Cell Compartment Research Articles

Macrophage membrane-reversibly camouflaged nanotherapeutics accelerate fracture healing by fostering MSCs recruitment and osteogenic differentiation

The fracture healing outcome is largely dependent on the quantities as well as osteogenic differentiation capacities of mesenchymal stem cells (MSCs) at the lesion site. Herein, macrophage membrane (MM)-reversibly cloaked nanocomplexes (NCs) are engineered for the lesion-targeted and hierarchical co-delivery of short stromal derived factor-1α peptide (sSDF-1α) and Ckip-1 small interfering RNA (Ckip-1 siRNA, siCkip-1) to promote bone repair by concurrently fostering recruitment and osteogenic differentiation of endogenous MSCs. To construct the NCs, a membrane-penetrating α-helical polypeptide first assembles with siCkip-1, and the cationic NCs are sequentially coated with catalase and an outer shell of sSDF-1α-anchored MM. Due to MM-assisted inflammation homing, intravenously injected NCs could efficiently accumulate at the fractured femur, where catalase decomposes the local hydrogen peroxide to generate oxygen bubbles that drives the shedding of sSDF-1α-anchored MM in the extracellular compartment. The exposed, cationic inner core thus enables robust trans-membrane delivery into MSCs to induce Ckip-1 silencing. Consequently, sSDF-1α-guided MSCs recruitment cooperates with siCkip-1-mediated osteogenic differentiation to facilitate bone formation and accelerate bone fracture healing. This study provides an enlightened strategy for the hierarchical co-delivery of macromolecular drugs into different cellular compartments, and it also renders a promising modality for the management of fracture healing.

Cytotoxic effects and comparative analysis of Ni ion uptake by osteoarthritic and physiological osteoblasts

Nickel(Ni)-containing materials have been widely used in a wide range of medical applications, including orthopaedics. Despite their excellent properties, there is still a problem with the release of nickel ions into the patient’s body, which can cause changes in the behaviour of surrounding cells and tissues. This study aims to evaluate the effects of Ni on bone cells with an emphasis on the determination of Ni localization in cellular compartments in time. For these purposes, one of the most suitable models for studying the effects induced by metal implants was used—the patient’s osteoarthritic cells. Thanks to this it was possible to simulate the pathophysiological conditions in the patient’s body, as well as to evaluate the response of the cells which come into direct contact with the material after the implantation of the joint replacement. The largest differences in cell viability, proliferation and cell cycle changes occurred between Ni 0.5 mM and 1 mM concentrations. Time-dependent localization of Ni in cells showed that there is a continuous transport of Ni ions between the nucleus and the cytoplasm, as well as between the cell and the environment. Moreover, osteoarthritic osteoblasts showed faster changes in concentration and ability to accumulate more Ni, especially in the nucleus, than physiological osteoblasts. The differences in Ni accumulation process explains the higher sensitivity of patient osteoblasts to Ni and may be crucial in further studies of implant-derived cytotoxic effects.

ICOS-expressing Regulatory T Cells Influence the Composition of Antitumor CTL Populations.

The role of ICOS in antitumor T cell responses and overall tumor progression has been controversial. In this study, we compared tumor progression in mice lacking ICOS selectively in regulatory T (Treg) cells or in all T cells. Using an experimental melanoma lung metastasis model, we found that Treg cell-specific ICOS knockout reduces the overall tumor burden compared with Cre control mice, with increased CD4+-to-Treg cell and CD8+-to-Treg cell ratios in the tumor. In contrast, there was no difference in the tumor burden in mice lacking ICOS in all of the T cell compartments. This suggests a dual role of ICOS costimulation in promoting protumor and antitumor T cell responses. Consistent with reduced tumor burden, we found that Treg cell-specific deletion of ICOS leads to an increase of CD8+ CTLs that express high levels of granzyme B and perforin. Moreover, single-cell transcriptome analysis revealed an increase of Ly108+Eomeshi CD8+ T cells at the cost of the Ly108+T-bethi subset in Treg cell-specific knockout mice. These results suggest that ICOS-expressing Treg cells suppress the CTL maturation process at the level of Eomes upregulation, a critical step known to drive perforin expression and cytotoxicity. Collectively, our data imply that cancer immunotherapies using ICOS agonist Abs may work better in Treg cell-low tumors or when they are combined with regimens that deplete tumor-infiltrating Treg cells.

