The glomerular filtration barrier (GFB) is a size- and charge-selective filter regulating the passage of blood-borne solutes into the urinary space. However, solutes within the GFB may also originate from podocyte secretion, including extracellular matrix (ECM) components and signaling molecules. We developed a two-dimensional computational solute transport model incorporating two cross-sectional GFB geometries: one based on averaged rodent data and one reconstructed from a healthy adult human glomerular image. Four cases were examined, defined by the solute's source and its ability to pass the podocyte slit diaphragm. To account for a wide range of solute types, solute mobility, described by the effective diffusion coefficient (Deff), was varied over six orders of magnitude. For blood-borne solutes unable to pass the slit diaphragm, a steep concentration gradient forms, with the highest concentration adjacent to the podocytes. This gradient becomes steeper as Deff decreases, corresponding to larger or less mobile solutes. This finding has implications for barrier clogging and for mechanisms that may increase Deff, including the role of ECM fixed charge density or ECM turnover. For podocyte-synthesized solutes to move against filtrate flow, without being rapidly lost to the urinary space, the model suggests solutes must possess properties preventing passage through the slit diaphragm. This result provides context for the relatively large signaling molecule complexes and ECM components. Together, these findings suggest that the structural organization of the GFB, particularly the slit diaphragm, enables solute distribution and directional transport, and therefore provides insight into GFB maintenance and pathology.
The use of cannabinoid has been implicated in the treatment of various skin disorders with obscure mechanism of action. This study aimed to investigate the physiological roles of GPR55 in regenerating skin wounds and protecting keratinocyte apoptosis induced by UVB radiation. Here, we found that O1602, a GPR55 agonist, accelerated wound healing in keratinocyte-like HaCaT cells, and this effect was suppressed by pretreatment with inhibitors of protein kinase A (PKA), AMP-activated protein kinase (AMPK), sirtuin-1 (SIRT-1), and extracellular signal-regulated kinase (ERK). Although O1602 treatment promoted keratinocyte proliferation in HaCaT cell line but its proliferative effect did not contribute to enhancing wound healing. Indeed, O1602 upregulated expression of MMP-9, suggesting the stimulation of cell migration. O1602 treatment protected against UVB-induced keratinocyte apoptosis, and this effect was abolished by pretreatment with inhibitors belonging to the same class as that which suppressed the wound-healing response. Furthermore, western blotting analyses revealed that O1602 treatment induced AMPK phosphorylation, and this effect was inhibited by pretreatment of PKA inhibitor. Moreover, O1602 promoted ERK phosphorylation, and this effect was aborted by pretreatment of either AMPK inhibitor or SIRT-1 inhibitor. Enzymatic activation of SIRT-1 induced by O1602 was absent in AMPK inhibitor-pretreated HaCaT cells. Altogether, GPR55 mediates keratinocyte regeneration and exhibits its protective effect against UVB exposure via PKA/AMPK/SIRT-1/ERK-dependent mechanism.
A key bottleneck in preclinical vaccine research is the lack of a human in vitro system that faithfully models the germinal center (GC) reactions, a critical process for generating protective antibodies. This gap hinders the accurate assessment of vaccine candidates. The tonsil is a key component of the mucosal immune system in the oropharynx, acting as its first-line immune sentinel. We established a novel human tonsil organoid platform and stimulated it with the chimpanzee adenovirus serotype 68-19 spike protein (AdC68-19S) SARS-CoV-2 vaccine candidate. Cellular immune phenotypes were analyzed by flow cytometry, while spatial organization was assessed via immunofluorescence. Functional immune responses were quantified using enzyme-linked immunosorbent assay, enzyme-linked immunospot assay, and pseudovirus neutralization tests to measure antigen-specific antibodies production and their neutralizing capacity. AdC68‑19S immunization elicited coordinated GC reactions in tonsil organoids, characterized spatially by the formation of discrete GC compartments, specifically an AICDA+ dark zone and a PD‑1+ light zone. This reorganization was accompanied by a marked expansion of key effector populations, including GC B cells and plasma cells. Functionally, the platform generated antibody‑secreting cells as well as antigen‑specific IgG and IgA antibodies, these antibodies demonstrated neutralizing capacity against the SARS‑CoV‑2 pseudovirus. The human tonsil organoids platform represents a paradigm shift in vitro immunology, establishing a system that recapitulates key features of adaptive immune responses induced by AdC68-19S vaccine. This approach provides a robust, physiologically relevant, and ethically viable model to advance our understanding of human immunity, oral immune barrier and accelerate vaccine development.
