Observing and Quantifying Fibroblast-mediated Fibrin Gel Compaction

Abstract

Cells embedded in collagen and fibrin gels attach and exert traction forces on the fibers of the gel. These forces can lead to local and global reorganization and realignment of the gel microstructure. This process proceeds in a complex manner that is dependent in part on the interplay between the location of the cells, the geometry of the gel, and the mechanical constraints on the gel. To better understand how these variables produce global fiber alignment patterns, we use time-lapse differential interference contrast (DIC) microscopy coupled with an environmentally controlled bioreactor to observe the compaction process between geometrically spaced explants (clusters of fibroblasts). The images are then analyzed with a custom image processing algorithm to obtain maps of the strain. The information obtained from this technique can be used to probe the mechanobiology of various cell-matrix interactions, which has important implications for understanding processes in wound healing, disease development, and tissue engineering applications. Video LinkThe video component of this article can be found at

Roles of adherent myogenic cells and dynamic culture in engineered muscle function and maintenance of satellite cells

“…S3B). An important factor in cell-mediated gel compaction is the presence of fibroblasts [23], which, consistent with the changes in bundle diameter, were found to more rapidly form dense outer layer in AF compared to FI bundles (Fig. S4).…”

“…Given the reported effects of shear stress on enhancing fibroblast migration [31] and proliferation [32], higher fibroblast density after 2 weeks of dynamic vs. static culture could be expected. Contraction of fibroblasts and secretion of proteolytic enzymes have been previously shown to contribute to hydrogel remodeling and compaction [23, 33] and thus increased compaction of dynamically cultured bundles at 2 weeks of culture could be at least in part attributed to their higher fibroblast density. Interestingly, we have also noticed a more rapid accumulation of fibroblasts at the periphery of AF bundles (starting as early as culture day 2) along with their accelerated initial compaction and smaller diameter at 2 weeks compared to those of FI bundles (Fig 1, S1).…”

Augmenting Surgery via Multi-scale Modeling and Translational Systems Biology in the Era of Precision Medicine: A Multidisciplinary Perspective

“…This behavior has been predicted by an image-based multiscale FE model that couples centimeter-scale tissue properties to micrometer-scale ECM restructuring 4, 94, 103 . These models have been benchmarked against in vitro time-lapse imaging experiments on fibroblast remodeled fibrin gels and demonstrate that the multiscale interplay between macroscopic domain geometry, boundary conditions, and cell traction forces drives short-term remodeling and the development of fibrin fiber alignment, which could be deterministic of the extent of scarring 27, 28 . An attractive feature of these models is that deterministic and stochastic fiber-based rules can be inserted into the modeling framework so that concepts such as strain stabilized enzymatic matrix remodeling 46 and gross tissue-level failure 45 can be explored as multiscale phenomena, which may have relevance for understanding fibrosis and wound strength, respectively.…”

Effects of mechanical stimulation on fibroblast-guided microstructural and compositional remodeling

“…Fibrin gels were prepared as described previously [86,91] Catalog No. P35G-0-20-C) or the viewport glass of a microscope-mounted bioreactor (described below).…”

“…Three explants were positioned at the vertices of a triangle with each side measuring approximately 2 mm from explant centroid-to-centroid (c.f., [91]). The cells were then allowed to settle and attach to the fibrin gel for approximately 2 hours before fresh medium with 10 µg/mL aprotinin was added in order to limit the potential for serine protease induced fibrin degradation [93].…”