American Journal of Pathology最新文献

Hematopoietic stem cell (HSC) aging leads to hematological dysfunction and diseases, but the regulatory factors involved remain incompletely characterized. In this study, the HSC Aging-Associated TFs Catalog System model was developed to identify transcription factors (TFs) that resist HSC aging. This approach revealed RAR-related orphan nuclear receptor alpha (RORA) as a key aging-negative-associated TF. Rora deletion in HSCs caused aged phenomes and functionally impaired their reconstitutive capacity. Additionally, Rora deficiency impaired leukemia stem cell proliferation and prevented chronic myelogenous leukemia. These findings establish RORA as a critical regulator in maintaining HSC function and provide insights into its therapeutic potential in hematological disorders.

Insights into how normal epithelial cells adapt to microenvironmental perturbations may reveal molecular vulnerabilities that become obscured later in carcinogenesis, and hypoxia is common in colorectal cancer (CRC). Although colon mucosa exists in a state of physiological hypoxia and is susceptible to ischemic injury, normal colon epithelial adaptive responses to changes in oxygenation are largely uncharacterized. In this study, human colon organoids (colonoids) were subjected to sustained hypoxia in vitro with characterization of consequent phenotypes and transcriptional changes. Hypoxia tolerance in human colonoids resulted in robust down-regulation of alcohol dehydrogenase 1C (ADH1C), which was also validated in archival tissue from patients with ischemic colitis. ADH1C transcripts revealed a nonuniform expression pattern in normal colon epithelium, with enrichment in transit-amplifying and progenitor epithelial cells. Ectopic expression of ADH1C in colonoids subjected to hypoxia increased reactive oxygen species and reduced NADPH compared with those in normoxia, suggesting that hypoxia-induced ADH1C down-regulation facilitates neutralization of reactive oxygen species. Hypoxia-induced ADH1C down-regulation also showed reduced transit-amplifying cell signatures and increased expression of regeneration-associated stem cell marker FGFBP1. Finally, ADH1C-low CRC showed significant enrichment for hypoxia-associated colon epithelial signatures compared with ADH1C-high CRC. Taken together, these results establish ADH1C as a mediator of colon epithelial hypoxia responses and epithelial identity with relevance to human CRC.

Corneal ectasias are a significant cause of vision morbidity worldwide. In humans, corneal ectasias are characterized by tissue mechanical weakening, stromal thinning, and bulging. Previous histopathology studies showed a high rate of keratocyte apoptosis in corneas with ectasia. A mouse model expressing a keratocyte lineage-specific reporter KeraRT/tetO-Cre/mTmG/DTR was created to elucidate the roles of keratocyte death in the development of corneal ectasias. This mouse model allows selective death of keratocytes at chosen times during stromal development and in mature stromas. Slit-lamp examination as well as histopathology and advanced imaging techniques were used to assess stromal structure after keratocyte genetic ablation. It was found that genetic ablation of keratocytes in the first 20 days after birth induces corneal thinning and ectasia. A corneal hydrops-like phenotype (severe ectasia) occurred more frequently if keratocyte death was induced in the first week after birth. Inducing keratocyte death at an age where some degree of corneal maturation has occurred, >3 weeks of age, did not create changes in corneal thickness, transparency, or curvature, or any noticeable abnormalities in microstructure.