Claudins were identified in 1998 as structural and functional components of tight junction (TJ) seals between adjacent epithelial cells. Since their identification, pharmaceutical research has mainly focused on junctional claudins. For example, permeation enhancers that modulate claudin-based TJ seals have been developed to enhance gastrointestinal, pulmonary, and epidermal absorption of drugs. Inflammation, a common feature of various diseases, is often accompanied by the disruption of claudin-based seals. Consequently, junctional claudin modulators have been developed for treating inflammatory diseases. In 2022, antibodies against non-junctional claudin-1 were produced, and these antibodies attenuated hepatic fibrosis by inhibiting a fibrotic signaling pathway that depends on non-junctional claudin-1. Claudin-targeted drug development has entered a new era, transitioning from the barrier function of TJ claudins to signaling hub-associated claudins. In this review, we discuss recent findings on claudins as drug targets in relation to fibrosis, autophagy, and metabolism, focusing specifically on their functions as signaling hubs.
The human small intestine depends on villi to generate the large absorptive surface area required for nutrient uptake and barrier integrity. Existing human in vitro models fail to reproduce early villus morphogenesis, as they lack developmental signaling and epithelial-mesenchymal interactions that drive villus initiation. Such models are crucial for understanding the mechanisms of human villus formation to study intestinal development and disease. This study aimed to establish a human organotypic intestine model that recapitulates early villus development and to compare its features with human embryos. Primary organoid-derived epithelial cells containing intestinal stem and progenitor populations, and Caco-2/HT29 cocultures (as reference) were both cultured on a hydrogel containing primary small-intestinal stromal cells in a Transwell system. Models were assessed by histology, electron microscopy, transepithelial electrical resistance (TEER), permeability assays, gene expression analysis, growth factor secretion, and comparison with human embryonic duodenum (Carnegie stages 20-23). Both models formed polarized epithelial monolayers with sparse microvilli compared with mature in vivo intestine. Strikingly, only the organoid-derived model generated stromal cell and extracellular matrix (ECM)-filled epithelial protrusions with localized laminin deposition. This model activated key developmental pathways (SHH, PDGF-AA, BMP4, and WNT5A), upregulated villus-associated transcription factors (FOXF1, FOXF2, and FOXL1), and expressed laminin isoforms linked to villus initiation. The morphology and height of the protrusions (approx. 28 µm) closely resembled early villi in Carnegie stage 21 embryos.
Erlotinib, an epidermal growth factor receptor (EGFR) inhibitor, is widely used in cancer therapy but frequently causes cutaneous adverse effects that suggest impairment of the epidermal barrier. To better understand the underlying mechanisms, we examined how erlotinib affects barrier integrity, with a focus on tight junctions (TJs) and their relation with the actin cytoskeleton. Using human and mouse ex vivo epidermis as well as cultured keratinocytes, we assessed junctional assembly and stability under pharmacological inhibition of EGFR and Src. Erlotinib treatment disrupted the epithelial barrier, as demonstrated by enhanced biotin tracer penetration and a marked reduction in transepithelial electrical resistance. In line with functional impairment, erlotinib reduced EGFR and Src activity disturbing maturation of junctions, as evidenced by discontinuous claudin-1 and ZO-1 localization. Furthermore, erlotinib induced a loss of the apically localized tension-sensitive conformation of α-catenin in the stratum granulosum and in cultured keratinocytes. This was accompanied by disorganization of cortical actin and increased presence of stress fibers, in parallel with elevated activation of RhoA and phosphorylation of MLC2. Inhibition of Src with PP2 led to similar effects on barrier integrity. However, this detrimental outcome could be rescued by EGF treatment. Together, these findings indicate that erlotinib impairs epidermal barrier function by affecting junctional maturation via disrupted α-catenin membrane distribution, and ultimately, TJ stability involving intracellular contraction and tension. Thus, strategies focused on targeting tension‑related mechanisms downstream of EGFR/Src might help prevent or alleviate the cutaneous toxicities associated with EGFR inhibitory therapies.