Beneficial Effect of Pretreatment Hyperosmolality on Outcome in Severe Traumatic Brain Injury: Evidence from a South Korean Multicenter Registry and Propensity Score Matching Analysis.

Hyperosmolar therapy has long been a cornerstone in managing increased intracranial pressure and improving outcomes in severe traumatic brain injury (TBI). This therapy hinges on elevating serum osmolality, creating an osmotic gradient that draws excess water from the brain's cellular and interstitial compartments and effectively reducing cerebral edema. Given this information, we hypothesized that the serum hyperosmolality prior to any treatment could significantly impact the clinical outcomes of patients with severe TBI, potentially mitigating secondary cerebral edema after trauma. Data were extracted from the Korean Multi-center Traumatic Brain Injury data bank, encompassing 4628 patients with TBI admitted between January 2016 and December 2018. Of these, 507 patients diagnosed with severe TBI (Glasgow Coma Scale score < 9) were selected for comprehensive analysis across four data domains: clinical, laboratory, initial computed tomography scan, and treatment. Serum osmolality was assessed prior to treatment, and the hyperosmolar group was defined by a pretreatment serum osmolality exceeding 320mOsm/L, whereas favorable outcomes were characterized by a modified Rankin Scale score of ≤ 3 at 6months after trauma. Multivariate regression with receiver operating characteristic curve analysis and propensity score matching were used to dissect the data set. Multivariate analysis showed serum osmolality is significantly associated with clinical outcome in patients with severe TBI (p < 0.001). The optimal cutoff value for predicting favorable outcome was 331mOsm/L, with a sensitivity of 38.9% and a specificity of 87.7%. Notably, the propensity score matching analysis comparing patients with pretreatment serum hyperosmolality with those without indicated a markedly improved functional outcome in the former group (32.5% vs 18.8%, p = 0.025). The present study has uncovered a significant correlation between the pretreatment serum osmolality and the clinical outcomes of patients with severe TBI. These findings offer a novel perspective, indicating that a serum hyperosmolality prior to any treatment might potentially have a neuroprotective effect in patients with severe TBI.

REPRODUCTIVE AGEING: Altered histone modification landscapes underpin defects in uterine stromal cell decidualization in aging females.

Advanced maternal age is associated with a higher rate of pregnancy complications that are unrelated to karyotypic abnormalities of the oocyte. This study shows that the murine uterine stroma undergoes profound epigenetic changes affecting active and repressive histone modification profiles that are associated with impaired endometrial functionality and underpin the decline in reproductive performance of aged females. Decidualization describes the transformation of the uterine stroma in response to an implanting embryo, a process critical for supporting the development of the early embryo, for ensuring normal placentation and ultimately for a healthy reproductive outcome. Maternal age has been found to impede the progression of decidualization, heightening the risk of reproductive problems. Here, we set out to comprehensively characterize this deficit by pursuing transcriptomic and epigenomic profiling approaches specifically in the uterine stromal cell (UtSC) compartment of young and aged female mice. We find that UtSCs from aged females are globally far less responsive to the decidualization stimulus triggered by exposure to the steroid hormones estrogen and progesterone. Despite an overall transcriptional hyperactivation of genes that are differentially expressed as a function of maternal age, the hormonally regulated genes specifically fail to be activated in aged UtSCs. Moreover, even in their unstimulated 'ground' state, UtSCs from aged females are epigenetically distinct, as determined by genomic enrichment profiling for the active and repressive histone marks H3K4me3 and H3K9me3, respectively. We find that many hormone-inducible genes exhibit a profound lack of promoter-associated H3K4me3 in aged UtSCs, implying that a significant enrichment of active histone marks prior to gene stimulation is required to enable the elicitation of a rapid transcriptional response. With this combination of criteria, our data highlight specific deficits in epigenetic marking and gene expression of ion channels and vascular markers. These results point to fundamental defects in muscle-related and perivascular niche functions of the uterine stroma with advanced maternal age.

Challenges of Spatially Resolved Metabolism in Cancer Research.

