Biomedical subjects

Valeria Mezzano

Publications and source records attributed to Valeria Mezzano.

3 recordsLinked to original sources

PubMed2026

Splenic extramedullary hematopoiesis in myelofibrosis is shaped by transcriptomic and epigenetic dysregulation.

Myelofibrosis (MF) is a chronic, progressive myeloproliferative neoplasm characterized by bone marrow fibrosis, ineffective blood cell production, and neoplastic extramedullary hematopoiesis (EMH) occurring primarily within the spleen. To explore the molecular mechanisms underlying splenic EMH, we performed single-cell transcriptional and chromatin profiling of cells from MF spleens that had been surgically removed. We demonstrate significant expansion of hematopoietic stem and progenitor cells, coupled with aberrant differentiation toward the erythroid and megakaryocytic lineages, associated with a significant enrichment of inflammatory pathways with enhanced NF-κB signaling and IFN responses, as well as dysregulation of the inferred function of differentiation-defining transcription factors. Finally, we report a significant remodeling of the immune microenvironment in MF spleens, characterized by emergence of dysfunctional T cell subsets and inflammatory memory B cells, suggesting the concomitant establishment of a pro-inflammatory and immune-tolerant tumor microenvironment within the spleen that influences hematopoietic cell differentiation and impairs tumor immune surveillance.

Primary Myelofibrosis↗

PubMed2026

Cardiomyocyte-Specific Plakophilin-2 Loss Is Sufficient to Induce Aging and Senescence of Nonmyocytes: Relevance to Arrhythmogenic Cardiomyopathy.

BACKGROUND: Pathogenic variants in PKP2 are the most common cause of familial arrhythmogenic right ventricular cardiomyopathy. This study tests whether plakophilin-2 (PKP2) deficiency only in cardiomyocytes is sufficient to provoke premature aging and proinflammatory senescence in nonmyocyte, cardiac resident cells. METHODS: We studied mice with cardiomyocyte-specific, tamoxifen-activated loss of PKP2 (cardiomyocyte-specific conditional knockout of plakophilin-2) using conventional and multiplex imaging, cytokine arrays, epigenetic clocks, spatial transcriptomics, expansion and structured illumination microscopy, and correlative data analysis. We examined nonmyocytes and cardiomyocytes for premature aging and senescence. RESULTS: We observed senescence-associated heterochromatin foci in nonmyocytes, predominantly in cells positive for α-smooth muscle actin staining. Cytokines in media of nonmyocyte cells were consistent with senescence-associated secretory phenotype. Epigenetic clocks identified premature aging. Multiplex immunohistochemistry showed nonmyocyte cells in niches, intermingled with cardiomyocytes. Spatial transcriptomics showed overrepresentation of senescence-associated secretory phenotype-related transcripts, predominantly in myocyte-rich areas of the left ventricle. Senescence-associated heterochromatin foci and increased epigenetic age were not found in cardiomyocytes from cardiomyocyte-specific conditional knockout of plakophilin-2 hearts, although we observed structural features associated with premature aging. Cross-reference analysis showed correlation between the cardiomyocyte-specific conditional knockout of plakophilin-2 cardiac proteome and that of mice 5 or 6 times their chronological age, as well as transcriptional signatures of neurodegenerative diseases. CONCLUSIONS: Loss of PKP2 expression only in adult cardiac myocytes is sufficient to induce proinflammatory senescence in nonmyocytes, and overall premature cardiac aging. This is the first study to intersect cellular senescence and premature aging with desmosomal arrhythmogenic cardiomyopathies. We speculate that cell-agnostic molecular signatures, biomarkers, and pharmacology of senescence and of neurodegenerative diseases may be relevant to diagnose or treat PKP2 arrhythmogenic right ventricular cardiomyopathy.

Animals↗

PubMed2025

Population analysis and immunologic landscape of melanoma in people living with HIV.

PURPOSE: To dissect the clinical and immunological features of people living with HIV (PLWH) diagnosed with melanoma, who have consistently exhibited worse clinical outcomes than HIV-negative individuals (PLw/oH) with the same cancer. EXPERIMENTAL DESIGN: We analyzed electronic health records from 1,019 PLWH and 373,121 PLw/oH diagnosed with melanoma. Demographic and clinical characteristics were compared. Spatial immune transcriptomics (72 immune-related genes) was performed on melanoma tumor samples (n=11), followed by downstream validation using multiplex immunofluorescence (n=15 PLWH, n=14 PLw/oH). RESULTS: PLWH were diagnosed with melanoma at a younger age, had a higher representation of Hispanic and Black individuals compared to PLw/oH, and a decreased survival rate. PLWH also showed a markedly increased risk of brain metastases. PLWH experienced significant delays in initiating immune checkpoint inhibitor (ICI) therapy and had worse survival outcomes following ICI, even after balancing for demographic covariates. Spatial transcriptomics revealed a more immunosuppressive tumor microenvironment in PLWH, with upregulation of immune checkpoints (PD1, LAG3) and reduced expression of antigen presentation markers (HLA-DRB, B2M), with distinct spatial distributions in tumors and their microenvironments. Multiplex immunofluorescence confirmed an exhausted CD8+ T cell compartment in PLWH, including enrichment of PD1intLAG3- and PD1intLAG3+ subpopulations, and a significant accumulation of immunosuppressive myeloid-derived suppressor cells (CD11b+ HLA-DR- CD33+). CONCLUSIONS: Our findings suggest chronic HIV infection fosters a permissive tumor microenvironment that might undermine effective immune responses and contribute to poor clinical outcomes for PLWH with melanoma. Targeting the actionable immune pathways identified in this study could inform tailored therapeutic strategies to mitigate these disparities.

HIV↗