Central nervous system (CNS) relapse is a serious complication of diffuse large B-Cell lymphoma (DLBCL), often associated with poor clinical outcomes. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) enables detection of subtle blood-brain barrier (BBB) leakage. We assessed BBB permeability, using the Patlak model, in 63 patients with DLBCL without CNS involvement and 11 healthy controls using DCE-MRI, and investigated associations with established risk factors for CNS relapse. Patients with high risk of CNS relapse (CNS-IPI ≥4) demonstrated near-significant increased BBB permeability in cortical gray matter (GM) compared with both low-risk patients (p = 0.053) and healthy controls (p = 0.02). BBB permeability in cortical GM and in cerebral white matter (WM) correlated positively with age (p < 0.001). After adjusting for age, patients with kidney and/or adrenal involvement exhibited significantly higher BBB permeability in cortical GM (p = 0.04). Furthermore, plasma albumin levels were inversely correlated with BBB permeability in both GM (p = 0.003) and WM (p = 0.005). These findings indicate that subclinical BBB dysfunction may contribute to CNS vulnerability in DLBCL, potentially predisposing patients to relapse even before CNS involvement occurs. The observed age-related increase in BBB permeability is consistent with previous reports and may represent an independent risk for CNS relapse. Collectively, these results suggest that BBB imaging could improve CNS risk stratification in DLBCL. Prospective studies are warranted to determine whether early BBB alterations can predict CNS relapse in individual patients.
Preterm infants are prone to gastrointestinal complications such as infectious diseases and necrotizing enterocolitis, which are associated with intestinal inflammation and increased intestinal permeability. Intestinal epithelial barrier (IEB) function is known to be immature in preterm neonates; however, our understanding of how the IEB develops - particularly the formation of junctional complexes - remains limited. Here, we analyzed intestinal tissue specimens from healthy resection margins of six very immature preterm infants who underwent bowel resection due to focal intestinal perforation (at the chronological age of 25 to 28 weeks' gestation), and compared the composition of tight junctions, adherens junctions and desmosomes to that of adults. Using immunostaining, our observations show, that tight junction proteins Claudin-2, Claudin-3 and Occludin, adherens junction proteins E-cadherin and β-Catenin as well as desmosomal proteins Plakoglobin and Plakophilin-2 appeared as mature as in adults as early as 25 weeks' gestation. However, Claudin-1, -4 and -5, as well as ZO-1 staining patterns increased and became more defined with increasing gestational age, suggesting junctional maturation during gestational week 26 and 27. Desmosomal protein Desmocollin-2 was increased until 26 weeks' gestation whereas Desmoglein-2 and Desmoplakin expression was immature at 28 weeks' gestation compared to the expression in adults. Our study provides the first sequential characterization of junctional protein maturation across all major IEB components early in life in human samples. These findings may help identify key mechanisms underlying intestinal barrier-associated pathologies in preterm infants.
Epidermal barrier (EB) function is too often reduced to the role of a passive, inanimate upper strata of dead corneocytes surrounded by extruded lipids. However, this summary fails to appreciate the lower strata keratinocytes (KCs) which serve as both sensors and effectors of immune signaling and thus contribute a dynamic, responsive nature to EB and maintenance and possible decline. In this context, underpinnings of chronic inflammatory skin diseases, e.g. psoriasis and atopic dermatitis, can be better recognized as a feed forward loop in which barrier dysfunction and runaway inflammatory signaling reinforce one another. Traditional therapies addressing these diseases focus on quelling effects and activities of pro-inflammatory extracellular cytokines and their cognate receptors. This paradigm overlooks the promising alternative of augmenting endogenous negative regulators of inflammatory signaling, e.g. the proteins A20 (TNFAIP3) and TNIP1 (ABIN-1) which we propose act as "guardians" restricting NF-κB-dependent inflammatory pathways. Here, we explore the rationale and possible means for targeting these regulators to protect or restore EB integrity. Bolstering these intrinsic quenchers of inflammatory signal progression may offer a path to restore tissue homeostasis and repair the EB in chronic inflammatory disease states.
The ability to overcome numerous tissue barriers during metastasis is a characteristic feature of tumor cells. This ability is acquired during tumor progression and represents a significant challenge for the development of therapeutic strategies. The intermediate filament protein vimentin is an important regulator of the cellular mechanisms that enable overcoming of tissue barriers. While vimentin was previously considered an activator of cell migration, raising hopes of halting metastasis by suppressing its expression, recent data indicate that vimentin's role in regulating tumor cell spreading is far more complex, and in some cases, vimentin suppression can stimulate migration. In this review, we analyze the latest data regarding the involvement of vimentin intermediate filaments in regulation of tumor cell migratory plasticity and examine the key cellular mechanisms involved in this regulation. Knowledge of these mechanisms is important for understanding the regulation of metastasis processes.