Stable isotope-resolved metabolomics comprises a critical set of technologies that can be applied to a wide variety of systems, from isolated cells to whole organisms, to define metabolic pathway usage and responses to perturbations such as drugs or mutations, as well as providing the basis for flux analysis. As the diversity of stable isotope-enriched compounds is very high, and with newer approaches to multiplexing, the coverage of metabolism is now very extensive. However, as the complexity of the model increases, including more kinds of interacting cell types and interorgan communication, the analytical complexity also increases. Further, as studies move further into spatially resolved biology, new technical problems have to be overcome owing to the small number of analytes present in the confines of a single cell or cell compartment. Here, we review the overall goals and solutions made possible by stable isotope tracing and their applications to models of increasing complexity. Finally, we discuss progress and outstanding difficulties in high-resolution spatially resolved tracer-based metabolic studies.

Partitioning of an Enzyme-Polymer Surfactant Nanocomplex into Lipid-Rich Cellular Compartments Drives In Situ Hydrolysis of Organophosphates.

Most organophosphates (OPs) are hydrophobic, and after exposure, can sequester into lipophilic regions within the body, such as adipose tissue, resulting in long term chronic effects. Consequently, there is an urgent need for therapeutic agents that can decontaminate OPs in these hydrophobic regions. Accordingly, an enzyme-polymer surfactant nanocomplex is designed and tested comprising chemically supercharged phosphotriesterase (Agrobacterium radiobacter; arPTE) electrostatically conjugated to amphiphilic polymer surfactant chains ([cat.arPTE][S-]). Experimentally-derived structural data are combined with molecular dynamics (MD) simulations to provide atomic level detail on conformational ensembles of the nanocomplex using dielectric constants relevant to aqueous and lipidic microenvironments. These show the formation of a compact admicelle pseudophase surfactant corona under aqueous conditions, which reconfigures to yield an extended conformation at a low dielectric constant, providing insight into the mechanism underpinning cell membrane binding. Significantly, it demonstrated that [cat.arPTE][S-] spontaneously binds to human mesenchymal stem cell membranes (hMSCs), resulting in on-cell OP hydrolysis. Moreover, the nanoconstruct can endocytose and partition into the intracellular fatty vacuoles of adipocytes and hydrolyze sequestered OP.

Unveiling the Culprit: IL17 Signaling in the Pancreatic Epithelium Drives Tumorigenesis.

IL17 signaling promotes pancreatic cancer development, yet the cell compartment responsible for the protumorigenic function of IL17 has not been defined. In this article, Castro-Pando and colleagues demonstrate that IL17/IL17 receptor A signaling in the pancreatic epithelium is critical for pancreatic cancer initiation and for establishing immunosuppression, whereas its signaling in the immune compartment is dispensable. This work provides an important mechanistic insight on the role of IL17 signaling and identifies a potential new immune checkpoint as a target in pancreatic cancer. See related article by Castro-Pando et al., p. XXX (3).

ATP-P2X7R pathway activation limits the Tfh cell compartment during pediatric RSV infection.

Follicular helper T cells (Tfh) are pivotal in B cell responses. Activation of the purinergic receptor P2X7 on Tfh cells regulates their activity. We investigated the ATP-P2X7R axis in circulating Tfh (cTfh) cells during Respiratory Syncytial Virus (RSV) infection. We analyzed two cohorts: children with RSV infection (moderate, n=30; severe, n=21) and healthy children (n=23). We utilized ELISA to quantify the levels of PreF RSV protein-specific IgG antibodies, IL-21 cytokine, and soluble P2X7R (sP2X7R) in both plasma and nasopharyngeal aspirates (NPA). Additionally, luminometry was employed to determine ATP levels in plasma, NPA and supernatant culture. The frequency of cTfh cells, P2X7R expression, and plasmablasts were assessed by flow cytometry. To evaluate apoptosis, proliferation, and IL-21 production by cTfh cells, we cultured PBMCs in the presence of Bz-ATP and/or P2X7R antagonist (KN-62) and a flow cytometry analysis was performed. In children with severe RSV disease, we observed diminished titers of neutralizing anti-PreF IgG antibodies. Additionally, severe infections, compared to moderate cases, were associated with fewer cTfh cells and reduced plasma levels of IL-21. Our investigation revealed dysregulation in the ATP-P2X7R pathway during RSV infection. This was characterized by elevated ATP levels in both plasma and NPA samples, increased expression of P2X7R on cTfh cells, lower levels of sP2X7R, and heightened ATP release from PBMCs upon stimulation, particularly evident in severe cases. Importantly, ATP exposure decreased cTfh proliferative response and IL-21 production, while promoting their apoptosis. The P2X7R antagonist KN-62 mitigated these effects. Furthermore, disease severity positively correlated with ATP levels in plasma and NPA samples and inversely correlated with cTfh frequency. Our findings indicate that activation of the ATP-P2X7R pathway during RSV infection may contribute to limiting the cTfh cell compartment by promoting cell death and dysfunction, ultimately leading to increased disease severity.

