An immunocompetent bioengineered human dermal equivalent to recapitulate scar tissue formation in vitro

Scar formation, a natural outcome of cutaneous repair, poses significant clinical challenges due to its aesthetic, functional, and psychological impacts. Existing experimental models, while enhancing our understanding of wound healing, often fail to capture the intricate cellular, molecular, and structural mechanisms underlying scar tissue formation. In this study, we present an advanced immunocompetent three-dimensional human dermal equivalent (3D-HDE) model that incorporates M2a macrophages to mimic inflammation and fibrosis in vitro. By inducing secondary intention wounds via punch biopsy and introducing M2a macrophages, the model successfully replicates key features of fibrotic tissue, including the overactivation of fibroblasts into myofibroblasts, aberrant extracellular matrix (ECM) production and dysfunctional ECM assembly. M2a macrophages were found to regulate the anomalous assembly of the ECM, driving the formation of densely packed and aligned collagen type I fibers, primarily by facilitating the transformation of fibroblasts into myofibroblasts. This innovative model provides a physiologically relevant platform for studying the dynamic interplay between macrophages, myofibroblasts, and ECM remodeling during scar evolution. The immunocompetent 3D-HDE model opens new avenues for investigating wound healing mechanisms, fibrosis and the development of targeted anti-fibrotic therapies. Statement of Significance: Current in vitro tissue models often fail to capture the complexities of human fibrosis at both the cellular and extracellular levels. To address this, our study introduces an immunocompetent three-dimensional human dermal equivalent (3D-HDE) model, incorporating M2 macrophages to explore the role of immune cells in scar tissue formation. This innovative model effectively replicates key features of fibrosis, including fibroblast activation, extracellular matrix (ECM) deposition and remodeling, and collagen alignment. The physiological relevance of our model not only facilitates the study of fibrosis but also enables the testing of anti-fibrotic therapies, providing deeper insights into macrophage-driven wound healing mechanisms. This work bridges a critical gap between traditional in vitro models and clinical applications, advancing our understanding of wound healing, immune responses, and tissue engineering.