Pancreatic ductal adenocarcinoma (PDAC) remains among the deadliest malignancies, driven by its invasive nature and lack of effective biomarkers. Disruption of the epithelial barrier, mediated by tight junction components, is a critical yet underexplored contributor to PDAC progression. Claudins, integral regulators of tight junction integrity, display altered expression across cancers, but their prognostic and immunomodulatory roles in PDAC remain unclear. We performed an integrative analysis of 177 RNA-Seq datasets from TCGA and GTEx to characterize Claudin family alterations in PDAC. Differential expression, copy number variation, methylation, and co-expression networks were analyzed alongside clinical and survival data. Prognostic significance was assessed using Kaplan - Meier and Cox regression analyses, while immune cell infiltration was examined using deconvolution algorithms. Functional validation of Claudin-1 was conducted in Capan-1 cells using CRISPR/Cas9 knockout, followed by proliferation, wound-healing, and Western blot assays. Ten Claudin genes were significantly dysregulated, with Claudin-1 and Claudin-4 frequently amplified and associated with advanced stage and poor survival. High Claudin-1 expression correlated with reduced immune infiltration, indicating an immune-excluded phenotype characterized by immune cells retained in the tumor stroma but largely absent from the tumor parenchyma. Claudin-1 knockout markedly inhibited proliferation, migration, and EMT, evidenced by downregulation of Snail and Slug and restoration of E-cadherin expression. This integrative transcriptomic and functional study identifies Claudin-1 as a key driver of PDAC aggressiveness and immune modulation. These findings establish Claudin-1 as a promising prognostic biomarker and therapeutic target for restoring epithelial integrity and counteracting immune evasion in pancreatic cancer.
Neurodevelopmental and psychiatric disorders, such as attention deficit hyperactivity disorder or autism spectrum disorder, have been intricately linked to structural impairments and compromised permeability of the blood-brain barrier (BBB). Occludin (ocln) is a tight junction (TJ) protein known for its role in maintaining BBB integrity. In the present manuscript, we report unexpected connection between ocln deficiency and behavioral alterations resembling neurodevelopmental and psychiatric disorders. Adolescent, occludin-deficient (ocln-/-) mice displayed an abnormal growth and neurological phenotype along with deterioration of motor functions as compared to wild-type controls. Moreover, adult ocln-/- mice exhibited increased hyperactivity, social difficulties, and attention deficits compared to control mice. Among the brain structures, the hippocampus appeared to be most susceptible to ocln deficiency as it exhibited higher expression levels of ocln than both the frontal cortex and striatum. Overall, the observed behavioral alteration patterns in ocln-/- mice indicated pronounced neurological motor dysfunction and behavioral changes that parallel those seen in attention deficit hyperactivity disorder and autism spectrum disorder. These findings are important for better understanding the role of ocln in neurodevelopmental and psychiatric disorders.
Psychiatric disorders such as depression, bipolar disorder, schizophrenia, and autism spectrum disorder are increasingly understood not only as disruptions in brain chemistry or circuitry but also as disorders of neural microenvironments and barriers. This review explores the critical role of claudins, transmembrane proteins that form tight junctions, in maintaining the integrity of the blood - brain barrier (BBB) and other brain structures. Claudin-5, prominently expressed in the BBB, and claudin-11, essential for myelin integrity, emerge as central players in psychiatric pathophysiology. Evidence from human postmortem studies, serum biomarkers, and animal models indicates that claudin-5 is downregulated in key brain regions in depression, bipolar disorder, and schizophrenia, contributing to BBB permeability and facilitating neuroinflammation. Similarly, claudin-11 deficits in schizophrenia suggest impaired myelination and disrupted neural connectivity. In autism and ADHD, altered tight junction protein profiles imply more subtle or context-dependent barrier dysfunction. Mechanistically, claudin dysregulation permits peripheral inflammatory mediators and immune molecules to access brain tissue, triggering neuroinflammation, oxidative stress, and synaptic dysfunction. Additionally, loss of myelin barrier function may impair signal timing and synchronization. These findings support a unifying hypothesis: that barrier dysfunction, mediated by claudin disruption, underlies diverse psychiatric symptoms by destabilizing the brain's protected environment. Recognizing the role of claudins in mental illness opens avenues for novel biomarker development and therapeutic strategies aimed at restoring barrier integrity, offering a new perspective on the intersection of neurobiology and psychiatry.
