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Adoptive Transfer Of Tolerogenic Dendritic Cells Promotes Angiogenesis And Wound Healing
Dominic Henn, MD1,2, Clark A. Bonham, Jr.1, Kelln Chen, PhD1, Jagannath Padmanabhan, PhD1, Artem Trotsyuk1, Janos A. Barrera, MD1, Katharina S. Fischer1, Sun Hyung Kwon, PhD1, Michael Januszyk, MD, PhD1, Geoffrey C. Gurtner, MD1.
1Hagey Laboratory for Pediatric and Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Stanford University, Stanford, CA, USA, 2Department of Hand, Plastic and Reconstructive Surgery, Ludwigshafen Trauma Center, Heidelberg University, Ludwigshafen, Germany.

PURPOSE:
Dendritic cells (DCs) are a heterogeneous cell population which critically regulates the adaptive immune response. Depending on their activation status, DCs can also promote peripheral immune tolerance, thus limiting the activation of the immune system and tissue damage. Cell based therapy approaches using DCs have been approved by the FDA and clinical trials using DC immunotherapy are being performed against a variety of cancer types. However, the role of DC therapy for wound healing has not yet been investigated.
METHODS: Hematopoetic stem cells (HSCs) were isolated from the bone marrow of green fluorescent protein (GFP) expressing mice and differentiated into DCs over a 7 day in vitro culture period. Tolerogenic DCs (TDCs) were induced by stimulation of cultures with 1,25-dihydroxyvitamin D3 (1α,25(OH)2D3), lipopolysaccharide or dexamethasone and the angiogenic potential of the cells was evaluated by endothelial cell (EC) tube formation assays in transwell as well as direct co-cultures. The protein levels of 52 cytokines were measured in the conditioned media of DC cultures using Luminex multiplex assays. The ability of TDCs to accelerate wound healing was evaluated by treating splinted excisional wounds in C57BL6/J mice weekly with pullulan-collagen hydrogels seeded with 1α,25(OH)2D3-stimulated TDCs, unstimulated DCs or blank hydrogels.
RESULTS: EC tube formation assays showed a significantly higher EC branch number and length when co-cultured with TDCs treated with 1α,25(OH)2D3 both in transwell as well as direct co-cultures. 1α,25(OH)2D3 treatment strongly enhanced vascular endothelial growth factor (VEGF) secretion compared to untreated DCs in vitro (14-fold). Excisional wounds treated with TDC-seeded hydrogels demonstrated significantly faster healing compared to untreated DCs and blank hydrogels.
CONCLUSION: Our data indicate that the induction of tolerogenicity in DCs by 1α,25(OH)2D3 enhances their secretion of VEGF, thus promoting EC tube formation and accelerating wound healing. Given their ready availability from human blood through established leukapheresis protocols and easy multiplication in vitro, TDCs are promising candidates for novel autologous cell-based therapy approaches for wound healing.


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