Advances in the Modulation of Cutaneous Wound Healing and Scarring

Cutaneous wounds inevitably heal with scars, which can be disfiguring and compromise function. In general, the greater the insult, the worse the scarring, although genetic make up, regional variations and age can influence the final result. Excessive scarring manifests as hypertrophic and keloid scars. At the other end of the spectrum are poorly healing chronic wounds, such as foot ulcers in diabetic patients and pressure sores. Current therapies to minimize scarring and accelerate wound healing rely on the optimization of systemic conditions, early wound coverage and closure of lacerations, and surgical incisions with minimal trauma to the surrounding skin. The possible benefits of topical therapies have also been assessed. Further major improvements in wound healing and scarring require an understanding of the molecular basis of this process. Promising strategies for modulating healing include the local administration of platelet derived growth factor (PDGF)-BB to accelerate the healing of chronic ulcers, and increasing the relative ratio of transforming growth factor (TGF)beta-3 to TGFbeta-1 and TGFbeta-2 in order to minimize scarring.     

Recombinant Hepatocyte Growth Factor Accelerates Cutaneous Wound Healing in a Diabetic Mouse Model

We examined effects of recombinant hepatocyte growth factor (HGF) on cutaneous wound healing, using a full-thickness cutaneous excision model in diabetic mice. Topical administration of HGF, as well as basic fibroblast growth factor (bFGF), promoted the rate of wound closure and re-epithelialization. Both HGF and bFGF enhanced expansion of the granulation tissue and stimulated neovascularization on day 7 postwounding, wherein the increase in microvessel density in HGF-treated wounds was higher than that in bFGF-treated wounds. Matrix metalloproteinases (MMP-2 and MMP-9) activities involved in cell migration, angiogenesis, and extracellular matrix (ECM) remodeling, were enhanced by HGF-treatment on day 7. On day 28 postwounding (later stages of wound healing), granulation tissue in bFGF-treated wounds remained to a greater extent than that seen in saline- and HGF-treated wounds. Likewise, bFGF- but not HGF-treatment stimulated DNA synthesis of fibroblasts in granulation tissue, suggesting that HGF stimulates wound healing with lesser degree of susceptibility to cutaneous scarring. We propose that supplement of HGF may be a potential therapeutic approach for treatment of cutaneous ulcer.     

Therapeutic Effects of Topical Application of Ozone on Acute Cutaneous Wound Healing

This study was undertaken to evaluate the therapeutic effects of topical ozonated olive oil on acute cutaneous wound healing in a guinea pig model and also to elucidate its therapeutic mechanism. After creating full-thickness skin wounds on the backs of guinea pigs by using a 6 mm punch biopsy, we examined the wound healing effect of topically applied ozonated olive oil (ozone group), as compared to the pure olive oil (oil group) and non-treatment (control group). The ozone group of guinea pig had a significantly smaller wound size and a residual wound area than the oil group, on days 5 (P<0.05) and 7 (P<0.01 and P<0.05) after wound surgery, respectively. Both hematoxylin-eosin staining and Masson-trichrome staining revealed an increased intensity of collagen fibers and a greater number of fibroblasts in the ozone group than that in the oil group on day 7. Immunohistochemical staining demonstrated upregulation of platelet derived growth factor (PDGF), transforming growth factor-β (TGF-β) and vascular endothelial growth factor (VEGF) expressions, but not fibroblast growth factor expression in the ozone group on day 7, as compared with the oil group. In conclusion, these results demonstrate that topical application of ozonated olive oil can accelerate acute cutaneous wound repair in a guinea pig in association with the increased expression of PDGF, TGF-β, and VEGF.     

水凝胶携带重组人促红细胞生成素对大鼠深Ⅱ度烫伤创面愈合的影响

目的:探讨水凝胶携带重组人促红细胞生成素(rHuEPO)对深Ⅱ度烫伤创面愈合的影响。方法:建立18只SD大鼠深Ⅱ度烫伤模型,随机分为三组,每组6只,分别给予PBS、水凝胶、水凝胶+rHuEPO治疗处理,分别于烫伤即刻、14天、21天测量创面面积,并计算创面愈合指数;治疗21天后取烫伤组织进行组织切片、HE染色和免疫组化检测,比较三组标本上皮化程度、肉芽组织生成和血管形成情况,并进行组织学评分;比较治疗21天后各组血管内皮生长因子(VEGF)的表达。结果:治疗21天,水凝胶+rHuEPO组组织学评分高于水凝胶组和PBS组,表现为较多的肉芽组织形成和血管生成(P<0.05),创面愈合指数大于PBS组和水凝胶组(P<0.05),VEGF表达量高于PBS组和水凝胶组(P<0.05)。结论:应用水凝胶携带rHuEPO治疗深Ⅱ度烫伤可以增加烫伤组织VEGF表达,促进血管生成、肉芽组织生长、内皮增生和迁移,从而促进烫伤愈合。     

