Hypoxic adipose stem cell-derived exosomes carrying high-abundant USP22 facilitate cutaneous wound healing through stabilizing HIF-1α and upregulating lncRNA H19.

Hypoxic preconditioning has been recognized as a promotive factor for accelerating cutaneous wound healing. Our previous study uncovered that exosomal lncRNA H19, derived from adipose-derived stem cells (ADSCs), plays a crucial role in orchestrating cutaneous wound healing. Herein, we aimed to explore whether there is a connection between hypoxia and ADSC-derived exosomes (ADSCs-exos) in cutaneous wound healing. Exosomes extracted from ADSCs under normoxic and hypoxic conditions were identified using transmission electron microscope (TEM) and particle size analysis. The effects of ADSCs-exos on the proliferation, migration, and angiogenesis of human umbilical vein endothelial cells (HUVECs) were evaluated by CCK-8, EdU, wound healing, and tube formation assays. Expression patterns of H19, HIF-1α, and USP22 were measured. Co-immunoprecipitation, chromatin immunoprecipitation, ubiquitination, and luciferase reporter assays were conducted to confirm the USP22/HIF-1α/H19 axis, which was further validated in a mice model of skin wound. Exosomes extracted from hypoxia-treated ADSCs (termed as H-ADSCs-exos) significantly increased cell proliferation, migration, and angiogenesis in H2O2-exposed HUVECs, and promoted cutaneous wound healing in vivo. Moreover, H-ADSCs and H-ADSCs-exos, which exhibited higher levels of H19, were found to be transcriptionally activated by HIF-1α. Mechanically, H-ADSCs carrying USP22 accounted for deubiquitinating and stabilizing HIF-1α. Additionally, H-ADSCs-exos improved cell proliferation, migration, and angiogenesis in H2O2-triggered HUVECs by activating USP22/HIF-1α axis and promoting H19 expression, which may provide a new clue for the clinical treatment of cutaneous wound healing.

Inhibition of Ubiquitin C-Terminal Hydrolase L1 Facilitates Cutaneous Wound Healing via Activating TGF-ß/Smad Signalling Pathway in Fibroblasts.

Ubiquitin C-terminal hydrolase L1 (UCHL1) plays vital roles in cell proliferation, angiogenesis, inflammation and oxidative stress. Nevertheless, it is unclear whether UCHL1 could regulate the biologic behaviour of cells and ultimately influences wound healing. We aim to illustrate the roles and the underlying mechanism of UCHL1 in cutaneous wound healing. Murine full-thickness excisional wound model was utilised to study the effects of UCHL1 on wound healing through topical administration of the UCHL1 inhibitor LDN57444, followed by assessment of wound areas and histological alterations. Subsequently, ethynyldeoxyuridine, scratch and transwell assays were performed to examine fibroblast migration and proliferation. The extracellular matrix (ECM)-related genes expression and transforming growth factor-ß (TGF-ß)/Smad signalling pathways activation were investigated by immuno-fluorescent staining, Western blots and quantitative reverse transcription polymerase chain reaction. We identified elevated UCHL1 expression in non-healing wound tissues. The UCHL1 expression displayed a dynamic change and reached a peak on Day-7 post-wounding during the healing process in mice. Cutaneous administration of LDN57444 promoted wound healing by facilitating collagen deposition, myofibroblast activation and angiogenesis. In vitro experiments demonstrated that UCHL1 concentration dependently inhibited migration, ECM synthesis and activation of human dermal fibroblasts, which was mechanistically related to downregulation of TGF-ß/Smad signalling. Furthermore, these effects could be reversed by TGF-ß inhibitor SB431542. Our findings reveal that UCHL1 is a negative regulator of cutaneous wound healing and considered as a novel prospective therapeutic target for effective wound healing.

Genome-wide screening of m6A profiling of cutaneous wound healing in diabetic mice.

