Abstract
A micrograft technique, which minces tissue into micro-fragments >50 μm, has been recently developed. However, its pathophysiological mechanisms in wound healing are unclear yet. We thus performed a wound healing study using normal mice. A humanized mouse model of a skin wound with a splint was used. After total skin excision, tissue micro-fragments obtained by the Rigenera protocol were infused onto the wounds. In the cell tracing study, GFP-expressing green mice and SCID mice were used. Collagen stains including Picrosirius red (PSR) and immunohistological stains for α-smooth muscle actin (αSMA), CD31, transforming growth factor-β1 (TGF-β1) and neutrophils were evaluated for granulation tissue development. GFP-positive cells remained in granulation tissue seven days after infusion, but vanished after 13 days. Following the infusion of the tissue micrograft solution onto the wound, TGF-β1 expression was transiently upregulated in granulation tissue in the early phase. Subsequently, αSMA-expressing myofibroblasts increased in number in thickened granulation tissue with acceleration of neovascularization and collagen matrix maturation. On such granulation tissue, regenerative epithelial healing progressed, resulting in wound area reduction. Alternative alteration after the micrograft may have increased αSMA-expressing myofibroblasts in granulation tissue, which may act on collagen accumulation, neovascularization and wound contraction. All of these changes are favorable for epithelial regeneration on wound.
Highlights
Unhealed chronic wounds that develop in patients with senile decay and/or metabolic disorders including diabetes cause serious problems for the individual, and society
transforming growth factor-β1 (TGF-β1) is a portent factor for wound contraction and extracellular matrix (ECM) deposition through the function of α-smooth muscle actin (αSMA) expressing myofibroblasts [5], by which ECM is remodeled in granulation tissue
In our tracing study of grafted tissue, the presence of GFP-expressing cells from the skin of green mice was limited in the early phase of granulation, but later on, no GFP-expressing cells were detected in matured granulation tissue
Summary
Unhealed chronic wounds that develop in patients with senile decay and/or metabolic disorders including diabetes cause serious problems for the individual, and society. Different growth factors are involved in the repair process [3], which include transforming growth factor-beta (TGF-β), platelet-derived growth factor (PDGF), connective tissue growth factor (CTGF), epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF). These factors act to manifest biological roles in granulation tissue, i.e., proliferation, chemotaxis, collagen synthesis, transdifferentiating and angiogenesis/neovascularization. TGF-β1 is a portent factor for wound contraction and ECM deposition through the function of αSMA expressing myofibroblasts [5], by which ECM is remodeled in granulation tissue. In the present study, we clarified the mechanism of action of micrograft in wound healing using our established mouse model [15]
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