Exosome-derived microRNAs: emerging players in vitiligo.

Exosome-derived microRNAs (miRNAs) are biomacromolecules and nanoscale extracellular vesicles originating from intracellular compartments that are secreted by most cells into the extracellular space. This review examines the formation and function of exosomal miRNAs in biological information transfer, explores the pathogenesis of vitiligo, and highlights the relationship between exosomal miRNAs and vitiligo. The aim is to deepen the understanding of how exosomal miRNAs influence immune imbalance, oxidative stress damage, melanocyte-keratinocyte interactions, and melanogenesis disorders in the development of vitiligo. This enhanced understanding may contribute to the development of potential diagnostic and therapeutic options for vitiligo.

Pancreatic epithelial IL-17/IL-17RA signaling drives B7-H4 expression to promote tumorigenesis.

IL-17 is required for the initiation and progression of pancreatic cancer, particularly in the context of inflammation, as previously shown by genetic and pharmacological approaches. The cellular compartment and downstream molecular mediators of IL-17-mediated pancreatic tumorigenesis have not been fully identified. We interrogated the cellular compartment required by generating transgenic animals with Interleukin 17 receptor A (IL-17RA) genetically deleted from the pancreatic epithelial compartment vs. the hematopoietic compartment via generation of IL-17RA-deficient (IL17-RA-/-) bone marrow chimeras, in the context of embryonically activated or inducible Kras. Deletion of IL-17RA from the pancreatic epithelial compartment, but not from hematopoietic, resulted in delayed premalignant lesions initiation and progression and increased CD8+ cytotoxic T cells infiltration to the tumor microenvironment. Absence of IL-17RA in the pancreatic compartment affected transcriptional profiles of epithelial cells, modulating stemness and immunological pathways. Interestingly, B7-H4, a known inhibitor of T cell activation encoded by the gene Vtcn1, was the most upregulated checkpoint molecule via IL17 early during pancreatic tumorigenesis, and its genetic deletion delayed pancreatic premalignant lesions development and reduced immunosuppression. We reveal pancreatic epithelial IL-17RA requirement for pancreatic tumorigenesis by reprogramming the immune pancreatic landscape which is partially orchestrated by regulation of B7-H4.

Liquid-Liquid Phase Separation Associated with Intrinsically Disordered Proteins: Experimental and Computational Tools.

The phenomenon of Liquid-Liquid Phase Separation (LLPS) serves as a vital mechanism for the spatial organization of biomolecules, significantly influencing the elementary processes within the cellular milieu. Intrinsically disordered proteins, or proteins endowed with intrinsically disordered regions, are pivotal in driving this biophysical process, thereby dictating the formation of non-membranous cellular compartments. Compelling evidence has linked aberrations in LLPS to the pathogenesis of various neurodegenerative diseases, underscored by the disordered proteins' proclivity to form pathological aggregates. This study meticulously evaluates the arsenal of contemporary experimental and computational methodologies dedicated to the examination of intrinsically disordered proteins within the context of LLPS. Through a discerning discourse on the capabilities and constraints of these investigative techniques, we unravel the intricate contributions of these ubiquitous proteins to LLPS and neurodegeneration. Moreover, we project a future trajectory for the field, contemplating on innovative research tools and their potential to elucidate the underlying mechanisms of LLPS, with the ultimate goal of fostering new therapeutic avenues for combating neurodegenerative disorders.

Flow cytometry in the differential diagnosis of myelodysplastic neoplasm with low blasts and cytopenia of other causes.

