High-mobility group box 1 protein in human and murine skin: involvement in wound healing

High-mobility group box 1 (HMGB1) protein is a multifunctional cytokine involved in inflammatory responses and tissue repair. In this study, it was examined whether HMGB1 plays a role in skin wound repair both in normoglycemic and diabetic mice. HMGB1 was detected in the nucleus of skin cells, and accumulated in the cytoplasm of epidermal cells in the wounded skin. Diabetic human and mouse skin showed more reduced HMGB1 levels than their normoglycemic counterparts. Topical application of HMGB1 to the wounds of diabetic mice enhanced arteriole density, granulation tissue deposition, and accelerated wound healing. In contrast, HMGB1 had no effect in normoglycemic mouse skin wounds, where endogenous HMGB1 levels may be adequate for optimal wound closure. Accordingly, inhibition of endogenous HMGB1 impaired wound healing in normal mice but had no effect in diabetic mice. Finally, HMGB1 had a chemotactic effect on skin fibroblasts and keratinoyctes in vitro. In conclusion, lower HMGB1 levels in diabetic skin may play an important role in impaired wound healing and this defect may be overcome by the topical application of HMGB1.     

Changes of human skin in subepidermal wound healing process

Background/purpose: The wound healing process involves unexplained mechanisms. An aberration in this process is known to cause dermal disorders such as keloid or hypertrophic scars, but the mechanism by which these scars are formed remains to be elucidated. Here we examined the usefulness of a non‐invasive optical imaging device to clarify mechanisms of wound healing and of scar formation. Methods: An 8 mm experimental wound was made in the forearms of six subjects by a suction blister method. To observe chronological changes associated with wound healing, horizontal cross‐sectional images were non‐invasively obtained of the wounded area from the skin surface down to 129 μm below at 21.5 μm intervals using in vivo laser confocal scanning microscopy (LCSM). Results: The wounds were covered with a new epidermis by week 2, at which time the dermal papilla count decreased while the thickness from the skin surface to the apex of the dermal papilla increased. The count and the thickness returned to the initial levels when the wound was healed. In two out of six subjects, fibrous tissues were observed in the upper dermis, whereas in one other subject, melanocyte‐like dendritic cells were observed in the epidermis–dermis border in later phases of wound healing. Conclusion: This non‐invasive method using in vivo LCSM revealed chronological changes in the dermis and epidermis during wound healing. In addition, although a scar was not formed in any of study subjects, this microscopy revealed aspects similar to the fibrous tissue overgrowth or to melanocyte migration, both of which may relate to wound healing. These results indicate the usefulness of this non‐invasive method in studies of wound healing and of scar formation.     

MicroRNAs in skin wound healing

Wound healing is a fundamental physiological progress to keep the integrity of the skin. The transition from inflammation to proliferation is a critical step during skin wound repair process. Impairment of this transition has been known as a common dominator in the pathophysiology of chronic non-healing wounds. MicroRNAs (miRNAs) are short non-coding RNAs regulating gene expression. Emerging evidence has revealed that miRNAs play important roles in both normal skin wound healing and in the pathogenesis of chronic wounds. We focus on the miRNAs regulating the inflammation-proliferation transition during wound healing and propose that these miRNAs may be promising targets for development of more effective wound therapy.     

An advanced mouse model for human skin wound healing

Here, we report a model for studying wound repair based on skin regenerated from human tissue culture‐expanded cells. The reconstituted skin (hRSK) responds to injury similar to that of intact human skin, and its constituent cells contribute to the healing process. As we have demonstrated that hRSK composed of GFP‐labelled cells also heals “normally,” we believe this model will be useful in analysing the wound repair process using genetically modified human cells.     

Toll-like receptors in wound healing: location, accessibility, and timing

Toll-like receptors (TLRs) are considered to be the first responders in the defense against invading pathogens. TLR engagement by ligands triggers inflammatory responses in injury and trauma, and thus can impair or contribute to the healing process, depending on TLRs' expression pattern, cellular localization, signaling, and deployment of inflammatory responses. Understanding these attributes could improve therapeutic strategies for treating chronic wounds.     

皮肤发育成形及创伤愈合与microRNA

microRNA是一类小分子非编码RNA,长度大约为21～25个核苷酸.其通过与靶mRNA的互补结合,造成mRNA降解、蛋白表达抑制,从而在多种种属、多种组织以及多种疾病中,发挥着转录后调控的作用.近年的研究表明,microRNA在皮肤发育成形中有着重要的调节作用,并且与许多皮肤疾病、肿瘤以及创伤修复存在着相关性.进一步研究microRNA与创伤愈合的关系,为皮肤创伤的治疗提供新的思路及新靶点.     