Topical Estrogen Accelerates Cutaneous Wound Healing in Aged Humans Associated with an Altered Inflammatory Response

The effects of intrinsic aging on the cutaneous wound healing process are profound, and the resulting acute and chronic wound morbidity imposes a substantial burden on health services. We have investigated the effects of topical estrogen on cutaneous wound healing in healthy elderly men and women, and related these effects to the inflammatory response and local elastase levels, an enzyme known to be up-regulated in impaired wound healing states. Eighteen health status-defined females (mean age, 74.4 years) and eighteen males (mean age, 70.7 years) were randomized in a double-blind study to either active estrogen patch or identical placebo patch attached for 24 hours to the upper inner arm, through which two 4-mm punch biopsies were made. The wounds were excised at either day 7 or day 80 post-wounding. Compared to placebo, estrogen treatment increased the extent of wound healing in both males and females with a decrease in wound size at day 7, increased collagen levels at both days 7 and 80, and increased day 7 fibronectin levels. In addition, estrogen enhanced the strength of day 80 wounds. Estrogen treatment was associated with a decrease in wound elastase levels secondary to reduced neutrophil numbers, and decreased fibronectin degradation. In vitro studies using isolated human neutrophils indicate that one mechanism underlying the altered inflammatory response involves both a direct inhibition of neutrophil chemotaxis by estrogen and an altered expression of neutrophil adhesion molecules. These data demonstrate that delays in wound healing in the elderly can be significantly diminished by topical estrogen in both male and female subjects.     

Neuropilin-1 Participates in Wound Angiogenesis

Angiogenesis, the formation of new capillaries from existing vasculature, plays an essential role in tissue repair. The rapid onset and predominance of proangiogenic factors optimizes healing in damaged tissues. One factor that directly mediates wound vessel angiogenesis is vascular endothelial growth factor (VEGF). Although much is known about the biology of VEGF and its cognate receptors, VEGFR1 and VEGFR2, the role of a recently identified co-receptor for VEGF, neuropilin-1, is not well understood. Using a murine model of dermal wound repair, we found that neuropilin-1 was abundantly expressed on new vasculature in healing wounds. Moreover, mice treated with anti-neuropilin-1 antibodies exhibited a significant decrease in vascular density within these wounds (67% decrease, P = 0.0132). In in vitro assays, VEGF induced formation of endothelial cord-like structures on collagen gel and endothelial cell migration toward VEGF was inhibited by antibodies directed against neuropilin-1. These results provide both in vitro and in vivo evidence for a critical role of neuropilin-1 in wound angiogenesis.     

Fetal Wound Healing Biomarkers

Fetal skin has the intrinsic capacity for wound healing, which is not correlated with the intrauterine environment. This intrinsic ability requires biochemical signals, which start at the cellular level and lead to secretion of transforming factors and expression of receptors, and specific markers that promote wound healing without scar formation. The mechanisms and molecular pathways of wound healing still need to be elucidated to achieve a complete understanding of this remodeling system. The aim of this paper is to discuss the main biomarkers involved in fetal skin wound healing as well as their respective mechanisms of action.     

Effect of Recombinant Human Epidermal Growth Factor Against Cutaneous Scar Formation in Murine Full-thickness Wound Healing

A visible cutaneous scar develops from the excess formation of immature collagen in response to an inflammatory reaction. This study examined the role of epidermal growth factor (EGF) in the formation of cutaneous scars. Twenty Crl:CD-1 (ICR) mice were used and 2 full-thickness skin wounds were made on the dorsum of each mouse. One of the wounds was treated with recombinant human EGF by local application and the other was treated with saline for control until complete healing was achieved. The EGF-treated group''s wounds healed faster than the control group''s. The width of the scar was smaller by 30% and the area was smaller by 26% in the EGF-treated group. Inflammatory cell numbers were significantly lower in the EGF-treated group. The expression of transforming growth factor (TGF)-β₁ in the EGF-treated group was increased. It was observed that the amount of collagen in the EGF-treated group was larger than the control group. In the EGF-treated group, the visible external scars were less noticeable than that in the control group. These results suggest that EGF can reduce cutaneous scars by suppressing inflammatory reactions, decreasing expression of TGF-β₁, and mediating the formation of collagen.     

