Substrate elasticity regulates the behavior of human monocyte-derived macrophages
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Macrophages play a key role in atherosclerosis, cancer, and in the response to implanted medical devices. In each of these situations, the mechanical environment of a macrophage can vary from soft to stiff. However, how stiffness affects macrophage behavior remains uncertain. Using substrates of varying stiffness, we show macrophage phenotype and function depends on substrate stiffness. Notably, the cell area increases slightly from a sphere after 18 h on substrates mimicking healthy arterial stiffness (1–5 kPa), whereas macrophages on stiffer substrates (280 kPa–70 GPa) increased in area by nearly eight-fold. Macrophage migration is random regardless of substrate stiffness. The total average track speed was 7.8 ± 0.5 μm/h, with macrophages traveling fastest on the 280-kPa substrate (12.0 ± 0.5 μm/h) and slowest on the 3-kPa substrate (5.0 ± 0.4 μm/h). In addition F-actin organization in macrophages depends on substrate stiffness. On soft substrates, F-actin is spread uniformly throughout the cytoplasm, whereas on stiff substrates F-actin is functionalized into stress fibers. The proliferation rate of macrophages was faster on stiff substrates. Cells plated on the 280-kPa gel had a significantly shorter doubling time than those plated on the softer substrate. However, the ability of macrophages to phagocytose 1-μm particles did not depend on substrate stiffness. In conclusion, the results herein show macrophages are mechanosensitive; they respond to changes in stiffness by modifying their area, migration speed, actin organization, and proliferation rate. These results are important to understanding how macrophages respond in complex mechanical environments such as an atherosclerotic plaque.
KeywordsMechanobiology Stiffness Proliferation Migration Spreading area Phagocytosis
We gratefully appreciate UMD undergraduates Megan Mathews and Connie Chen for making polyacrylamide gels and analyzing data, as well as UTD undergrad Melanie Maurer for conducting some of the proliferation studies. Funding was provided by the National Science Foundation CMMI-0643783 and Human Frontier Science Project Organization RGP0058/2012 (H.A.E.).
- Aikawa M, Rabkin E, Sugiyama S, Voglic SJ, Fukumoto Y, Furukawa Y, Shiomi M, Schoen FJ, Libby P (2001) An HMG-CoA reductase inhibitor, cerivastatin, suppresses growth of macrophages expressing matrix metalloproteinases and tissue factor in vivo and in vitro. Circulation 103:276–283CrossRefPubMedGoogle Scholar
- Huynh J, Nishimura N, Rana K, Peloquin JM, Califano JP, Montague CR, King MR, Schaffer CB, Reinhart-King CA (2011) Age-related intimal stiffening enhances endothelial permeability and leukocyte transmigration. Sci Transl Med 3:112ra122. doi:10.1126/scitranslmed.3002761 PubMedPubMedCentralGoogle Scholar
- Jacobs CR, Huang H, Kwon RY (2013) Introduction to cell mechanics and mechanobiology. Garland Science, New YorkGoogle Scholar
- Rambhia SH, Liang X, Xenos M, Alemu Y, Maldonado N, Kelly A, Chakraborti S, Weinbaum S, Cardoso L, Einav S, Bluestein D (2012) Microcalcifications increase coronary vulnerable plaque rupture potential: a patient-based micro-CT fluid-structure interaction study. Ann Biomed Eng 40:1443–1454. doi:10.1007/s10439-012-0511-x CrossRefPubMedGoogle Scholar
- Robbins CS, Hilgendorf I, Weber GF, Theurl I, Iwamoto Y, Figueiredo JL, Gorbatov R, Sukhova GK, Gerhardt LM, Smyth D, Zavitz CC, Shikatani EA, Parsons M, van Rooijen N, Lin HY, Husain M, Libby P, Nahrendorf M, Weissleder R, Swirski FK (2013) Local proliferation dominates lesional macrophage accumulation in atherosclerosis. Nat Med 19:1166–1172. doi:10.1038/nm.3258 CrossRefPubMedPubMedCentralGoogle Scholar
- Van Goethem E, Poincloux R, Gauffre F, Maridonneau-Parini I, Le Cabec V (2010) Matrix architecture dictates three-dimensional migration modes of human macrophages: differential involvement of proteases and podosome-like structures. J Immunol 184:1049–1061. doi:10.4049/jimmunol.0902223 CrossRefPubMedGoogle Scholar
- Vengrenyuk Y, Carlier S, Xanthos S, Cardoso L, Ganatos P, Virmani R, Einav S, Gilchrist L, Weinbaum S (2006) A hypothesis for vulnerable plaque rupture due to stress-induced debonding around cellular microcalcifications in thin fibrous caps. Pro Natl Acad Sci USA 103:14678–14683. doi:10.1073/pnas.0606310103 CrossRefGoogle Scholar