OBJECTIVE: Impaired wound healing in diabetes mellitus (DM) is a major health burden on patients, their families, and society. The present study aimed to systematically profile the m6A modification landscape in cutaneous wounds in a diabetic mouse model. APPROACH: Diabetes was induced in mice through a single intraperitoneal injection of streptozotocin (STZ); a single intraperitoneal injection of PBS was made in control mice for comparisons. Both groups then received an 8-mm diameter, full-thickness dorsal body wound with a biopsy punch. Five days after wound surgery, western blot analysis of harvested wound tissues from both groups was used to assess the expression of m6A-related enzymes. Genome-wide profiling of m6A-tagged transcripts was performed through MeRIP-seq and RNA-seq. RESULTS: ALKBH5, an m6A eraser, was significantly upregulated, while METTL3, METTL14, and WTAP, m6A writers, were markedly downregulated in the diabetic wounds. Additionally, a total of 1335 m6A peaks were differentially expressed in MeRIP-seq and RNA-seq analyses, with 558 upregulated and 777 downregulated peaks. Finally, there was hypomethylated and hypermethylated differentiation at the gene and transcript levels. INNOVATION: The present study was the first to reveal the m6A landscape in diabetic wounds in an animal model. CONCLUSION: This study, by deeply analyzing the role of m6A modifications in diabetic wound healing, provides new insights and understanding into the molecular mechanisms of diabetic wound healing. Future research could further explore how m6A modifications regulate the wound healing process, thereby offering new potential targets for the treatment of diabetic wounds.

Exploring Skin Wound Healing Models and the Impact of Natural Lipids on the Healing Process.

Cutaneous wound healing is a complex biological process involving a series of well-coordinated events aimed at restoring skin integrity and function. Various experimental models have been developed to study the mechanisms underlying skin wound repair and to evaluate potential therapeutic interventions. This review explores the diverse array of skin wound healing models utilized in research, ranging from rodent excisional wounds to advanced tissue engineering constructs and microfluidic platforms. More importantly, the influence of lipids on the wound healing process is examined, emphasizing their role in enhancing barrier function restoration, modulating inflammation, promoting cell proliferation, and promoting remodeling. Lipids, such as phospholipids, sphingolipids, and ceramides, play crucial roles in membrane structure, cell signaling, and tissue repair. Understanding the interplay between lipids and the wound microenvironment provides valuable insights into the development of novel therapeutic strategies for promoting efficient wound healing and tissue regeneration. This review highlights the significance of investigating skin wound healing models and elucidating the intricate involvement of lipids in the healing process, offering potential avenues for improving clinical outcomes in wound management.

Enhancing Human Cutaneous Wound Healing through Targeted Suppression of Large Conductance Ca2+-Activated K+ Channels.

The modulation of K+ channels plays a crucial role in cell migration and proliferation, but the effect of K+ channels on human cutaneous wound healing (CWH) remains underexplored. This study aimed to determine the necessity of modulating K+ channel activity and expression for human CWH. The use of 25 mM KCl as a K+ channel blocker markedly improved wound healing in vitro (in keratinocytes and fibroblasts) and in vivo (in rat and porcine models). K+ channel blockers, such as quinine and tetraethylammonium, aided in vitro wound healing, while Ba2+ was the exception and did not show similar effects. Single-channel recordings revealed that the Ba2+-insensitive large conductance Ca2+-activated K+ (BKCa) channel was predominantly present in human keratinocytes. NS1619, an opener of the BKCa channel, hindered wound healing processes like proliferation, migration, and filopodia formation. Conversely, charybdotoxin and iberiotoxin, which are BKCa channel blockers, dramatically enhanced these processes. The downregulation of BKCa also improved CWH, whereas its overexpression impeded these healing processes. These findings underscore the facilitative effect of BKCa channel suppression on CWH, proposing BKCa channels as potential molecular targets for enhancing human cutaneous wound healing.

Comparison of different modern wound dressings on full-thickness murine cutaneous wound healing with wild-type and type-2 diabetes db/db mice.

BACKGROUND: To evaluate the process of cutaneous wound healing, experiments have been conducted. However, to date, what modern wound dressings are suitable remains unclear. Therefore, this study aimed to compare the healing process in different modern wound dressings to determine their suitability in experimental acute wound and chronic diabetic wound. MATERIALS AND METHODS: Twelve C57BL/6J mice and eleven db/db mice were subjected to full-thickness wound injuries. The mice were divided into the following four groups: hydrocolloid, form, film, and gauze groups in both wild-type and db/db mice. Wound healing was assessed until day 14. RESULTS: In the wild-type groups, all wounds were healed and completed re-epithelialization by day 14. However, the wound surface was dry, and the periwound was hypercontracted in the wild-type-form and wild-type-gauze groups. In the db/db groups, wounds were not healed until day 14. Wound exudates in the db/db-hydrocolloid group were abundant and gradually increased until day 14. Wound exudates in the db/db-film group were present until day 14. Conversely, in the db/db-form and db/db-gauze groups, the wound surface was dry, and the periwound was hypercontracted. CONCLUSION: These results showed that hydrocolloid and film dressings are suitable modern wound dressings for the mice wound models of acute wound and chronic diabetic wound. Moreover, using either hydrocolloid or film dressing depending on the purpose of the study on cutaneous wound healing in diabetes is necessary.