Ischemic stroke disrupts blood-brain barrier (BBB) integrity and alters small extracellular vesicle (sEV) signaling, yet the mechanisms underlying sEV transport across compromised barriers remain poorly understood. This study investigated BBB-sEV interactions under normal and stroke-mimicking oxygen/glucose deprivation (OGD) conditions using an in vitro human BBB co-culture model consisting of brain capillary endothelial (BCECs, hCMEC/D3) and astrocytoma cells (1321N1). Model characterization revealed that co-culture with 1321N1 cells enhanced BBB vulnerability to OGD compared to hCMEC/D3 mono-culture. OGD exposure (5 h and 24 h) progressively decreased transendothelial electrical resistance (TEER) and increased FITC-dextran 4 (FD4) permeability, with more severe impairment in co-cultures (e.g. TEER - after 5 h: 0.85-fold, after 24 h: 0.55-fold for co-culture related to mono-culture). Following 19 h oxygen and glucose restoration ('recovery') after 5 h OGD, barrier integrity loss was halted but not reversed. Transcriptomic analysis revealed adaptive cellular responses including upregulated glucose transporter 1 (GLUT1) and vascular endothelial growth factor (VEGF), alongside temporal changes in tight junction protein expression (CLDN5, CDLN6). sEV secretion kinetics in apical and basolateral compartments demonstrated that both cell types released particles in response to OGD in a time-dependent manner, with co-cultures showing enhanced secretion compared to mono-cultures. sEV uptake and permeation studies using eight cancer cell line-derived sEVs revealed cell-origin dependent internalization patterns by BCECs, with the highest uptake for HEK293T and SH-SY5Y sEVs. These internalized sEVs were predominantly targeted to lysosomes. Despite severe barrier disruption due to OGD transcellular permeation of single sEV particles was not detectable.
The oral mucosal barrier, the primary entry point for essential substances (water, food, air), is crucial for oral and systemic health. Comprising a salivary gel layer, commensal microbiota, stratified epithelia, underlying connective tissues, and immunocompetent cells, this complex interface orchestrates selective defense against pathogens and physical and chemical factors while facilitating the absorption of nutrient and bioactive compound. Disruption of this barrier is associated with oral pathologies (e.g. periodontitis) and systemic dysfunction, including cardiovascular, neurodegenerative, and metabolic diseases, underscoring its significance as a key determinant of systemic health. Although the etiology is multifactorial, the precise mechanisms linking oral mucosal barrier disruption to distant organ dysfunction remain incompletely characterized. Consequently, elucidating the underlying molecular networks and cross-organ communication pathways is imperative for oral and systemic health maintenance, as well as development of novel therapeutic strategies target oral and systemic diseases. This review synthesizes recent advances in understanding the molecular architecture of the oral mucosal barrier, explores its local and systemic regulatory networks, and evaluates emerging innovations in barrier-targeted precision medicine approaches.
Epithelial to mesenchymal transition (EMT) has been widely implicated in diverse cellular processes such as development, would healing, as well as in cancer metastasis and therapy resistance. Exosomes are nanosized vesicles that carry cellular products and are known to mediate cell-cell communication. We describe here how a systems biology approach relying on simple experimental data in combination with in silico tools and mathematical modeling can be used to understand complex biological phenomenon such as EMT.
Diabetic foot ulcer (DFU) is a chronic and predominantly microvascular and neuropathic complication in more severe or chronic cases of diabetes mellitus. It is characterized by chronic nonhealing wounds, vascular impairment, and delayed healing process, leading to severe complications, limb amputations, and increased mortality. With an annual incidence rate of approximately 2%, DFU poses a significant global healthcare and economic burden. Despite its prevalence, current treatment options remain limited, necessitating the urgent need for a deeper understanding of the underlying molecular pathways or mechanisms to develop effective therapeutic strategies. Present work is emphasized on molecular mechanisms involved in pathogenesis of DFU and current and emerging therapeutic interventions for the treatment of DFU. Due to its high prevalence, multifaceted pathophysiology, and significant healthcare and economic burden, a thorough understanding of molecular pathways underlying DFU is essential to develop precise therapeutic interventions to improve clinical outcome and reduce the healthcare burden associated with DFU. Several therapeutic interventions have been utilized, like modulators of key signaling pathways (Wnt/β-catenin, PI3K/Akt/mTOR, JAK/STAT, and Notch), repurposed pharmacological agents (e.g. metformin, colchicine, deferoxamine, and lithium carbonate), and advanced local treatments such as bioactive hydrogels and next-generation dressings. Furthermore, regenerative approaches like gene therapy, stem cell transplantation, therapeutic peptides, and 3D-bioprinted adipose tissue constructs provide a promising strategy for restoring tissue integrity and promoting healing.
