Human multipotent adult progenitor cell-conditioned medium improves wound healing through modulating inflammation and angiogenesis in mice

BACKGROUND: Stem cell therapies have been widely investigated for their healing effects. However, the translation of these therapies has been hampered by the requirement to deliver live allogeneic or autologous cells directly to the wound in a clinical setting. Multipotent adult progenitor cells (MAPC® cells) are a subpopulation of bone marrow-derived adherent stem cells that secrete a wide range of factors known to accelerate the wound healing process. The aim of this study was to determine the impact of MAPC cells secretome on healing outcomes without the presence of MAPC cells. METHODS: The effect of MAPC-conditioned medium (MAPC-CM) on the capacity of keratinocytes, fibroblasts and endothelial cells to migrate and proliferate was determined in vitro using scratch wound closure and WST1 assay, respectively. The effect of MAPC-CM on collagen deposition and angiogenesis was also assessed using in vitro methods. Additionally, two excisional wounds were created on the dorsal surface of mice (n = 8/group) and 100 μL of 20× MAPC-CM were intradermally injected to the wound margins. Wound tissues were collected at 3, 7 and 14 days post-wounding and stained with H&E for microscopic analysis. Immunohistochemistry was performed to investigate inflammation, angiogenesis and collagen deposition in the wounds. RESULTS: Skin fibroblasts, keratinocytes and endothelial cells treated with MAPC-CM all showed improved rates of scratch closure and increased cellular proliferation. Moreover, fibroblasts treated with MAPC-CM deposited more collagens I and III and endothelial cells treated with MAPC-CM showed increased capillary tube formation. Murine excisional wounds intradermally injected with MAPC-CM showed a significant reduction in the wound area and an increase in the rate of reepithelialisation. The results also showed that inflammatory cell infiltration was decreased while an increase in angiogenesis, as well as collagens I and III expressions, was observed. CONCLUSION: These findings suggest that factors produced by MAPC cells can have an important effect on cutaneous wound healing by affecting skin cell proliferation and migration, balancing inflammation and improving the formation of extracellular matrix and angiogenesis. Development of stem cell-free therapy for the treatment of wounds may be a more clinically translatable approach for improving healing outcomes.