulatory networks. Functional enrichment analysis revealed Gene Ontology biological processes associated with synaptic signalling, mitochondrial function, RNA metabolism and neuroinflammatory responses across neurodegenerative conditions. The inferred regulatory networks suggested both disease-specific and shared post-transcriptional regulatory modules involving key hub genes and non-coding RNAs. Additionally, putative sequence variants were identified within untranslated regions of selected hub genes, suggesting potential alterations in miRNA-mediated regulations. Therefore, this study provides a systems-level view of transcriptomic dysregulation across major neurodegenerative diseases and identifies candidate regulatory interactions and molecular targets for future functional investigation

IntroductionThe quality of preclinical studies for rare diseases, such as Duchenne muscular dystrophy (DMD), relies on the availability of comprehensive natural disease history data. In addition to the classic BL10-mdx mouse, in recent years, the D2-mdx model has increasingly been used as an alternative model due to its reportedly more severely impaired phenotype. To improve our understanding of disease progression in these two DMD models, we conducted a comprehensive natural history study. Materials and MethodsThis involved a cross-sectional analysis of key in vivo and ex vivo outcome measures performed in two independent laboratories, using the same study setup in compliance with TREAT-NMD Standard Operating Procedures (SOPs), while also taking advantage of site-specific expertise. Globally, largely comparable results were obtained across the two study sites. ResultsBody composition showed pronounced differences between the strains, with BL10-mdx mice displaying a hypertrophic and D2-mdx mice displaying an atrophic phenotype. Dystrophic mice of each strain exhibited significant alterations of disease-relevant indices related to muscle functionality and integrity, mostly worsening with age, in comparison to their wildtypes. Cardiac function was affected earlier and more severely in D2-mdx mice. DiscussionNotably, for some parameters, genetic-background related differences were observed, emphasizing the need to include control groups with matching genetic backgrounds in experimental designs. ConclusionsCollectively, our natural history study provides benchmark data for these two mdx mouse strains to guide model selection for preclinical DMD studies, allowing accurate data interpretation. HighlightsO_LIDistinct body composition phenotypes: BL10-mdx mice exhibit pseudohypertrophy while D2-mdx mice display pronounced atrophy. C_LIO_LIEarlier cardiac dysfunction in D2-mdx: D2-mdx mice develop reduced ejection fraction and stroke volume from 28 weeks, while BL10-mdx only at 52 weeks. C_LIO_LIGenetic background-dependent variations: Intrinsic deficits in wildtype D2 mice demonstrate that genetic background influences outcome measures independent of dystrophic pathology. C_LIO_LIComparable ex vivo muscle physiology: Despite divergent in vivo phenotypes, isolated muscle contractile parameters show similar impairment in both dystrophic models. C_LIO_LIMulti-site standardized validation: Cross-sectional study at two independent laboratories following harmonized TREAT-NMD Standard Operating Procedures. C_LI

The neuromuscular junction (NMJ) is a specialised synapse between motor neurons and skeletal muscle, and its progressive deterioration contributes to age-related and metabolic disease-associated declines in muscle function. Advanced glycation end-products (AGEs) accumulate in tissues during ageing, diabetes, and chronic metabolic dysfunction and have been implicated in neuromuscular degeneration, yet their effects on the intact NMJ have not previously been examined in a human model system. This study employed a fully human, serum-free, and neural growth factor-free NMJ co-culture system, combining neural progenitor cells with immortalised human myoblasts derived from an 83-year-old donor, to investigate the effects of AGE exposure on neuromuscular integrity across structural, metabolic, functional, and secretory outcomes. AGE exposure induced significant reductions in motor neuron axonal length, myotube remodelling with centralised nuclear positioning, mitochondrial membrane depolarisation, elevated mitochondrial superoxide production, mitochondrial uncoupling, and reductions in spontaneous contraction intensity and frequency. Neurotrophic and myogenic growth factor signalling was significantly downregulated in AGE-treated co-cultures. These findings identify the NMJ as a sensitive target of glycation stress and establish this fully human co-culture platform as a physiologically relevant model for investigating glycation-related neuromuscular pathology and evaluating candidate therapeutic interventions.

