Qianqian Yin

Telmisartan, an angiotensin II type 1 receptor blocker with established anti-inflammatory and antihypertensive properties, has been reported to inhibit tumor cell proliferation, yet its impact on the tumor immune microenvironment remains poorly understood. In this study, we evaluated the immunomodulatory effects of telmisartan using a syngeneic MC38 colorectal cancer model in C57BL/6 mice. Daily intragastric administration of telmisartan significantly suppressed tumor growth and reduced endpoint tumor weight compared with controls. To elucidate the underlying mechanisms, we performed single-cell RNA sequencing on tumor-infiltrating CD45⁺ immune cells and revealed a macrophage-dominated immune landscape comprising multiple transcriptionally distinct subclusters. Telmisartan broadly downregulated pro-tumoral and M2-associated macrophage programs, including decreased expression of genes such as Mrc1 and Spp1, while also suppressing cell proliferation-related pathways. In contrast to its overall suppressive impact on macrophages, telmisartan increased the proportion of cytotoxic CD8⁺ T cells, reduced regulatory T cell counts, and enhanced major histocompatibility complex class I antigen presentation, consistent with an immune-activating effect. These results indicate that telmisartan reshapes the colorectal tumor immune microenvironment by simultaneously attenuating tumor-promoting macrophage activity and augmenting cytotoxic T cell responses. Overall, this study provides a single-cell framework to understand how angiotensin receptor blockade reshapes tumor-infiltrating immune programs, highlighting the translational potential of repurposing telmisartan for novel cancer immunotherapy strategies.

BACKGROUND: The adult mammalian heart is incapable of regeneration, whereas a transient regenerative capacity is maintained in the neonatal heart, primarily through the proliferation of preexisting cardiomyocytes. Neonatal heart regeneration after myocardial injury is accompanied by an expansion of cardiac fibroblasts and compositional changes in the extracellular matrix. Whether and how these changes influence cardiomyocyte proliferation and heart regeneration remains to be investigated. METHODS: We used apical resection and myocardial infarction surgical models in neonatal and adult mice to investigate extracellular matrix components involved in heart regeneration after injury. Single-cell RNA sequencing and liquid chromatography–mass spectrometry analyses were used for versican identification. Cardiac fibroblast–specific Vcan deletion was achieved using the mouse strains Col1a2-2A-CreER and Vcan ^fl/fl . Molecular signaling pathways related to the effects of versican were assessed through Western blot, immunostaining, and quantitative reverse transcription polymerase chain reaction. Cardiac fibrosis and heart function were evaluated by Masson trichrome staining and echocardiography, respectively. RESULTS: Versican, a cardiac fibroblast–derived extracellular matrix component, was upregulated after neonatal myocardial injury and promoted cardiomyocyte proliferation. Conditional knockout of Vcan in cardiac fibroblasts decreased cardiomyocyte proliferation and impaired neonatal heart regeneration. In adult mice, intramyocardial injection of versican after myocardial infarction enhanced cardiomyocyte proliferation, reduced fibrosis, and improved cardiac function. Furthermore, versican augmented the proliferation of human induced pluripotent stem cell–derived cardiomyocytes. Mechanistically, versican activated integrin β1 and downstream signaling molecules, including ERK1/2 and Akt, thereby promoting cardiomyocyte proliferation and cardiac repair. CONCLUSIONS: Our study identifies versican as a cardiac fibroblast–derived pro-proliferative proteoglycan and clarifies the role of versican in promoting adult cardiac repair. These findings highlight its potential as a therapeutic factor for ischemic heart diseases.

The transdifferentiation from cardiac fibroblasts to myofibroblasts is an important event in the initiation of cardiac fibrosis. However, the underlying mechanism is not fully understood. Circ-sh3rf3 (circular RNA SH3 domain containing Ring Finger 3) is a novel circular RNA which was induced in hypertrophied ventricles by isoproterenol hydrochloride, and our work has established that it is a potential regulator in cardiac hypertrophy, but whether circ-sh3rf3 plays a role in cardiac fibrosis remains unclear, especially in the conversion of cardiac fibroblasts into myofibroblasts. Here, we found that circ-sh3rf3 was down-regulated in isoproterenol-treated rat cardiac fibroblasts and cardiomyocytes as well as during fibroblast differentiation into myofibroblasts. We further confirmed that circ-sh3rf3 could interact with GATA-4 proteins and reduce the expression of GATA-4, which in turn abolishes GATA-4 repression of miR-29a expression and thus up-regulates miR-29a expression, thereby inhibiting fibroblast–myofibroblast differentiation and myocardial fibrosis. Our work has established a novel Circ-sh3rf3/GATA-4/miR-29a regulatory cascade in fibroblast–myofibroblast differentiation and myocardial fibrosis, which provides a new therapeutic target for myocardial fibrosis.