Wound healing is a complex and dynamic process that involves three major, interconnected stages: epithelial formation, connective tissue deposition, and tissue contraction. Among these, the contraction phase plays a critical role in reducing wound size and restoring tissue integrity. This process is largely mediated by specialized fibroblasts known as myofibroblasts, which possess contractile properties similar to smooth muscle cells. These cells actively generate tension within the extracellular matrix (ECM), facilitating wound closure.
To investigate the mechanisms underlying fibroblast-mediated contraction, three-dimensional (3D) collagen gels have emerged as a physiologically relevant in vitro model. Unlike traditional two-dimensional (2D) culture systems, 3D collagen matrices better mimic the in vivo microenvironment, allowing for more accurate studies of fibroblast behavior, integrin-mediated signaling, cytoskeletal reorganization, and cell apoptosis under conditions that resemble natural tissue architecture.
In Vitro Culture Models for Fibroblast-Mediated Contraction
We propose two distinct in vitro culture models to assess the capacity of fibroblasts to remodel and contract collagen matrices:
The 2-Step Contraction Model
In this approach, fibroblasts are first cultured in an attached collagen matrix, which generates mechanical stress as the cells pull on the surrounding matrix. This initial phase establishes a mechanical load, inducing cellular responses to tension. Following this, the matrix is released from its attachment, creating a period of mechanical unloading. The subsequent secondary contraction occurs as the mechanical stress dissipates, providing insight into the fibroblasts’ ability to adapt to dynamic mechanical conditions and remodel the matrix in response to changes in tension.
The Floating Matrix Contraction Model
In this model, a freshly polymerized collagen gel containing fibroblasts is freely suspended in culture medium, without attachment to the culture dish. Here, contraction occurs independently of external mechanical load. Interestingly, cells in this setup do not develop prominent stress fibers, indicating that matrix contraction can be mediated through alternative mechanisms, potentially relying more on cell-matrix interactions and intrinsic contractile activity rather than on pre-existing cytoskeletal tension.
Together, these models provide complementary tools for studying fibroblast-mediated matrix contraction. The 2-step model emphasizes the effects of mechanical load and stress release, while the floating matrix model isolates the intrinsic contractile behavior of fibroblasts in a low-tension environment. Using both approaches can improve our understanding of cellular mechanics, matrix remodeling, and wound healing processes, which is essential for developing therapies aimed at enhancing tissue repair and minimizing fibrosis.
