PhD Scientific Days 2026

Cardiovascular Medicine and Research 3.

Mast Cell Secretome and Its Functional Impact on Cardiomyocytes

Name of the presenter

Fletcher, Kelsey

Institute/workplace of the presenter

Department of Genetics, Cell- and Immunobiology, Semmwelweis University.

Authors

Kelsey Fletcher¹, Tamás Visnovitz¹, Zsófia Szász¹, Tamara Hermans¹, Tünde Bárkai¹, Dorina Lenzinger¹, Nagy Bence¹, Péter Lőrincz², Zsófia Fodor¹, Edit I. Buzás¹, Krisztina V. Vukman¹
1: Semmelweis University, Department of Genetics, Cell- and Immunobiology, Nagyvárad tér 4. 1089 Budapest, Hungary
2: ELTE Eötvös Loránd University, Department of Anatomy, Cell and Developmental Biology, Pázmány Péter sétány 1/c, 1117 Budapest, Hungary

Text of the abstract

Introduction
Mast cells (MCs) contribute to cardiac pathology. Through classical degranulation, MCs release pre‑formed mediators, while they also secrete extracellular vesicles (EVs) involved in inflammation and tissue‑remodeling. However, similarities in size, makeup, and function between extracellular granules (EGs) and EVs complicate interpretation of MC-derived extracellular particles (EPs) and limit understanding of how activation pathways shape EP output and cardiomyocyte responses.

Aims
To characterize MC derived EPs heterogeneity, determine how activation pathways shape EP composition, identify features distinguishing EGs from EVs and assess their functional impact on cardiomyocytes.

Methods
Bone marrow-derived murine MCs were stimulated with A23187, DNP/IgE, LPS or control conditions. EPs were isolated with differential and density gradient centrifugation and analyzed by flow cytometry, confocal microscopy, TEM and biochemical assays. HL-1 cardiomyocytes were cultured with separated EPs. EP-uptake, viability, morphology and senescence was assessed.

Results
Activated MCs secrete a heterogeneous particle population: IgE-DNP activation predominantly produced EG-like, detergent-sensitive, histamine-rich particles. These EPs were well tolerated by cardiomyocytes. In contrast, LPS stimulation favored EV-like, detergent-resistant particles with lower histamine, inducing senescence, reduced viability, decreased metabolic activity and altered cell density in HL-1 cells. A23187 generated a mixed EG/EV output.

Conclusion
MCs release multiple EP subtypes, and the EG-EV balance is dictated by the activating stimulus. Clear discrimination of these populations is crucial for accurate interpretation of MC secretion in immunological and EV research. In the cardiac context, stimulus-dependent EP composition is a critical determinant of their influence on cardiomyocytes, and may ultimately be leveraged to develop therapies for cardiac disease.

Funding
STARTING_25 grant (No. 152115), VEKOP‑2.3.2‑16‑2016‑00002, VEKOP‑2.3.3‑15‑2017‑00016, the Higher Education Excellence Program (FIKP), the Therapeutic Thematic Program (TKP2021‑EGA‑23), RRF‑2.3.1‑21‑2022‑00003, 2019‑2.1.7‑ERA‑NET‑2021‑00015, European Union’s Horizon 2020 program (No. 739593) (EIB), János Bolyai Research Scholarship of the Hungarian Academy of Sciences.