(77f) Optimization of Mesenchymal Stem Cell Migration In the Wound Bed

Kevin Rodriguez, Deepraj Ghosh, Kathleen McAndrews, Daniel McGrail, Michelle Dawson

Georgia Institute of Technology, Atlanta, GA

Upon injury to the skin, the epidermal barrier is disrupted and the complex process of wound healing begins. Growth factors are essential in mediating the stages of wound healing, which proceed continuously from the time of epidermal damage to scar formation (Martin 1997). Elderly patients and patients suffering from chronic illness, including diabetes, ischemia, or hypertension, develop chronic wounds when the wound healing process is arrested in a state of chronic inflammation. Two of the factors that have been associated with the formation of chronic wounds are: (1) impaired growth factor production and (2) reduced angiogenesis (Wu, Chen et al. 2007). Mesenchymal stem cells (MSCs) have been shown to secrete cytokines, which promoted more rapid wound healing in normal and diabetic mice (Wu, Chen et al. 2007). Our studies are focused on optimization of the mechanical properties of MSCs for more rapid migration in wound tissue. We hypothesize that migrating MSCs that disseminate throughout the wound will contribute to the formation of granulation tissue, which will constrict the wound for more rapid wound closure.

Cell-based therapies often suffer from in vivo transport limitations. Previous studies have demonstrated that MSC treatment with soluble growth factors results in increased in vitro cell migration; however, little is known about the effects of these proteins on the mechanical properties and in vivo migration of MSCs. We systematically characterized the effects of tumor conditioned medium (TCM), a cocktail of soluble factors secreted by tumor cells in culture, and TGF-b1, a soluble factor involved in wound healing, on the mechanical properties of bone marrow-derived murine MSCs. Treatment of MSCs with TCM and TGF-b1 resulted in increased cytoskeletal elasticity, measured with multiple particle tracking microrheology, dramatic cell elongation, and increased cell migration. In vitro characterization of the mechanical properties of treated and control MSCs was used to design an in vivo murine wound healing model. Two full-thickness 5-mm skin biopsy punch wounds were created on either side of the dorsal midline on Balb-C mice. Treated and control fluorescently-labeled MSCs were injected at the periphery of the wound. Wound healing was monitored for 7 or 14 days, and the migration of MSCs in the wound bed was quantified with intravital epifluorescent microscopy. We found that TCM treatment significantly increased MSC migration in the wound bed and increased the rate of wound closure. The optimization of MSC migration may be an important step in the development of more effective MSC-based wound healing therapeutics.

Martin, P. (1997). "Wound healing-aiming for perfect skin regeneration." Science 276(5309): 75-81.

Wu, Y., L. Chen, et al. (2007). "Mesenchymal stem cells enhance wound healing through differentiation and angiogenesis." Stem Cells 25(10): 2648-59.