Myelodysplastic neoplasms (MDS) are characterized by cytopenia, morphologic dysplasia, and genetic abnormalities. Multiparameter flow cytometry (FCM) is recommended in the diagnostic work-up of suspected MDS, but alone is not sufficient to establish the diagnosis. Our aim was to investigate the diagnostic power of FCM in a heterogeneous population of patients with cytopenia, excluding cases with increased blast count. We analyzed bone marrow samples from 179 patients with cytopenia (58 MDS, 121 non-MDS) using a standardized 8-color FCM method. We evaluated the sensitivity, specificity, and accuracy of several simple diagnostic approaches, including Ogata score, extended Ogata score, the WHO and ELN iMDSFlow recommended "3 aberrations in two cell compartments method," and the combination of the Ogata score and "3 aberrations in two cell compartments method." The patients were followed until the diagnosis was confirmed, with a median follow-up of 2months (range 0.2-27). The combination of Ogata score and "3 aberrations in two cell compartments method" achieved the highest diagnostic accuracy (78%) with sensitivity and specificity 61% and 86%, respectively. When using only the "3 aberrations in two cell compartments method," the accuracy was 77% with a sensitivity of 72% and a specificity of 79%. The most frequently observed etiologies among the false positive cases were substrate deficiencies, inflammation/infection, or toxic effects. MDS can be excluded in all these cases after a thorough clinical evaluation and a relatively short follow-up. FCM remains an important but supplementary part in an integrated diagnostic process of MDS with low blasts. The combination of the Ogata score and the "3 aberrations in two cell compartments method" slightly improves accuracy compared to the detection of "3 aberrations in two cell compartments method" alone.

QMAP enabled microanatomical mapping of human skin aging.

Aging is a major driver of diseases in humans. Identifying features associated with aging is essential for designing robust intervention strategies and discovering novel biomarkers of aging. Extensive studies at both the molecular and organ/whole-body physiological scales have helped determined features associated with aging. However, the lack of meso-scale studies, particularly at the tissue level, limits the ability to translate findings made at molecular scale to impaired tissue functions associated with aging. In this work, we established a tissue image analysis workflow - quantitative micro-anatomical phenotyping (qMAP) - that leverages deep learning and machine vision to fully label tissue and cellular compartments in tissue sections. The fully mapped tissue images address the challenges of finding an interpretable feature set to quantitatively profile age-related microanatomic changes. We optimized qMAP for skin tissues and applied it to a cohort of 99 donors aged 14 to 92. We extracted 914 microanatomic features and found that a broad spectrum of these features, represented by 10 cores processes, are strongly associated with aging. Our analysis shows that microanatomical features of the skin can predict aging with a mean absolute error (MAE) of 7.7 years, comparable to state-of-the-art epigenetic clocks. Our study demonstrates that tissue-level architectural changes are strongly associated with aging and represent a novel category of aging biomarkers that complement molecular markers. Our results highlight the complex and underexplored multi-scale relationship between molecular and tissue microanatomic scales.

Single cell view of tumor microenvironment gradients in pleural mesothelioma.

Immunotherapies have shown great promise in pleural mesothelioma (PM), yet most patients still do not achieve significant clinical response, highlighting the importance of improving understanding of the tumor microenvironment (TME). Here, we utilized high-throughput, single-cell RNA-sequencing to de novo identify 54 expression programs and construct a comprehensive cellular catalogue of the PM TME. We found four cancer-intrinsic programs associated with poor disease outcome and a novel fetal-like, endothelial cell population that likely responds to VEGF signaling and promotes angiogenesis. Throughout cellular compartments, we observe substantial difference in the TME associated with a cancer-intrinsic sarcomatoid signature, including enrichment in fetal-like endothelial cells, CXCL9+ macrophages, cytotoxic, exhausted, and regulatory T cells, which we validated using imaging and bulk deconvolution analyses on independent cohorts. Finally, we show, both computationally and experimentally, that NKG2A-HLA-E interaction between NK and tumor cells represents an important new therapeutic axis in PM, especially for epithelioid cases.

IDO+ Endothelial Cells in Glomeruli of Kidney Transplantation Patients With Glomerulitis.

