Characterization of thymic involution and how it contributes to immunosenescence in mice

• Grant number: 25/16622-8
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: October 30, 2025
• End date: October 29, 2026
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Principal Investigator: Marcelo Alves da Silva Mori
• Grantee: Niedson Correia de Lima Junior
• Supervisor: Philipp e Scherer
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: University of Texas Southwestern Medical Center, Dallas (UT Southwestern), United States
• Associated to the scholarship: 23/01703-7 - Characterization of thymic involution and how it contributes to immunosenescence in mice, BP.PD

Abstract

The study investigates thymic involution in the context of obesity, aging, and lipodystrophy, using wild-type (Lox) and AdicerKO mice at different ages (1, 6, and 18 months), fed either a standard diet (chow) or a high-fat diet (HFD). Histological analysis (H&E) revealed progressive structural changes in the thymus: at 6 months, AdicerKO on a chow diet and Lox on HFD already showed partial loss of thymic architecture, while AdicerKO on HFD exhibited almost complete replacement by adipocytes. At 18 months, the changes were even more pronounced, highlighting the synergistic effect of age and metabolic dysfunction. snRNAseq analysis showed an increase in adipocytes and a significant reduction in thymic epithelial cells (TECs) in aged animals. Two distinct subpopulations of adipocytes were identified: one with high expression of thermogenic markers and another with low expression, both increasing with age. Histologically, multilocular adipocytes were located in the thymic capsule and unilocular adipocytes in the parenchyma. Experiments with Trpv1Cre/Rosa26mtmg mice demonstrated adipocytes derived from TRPV1+ cells, and snRNAseq revealed low but detectable TRPV1 expression in TECs and thymocytes, suggesting partial origin from this population. Hormonal changes appeared early (1 month), before the onset of lipodystrophy, with reduced serum adiponectin levels. The central questions of the study include: (1) which thymic populations have adipogenic potential, (2) which factors induce this differentiation, and (3) what mechanisms act in each population. The objectives are to: identify populations with adipogenic potential, define molecular factors driving adipogenesis in the aged thymus, and clarify whether adiponectin regulates involution and adipogenic differentiation. The experimental design includes: Assessing whether the hormonal profile drives thymic involution: use ¿Gly mice (overexpressing adiponectin) to test whether sustained levels prevent involution, and Adipoq-/- mice to determine if absence accelerates the process; generate conditional knockouts for the AdipoR2 receptor in TECs (Foxn1Cre) and stromal progenitors (PdgfraCre and TRPV1Cre); test inducible overexpression of AdipoR2 to investigate protection against involution. Immunological and histological analyses: evaluate the weight of lymphoid organs, thymic morphology (H&E), T cell profile (CD4, CD8, CD44, CD62L), and mTEC/cTEC proportion by flow cytometry; investigate markers of senescence, adipogenesis, and thymic function by IHC and qPCR. Tracking adipocyte precursors: cross Rosa26mTmG with FOXN1Cre, PdgfraCre, and TRPV1Cre lines to trace the origin of adipocytes; apply immunofluorescence to distinguish multilocular adipocytes (derived from TECs) and unilocular adipocytes (derived from Pdgfra+), analyzing animals at 1 and 6 months under chow and HFD. The dataset and experimental approach aim to clarify how hormonal changes, aging, and metabolic dysfunction modulate intrathymic adipogenesis and accelerate involution, with special focus on the role of adiponectin and specific cellular precursors. (AU)