J. Mol. Pathol., Volume 7, Issue 3 (September 2026) – 4 articles

Both SARS-CoV-2 infection and COVID-19 vaccination have been associated with renal complications. In the context of SARS-CoV-2 infection, kidney injury is primarily attributed to a complex interplay of systemic immune dysregulation and vascular damage. Severe infection triggers a cytokine-mediated inflammatory response characterized by elevated levels of pro-inflammatory mediators, resulting in systemic hemodynamic instability, increased capillary permeability, and renal hypoperfusion, ultimately leading to acute tubular injury. In addition, virus-induced endothelial activation promotes a prothrombotic state, microvascular injury, and further impairment of renal perfusion. Collectively, these processes converge to produce acute kidney injury (AKI) and, in severe or prolonged cases, may contribute to chronic tubulointerstitial damage and progressive renal dysfunction. In contrast, renal manifestations following COVID-19 vaccination are relatively uncommon and are thought to arise primarily from immune-mediated dysregulation rather than direct cytopathic effects. Reported cases include minimal change disease, IgA nephropathy, focal segmental glomerulosclerosis (FSGS), acute interstitial nephritis and other glomerulopathies, which present as either new-onset disease or relapses. These lesions are thought to result from transient immune activation following vaccination, including T-cell stimulation and altered humoral responses, which may trigger or unmask an underlying susceptibility to renal injury. Careful post-vaccination monitoring in high-risk populations may be warranted, and further molecular and population-level studies are needed to elucidate the underlying mechanisms and refine risk assessment. Full article

Background/Objectives: PgRMC1 is a progesterone-binding protein often overexpressed in breast cancer, correlating with tumor progression and chemoresistance. Identifying predictive markers for neoadjuvant chemotherapy (NAC) response is crucial for guiding therapeutic decisions. This study examines PgRMC1 expression in breast cancer tissues and its correlation with clinicopathological characteristics and NAC response. Methods: PgRMC1 expression in normal and cancerous breast tissues was evaluated via immunohistochemistry (IHC). Expression of ER, PgR, HER2, AR, and PGRMC1 mRNA was determined by qPCR in 112 patients. A separate 44-patient neoadjuvant chemotherapy (NAC) cohort was assessed for intrinsic subtypes (pretreatment biopsies) alongside PgRMC1 IHC expression and pathological response (post-NAC surgical specimens). In vitro chemoresistance and qPCR analyses were performed in breast cancer cell lines following PgRMC1 overexpression or siRNA-mediated knockdown. Results: PgRMC1 expression was detected in breast cancer tissue, while no immunoreactivity was observed in normal breast tissue. PGRMC1 mRNA expression levels were significantly higher in luminal and HER2 subtypes. In the distinct cohort of patients treated with NAC, those with a poorer pathological response had significantly higher PgRMC1 expression than those with a good response. In vitro, forced overexpression of PgRMC1 in two breast cancer cell lines, MCF7 and MDA-MB-468, significantly reduced chemosensitivity. Overexpression of PgRMC1 modulated the expression of epithelial and differentiation markers, including CDH1, AR, KRT19, and GATA3. Conclusions: PgRMC1 may contribute to chemoresistance and serves as a candidate biomarker for assessing neoadjuvant chemotherapy sensitivity. Full article

Background: Tight junctions are major components of apical junction complexes and are crucial for the maintenance of cell polarity, healthy tissue architecture, adhesion, and permeability. These junctions include the claudin family of transmembrane proteins, which act as paracellular barriers to regulate selective permeability. Abnormal claudin expression disturbs cell adhesions and is associated with cancer through promoting cell invasion, migration, and metastasis. Claudin 6 (CLDN6) overexpression, in particular, is linked to several types of cancer with malignant phenotypes. The present study aimed to investigate the association between CLDN6 protein expression and its copy number variations (CNVs) with clinicopathological features and survival outcomes of ovarian cancer (OC) patients. Methods: A total of 114 formalin-fixed paraffin-embedded blocks from primary OC patients were used to construct tissue microarray slides. Automated immunostaining was used to assess CLDN6 protein expression levels, and next-generation knowledge discovery platforms were used to further evaluate CLDN6 CNV levels using The Cancer Genome Atlas open-source data. The relationships between CLDN6 CNVs and tumor stage, overall survival, disease-specific survival (DSS), and disease-free survival (DFS) were investigated. Results: This study demonstrated that CLDN6 had a mixed membranous-cytoplasmic expression pattern. The cytoplasmic expression of CLDN6 was significantly associated with tumor stage (p = 0.05), tumor size (p = 0.04), and recurrence (p = 0.05). In Univariate analysis, Kaplan–Meier analysis demonstrated that CLDN6 expression was significantly correlated with DFS (p = 0.01). OC patients with lower cytoplasmic CLDN6 expression levels lived longer and had lower recurrence rates. These findings were further confirmed through CLDN6 CNVs analysis, where OC with lower CLDN6 cytoplasmic expression positively correlated with longer DFS and DSS. No independent prognosticator was found when using Cox-regression multivariate analysis (p > 0.05). Conclusions: These results suggest CLDN6 as an interesting prognosticator to identify OC patients at a higher risk of recurrence in order to provide personalized management, alleviate the burden of this disease on women’s health, and improve their survival outcomes. Full article

Atrial fibrillation (AF) is the most prevalent sustained arrhythmia and is increasingly driven by cardiometabolic disease, including type 2 diabetes mellitus (T2DM), obesity, and insulin resistance. These conditions promote atrial electrical instability and a permissive substrate through mitochondrial dysfunction, oxidative stress, inflammation, calcium-handling abnormalities, and profibrotic signaling, culminating in atrial fibrosis and conduction heterogeneity. Metformin, the foundational glucose-lowering therapy for T2DM, exerts pleiotropic actions that intersect with these upstream pathways. Beyond glycemic control, metformin induces mild mitochondrial complex I modulation with reduction of reverse electron transfer-derived reactive oxygen species, activates adenosine monophosphate (AMP) activated protein kinase, and attenuates nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-mediated cytokine signaling; experimental data further suggest favorable effects on adiponectin–sarcoendoplasmic reticulum calcium adenosine triphosphatase (SERCA) 2a-dependent calcium cycling, connexin expression, small-conductance Ca²⁺-activated K+ channel remodeling, lipid handling, and transforming growth factor-β (TGF)-β-associated fibrotic remodeling. Observational cohort studies have reported associations between metformin exposure and a modest reduction in incident AF, particularly with longer treatment duration and in higher-risk metabolic phenotypes; device-based surveillance cohorts support a preventive association for new-onset AF rather than reduction of established AF burden. Data after catheter ablation suggest improved freedom from recurrence in metformin-treated patients, whereas evidence in postoperative AF is largely neutral, likely reflecting distinct acute mechanisms. Collectively, metformin may be best conceptualized as a potential substrate-modifying, upstream therapy candidate; however, confounding, exposure misclassification, and heterogeneity in comparators limit causal inference, underscoring the need for prospective randomized trials with AF endpoints. In practice, integration with comprehensive risk-factor modification (blood pressure, weight, sleep apnea, and glycemic optimization) remains essential when considering AF prevention strategies. Full article