Photoreceptors are among the most metabolically active cells in the retina and are therefore highly sensitive to fluctuations in oxygen availability. Age-related tissue changes in the eye affect oxygen delivery to the outer retina, which may result in hypoxic stress within photoreceptors and can contribute to disease development and retinal degeneration. To investigate how chronic hypoxic signalling affects photoreceptor metabolism, we examined a rod-pecific Vhl knockout mouse (RodVhl), in which constitutive HIF activation mimics the molecular response to hypoxia. Combining a cell-type-enriched multi-omics approach with metabolic flux analysis, we identified an early metabolic response in the retina of Rod{Delta}Vhl mice prior to degeneration. This response was characterized by a shift towards an oxidative redox environment indicated by a decrease in nucleotide precursors and an increased antioxidant response. While steady-state glycolytic flux remained unchanged, the dynamic 13C-glucose tracing revealed accelerated carbon flow through the three-carbon glycolytic intermediates, indicating a carbon rerouting. Outer segment lipidomics revealed selective remodelling of phosphatidylcholine and phosphatidylethanolamine species toward more oxidation-resistant and elongated acyl chains, supported by early gene upregulation of essential enzymes involved in fatty acid elongation, desaturation and oxidation. Together, these findings indicate a coordinated shift in metabolic and lipid pathways in photoreceptors under chronic hypoxic stress, consistent with an adaptive response that may help preserve outer segment integrity and improve stress resilience.

The aggregation of -synuclein (Syn) is a molecular hallmark of Parkinson's disease (PD) and other synucleinopathies. Understanding the molecular mechanisms that determine the aggregation of this protein may thus facilitate the development of disease-modifying therapies. While Syn is most commonly expressed as a 140-residue protein (Syn-140), recent evidence suggests an involvement of alternatively spliced Syn isoforms in disease onset and progression. Here, we report and characterise the interaction between Syn-140 and the aggregation-prone Syn-112 variant, one of the most abundant Syn splice isoforms. We found that amounts as low as 1% of Syn-112 accelerate the nucleation and aggregation of Syn-140. To further investigate this phenomenon, we employed MALDI-MS and NMR spectroscopy, confirming that Syn-140 and Syn-112 monomers interact strongly with one another. Furthermore, to assess the association of Syn-112 with disease pathology, we performed immunohistochemical staining combined with confocal microscopy on PD brain samples. Thereby, we found an increase in the number as well as the area of Syn-112 immunoreactive aggregates compared to healthy controls. These results illustrate how low-abundance Syn splice isoforms can modulate the aggregation landscape of Syn-140 and in turn contribute to the molecular heterogeneity of synucleinopathies.

The endoplasmic reticulum (ER) and its muscle-specialized form, the sarcoplasmic reticulum (SR), are crucial organelles in muscle cells, involved notably in protein synthesis, calcium regulation and muscle contraction. A well-known process involved in ER remodeling and homeostasis is ER-phagy, also called reticulophagy, a selective form of autophagic process in which ER-phagy receptors mediate the delivery of ER portions to lysosomes for degradation. SH3KBP1 is an adaptor protein involved in membrane trafficking. Recently, it was shown to control ER morphology and SR formation in striated skeletal muscle. In this study, we demonstrate that SH3KBP1 can bind to LC3B and CKAP4 proteins, bridging ER to autophagosome membranes, and is degraded by autophagy, in developing muscle fibers. Moreover, SH3KBP1 down-regulation impacts basal autophagy efficiency and ER-phagy stimulation; it also impairs the turnover of numerous ER-resident proteins. Our work highlights a new role for SH3KBP1 as a soluble ER-phagy receptor in striated skeletal muscle.

