Simon D D, Niklason L E, Humphrey J D
Department of Biomedical Engineering, Yale University, New Haven, Conn., USA.
Cells Tissues Organs. 2014;200(2):104-17. doi: 10.1159/000381015. Epub 2015 Apr 22.
Cell-populated collagen gels have provided significant insight into the cellular contractile mechanisms and cell-matrix interactions that are necessary for compacting and remodeling extant matrix. Nevertheless, little research has been devoted towards determining how cells entrench these deformations that contribute to establishing a preferred mechanical state. To this end, we examined the roles of two covalent matrix cross-linkers, i.e. tissue transglutaminase and lysyl oxidase, during global remodeling of the free-floating fibroblast-populated collagen lattice. Inhibition of tissue transglutaminase resulted in a reduced rate of compaction compared to controls during early remodeling (up to 2 days). In contrast, inhibition of lysyl oxidase did not alter the early compaction of these lattices, but it reduced the compaction after 2 days of culture. Acute inhibition of different contractile mechanisms suggested further that calcium-dependent contractility may have dominated during the initial remodeling of the collagen lattice before giving way to calcium-independent contractility at later times. In summary, these findings suggest that early remodeling of the free-floating collagen lattice is facilitated by calcium-dependent cell contraction while entrenchment is dominated by a tissue transglutaminase-mediated cross-linking of the extant matrix. As remodeling continues, however, lysyl oxidase increases its contribution, perhaps by consolidating de novo collagen fibrils into fibers to continue the remodeling while the cells transition to a more sustained, calcium-independent contractility. These results promise to influence future tissue engineering studies as well as computational simulations aimed at understanding matrix remodeling in complex in vivo situations.
细胞填充的胶原凝胶为深入了解细胞收缩机制和细胞与基质的相互作用提供了重要见解，这些机制对于压实和重塑现有基质是必不可少的。然而，对于确定细胞如何巩固这些有助于建立优选机械状态的变形，相关研究却很少。为此，我们研究了两种共价基质交联剂，即组织转谷氨酰胺酶和赖氨酰氧化酶，在游离漂浮的成纤维细胞填充的胶原晶格整体重塑过程中的作用。在早期重塑阶段（长达2天），与对照组相比，抑制组织转谷氨酰胺酶导致压实速率降低。相比之下，抑制赖氨酰氧化酶并没有改变这些晶格的早期压实情况，但在培养2天后降低了压实程度。对不同收缩机制的急性抑制进一步表明，在胶原晶格的初始重塑过程中，钙依赖性收缩可能占主导地位，随后在后期让位于非钙依赖性收缩。总之，这些发现表明，游离漂浮的胶原晶格的早期重塑由钙依赖性细胞收缩促进，而巩固则由组织转谷氨酰胺酶介导的现有基质交联主导。然而，随着重塑的继续，赖氨酰氧化酶的贡献增加，可能是通过将新生胶原原纤维整合为纤维来继续重塑，同时细胞转变为更持久的非钙依赖性收缩。这些结果有望影响未来的组织工程研究以及旨在理解复杂体内情况下基质重塑的计算模拟。
