The Nahrendorf laboratory focuses on the role of immunity in cardiovascular health and disease, specifically in atherosclerosis and heart failure. Of particular interest are the function, supply and production of leukocytes, and the signals that regulate hematopoiesis after injuries such as myocardial infarction or stroke. We described that after MI, the spleen releases a large population of ready-made leukocytes that travel to the ischemic heart (Science 2009, New York Times 2009). We further found that MI, chronic stress and sedentary life style modulate the hematopoietic stem cell niche, activating migration and proliferation of myeloid progenitor cells (Nature 2012, Nature Med 2014, Nature Med 2019). Resident macrophages, on the other hand, do not derive from circulating cells and promote steady state functions such as cardiac conduction (Cell 2017). The laboratory also develops and employs imaging to sample biology non-invasively, using MR, nuclear, optical and microscopic modalities.
Steffens S, Nahrendorf M, Madonna R Immune cells in cardiac homeostasis and disease: emerging insights from novel technologies. Eur Heart J. 2021;:ePub - PMID: 34897403 - DOI: 10.1093/eurheartj/ehab842
Ott C, Pappritz K, Hegemann N, John C, Jeuthe S, McAlpine CS, Iwamoto Y, Lauryn JH, Klages J, Klopfleisch R, Van Linthout S, Swirski F, Nahrendorf M, Kintscher U, Grune T, Kuebler WM, Grune J Spontaneous Degenerative Aortic Valve Disease in New Zealand Obese Mice. J Am Heart Assoc. 2021;10(23):e023131 - PMID: 34779224 - DOI: 10.1161/JAHA.121.023131
Ryu WS, Schellingerhout D, Hong KS, Jeong SW, Kim BJ, Kim JT, Lee KB, Park TH, Park SS, Park JM, Kang K, Cho YJ, Park HK, Lee BC, Yu KH, Oh MS, Lee SJ, Kim JG, Cha JK, Kim DH, Lee J, Han MK, Park MS, Choi KH, Nahrendorf M, Lee J, Bae HJ, Kim DE Relation of Pre-stroke Aspirin Use With Cerebral Infarct Volume and Functional Outcomes. Ann Neurol. 2021;90(5):763-776 - PMID: 34536234 - DOI: 10.1002/ana.26219
Barrett TJ, Corr EM, van Solingen C, Schlamp F, Brown EJ, Koelwyn GJ, Lee AH, Shanley LC, Spruill TM, Bozal F, de Jong A, Newman AAC, Drenkova K, Silvestro M, Ramkhelawon B, Reynolds HR, Hochman JS, Nahrendorf M, Swirski FK, Fisher EA, Berger JS, Moore KJ Chronic stress primes innate immune responses in mice and humans. Cell Rep. 2021;36(10):109595 - PMID: 34496250 - PMCID: PMC8493594 - DOI: 10.1016/j.celrep.2021.109595
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Leukocytes in cardiovascular health
The Nahrendorf laboratory shares a longstanding interest with the Swirski lab in innate immune cells, especially myeloid cells. We discovered that healing after myocardial infarction involves time-resolved monocyte and macrophage subset dynamics. We identified a splenic monocyte reservoir, which deploys within 24 hours after myocardial infarction. This reservoir contributes half of all monocytes recruited to the infarct. In atherosclerosis and chronic heart failure, macrophages expand by proliferating locally, and there is interaction between local and systemic inflammation, including in the remote myocardium after ischemic injury. In the healthy heart, cardiac resident macrophages connect to myocytes via gap junctions and participate in electric conduction; their depletion leads to conduction abnormalities such as AV block.
Activation of hematopoiesis in cardiovascular disease
We described the mechanisms behind acceleration of atherosclerotic disease after a first infarct in the heart or brain. Infarct-induced sympathetic nervous system signaling in the bone marrow activates hematopoietic stem cells, which begin to proliferate and relocate to the spleen where they over-produce leukocytes. The most upstream point of hematopoiesis activation rests in CCR2+ hematopoietic stem cells. Newly produced leukocytes migrate to the atherosclerotic plaque, rendering it more inflamed and vulnerable to rupture, triggering reinfarction, a frequent clinical event that was previously unexplained. The findings are clinically important as they provide a new therapeutic opportunity to prevent secondary complications of atherosclerosis. We subsequently observed similar pathway activation after ischemic stroke and during exposure to chronic psychosocial stress.
In vivo RNAi for immunomodulation
In collaboration with MIT and Alnylam, we pioneered in vivo RNAi to silence the chemokine receptor CCR2, and subsequently other targets, in monocytes, macrophages and endothelial cells. Delivered by nanoparticles, siRNA is incorporated into splenic and circulating monocytes and macrophages, resulting in efficient silencing of gene expression. These cells 'lose their GPS', i.e. they are no longer able to migrate to the site of inflammation. This new class of anti-inflammatory therapy is highly selective, as it only targets certain genes. Subsequently we have targeted other proteins in myeloid cells and their progenitors as well as endothelial cells.