Purpose: Lymphatic system plays a critical role in fluid regulation and immune response. The conjunctiva of the ocular surface is endowed with a rich lymphatic network, and it provides an ideal site to study lymphatic structure and function. The purpose of this study is to investigate potential morphological and functional changes of conjunctival lymphatics with aging, a time-dependent biological deterioration process. Methods: Young and aged fluorescently labeled transgenic mice of Prox-1, the master control gene for lymphatic determination, were used in the study. For morphological assessment, conjunctival lymphatic vessels were examined in vivo by our advanced live imaging system. For functional analysis, lymphatic drainage efficiencies were measured by fluorescently labeled tracer injection. Results: Compared to young mice, both vascular branching points and intraluminal valves were significantly reduced in conjunctival lymphatic vessels of aged mice. Moreover, lymphatic functional deterioration and drainage deficiencies, such as fluid leakage and reflux, were also detected in the aged condition. Conclusions: Conjunctival lymphatic system undergoes morphological as well as functional changes with aging. Further investigation into this phenomenon may provide novel insights into lymphatic and age-related diseases inside and outside the eye.

BackgroundBiliary atresia (BA) is a severe neonatal liver disease characterized by progressive fibrosis and bile duct obliteration. ObjectiveAlthough immune dysregulation is implicated in the pathogenesis of BA, the specific mechanisms driving bile duct injury remain incompletely understood. This study aimed to characterize tertiary lymphoid structures (TLSs) within extrahepatic biliary remnants (EBRs), identify their cellular mediators, and evaluate the therapeutic potential of targeting IL-21 receptor signaling. DesignWe performed integrated bulk RNA sequencing, single-cell RNA sequencing, spatial transcriptomics, multiplex immunohistochemistry, and flow cytometry on clinical samples from BA patients and non-BA cholestatic controls. TLS maturation was assessed by CD23 immunohistochemistry in EBRs from 148 BA patients and correlated with clinical parameters. Anti-IL-21R antibody treatment was evaluated in a rhesus rotavirus-induced BA mouse model, with treatment initiated on day 4 post-infection. ResultsTLSs were identified in BA EBRs with significantly higher prevalence than in matched liver tissues. Mature TLSs containing CD23 germinal centers were associated with elevated serum matrix metalloproteinase-7, more advanced hepatic fibrosis, and localized autoantibody deposition on injured bile ducts. Single-cell profiling revealed expanded CD4+ T peripheral helper (Tph) cells expressing IL-21 and CXCL13 within TLS-containing EBRs. Tph cells were enriched in peripheral blood of BA patients compared to non-BA cholestatic controls (P = 0.0025), and serum IL-21 was significantly elevated (P < 0.0001). Post-infection IL-21R blockade in the mouse model reduced jaundice incidence, improved weight gain, prevented extrahepatic biliary obstruction, and significantly improved long-term survival. ConclusionTLSs in BA extrahepatic biliary remnants harbor expanded Tph cells associated with IL-21-mediated B cell activation and bile duct injury. IL-21R blockade ameliorated disease in a murine BA model, identifying the IL-21/IL-21R axis as a potential therapeutic target warranting further investigation. Key MessagesO_ST_ABSWhat is already known on this topicC_ST_ABSImmune dysregulation contributes to biliary atresia (BA), with documented lymphocyte infiltration and defective B cell tolerance. However, the cellular mechanisms linking local immune activation to bile duct injury are unclear, and the roles of organized lymphoid structures and specific CD4 T cell subsets in orchestrating local humoral responses have not been characterized. What this study addsThis study demonstrates that mature tertiary lymphoid structures in extrahepatic biliary remnants are associated with disease severity markers and localized bile duct injury in BA. We identify T peripheral helper cells as an expanded IL-21-producing CD4 T cell population within these structures, and show that post-infection IL-21 receptor blockade prevents biliary obstruction and improves survival in a murine BA model. How this study might affect research, practice or policyThese findings identify the IL-21/IL-21R signaling axis as a candidate therapeutic target in BA warranting further preclinical and translational investigation. TLS maturation status in biliary remnants and serum autoantibody levels may serve as potential biomarkers of disease severity, meriting prospective evaluation in clinical cohorts.