Epithelial barrier dysfunction is a hallmark of inflammatory bowel diseases; however, the mechanisms underlying such impairment remain incompletely understood. In the present study, a dextran sulfate sodium-induced colitis model was used to investigate how the inflammatory environment damages the intestinal mucosa. The results demonstrated that colitogenic ambiance enhances intestinal epithelial cell death, delays epithelial cell proliferation, and exacerbates mucosal erosion. Unexpectedly, this work identified a previously unrecognized role for Notch signaling in mediating these effects. Specifically, the colitogenic milieu reduces Notch/mechanistic target of rapamycin complex 1 (mTORC1)-mediated intestinal epithelial cell proliferation to promote goblet cell differentiation. Chemical activation of Notch signaling stimulated intestinal epithelial cell proliferation and reduced goblet cell differentiation in the colitic mucosa, further aggravating mucosal damage. Conversely, inhibition of Notch or mTORC1 signaling during mucosal repair reduced intestinal epithelial cell proliferation and enhanced goblet cell differentiation, corroborating the implication of Notch and mTORC1 signaling in both processes. Collectively, these findings uncover a context-dependent role for the Notch-mechanistic target of rapamycin axis in regulating intestinal epithelial cell proliferation and differentiation in the colitic mucosa and suggest that its targeted modulation may hold therapeutic potential in inflammatory bowel diseases.

Glaucoma is a leading cause of irreversible blindness, characterized by retinal ganglion cell degeneration and neuroinflammation. Retinal microglia are key modulators of this pathology. Using single-cell transcriptomic analysis of human glaucomatous retinas, a distinct population of disease-associated microglia (DAM) was identified, defined by elevated triggering receptor expressed on myeloid cells 2 (TREM2) and other neurodegeneration-related genes. DAM exhibited enriched transcriptional programs associated with phagocytosis, antigen presentation, and immune regulation, with TREM2^high microglia predominating. In a mouse model of retinal ischemia-reperfusion injury, Trem2 knockout (Trem2^-/-) mice exhibited exacerbated retinal neurodegeneration and neuroinflammation, impaired microglial phagocytosis, and antigen presentation relative to wild-type controls. Furthermore, Trem2^-/- microglia failed to acquire a DAM-like or anti-inflammatory (M2) phenotype, instead adopting a proinflammatory (M1)-skewed state. Flow cytometry and immunofluorescence analyses of cervical lymph nodes revealed increased frequencies of CD8⁺ T cells and CD19⁺ B cells, along with a reduction in forkhead box P3 (FOXP3)⁺ regulatory T cells in Trem2^-/- mice. CD8⁺ T cells displayed heightened proliferation and diminished exhaustion, indicating sustained effector function. Transcriptomic profiling further confirmed enhanced lymphocyte activation, inflammasome signaling, and suppression of immunoregulatory pathways, including transforming growth factor-β and IL-2 signaling critical for regulatory T cell induction. Collectively, these findings establish TREM2 as a central regulator of disease-associated microglial activation and immune homeostasis in glaucoma. Loss of TREM2 compromises both innate and adaptive immune regulation, leading to sustained inflammation and exacerbated retinal neurodegeneration.

This study evaluated the function of peroxisome proliferator-activated receptor α (PPARα) in vascular endothelial cells (ECs) under physiological and disease conditions. Vascular density and avascular area were evaluated in Griffonia simplicifolia isolectin B4-stained retinas. Endothelial progenitor cells were quantified using flow cytometry. Vascular leakage was evaluated by Evans Blue. The mitochondrial function and morphology were evaluated by a Seahorse analyzer and immunofluorescence staining. Cell senescence was assessed by a senescence-associated β-galactosidase activity assay and Western blot analysis. A significant reduction in the retinal vessel length and vascular mesh density was found in EC-specific PPARα conditional knockout (PPARα^ECKO) mice. Relative to PPARa^flox-KO mice with oxygen-induced retinopathy (OIR), PPARα^ECKO OIR retina showed enlarged avascular areas and decreased endothelial progenitor cell number, whereas EC-specific PPARα conditional transgenic mice showed reduced avascular areas in the OIR retina. Compared with diabetic PPARa^flox-KO mice, diabetic PPARα^ECKO mice showed declined electroretinographic amplitudes, decreased retinal thickness, and increased retinal vascular leakage. PPARα deficiency exacerbated, whereas PPARα activation alleviated, EC mitochondrial dysfunction induced by diabetic stressors. PPARα^-/- ECs developed senescence, prominent oxidant-induced mitochondria fragmentation, and down-regulation of translocase of outer mitochondrial membrane 20 and peroxisome proliferator-activated receptor γ coactivator 1α, relative to wild-type ECs. These results suggest that PPARα in microvascular ECs regulates retinal vascular development and protects ECs against diabetes/hypoxia-induced vascular dysfunction through mitochondrial protective and anti-senescence activities.

