Ex vivo expanded haematopoietic progenitor cells improve dermal wound healing by paracrine mechanisms

Background: Although dermal wounds are common, treatment remains limited and largely ineffective. Recent studies suggest that therapeutic application of progenitor cells is useful for tissue regeneration. Objective: We here investigated the effects exerted by the recently characterized immortalized haematopoietic progenitor cell line DKmix and their conditioned medium in a murine wound healing model. Methods and Results: Injection of both DKmix cells and their conditioned medium accelerated wound repair between days 3 and 10 compared with PBS-injected control mice (n = 8, P < 0.01 DKmix cells vs control, P < 0.01 conditioned medium vs control at day 6). The treated groups exhibited more CD31⁺-capillaries at day 6 after injury compared with the control group (n = 4, P < 0.01 DKmix cells vs control, P < 0.001 conditioned medium vs control), whereas there was no change in infiltrated CD68 + macrophages. Conditioned medium of DKmix cells induced tube formation of human endothelial cells in Matrigel assays (n = 4-6, P < 0.05 conditioned medium vs control) as well as migration (n = 4, P < 0.01 conditioned medium vs control) and proliferation of murine 3T3 fibroblasts (n = 5, P < 0.05 conditioned medium vs control). Abundant levels of matrix metalloproteinase -2 and -9 in the supernatants were detected. Protein arrays of the supernatants revealed a strong secretion of cytokines and growth factors, such as monocyte chemoatractant protein-1 and GM-CSF from DKmix cells. Conclusions: DKmix cells improve skin-substitute wound healing by promoting angiogenesis as well as migration and proliferation of fibroblasts. These data suggest that immortalized haematopoietic progenitor cells significantly improve dermal wound healing by paracrine effects.