Transcutaneous Electrical Nerve Stimulation (TENS) Accelerates Cutaneous Wound Healing and Inhibits Pro-inflammatory Cytokines

The purpose of this study was to evaluate transcutaneous electrical nerve stimulation (TENS) and other common treatment methods used in the process of wound healing in terms of the expression levels of pro-inflammatory cytokines. In the study, 24 female and 24 male adult Wistar–Albino rats were divided into five groups: (1) the non-wounded group having no incision wounds, (2) the control group having incision wounds, (3) the TENS (2 Hz, 15 min) group, (4) the physiological saline (PS) group and (5) the povidone iodine (PI) group. In the skin sections, interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were assessed with enzyme-linked immunosorbent assay and immunohistochemical methods. In the non-wounded group, the expression of IL-1β, IL-6, and TNF-α signaling molecules was weaker in the whole tissue; however, in the control group, significant inflammatory response occurred, and strong cytokine expression was observed in the dermis, granulation tissue, hair follicles, and sebaceous glands (P?<?0.05). In the TENS group, the decrease in TNF-α, IL-1β, and IL-6 immunoreaction in the skin was significant compared to the other forms of treatment (P?<?0.05). Distinctive decreases of pro-inflammatory cytokines observed in the dermis in the TENS group suggest that TENS shortened the healing process by inhibating the inflammation phase.     

MMP-13 Plays a Role in Keratinocyte Migration,Angiogenesis, and Contraction in Mouse Skin Wound Healing

Matrix metalloproteinases (MMPs) have been implicated in wound healing. To analyze the roles of MMP-9 and MMP-13 in wound healing, we generated full-thickness cutaneous wounds in MMP-9 knockout (KO), MMP-13 KO, MMP-9/13 double KO, and wild-type mice. Macroscopic wound closure was delayed in all of the KO mice, as compared with wild-type mice. The rate of re-epithelialization was significantly delayed in MMP-9 KO and MMP-13 KO mice and remarkably delayed in MMP-9/13 double KO mice, as compared with wild-type mice. Both MMP-9 and MMP-13 were expressed by the leading edges of epidermal cells in wild-type mice, and the migration of keratinocytes was suppressed by treatment with an MMP inhibitor or transfection of small interfering RNAs for MMP-9 or MMP-13, as compared with controls. The vascular density in wound granulation was significantly lower in both MMP-13 KO and MMP-9/13 double KO mice than in wild-type mice. Degradation of connective tissue growth factor in wound tissue was transiently prevented in MMP-13 KO mice. Morphometric analyses demonstrated a reduction in both wound contraction and myofibroblast formation in both MMP-13 KO and MMP-9/13 double KO mice. Proliferation and transforming growth factor-β1-induced myofibroblast differentiation of dermal fibroblasts from MMP-13 KO mice were decreased, as compared with wild-type dermal fibroblasts. These data suggest that MMP-13 plays a role in keratinocyte migration, angiogenesis, and contraction in wound healing, while MMP-9 functions in keratinocyte migration.Wound healing is a complex process that includes an acute inflammatory reaction, regeneration of parenchyma cells, cell migration and proliferation, angiogenesis, extracellular matrix (ECM) synthesis, contraction, and tissue remodeling.^1,2,3 Cutaneous wound healing by second intention is characterized by the following three continuous and overlapping processes: an inflammatory phase, a proliferative phase, and a contraction and remodeling phase.² In the inflammatory phase, tissue injury causes the loss of cells and tissue, disruption of blood vessels, extravasation of blood constituents and infiltration of inflammatory cells, composed mainly of neutrophils and macrophages, and provides a provisional ECM for keratinocyte migration. The major events during the proliferative phase are re-epithelialization and angiogenesis, both of which require cell proliferation and migration of keratinocytes and endothelial cells, respectively. In the contraction and remodeling phase, myofibroblasts differentiated from fibroblasts play a key role in wound contraction and controlled synthesis and degradation of ECM proteins, especially collagens, leading to increased wound strength. All of these events occurring during wound healing require the collaborative efforts of many different tissues and cell types.Accumulated lines of evidence have demonstrated that members of the matrix metalloproteinase (MMP) gene family are essential to the degradation of ECM macromolecules and non-ECM molecules such as growth factors and cytokines under various pathophysiological conditions.^4,5 Enhanced expression of MMPs 1, 2, 3, 8, 9, 10, 13, 14, 19, and 26 in wound tissues has been reported in experimental animals and humans.^{6,7,8,9,10,11,12,13} It is clear that MMP activity is required in wound closure by keratinocyte re-epithelialization and migration and angiogenesis, since broad-spectrum MMP inhibitors inhibit the processes.^{14,15,16,17,18} However, since many MMPs are expressed by re-epithelializing keratinocytes, inflammatory cells, fibroblasts, and endothelial cells, it is uncertain which MMP species plays a central role in the process of wound healing and how these MMPs function in wounded tissues.One of the most powerful methods to directly address these questions is to analyze wound healing in MMP knockout (KO) mice. Indeed, wound healing of the skin has been studied in mice deficient for the MMP-3, MMP-8, MMP-9, MMP-13, or MMP-14 genes.^{13,19,20,21,22} However, all of these KO mice, except for the MMP-8 KO mice, had negative results. In the MMP-8 KO mice, wound closure and re-epithelialization were inhibited mainly due to impaired infiltration of neutrophils,²⁰ which are responsible for MMP-8 production. The study suggested that the effect of MMP-8 on the wound healing is secondary to persistent inflammation at the later time point and alterations in transforming growth factor-β (TGF-β) signaling.²⁰ Keratinocytes at the leading edge of the cutaneous wound express MMP-9 and MMP-13.^13,21 Induction of MMP-9 at the wound site in vitro²³ and in vivo²⁴ promotes migration of keratinocytes probably because of its effect on detachment of basal keratinocytes from the basal membrane. Keratinocyte migration over the wound bed is known to be dependent on the attachment of keratinocytes to fibrillar type I collagen through integrins α1β1 and α2β1 and subsequent degradation of the collagen by collagenolytic MMPs.^25,26 These studies suggest that both MMP-9 and MMP-13 are involved in re-epithelialization in wound healing in mice, a species that lacks the gene for MMP-1.²⁷ However, previous studies on wound healing in MMP-9 KO and MMP-13 KO mice failed to demonstrate significant difference or showed even acceleration of wound closure and re-epithelialization, as compared with that in wild-type mice.^13,21 These studies did not provide the reasonable explanations for the unexpected findings except for redundancy among MMPs.¹³ MMP-9 and MMP-13 synergize with each other during endochondral ossification at the growth plates.²⁸ Thus, MMP-9/13 double KO mice could identify additive effects of MMP-9 and MMP-13 on wound healing, although no such studies have been reported.In the present study, we developed the MMP-9/13 double KO mice by crossing the MMP-9 KO mice with the MMP-13 KO mice, and evaluated the influence of targeted deletion of the MMP-9 and/or MMP-13 genes on healing by secondary intention by generating large skin wounds in MMP-9 KO, MMP-13 KO, MMP-9/13 double KO, and wild-type mice. Our study provides the first evidence that MMP-13 plays a key role in keratinocyte migration, angiogenesis, and contraction in wound healing, and that MMP-9 is implicated in keratinocyte migration.     

