Mechanical Properties of the Tumor Stromal Microenvironment Probed In Vitro and Ex Vivo by In Situ-Calibrated Optical Trap-Based Active Microrheology
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One of the hallmarks of the malignant transformation of epithelial tissue is the modulation of stromal components of the microenvironment. In particular, aberrant extracellular matrix (ECM) remodeling and stiffening enhances tumor growth and survival and promotes metastasis. Type I collagen is one of the major ECM components. It serves as a scaffold protein in the stroma contributing to the tissue’s mechanical properties, imparting tensile strength and rigidity to tissues such as those of the skin, tendons, and lungs. Here we investigate the effects of intrinsic spatial heterogeneities due to fibrillar architecture, pore size and ligand density on the microscale and bulk mechanical properties of the ECM. Type I collagen hydrogels with topologies tuned by polymerization temperature and concentration to mimic physico-chemical properties of a normal tissue and tumor microenvironment were measured by in situ-calibrated Active Microrheology by Optical Trapping revealing significantly different microscale complex shear moduli at Hz-kHz frequencies and two orders of magnitude of strain amplitude that we compared to data from bulk rheology measurements. Access to higher frequencies enabled observation of transitions from elastic to viscous behavior that occur at ~200–2750 Hz, which largely was dependent on tissue architecture well outside the dynamic range of instrument acquisition possible with SAOS bulk rheology. We determined that mouse melanoma tumors and human breast tumors displayed complex moduli ~5–1000 Pa, increasing with frequency and displaying a nonlinear stress–strain response. Thus, we show the feasibility of a mechanical biopsy in efforts to provide a diagnostic tool to aid in the design of therapeutics complementary to those based on standard histopathology.
KeywordsMicrorheology Optical traps Biomaterials Tissue mechanics Hydrogels Biopsy
This effort was supported by the Intramural Research Program of the National Institutes of Health, the National Cancer Institute. We thank Ben Blehm for helpful technical discussions and George Leiman for critical reading of the manuscript. We also thank Daniel Blair, and Xinran Zhang of Georgetown University for assistance with bulk rheometry.
Conflict of interest
Dr. Tanner and Alexus Devine have an international stage PCT application pending. Jack R Staunton, Wilfred Vieira, King Leung Fung and Ross Lake, all declare that they have no conflict of interest.
Animal studies were conducted under protocols approved by the National Cancer Institute, and the National Institutes of Health Animal Care and Use Committee. No human subjects research was performed in this studies.
- 1.Abidine, Y., R. Michel, A. Duperray, L. Iulian, C. Verdier, Y. Abidine, et al. Physical properties of polyacrylamide gels probed by AFM and rheology. EPL Eur. Phys. Soc. 109:38003, 2015.Google Scholar
- 5.An, K. N., Y. L. Sun, and Z. P. Luo. Flexibility of type I collagen and mechanical property of connective tissue. Biorheology 41(3–4):239–246, 2004.Google Scholar
- 25.Entenberg, D., Kedrin, D., Wyckoff, J., Sahai, E., Condeelis, J., & Segall, J. E. (2013). Imaging tumor cell movement in vivo. Curr. Protoc. Cell Biol. Chapter 19, Unit19.7. 10.1002/0471143030.cb1907s58.
- 31.Fischer, M., and K. Berg-sørensen. Calibration of trapping force and response function of optical tweezers in viscoelastic media. J. Opt. A 9(8): S239. Retrieved from http://stacks.iop.org/1464-4258/9/i=8/a=S18, 2007
- 48.Kamm, R. D., and M. R. Mofrad. In: Cytoskeletal Mechanics: Models and Measurements1st, edited by R. D. Kamm, and M. R. Mofrad. New York: Cambridge University Press, 2006.Google Scholar
- 70.Paget, S. The distribution of secondary growths in cancer of the breast. 1889. Cancer Metastasis Rev. 8(2):98–101, 1989.Google Scholar
- 72.Patsialou, A., J. J. Bravo-Cordero, Y. Wang, D. Entenberg, H. Liu, M. Clarke, and J. S. Condeelis. Intravital multiphoton imaging reveals multicellular streaming as a crucial component of in vivo cell migration in human breast tumors. Intravital 2(2):e25294, 2013. doi: 10.4161/intv.25294.CrossRefGoogle Scholar
- 100.Weber, F., L. Shen, K. Fukino, A. Patocs, G. L. Mutter, T. Caldes, and C. Eng. Total-genome analysis of BRCA1/2-related invasive carcinomas of the breast identifies tumor stroma as potential landscaper for neoplastic initiation. Am. J. Hum. Genet. 78(6):961–972, 2006. doi: 10.1086/504090.CrossRefGoogle Scholar
- 103.Williams, B. R., R. A. Gelman, D. C. Poppke, and K. A. Piez. Collagen fibril formation. Optimal in vitro conditions and preliminary kinetic results. J. Biol. Chem. 253(18):6578–6585, 1978Google Scholar