Reprogrammed Mesenchymal stem cells to treat biofilm-infected wounds: a novel approach to chronic wound care
Background: Chronic wounds are a serious medical condition affecting over 6 million people in the United States. Biofilms, which are communities of bacteria attached to a surface and protected by a polysaccharide coating, are intimately associated with the development of chronic wounds. They alter the host immune response and establish a microenvironment that prevents wound healing. Current treatment options do not target biofilms. One novel treatment solution for chronic wounds involves the paracrine factors from mesenchymal stem cells (MSCs), which have been shown to stimulate wound healing in non-infected wounds. The aim of this dissertation was to examine the effects of reprogrammed MSCs and their paracrine factors on ameliorating infection and accelerating wound closure in biofilm infected wounds. Methods: MSCs were reprogrammed by 3 strategies: seeding on an extracellular matrix (ECM), as spheroids in static culture, and as spheroids in a bioreactor. The paracrine factors were analyzed using a 14-plex cytokine assay to confirm changes from baseline. The paracrine factors were applied to mature P. aeruginosa biofilms in vitro and the number of viable bacteria were quantitated. They were also used to stimulate RAW 264.7 murine macrophages and analyzed for the presence of CD206, a marker of anti-inflammatory macrophage phenotype. BALB/cJ mice were wounded and infected with P. aeruginosa biofilms and the paracrine factors from reprogrammed MSCs were applied topically. The wound area and CFU counts of the treatment group were compared to the control and untreated groups. Results: MSCs grown as spheroids in a bioreactor produced significant increases in IL-6 and IL-8 after 3 and 7 days (p<0.05 and p<0.0001). The paracrine factors from MSCs grown on ECM were found to reduce P. aeruginosa biofilm growth significantly (p<0.01). Spheroids grown statically and in a bioreactor increased the amount of macrophages expressing CD206. Mice wounds receiving the paracrine factors from MSCs grown on ECM had lower bacterial counts and an increased rate of wound closure compared to non-treated mice wounds. Conclusions: The results indicate that paracrine factors from reprogrammed MSCs accelerated wound healing and reduced the bacterial burden in biofilm infected wounds.