Background: Abdominal aortic aneurysms (AAA) are characterized by dilation of the aorta that can lead to aortic rupture and death. The transcriptional co-activators Yes-Associated Protein (YAP) and WW-domain-containing transcriptional co-activator with PDZ-binding motif (TAZ) are mechanosensitive effectors of the highly conserved Hippo signaling pathway. It is hypothesized that cell-specific YAP/TAZ signaling in endothelial cells (EC) plays a pivotal role in mediating AAA formation and rupture. Methods: Single-cell RNA-sequencing in human AAAs was performed and differentially expressed genes (DEGs) were identified in the endothelial cell cluster. YAP/TAZ mRNA and protein expression were also assessed in human AAA and control aortic tissue. Two established murine AAA models were used with male C57BL/6 and EC-CreERT2-YAPfl/fl/TAZfl/fl mice with/without Verteporfin (VPF, YAP/TAZ inhibitor) and XMU-MP-1 (YAP/TAZ activator) treatments. On postoperative days 14 and 28, aortic diameter, histology, cytokine, and MMP2 expressions were evaluated. Results: A significant alteration in EC-specific differentially expressed YAP/TAZ-related genes was observed in which 242 genes were upregulated and 71 genes were downregulated in AAA compared to controls. Human AAA tissue showed a significant increase in YAP and TAZ protein expressions compared to controls. Elastase-treated EC-YAP/TAZ-/- mice showed a significant decrease in AAA diameter compared to littermate controls. Histological quantification revealed preservation of -smooth muscle actin, reduced elastin fiber breaks, and decreased macrophage infiltration in EC-YAP/TAZ-/- mice compared to littermate controls. Importantly, pharmacological inhibition of YAP/TAZ using VPF significantly attenuated AAAs in two experimental murine models. In vitro data demonstrates that VPF inhibits endothelial cell YAP expression, downregulating pathways associated with pathogenic angiogenesis and vascular inflammation. Conclusions: These data suggest that EC-specific YAP/TAZ signaling mediates AAA formation. Pharmacological inhibition of the Hippo pathway can significantly mitigate aortic inflammation and vascular remodeling to decrease the progression of AAAs and prevent aortic rupture.

Hereditary spastic paraplegia type 7 (SPG7) is a neurodegenerative disorder characterized by progressive motor impairment and cerebellar dysfunction. Mutations in the SPG7 gene, encoding the mitochondrial metalloprotease paraplegin, disrupt mitochondrial homeostasis and lead to neuronal vulnerability and deficits in motor coordination. Recent studies have identified defective flickering of the mitochondrial permeability transition pore (mPTP) in SPG7 models, suggesting that altered pore dynamics may represent a functional biomarker of mitochondrial dysfunction. Here, we investigated whether pharmacological modulation of mPTP activity could improve mitochondrial function and motor performance in SPG7 models. Mitochondrial flickering was assessed in vitro, while motor behavior was evaluated in vivo following chronic treatment with berberine, a natural isoquinoline alkaloid known to modulate mitochondrial bioenergetics. Spg7-/- mice and age-matched Spg7+/ littermate controls received daily oral berberine administration for several weeks, and motor coordination was assessed using the accelerating rotarod test. Untreated Spg7-/- mice exhibited reduced rotarod performance compared with controls, indicating impaired motor coordination. Berberine treatment significantly improved motor performance in pre-symptomatic mutant mice. These findings indicate that pharmacological modulation of mitochondrial permeability transition pore dynamics can ameliorate motor dysfunction associated with SPG7 deficiency and highlight mPTP flickering as a functional readout of mitochondrial health.