MFG-E8的生物学功能及应用

乳脂球表皮生长因子8(milk fat globule EGF factor Ⅷ,MFG-E8)是一种乳汁脂肪小球表面的亲脂性糖蛋白,广泛参与多种细胞间的相互作用,如介导精子与卵子外膜间的结合、维持附睾上皮细胞与精子细胞膜的黏附、参与肠上皮细胞的维持与修复、促进乳腺支化形成和成人组织新生血管形成、增强树突状细胞外泌体功能以及参与吞噬清除凋亡细胞的过程.此外,MFG-E8也显示良好的应用前景,有可能作为潜在的治疗和检测手段.     

Cell Therapy for Wound Healing

In covering wounds, efforts should include utilization of the safest and least invasive methods with goals of achieving optimal functional and cosmetic outcome. The recent development of advanced wound healing technology has triggered the use of cells to improve wound healing conditions. The purpose of this review is to provide information on clinically available cell-based treatment options for healing of acute and chronic wounds. Compared with a variety of conventional methods, such as skin grafts and local flaps, the cell therapy technique is simple, less time-consuming, and reduces the surgical burden for patients in the repair of acute wounds. Cell therapy has also been developed for chronic wound healing. By transplanting cells with an excellent wound healing capacity profile to chronic wounds, in which wound healing cannot be achieved successfully, attempts are made to convert the wound bed into the environment where maximum wound healing can be achieved. Fibroblasts, keratinocytes, adipose-derived stromal vascular fraction cells, bone marrow stem cells, and platelets have been used for wound healing in clinical practice. Some formulations are commercially available. To establish the cell therapy as a standard treatment, however, further research is needed.