Metastasis is a major threat in breast cancer, often involving lymph node (LN) dissemination. However, the cellular composition and signaling networks within the metastatic microenvironment remain incompletely characterized, resulting in limited understanding of the molecular mechanisms driving LN metastasis. In this study, a comprehensive single-cell atlas of metastatic niches was constructed using single-cell RNA-sequencing data from 78 primary breast tumors and their paired LN metastatic samples. Among the epithelial cell subpopulations, distinct clusters representing early-disseminated cancer cells were identified. Notably, profound metabolic reprogramming and immune modulation was observed during the malignant transformation of epithelial cells, which may contribute to the invasive and metastatic phenotype of early-disseminated cancer cells. Furthermore, the communication network within the metastatic microenvironment has also been delineated systematically, where crosstalk among lymphocyte, macrophage, and epithelial cells drove immunosuppressive features of LN metastasis. To explore potential therapeutic interventions, computational drug repositioning was conducted and four tyrosine kinase receptor inhibitors were identified that may target key interactions within this crosstalk. These results were validated using spatial transcriptomics data of four metastatic LN tissue sections from an integrated single-cell RNA-sequencing cohort. Collectively, this study discussed the cellular architecture and regulatory interplay underlying LN metastasis in breast cancer, offering novel insights that may inform targeted therapeutic strategies for patients with metastatic disease.

Neonatal thymectomy (TX) has been known to induce experimental autoimmune disease models in mice for over half a century. The thymic microenvironment, including thymic epithelial cells (TECs), plays a crucial role in establishing self-tolerance in T cells. However, the extent to which the dynamic changes in the neonatal thymic environment contribute to the onset of autoimmunity remains incompletely understood. In this study, the detailed alterations in the neonatal thymus and peripheral lymphoid organs were analyzed using a mouse model of primary Sjögren disease. Mice treated with TX at 3 days after birth (day 3-TX) exhibited significantly more severe autoimmune pathology than those treated with TX at 7 days after birth. Around day 3, T-cell differentiation and the expansion of TECs, particularly medullary TECs, were markedly accelerated in the neonatal thymus. Furthermore, in day 3-TX mice, the expansion of peripherally induced regulatory T (Treg) cells was impaired, along with the loss of thymic-derived Treg cell output that typically undergoes robust expansion around day 3 after birth. The suppressive activity of Treg cells from day 3-TX mice was significantly impaired compared with that of control Treg cells. These findings suggest that the neonatal thymic environment plays a critical role in regulating peripheral immune tolerance and may influence the pathogenesis of autoimmune diseases.

Cellular heterogeneity plays a critical role in tissues and diseases, including cancer. Single-cell technologies are required to provide detailed information about the phenotype and genotype of individual cells. Despite several approaches to analyzing different analytes at the single-cell level, it is challenging to assess DNA, RNA, and protein simultaneously. Here, a single-cell triomics method to assess DNA, RNA, and proteins from the same cell using a targeted sequencing approach is shown. Breast cancer cells cultured in monolayers and in patient-derived scaffolds that mimic in vivo-like growth conditions, both with and without chemotherapy treatment, were analyzed. Data showed that DNA, RNA, and protein biomarkers could be reliably analyzed, providing biological insights into breast cancer cell heterogeneity. In addition, chemotherapy treatment caused changes in subpopulations and expressions of biomarkers. Furthermore, cells growing in patient-derived scaffolds generated from various breast cancers affected cell heterogeneity and drug resistance differently as a result of the unique tumor-specific microenvironments. The data show that single-cell triomics provides new means to assess cancer cell heterogeneity at DNA, RNA, and protein levels.