miR-499 in Platelet-Derived Extracellular Vesicles Augments Inflammatory Cell Generation and Cardiac Remodeling After
Lee Ohayon-Steckel1,2, Xinyi Zhang3, Shagufta Haque1,2
1Pittsburgh Heart, Lung, Blood, and Vascular Medicine Institute (L.O.-S., S.H., M.A.U., A.D., D.G.K., N.N., E.J., A.D., C.E.-D., B.W., P.D.), University of Pittsburgh, PA.
Insights
Platelet-derived extracellular vesicles (pEVs) released after myocardial infarction (MI) drive emergency hematopoiesis, increasing inflammatory myeloid cells. Inhibiting pEVs offers a therapeutic strategy for reducing cardiac inflammation and remodeling post-MI.
Area of Science:
- Cardiovascular Biology
- Hematology
- Cellular and Molecular Medicine
Background:
- Emergency myelopoiesis by bone marrow hematopoietic stem and progenitor cells (HSPCs) worsens pathology in chronic diseases like myocardial infarction (MI).
- Mechanisms triggering bone marrow myelopoiesis following distant organ injury, such as MI, are not well understood.
Purpose of the Study:
- To investigate the role of platelet-derived extracellular vesicles (pEVs) in mediating emergency myelopoiesis after MI.
- To identify molecular mechanisms by which pEVs influence HSPC behavior and inflammatory cell generation.
- To explore potential therapeutic targets for mitigating cardiac inflammation and remodeling post-MI.
Main Methods:
- Induction of MI in mice via left descending coronary artery ligation.
- Detection and quantification of circulating pEVs in mice and human MI patients using NanoSight, ImageStream, and flow cytometry.
- Assessment of pEVs' effects on HSPC lineage commitment and inflammatory cell generation using parabiosis, flow cytometry, and adoptive transfer experiments.
- RNA sequencing, luciferase assays, and gene overexpression studies to elucidate molecular pathways.
Main Results:
- MI induces a significant increase in circulating pEVs, which promote HSPC proliferation and inflammatory myeloid cell generation in both mice and humans.
- Cardiomyocyte-derived S100A8/9 alarmin complex stimulates pEV secretion; inhibiting platelet activation/exocytosis reduces pEV production and emergency hematopoiesis.
- MI-derived pEVs are enriched with miR-499 and miR-184, which directly promote HSPC proliferation and myelopoiesis by downregulating lactoferrin/lactotransferrin.
Conclusions:
- Platelet-derived extracellular vesicles (pEVs) are key mediators of emergency myelopoiesis and inflammatory cell generation following myocardial infarction (MI).
- The miR-499/lactoferrin axis within pEVs plays a critical role in promoting myelopoiesis and cardiac remodeling post-MI.
- Targeting pEVs and their cargo presents a promising therapeutic strategy to reduce cardiac inflammation and improve outcomes after MI.
Background:
Emergency myelopoiesis by bone marrow hematopoietic stem and progenitor cells (HSPCs) exacerbates disease pathology in various chronic diseases, including myocardial infarction (MI) and atherosclerosis. However, the mechanisms triggering myelopoiesis in the bone marrow after a distant organ injury, such as MI, remain unknown.
Methods:
We ligated the left descending coronary artery to induce MI in mice. Platelet-derived extracellular vesicles (pEVs) were detected and enumerated in mice and patients with MI using NanoSight, ImageStream, and flow cytometry. microRNA in pEVs was quantified using a microRNA array. We used parabiosis, flow cytometry, adoptive transfer experiments, and transgenic mice to assess the effects of pEVs and microRNA on HSPC lineage commitment and inflammatory cell generation. In addition, we carried out RNA sequencing, luciferase assay, lentivirus-mediated in vivo gene overexpression, and echocardiography to evaluate the merit of lactoferrin/lactotransferrin in post-MI pathogenesis.
Results:
In this study, we demonstrate that patients and mice with MI and mice with hindlimb ischemia exhibit an increased number of circulating pEVs, which, in turn, augment HSPC number and proliferation in the bone marrow, leading to inflammatory myeloid cell generation and disease progression. S100A8/9 (S100 calcium-binding protein A8/A9), an alarmin complex produced by cardiomyocytes after MI, induced pEV secretion. In vivo and in vitro inhibition of platelet activation and exocytosis, and HSPC endocytosis, markedly lessened the production of pEV, HSPC proliferation, and myeloid cell generation in emergency hematopoiesis. A microRNA array revealed that pEVs isolated after MI had elevated cargo levels of miR-499 and miR-184, which were enriched in reticulated platelets after MI. miR-499 and miR-184 overexpression in mouse and human HSPCs resulted in enhanced hematopoiesis and myelopoiesis. miR-499-deficient pEVs were inefficient in stimulating emergency myelopoiesis and inducing cardiac remodeling after MI. RNA sequencing analysis, luciferase assay, and lentivirus-mediated in vivo gene overexpression demonstrated that miR-499 bound to the 3' region of lactoferrin/lactotransferrin in HSPC to downregulate this gene, promoting myelopoiesis and unleashing inflammation.
Conclusions:
Our study suggests that pEVs generated after MI induce HSPC proliferation and inflammatory cell generation. These discoveries uncover several therapeutic targets to reduce cardiac inflammation and remodeling after MI.
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