Meta-analysis on the impact of immune senescence: Unravelling the interplay in cutaneous wound healing and lung cancer progression.

The primary objective of this meta-analysis was to provide the comprehensive understanding of the intricate correlation that existed between immune senescence and its effects on the advancement of lung cancer as well as recovery of cutaneous wounds. By conducting this systematic review of six rigorous studies utilizing databases such as PubMed and Web of Science, this research examined the multitude of facets pertaining to immune aging and consequences it bear on the health outcomes. The incorporated studies encompassed wide range of geographical and methodological viewpoints, with the specific emphasis on non-small-cell lung cancer and diverse scenarios related to wound recovery. This analysis synthesized discoveries regarding therapeutic responses, cellular and molecular mechanisms and impact of lifestyle factors on immune senescence. The findings suggested that immune senescence has substantial impact on the effectiveness of treatments for lung cancer and cutaneous wounds healing process; therefore, targeted therapies and holistic approaches may be able to mitigate these effects. By following the revised PRISMA guidelines, this meta-analysis guarantee thorough and ethically sound methodology for amalgamating pre-existing literature. The study concluded by emphasizing the critical nature of comprehending immune senescence in the context of clinical practice and proposed avenues for further investigation to enhance health results among the elderly.

Impact of preoperative chemotherapy on cutaneous wound healing in lung cancer patients: A meta-analysis.

As part of their treatment, lung cancer patients frequently endure thoracic oncological surgery, with preoperative chemotherapeutic interventions being the common approach. However, the potential impact of these chemotherapeutic regimens on cutaneous wound healing outcomes following surgery remains the topic of considerable clinical interest. This meta-analysis sought to evaluate comprehensively the effect of preoperative chemotherapeutic regimens on cutaneous wound healing in lung cancer patients following thoracic oncological surgery. Extensive literature searches were conducted using the leading databases PubMed, Embase, Cochrane Library and Scopus. Eight studies out of 1342 identified satisfied the inclusion criteria. Consideration was given to both randomized controlled trials (RCTs) and observational studies. Data pertaining to study characteristics, patient demographics, chemotherapeutic regimens and wound healing outcomes were extracted with great attention to detail. The examination of these varied studies provided insights into the fluctuations in rates of recovery following treatment, incidences of wound infections and frequencies of surgical complications. The research studies provided odds ratios for recovery that varied significantly in magnitude from 0.95 to 0.38, with regard to the probability of wound infection. Furthermore, a range of odds ratios for complications were disclosed, with certain odds ratios displaying narrow confidence intervals. The complexity of the effect of preoperative chemotherapy on wound closure subsequent to thoracic oncologic surgery is highlighted by our findings. The results underscore the need for individualized treatment strategies for lung cancer patients undergoing surgical procedures that strike a balance between patient safety and optimal clinical outcomes.

KY19382 Accelerates Cutaneous Wound Healing via Activation of the Wnt/ß-Catenin Signaling Pathway.

The Wnt/ß-catenin signaling pathway plays important roles in the multi-phases of wound healing: homeostasis, inflammation, proliferative, and remodeling phases. However, there are no clinically available therapeutic agents targeting the Wnt/ß-catenin pathway. In this study, we tested the effect of 5, 6-dichloroindirubin-3'-methoxime (KY19382), a small molecule that activates the Wnt/ß-catenin pathway via interference with the function of the negative feedback regulator CXXC5, on cutaneous wound healing. KY19382 significantly enhanced cell migration of human keratinocytes and dermal fibroblasts with increased levels of ß-catenin, phalloidin, Keratin 14, proliferating cell nuclear antigen (PCNA), Collagen I, and alpha-smooth muscle actin (α-SMA) by activating the Wnt/ß-catenin signaling pathway without causing significant cytotoxicity. In addition, levels of Collagen I, Keratin 14, PCNA, and stem cell markers were significantly increased by KY19382 in a cutaneous murine wound healing model. Moreover, KY19382 treatment accelerated re-epithelialization and neo-epidermis formation with collagen deposition and stem cell activation at an early stage of cutaneous wound healing. Overall, KY19382 accelerates wound healing via activating the Wnt/ß-catenin pathway, and may have the potential to be used for the development of a new wound healing agent.