Neuroinfectious diseases such as meningitis, encephalitis, and myelitis continue to be a significant health issue especially in low- and middle-income nations where the timely identification and successful treatment are mostly not yet available. There is also the complicating factor of the restrictive nature of the blood-brain barrier (BBB) which greatly limits the passage of antimicrobial and anti-inflammatory agents through into the central nervous system. Exosomes which are nano-sized extracellular vesicles released by a vast variety of cells have been proposed as a promising solution to overcome this barrier because of their natural biocompatibility, low immunogenicity and capacity to enter the BBB by receptor-mediated, adsorptive-mediated and carrier-mediated processes. This review critically discusses the structural and functional dynamics of the BBB in infection, the recent discoveries in the exosome trafficking pathways, and the diagnostic and therapeutic role of exosomes in infection, including infections related to HIV-associated neurocognitive disorders, tuberculous meningitis, cryptococcal meningitis, neurotoxoplasmosis. Special consideration will be given to engineered exosomes and how they could be used to improve targeted delivery of drugs, decrease systemic toxicity and offer minimally invasive biomarkers platforms to detect disease earlier. He/she points possible solutions to CNS infections by combining mechanistic understanding with newly acquired pre-clinical and clinical results, this review emphasizes the increasing promise of exosome-based nanomedicine as a transformational technology.
Nanoparticle (NP)-based technologies are transforming the management of central nervous system (CNS) disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and brain cancer (BC), glioblastoma, by surpassing the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB). This review integrates NP approaches, comprising organic (e.g. liposomes, polymeric NPs), inorganic (e.g. gold, iron oxide), carbon-based, and hybrid systems, to overcome disease-specific barriers. In AD, superparamagnetic iron oxide NPs (SPIONs) and gold NPs (AuNPs) improve amyloid-beta plaque and tau protein detection, while liposomes precisely deliver anti-amyloid drugs. For PD, dopamine-loaded liposomes and cerium oxide NPs reinstate dopaminergic function and decrease oxidative stress, with improved motor outcomes. In MS, PEGylated liposomes and PLGA NPs regulate autoimmune responses, inducing remyelination and attenuating neuroinflammation. For BC, dendrimers and magnetic NPs facilitate targeted chemotherapy delivery across the BBB/BBTB, improving glioblastoma treatment outcomes. We compare NP types critically based on physicochemical characteristics, efficacy, toxicity, and clinical translation potential, highlighting gaps in long-term safety and scalability. Challenges like NP toxicity and regulatory complexities are discussed, suggesting biocompatible designs and standardized FDA/EMA pathways. By consolidating diagnostic and therapeutic innovations, this review outlines a roadmap for NP-based precision medicine, paving the way for clinical translation and better patient outcomes in CNS disorders and brain cancer.
The placenta possesses several structural and immunological barriers against viral infections, the SARS-CoV-2 detection in placental tissues has raised concerns regarding possible alternative viral entry mechanisms beyond the canonical ACE2/TMPRSS2-mediated pathway. In this context, the present study evaluated the immunohistochemical expression patterns of ADAM17, Cathepsin L, Clathrin, ACE-2, Furin, NRP-1, and TMPRSS2-molecules involved in SARS-CoV-2 placental entry pathways - as well as the detection of viral RNA by RT-qPCR in paraffin-embedded samples. The study included 75 paraffin-embedded placental samples (decidua and villi) collected after spontaneous placental delivery at birth from patients who tested positive for COVID-19 (COVID-19 Group), and 19 paraffin-embedded control placental samples collected prior to the COVID-19 pandemic (NON-COVID-19 Group). A statistically significant reduction in NRP-1 expression was observed in the COVID-19 group decidua (p < 0.001), including in RT-qPCR - positive samples (p = 0.001), regardless of comorbidities or underlying conditions. A statistically significant reduction in Clathrin expression was also found in the decidual samples of the COVID-19 group and in RT-qPCR - positive samples (p = 0.05and 0.013, respectively), while Cathepsin L expression was significantly increased in the placental villi of the COVID-19 group (p < 0.001) and in RT-qPCR - positive samples (p = 0.005). These findings may contribute to a better understanding of the mechanisms underlying SARS-CoV-2 interaction with the placenta, possibly through auxiliary and/or endocytic entry pathways, and may support future investigations into the impact of these alterations in the context of maternal SARS-CoV-2 infection.