Graphical Abstract

相似文献   

CD19, a Response Regulator of B Lymphocytes,Regulates Wound Healing through Hyaluronan-Induced TLR4 Signaling

Immune cells are critical to the wound-healing process, through both cytokine and growth factor secretion. Although previous studies have revealed that B cells are present within wound tissue, little is known about the role of B cells in wound healing. To clarify this, we investigated cutaneous wound healing in mice either lacking or overexpressing CD19, a critical positive-response regulator of B cells. CD19 deficiency inhibited wound healing, infiltration of neutrophils and macrophages, and cytokine expression, including basic and acidic fibroblast growth factor, interleukin-6, platelet-derived growth factor, and transforming growth factor-β. By contrast, CD19 overexpression enhanced wound healing and cytokine expression. Hyaluronan (HA), an endogenous ligand for toll-like receptor (TLR)-4, stimulated B cells, which infiltrates into wounds to produce interleukin-6 and transforming growth factor-β through TLR4 in a CD19-dependent manner. CD19 expression regulated TLR4 signaling through p38 activation. HA accumulation was increased in injured skin tissue relative to normal skin, and exogenous application of HA promoted wound repair in wild-type but not CD19-deficient mice, suggesting that the beneficial effects of HA to the wound-healing process are CD19-dependent. Collectively, these results suggest that increased HA accumulation in injured skin induces cytokine production by stimulating B cells through TLR4 in a CD19-dependent manner. Thus, this study is the first to reveal a critical role of B cells and novel mechanisms in wound healing.Healing of cutaneous wounds is a complex biological event that results from the interplay of a large number of resident and infiltrating cell types, including leukocytes.¹ Accumulating evidence has revealed a critical role of leukocytes in wound healing. Infiltrating neutrophils form a first line of defense against local infections and are also a source of pro-inflammatory cytokines to activate fibroblasts and keratinocytes.² Macrophages also regulate wound healing by antimicrobial function, wound debridement, and production of various growth factors, such as platelet-derived growth factor (PDGF), transforming growth factor (TGF)-β, basic fibroblast growth factor (bFGF), heparin binding epidermal growth factor, and TGF-α.^3,4,5,6 These factors stimulate the synthesis of extracellular matrix by local fibroblasts, generate new blood vessels, promote the granulation tissue formation, and enhance re-epithelialization.^4,5 Furthermore, a series of experimental studies have indicated a significant role for T lymphocytes in wound healing as growth factor-producing cells as well as immunological effector cells.^1,7,8,9 Thus, immune cells have an integral function in wound healing beyond their role in inflammation and host defense, mainly through the secretion of signaling molecules, such as cytokines and growth factors.⁶However, little is known regarding a role of B cells in wound healing. Previous studies have revealed that B cells are present within wound tissue^9,10,11 and that B cell count is rapidly increased in the first 4 days after wounding, and thereafter reaches a plateau before falling as the wounds heal.¹¹ Furthermore, recent assessment of the role of B cells in the immune system has indicated that B cells are more than just the precursors of antibody (Ab)-secreting cells.¹² B cells have essential functions in regulating immune responses, including the production of various cytokines and growth factors, antigen presentation, regulation of T cell activation and differentiation, and regulation of lymphoid organization.¹² Therefore, the increased numbers of B cells within wound tissue may reflect a role for these cells that has hitherto been unrecognized.Both innate and adaptive immune responses contribute to host defense cooperatively. B cells play a principal role in adaptive immune response through B cell antigen receptor (BCR). BCR-induced signals are further modified by other cell surface molecules including CD19. CD19, a major positive response regulator, is a critical B cell-specific signal transduction molecule of the immunoglobulin superfamily expressed by early pre-B cells from the time of heavy chain rearrangement until plasma cell differentiation.¹³ B cells also primarily participate in innate immunity; indeed, B cells express toll-like receptors (TLRs) and respond to exogenous innate stimuli such as lipopolysaccharide (LPS), a major component of Gram-negative bacteria. CD19 also regulates LPS signaling: B cells from CD19-deficient (CD19^−/−) mice are hyporesponsive to most transmembrane signals, including BCR ligation and LPS, while B cells from CD19-transgenic (CD19Tg) mice that overexpress CD19 by ∼threefold are hyperresponsive to these signals.^14,15 Thus, CD19 regulates both adaptive and innate immune responses.In the current study, to clarify the roles of B cells in wound healing, we investigated the wound-healing model in CD19^−/− and CD19Tg mice. The results of this study indicate that CD19 controls cytokine and growth factor production by B cells mainly through TLR4 signaling, which was activated by an endogenous TLR4 ligand hyaluronan (HA) increased in the wounded skin, and thereby CD19 regulates the skin wound-healing process.