Kidney transplantation is the preferred treatment option for patients with end-stage renal disease. However, long-term graft survival remains a challenge. The enzyme indoleamine 2,3 dioxygenase (IDO) has been reported to have immunomodulatory effects with IDO transcripts being elevated in both antibody-mediated rejection and T cell-mediated rejection. A metal-conjugated antibody panel for the staining of kidney biopsies was developed, allowing the visualization of 41 structural and immune markers on a single tissue slide to gain in-depth insight into the composition and localization of the immune cell compartment. Staining was applied to week 4 and 24 protocol biopsies of 49 patients as well as on 15 indication biopsies of the TRITON study and 4 additional transplantation biopsies with glomerulitis. A highly distinctive and specific glomerular IDO expression was observed in biopsies from 3 of 49 patients in imaging mass cytometry. Immunohistochemistry confirmed IDO expression in glomeruli of 10 of 10 cases with glomerulitis. IDO was found to be expressed by CD31+ glomerular endothelial cells, accompanied by the presence of granzyme-B+Tbet+CD7+CD45RA+ natural killer cells and CD68+ macrophages. Furthermore, a proportion of both the immune cells and endothelial cells expressed Ki-67, indicative of cell proliferation, which was not observed in control glomeruli. Our results show glomerular IDO expression in transplanted kidneys with glomerulitis, which is accompanied by increased numbers of natural killer cells and macrophages and likely reflects local immune activation.

A cargo sorting receptor mediates chloroplast protein trafficking through the secretory pathway.

Nucleus-encoded chloroplast proteins can be transported via the secretory pathway. The molecular mechanisms underlying the trafficking of chloroplast proteins between the intracellular compartments are largely unclear, and a cargo sorting receptor has not previously been identified in the secretory pathway. Here we report a cargo sorting receptor that is specifically present in Viridiplantae and mediates the transport of cargo proteins to the chloroplast. Using a forward genetic analysis, we identified a gene encoding a transmembrane protein (MtTP930) in barrel medic (Medicago truncatula). Mutation of MtTP930 resulted in impaired chloroplast function and a dwarf phenotype. MtTP930 is highly expressed in the aerial parts of the plant and is localized to the ER exit sites (ERESs) and Golgi. MtTP930 contains typical cargo sorting receptor motifs, interacts with Sar1, Sec12 and Sec24, and participates in coat protein II (COPII) vesicular transport. Importantly, MtTP930 can recognize the cargo proteins plastidial N-glycosylated nucleotide pyrophosphatase/ phosphodiesterase (MtNPP) and α-carbonic anhydrase (MtCAH) in the ER, and then transport them to the chloroplast via the secretory pathway. Mutation of a homolog of MtTP930 in Arabidopsis (Arabidopsis thaliana) resulted in a similar dwarf phenotype. Furthermore, MtNPP-GFP failed to localize to chloroplasts when transgenically expressed in Attp930 protoplasts, implying that these cargo sorting receptors are conserved in plants. These findings fill a gap in our understanding of the mechanism by which chloroplast proteins are sorted and transported via the secretory pathway.

Nasal tau immunotherapy clears intracellular tau pathology and improves cognitive functions in aged tauopathy mice.

Pathological tau aggregates cause cognitive decline in neurodegenerative tauopathies, including Alzheimer's disease (AD). These aggregates are prevalent within intracellular compartments. Current tau immunotherapies have shown limited efficacy in clearing intracellular tau aggregates and improving cognition in clinical trials. In this study, we developed toxic tau conformation-specific monoclonal antibody-2 (TTCM2), which selectively recognized pathological tau aggregates in brain tissues from patients with AD, dementia with Lewy bodies (DLB), and progressive supranuclear palsy (PSP). TTCM2 potently inhibited tau-seeding activity, an essential mechanism underlying tauopathy progression. To effectively target intracellular tau aggregates and ensure rapid delivery to the brain, TTCM2 was loaded in micelles (TTCM2-ms) and administered through the intranasal route. We found that intranasally administered TTCM2-ms efficiently entered the brain in hTau-tauopathy mice, targeting pathological tau in intracellular compartments. Moreover, a single intranasal dose of TTCM2-ms effectively cleared pathological tau, elevated synaptic proteins, and improved cognitive functions in aged tauopathy mice. Mechanistic studies revealed that TTCM2-ms cleared intracellular, synaptic, and seed-competent tau aggregates through tripartite motif-containing 21 (TRIM21), an intracellular antibody receptor and E3 ubiquitin ligase known to facilitate proteasomal degradation of cytosolic antibody-bound proteins. TRIM21 was found to be essential for TTCM2-ms-mediated clearance of tau pathology. Our study collectively provides evidence of the effectiveness of nasal tau immunotherapy in targeting and clearing intracellular tau pathology through TRIM21 and enhancing cognition in aged tauopathy mice. This study could be valuable in designing effective tau immunotherapies for AD and other tauopathies.