Involvement of PAR-2 in the Induction of Cell-Specific Matrix Metalloproteinase-2 by Activated Protein C in Cutaneous Wound Healing.

We previously reported that human keratinocytes express protease-activated receptor (PAR)-2 and play an important role in activated protein C (APC)-induced cutaneous wound healing. This study investigated the involvement of PAR-2 in the production of gelatinolytic matrix metalloproteinases (MMP)-2 and -9 by APC during cutaneous wound healing. Full-thickness excisional wounds were made on the dorsum of male C57BL/6 mice. Wounds were treated with APC on days 1, 2, and 3 post-wounding. Cultured neonatal foreskin keratinocytes were treated with APC with or without intact PAR-2 signalling to examine the effects on MMP-2 and MMP-9 production. Murine dermal fibroblasts from PAR-2 knock-out (KO) mice were also assessed. MMP-2 and -9 were measured via gelatin zymography, fluorometric assay, and immunohistochemistry. APC accelerated wound healing in WT mice, but had a negligible effect in PAR-2 KO mice. APC-stimulated murine cutaneous wound healing was associated with the differential and temporal production of MMP-2 and MMP-9, with the latter peaking on day 1 and the former on day 6. Inhibition of PAR-2 in human keratinocytes reduced APC-induced MMP-2 activity by 25~50%, but had little effect on MMP-9. Similarly, APC-induced MMP-2 activation was reduced by 40% in cultured dermal fibroblasts derived from PAR-2 KO mice. This study shows for the first time that PAR-2 is essential for APC-induced MMP-2 production. Considering the important role of MMP-2 in wound healing, this work helps explain the underlying mechanisms of action of APC to promote wound healing through PAR-2.

Sustained Exosome-Guided Macrophage Polarization Using Hydrolytically Degradable PEG Hydrogels for Cutaneous Wound Healing: Identification of Key Proteins and MiRNAs, and Sustained Release Formulation.

Macrophages (Mφs) are characterized by remarkable plasticity, an essential component of chronic inflammation. Thus, an appropriate and timely transition from proinflammatory (M1) to anti-inflammatory (M2) Mφs during wound healing is vital to promoting resolution of acute inflammation and enhancing tissue repair. Herein, exosomes derived from M2-Mφs (M2-Exos), which contain putative key regulators driving Mφ polarization, are used as local microenvironmental cues to induce reprogramming of M1-Mφs toward M2-Mφs for effective wound management. As an injectable controlled release depot for exosomes, hydrolytically degradable poly(ethylene glycol) (PEG) hydrogels (Exogels) are designed and employed for encapsulating M2-Exos to maximize their therapeutic effects in cutaneous wound healing. The degradation time of the hydrogels is adjustable from 6 days or up to 27 days by controlling the crosslinking density and tightness. The localization of M2-Exos leads to a successful local transition from M1-Mφs to M2-Mφs within the lesion for more than 6 days, followed by enhanced therapeutic effects including rapid wound closure and increased healing quality in an animal model for cutaneous wound healing. Collectively, the hydrolytically degradable PEG hydrogel-based exosome delivery system may serve as a potential tool in regulating local polarization state of Mφs, which is crucial for tissue homeostasis and wound repair.

Adipose-derived stem cells-derived exosomes facilitate cutaneous wound healing by delivering XIST and restoring discoidin domain receptor 2.

BACKGROUND: Adipose-derived stem cells (ADSCs) and their derived exosomes (ADSC-Exos) have shown potential functions in tissue repair. This study focuses on the effects of ADSCs-Exos on cutaneous wound healing and the potential involvement of the long non-coding RNA (lncRNA) XIST/microRNA-96-5p (miR-96-5p)/discoidin domain receptor 2 (DDR2) axis. METHODS: Exos were isolated from the ADSCs and identified. A mouse model of full-thickness skin wounds was established. The mice were treated with ADSC-Exos to evaluate the function of ADSC-Exos in wound healing. Mouse dermal fibroblasts (MDFs) were co-cultured with the ADSC-Exos for in vitro experiments. The most differentially expressed lncRNAs in mouse skin tissues after ADSC-Exo treatment were screened by microarray analysis. The downstream molecules were analyzed by bioinformatics tools. Gain- and loss-of-function studies were performed to examine the functions of the XIST/miR-96-5p/DDR2 axis in wound healing. RESULTS: ADSC-Exos facilitated wound healing in mice, reduced inflammatory infiltration, and increased collagen deposition in the wound skin tissues. In vitro, the ADSC-Exos promoted proliferation, migration of the MDFs. XIST was the most upregulated lncRNA in MDFs after ADSC-Exo treatment. Downregulation of XIST suppressed the promoting role of ADSC-Exos in wound healing. XIST bound to miR-96-5p to restore the expression of DDR2 mRNA. Either silencing of miR-96-5p or overexpression of DDR2 restored the promoting functions of ADSC-Exos in proliferation and migration of MDFs. CONCLUSION: This study demonstrates that ADSC-Exos-carried XIST accelerates cutaneous wound healing through suppressing miR-96-5p and restoring the DDR2 expression.

