Plastic Surgery Research Council
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Presenter: Robert C Rennert, MD
Co-Authors: Sorkin M; Garg RK; Januszyk M; Gurtner GC
Stanford University

Introduction: Extracellular matrices (ECMs) are used for a variety of wound management and reconstructive applications. ECMs act as a scaffold for cellular infiltration, and ideally undergo remodeling to resemble host tissue. PriMatrixTM is a novel acellular collagen matrix derived from fetal bovine dermis that is designed for use in partial- and full-thickness wounds. This study analyzes the immune and stem cell response to PriMatrix in vivo, as well as the remodeling capacity of implanted matrix and its ability to facilitate normal tissue regeneration.

Methods: Rehydrated PriMatrix samples were implanted subcutaneously on the dorsum of wild-type mice. Inflammatory response, stem cell recruitment and tissue remodeling were evaluated at multiple time points using H&E and trichrome stains, as well as immunohistochemical (IHC) and flow cytometric analyses. Healthy skin and sham-operated sites without PriMatrix implantation were used as controls.

Results: PriMatrix implants were found to go through a biological remodeling initiated by a transient infiltrate of inflammatory cells (Figure 1), followed by mesenchymal stem cell (MSC) recruitment and vessel formation (Figure 2). Immunohistochemical analysis revealed that the majority of the implanted fetal dermal collagen fibers persisted through day 28, but H&E and trichrome staining demonstrate that implants underwent remodeling and cellular re-population to form tissue with a density and morphology consistent with healthy dermis.

Conclusions: PriMatrix implants undergo progressive in vivo remodeling, facilitating the regeneration of histologically normal tissue through a transient inflammatory and stem cell response. Regeneration of normal tissue is especially important in a wound environment, and these findings warrant further investigation of PriMatrix in this setting.

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