Activation of NLRP3 signalling accelerates skin wound healing

The process of skin wound healing involves the following three steps: inflammation, tissue formation and tissue remodelling. These optimal steps are required for the development of normal wound healing. Recent reports demonstrated that inflammasomes are involved in the innate immune response. In the present study, we examined whether the activation of inflammasomes affects the process of skin wound repair. The skin wound repair model was established using wild‐type (WT), NACHT, LRR and PYD domains‐containing protein 3 (NALP3) knockout (KO) and ASC‐KO mice. The wounds were observed every other day, and changes in wound size over time were calculated using photography. Wound repair in NALP3‐KO and ASC‐KO mice was significantly impaired compared with WT mice. Isoliquiritigenin, an inhibitor of NALP3, decreased the rate of wound repair in WT mice. mRNA expression of pro‐inflammatory cytokines in the wound sites of NALP3‐KO mice was markedly decreased compared with WT mice. Treatment with adenosine triphosphate (ATP), a ligand of NALP3, upregulated the mRNA expression of pro‐inflammatory cytokines at the wound site and accelerated wound healing in the WT mice. Scratch assay revealed that ATP accelerated wound closure in mouse embryonic fibroblasts from WT mice but not from NALP3‐KO mice. In conclusion, the present study demonstrated that NALP3 pathway activation is involved in wound repair, and the topical use of ATP may be useful as an effective treatment for accelerating wound healing.     

Expression of SKALP/elafin during wound healing in human skin

Skin-derived antileukoproteinase (SKALP), also known as elafin, is a proteinase inhibitor with specificity for polymorphonuclear leucocyte (PMN)-derived elastase and proteinase-3. SKALP is absent in normal human epidermis, but is strongly induced in inflammatory dermatoses such as psoriasis. SKALP is putatively involved in the regulation of cutaneous inflammation by inhibiting PMN derived proteinases. The aim of this study was to investigate SKALP expression and PMN infiltration during wound healing in human skin. This was examined in healing excisional wounds in normal skin and in impaired healing in various types of chronic venous ulcers. Tissues were analysed using immunohistochemistry and Northern blot analysis. Healing of excisional wounds was studied from day 0 to day 14. An influx of PMN was seen rapidly after wounding and was maximal between day 2 and 4 and then subsided. SKALP was induced within 48 h and was expressed in the suprabasal keratinocytes of the wound edge and the migrating epidermal sheet. SKALP expression was maximal on day 4 and was downregulated at the time of complete reepithelialization (7–14 days). In venous ulcers, PMN were abundant in the wound bed and scarce under the wound edge. SKALP was strongly expressed in the keratinocytes of the wound edge in all types of ulcers studied. In the wound bed, SKALP was not detectable. Our results suggest that SKALP plays a role in the acute, inflammatory phase of wound healing. From the kinetics and topology of SKALP expression we surmise that it negatively regulates PMN infiltration. Some of the results reported here were presented at the meeting of the European Society for Dermatological Research in Vienna, September 1994.     

Toll样受体7与皮肤病的研究进展

Toll样受体是一类模式识别受体,通过识别病原相关分子模式参与先天性免疫和获得性免疫.Toll样受体有10余种家族成员,Toll样受体7是其中一种,分布于细胞内噬体膜上,主要识别内噬体中的单链核酸,在病毒识别及病毒感染的传递中起重要作用.近期研究发现,Toll样受体7在一些皮肤病中起重要作用,Toll样受体7既可诱发和加重白癜风、红斑狼疮、银屑病,也可在部分皮肤病中发挥积极的作用,如Toll样受体7可激发宿主抗真菌感染的免疫应答;在特应性皮炎中促进向Th1型免疫应答转化;Toll样受体7还可通过其特效激动剂咪喹莫特辅助治疗皮肤肿瘤及尖锐湿疣.     