TDP-43 in nuclear condensates: where, how, and why.

TDP-43 is an abundant and ubiquitously expressed nuclear protein that becomes dysfunctional in a spectrum of neurodegenerative diseases. TDP-43's ability to phase separate and form/enter biomolecular condensates of varying size and composition is critical for its functionality. Despite the high density of phase-separated assemblies in the nucleus and the nuclear abundance of TDP-43, our understanding of the condensate-TDP-43 relationship in this cellular compartment is only emerging. Recent studies have also suggested that misregulation of nuclear TDP-43 condensation is an early event in the neurodegenerative disease amyotrophic lateral sclerosis. This review aims to draw attention to the nuclear facet of functional and aberrant TDP-43 condensation. We will summarise the current knowledge on how TDP-43 containing nuclear condensates form and function and how their homeostasis is affected in disease.

P-354 Advanced Paternal Age (APA) amplifies cryopreservation-induced stress in human spermatozoa

Abstract Study question Does paternal age intensify the negative effects of cryopreservation on sperm quality? Summary answer Paternal age exacerbates the adverse impact of cryopreservation on sperm quality. What is known already Despite mounting evidence indicating age-related declines in sperm quality, the impact of APA on male fertility remains unclear. APA raises questions about DNA fragmentation and mitochondrial activity, a robust indicator of sperm functionality. While sperm cryopreservation is extensively employed in fertility preservation and assisted reproductive technology (ART), its potentially detrimental effects on cells compartments, including mitochondria, persist. The mechanisms of APA on sperm susceptibility to cryopreservation-induced cellular damage still need to be addressed. Study design, size, duration This prospective multicentric study, conducted between January and October 2023, comprised 200 men. Only normozoospermic samples were included in the research (n = 81). Then, based on their age, the participants were categorised into two groups: ages ≤35 (non-APA, n = 40) and ages ≥42 (APA, n = 41). The cohorts were stratified into distinct subgroups, encompassing both fresh and frozen/thawed specimens of APA and non-APA sperm, and subjected to evaluations encompassing mitochondrial functionality, acrosomal reaction, DNA fragmentation and Tyrosine phosphorylation. Participants/materials, setting, methods Semen samples were collected after 2-7 days abstinence and analysed according to WHO 2021 guidelines. Acrosomal status was determined using FITC-conjugate PSA. DNA fragmentation was examined with the Halosperm kit. Mitochondrial functionality was gauged using MitoTracker Red CMXRos through the percentage of stained cells and fluorescence intensity and PCR for mitochondrial DNA copy number (mtDNAcn). Tyrosine phosphorylation was assessed through immunofluorescence and Western Blotting. Main results and the role of chance Non-APA group exhibited significantly superior fresh semen characteristics. DNA fragmentation was notably elevated in fresh semen from APA group, reaching 21.7%, compared to 15.4% non-APA individuals. After cryopreservation, the DNA fragmentation index further increased in men over 42 years to 26.7%. Mitochondrial functionality analysis indicated a significant decrease in staining intensity in cryopreserved sperm, notably in the APA group, with mean fluorescence intensity decreasing from 3.35±1.5 to 1.8±0.5. In contrast, the non-APA group experienced a drop from 3.33±1.6 to 2.53±1.6. Additionally, in the APA group, a significant increase in mtDNAcn was observed in both fresh and frozen/thawed sperm compared to the younger counterparts, indicative of poor mitochondrial quality. Cryopreservation negatively impacted acrosome integrity in both age groups, with a significant decrease observed in unreacted acrosomes from 71.5% to 57.7% in the non-APA group and from 75% to 63% in the APA group. Furthermore, exploration of capacitation-like changes, like tyrosine phosphorylation, demonstrated a significant decrease with age and a negative impact of cryopreservation on tyrosine phosphorylation in sperm from young males. Limitations, reasons for caution Main limitations are the small number of examined samples and the inclusion of only normozoospermic patients. Therefore, future investigations are needed to provide a more comprehensive understanding of the impact of paternal age on cryopreservation-induced stress in human spermatozoa. Wider implications of the findings Our research sheds light on the influence of paternal age on sperm cryopreservation, revealing higher vulnerability of mitochondria and elevated DNA fragmentation in APA. These findings should be considered when advising older men on choosing cryopreservation techniques in assisted reproductive treatments. Trial registration number Not applicable