Noninvasive Assessment of Progenitor Cell Persistence in Wound Beds of Immunocompetent Mice
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Abstract: Synthetic grafts have become a clinical standard for the acute and chronic surgical care of wounds. While these grafts provide basic wound site coverage, the final outcomes of repair are often inadequate in terms of minimizing scar formation, restoring tissue functionality, and maintaining durability of the repaired site. Accordingly, there is a significant unmet need to develop a “next generation” graft matrices that can actively enhance tissue repair, remodeling and regeneration. To this end, the development of molecular tools to better understand the molecular physiology of wound repair is essential. In the experiments described here, we exploited advances in technologies that enable the noninvasive monitoring of endogenous gene expression, to evaluate the long-term persistence of grafted and engrafted progenitor cells in the wound bed. We show how a preclinical model using an actin promoter-driven bioluminescent reporter gene can provide a quantitative and non-invasive image assessment of bone marrow cell persistence in an Integra® (Integra LifeSciences, Plainsboro, NJ) graft for at least 2 weeks. This approach, along with other cell and tissue-specific promoters, can be used to develop wound healing models in which it is possible to better understand the pathophysiological relevance of tissue repair therapies. We suggest that the development of an increasing number of transgenic reporter mice that express bioluminescent genes under the regulation of specific promoters can be used as donors to characterize the molecular physiology of wound healing and evaluate the biological effectiveness of innovative engineered biomaterials.
From the Department of Surgery, University of California San Diego
Address correspondence to:
Andrew Baird, PhD
Division of Trauma, Surgical Critical Care, and Burns
Department of Surgery
University of California San Diego
212 Dickinson Street, MC 8236
San Diego, CA 92103
Synthetic matrices have been widely deployed as grafts for acute and chronic wounds, providing physical protection and coverage of the wound bed while supporting wound healing and optimizing subsequent autogenous skin grafting. While these matrices are currently imperfect with respect to the rate of wound closure, the decrease in final tensile strength, and the extent of scarring, the capacity for these matrices to provide a protected microenvironment for the recruitment and integration of progenitor cells has become an important objective of graft matrix development. For example, many studies have examined the capacity of dissociated keratinocytes, primary cultured fibroblasts and purified progenitor cells from blood and bone marrow, to be applied to the wound bed with the goal of accelerating the rate of wound healing.1–4 Although these strategies have helped identify specific stem cell/stem cell-like populations within the dermis, advances in skin cell biology and tissue engineering have yet to yield a biologically, structurally, cosmetically, and economically adequate substitute for skin.
In the experiments described here, we examine and then discuss the potential of emerging bioluminescent technologies to evaluate the role of progenitor cells—specifically, their persistence in the process of repair and regeneration in the wound bed. We examined the persistence of donor bioluminescent syngeneic mouse bone marrow cells when injected in a murine model of cutaneous wound healing that uses an Integra® (Integra LifeSciences, Plainsboro, NJ) graft. The results largely corroborate findings obtained with transplanted bone marrow cells in a graft but gain particular relevance because of the immunocompetent mouse used.
Materials and Methods
Surgery. Integra was sutured into a 1.5 cm full-thickness section of skin on the dorsum of FVB strain-matched mice.