Some factors affecting skin and wound healing

The domestic pig is the preferred animal for studying the effects of environmental factors on skin and wound because its integument is more like that of man than any other. The three factors that most drastically affect the pattern, speed and quality of healing are dehydration of exposed tissues, the status of the blood supply bringing oxygen and nutrients to the area and sepsis. Wounds exposed to the air lose water vapour, the upper dermis dries and healing takes place beneath a dry scab. Covering a wound with an occlusive dressing prevents scab formation and radically alters the pattern of epidermal wound healing. Blowing on wounds creates a scab within three hours instead of the normal 24 hours but more tissue is sacrificed in the process. This may only be justified if it can be shown that rapid artificial scab formation significantly cuts down the incidence of severe infections, i.e. in large burns. Less serious wounds heal faster when covered with a suitable occlusive dressing. Indolent wounds are characterised by a rim of infected, necrotic tissue in which leucocytes and macrophages are unable to function effectively through lack of oxygen. A suitable dressing changed frequently can bring about mild debridement and re-establish the conditions for healing.     

E-cadherin expression in wound healing of mouse skin

BACKGROUND: E-cadherin has been studied extensively in other systems but little attention has been paid to its role in wound healing. We investigated E-cadherin expression in epithelial wound healing in vivo by focusing on the migrating cells in the epithelial tongue and the mitotic cells in the non-injured side apart from the original wound edge. METHODS: Round full-thickness excisional wounds (6 mm in diameter) and full-thickness incisional wounds were prepared dorsally in mice. On various days after the operation, E-cadherin expression was examined by immunohistochemical staining using a monoclonal antibody specific for E-cadherin. RESULTS: In both models, the level of E-cadherin expression did not decrease on the 1st postoperative (P.O.) day. After the 2nd P.O. day, E-cadherin expression decreased in cells at a site 500 microm apart from the original wound edge. After the 3rd P.O. day, decreased expression was also observed in cells at the top and in the basal layer of the epithelial tongue. This decreased expression continued for 1 or 2 days after the meeting of the epithelial tongue. There was no significant difference in the expression of E-cadherin between two models. CONCLUSIONS: The results suggested that E-cadherin expression decreases in epithelial cells. This decrease may depend on the activity of migration and mitosis. In addition, the change was similar in both the excisional and incisional wounds.     

Simultaneous detection of receptor mRNA and ligand protein in human skin tissues

BACKGROUND: In situ hybridization techniques allow a cell-type-specific messenger RNA (mRNA) analysis in complex tissues such as human skin. METHODS: To evaluate both the expression of mRNA and protein within the same tissue section, we developed a protocol of combined non-radioactive in situ hybridization and immunohistochemistry for use in dermatohistopathology. To validate the technique, we assessed the distribution of vasoactive intestinal polypeptide (VIP) protein and its receptor, VPAC2 mRNA, in human skin samples. RESULTS: Simultaneous detection of VPAC2 mRNA and VIP immunoreactivity led to abundant staining for both signals in a variety of cell types. There was marked staining for VPAC2 mRNA in epidermal cells, with most pronounced hybridization signals found in keratinocytes of the basal layer and in glandular cells surrounded by VIP-immunoreactive nerve fibers. Hair follicle cells next to VIP-positive fibers also exhibited hybridization signals. Specific staining was also detected in endothelial and mononuclear cells. The findings of simultaneous in situ hybridization and immunohistochemistry were identical to results obtained by the single application of both methods. CONCLUSIONS: The combination of in situ hybridization and immunohistochemistry appears to be a promising technique to assess the expression of both protein and mRNA in skin samples and may be used for various purposes in experimental and clinical dermatopathology.     

Abnormal wound healing in UV-irradiated skin of Sencar mice

Sencar mice demonstrate an unusual sensitivity to epidermal carcinogenesis by initiation-promotion or single high-dose exposure to ultraviolet radiation (UVR). These mice exhibited an exaggerated and persistent epidermal hyperplasia in response to tissue damage caused by UVR. The persistent hyperplasia was not present in similarly treated BALB/c mice, a strain that is relatively resistant to skin carcinogenesis by initiation-promotion or single-exposure UVR. Epithelial cell proliferation and migration were examined by autoradiography to determine the cellular basis for the persistence of hyperplasia in Sencar mouse skin. Twelve weeks after irradiation, the rate of epidermal basal cell proliferation was approximately 4 times greater in Sencar mice than in BALB/c mice, whereas epidermal cell transit times were similar in the two strains. This result indicated that persistent hyperplasia was due to sustained epithelial cell division rather than delayed cell maturation. Surgical incision of Sencar skin did not cause abnormal hyperplasia, nor did this procedure enhance the induction of tumors by UVR. These findings suggest that Sencar mice may possess a heritable defect that mediates both tissue regeneration and tumorigenesis in UV-irradiated skin.