Macrophage-like U937 cells recognize collagen fibrils with strain-induced discrete plasticity damage
Article first published online: 15 APR 2014
© 2014 Wiley Periodicals, Inc.
Journal of Biomedical Materials Research Part A
Volume 103, Issue 1, pages 397–408, January 2015
How to Cite
How to cite this article: 2015. Macrophage-like U937 cells recognize collagen fibrils with strain-induced discrete plasticity damage. J Biomed Mater Res Part A 2015:103A:397–408., , .
- Issue published online: 25 NOV 2014
- Article first published online: 15 APR 2014
- Accepted manuscript online: 10 MAR 2014 04:57AM EST
- Manuscript Accepted: 21 FEB 2014
- Manuscript Revised: 14 FEB 2014
- Manuscript Received: 20 JAN 2014
- Killam Trust (Postdoctoral Funding to S.P.V.)
- Natural Sciences and Engineering Research Council of Canada (NSERC) (to J.M.L.)
- collagen fibril;
- discrete plasticity;
- mechanical overload;
At its essence, biomechanical injury to soft tissues or tissue products means damage to collagen fibrils. To restore function, damaged collagen must be identified, then repaired or replaced. It is unclear at present what the kernel features of fibrillar damage are, how phagocytic or synthetic cells identify that damage, and how they respond. We recently identified a nanostructural motif characteristic of overloaded collagen fibrils that we have termed discrete plasticity. In this study, we have demonstrated that U937 macrophage-like cells respond specifically to overload-damaged collagen fibrils. Tendons from steer tails were bisected, one half undergoing 15 cycles of subrupture mechanical overload and the other serving as an unloaded control. Both halves were decellularized, producing sterile collagen scaffolds that contained either undamaged collagen fibrils, or fibrils with discrete plasticity damage. Matched-pairs were cultured with U937 cells differentiated to a macrophage-like form directly on the substrate. Morphological responses of the U937 cells to the two substrates—and evidence of collagenolysis by the cells—were assessed using scanning electron microscopy. Enzyme release into medium was quantified for prototypic matrix metalloproteinase-1 (MMP-1) collagenase, and MMP-9 gelatinase. When adherent to damaged collagen fibrils, the cells clustered less, showed ruffled membranes, and frequently spread: increasing their contact area with the damaged substrate. There was clear structural evidence of pericellular enzymolysis of damaged collagen—but not of control collagen. Cells on damaged collagen also released significantly less MMP-9. These results show that U937 macrophage-like cells recognize strain-induced discrete plasticity damage in collagen fibrils: an ability that may be important to their removal or repair. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 397–408, 2015.