Euodia daniellii Hemsl. Extract and Its Active Component Hesperidin Accelerate Cutaneous Wound Healing via Activation of Wnt/ß-Catenin Signaling Pathway.

The activation of the Wnt/ß-catenin signaling pathway plays a key role in the wound-healing process through tissue regeneration. The extract of Euodia daniellii Hemsl. (E. daniellii), a member of the Rutaceae family, activates the Wnt/ß-catenin signaling pathway. However, the function of E. daniellii in wound healing has not yet been elucidated. We performed a migration assay to determine the wound-healing effect of E. daniellii extract in vitro using human keratinocytes and dermal fibroblast. In addition, a mouse acute wound model was used to investigate the cutaneous wound-healing effect of E. daniellii extract in vivo and confirm the potential mechanism. E. daniellii extract enhanced the migration of human keratinocytes and dermal fibroblasts via the activation of the Wnt/ß-catenin pathway. Moreover, the E. daniellii extract increased the levels of keratin 14, PCNA, collagen I, and α-SMA, with nuclei accumulation of ß-catenin in vitro. E. daniellii extract also efficiently accelerated re-epithelialization and stimulated wound healing in vivo. Furthermore, we confirmed that hesperidin, one of the components of E. daniellii, efficiently accelerated the migration of human keratinocytes and dermal fibroblasts, as well as wound healing in vivo via the activation of the Wnt/ß-catenin pathway. Overall, E. daniellii extract and its active component, hesperidin, have potential to be used as therapeutic agents for wound healing.

Exosomes derived from ADSCs containing miR-378 promotes wound healing by targeting caspase-3.

Pathological scars and chronic wounds caused by injury, aging, or surgery have always been important public health problems, and there is an urgent need to study the driving forces to find more effective treatments. In this study, we extracted and identified ADSCs exosomes and found that they have the ability to protect HaCat cells from oxidative damage, including promoting proliferation and migration and reducing apoptosis. Further studies determined that the expression of miR-378 was significantly enriched in exosomes. Studies have found that miR-378 mimic can produce protection similar to ADSCs-exo. However, when miR-378 inhibitors are used on ADSCs, the damage protection of the secreted exosomes disappears. This proves that miR-378 enriched in exosomes can improve HaCat's oxidative stress damage. Luciferase experiments show that this effect is achieved by targeting caspase-3. These results indicate that ADSCs play a protective role in wound healing by secreting miR-378-rich exosomes.

Porcine acellular dermal matrix accelerates wound healing through miR-124-3p.1 and miR-139-5p.

BACKGROUND AIMS: Cutaneous wound management is a major health problem and imposes a huge economic burden worldwide. Previous studies have demonstrated that wound healing is a highly coordinated process including epithelialization, angiogenesis, remodeling and scarring. This progression requires self-renewal, preservation and repair properties of stem cells. However, our understanding of the detailed internal regulatory mechanism following injury and the means to accelerate wound healing are limited. METHODS: Our previous research revealed that porcine acellular dermal matrix (ADM) effectively promotes wound healing and scar formation through epidermal stem cells (ESCs), and this process is relevant to the alteration of internal miRNA levels. In this study, we investigated the regulatory function of porcine ADM treatment on miRNAs in ESCs. RESULTS: We report that the treatment of porcine ADM reduced the levels of miR-124-3p.1 and miR-139-5p in wounds. MiR-124-3p.1 and miR-139-5p inhibited the expression of JAG1 and Notch1, respectively, by directly targeting miRNAs in ESCs. CONCLUSIONS: This work demonstrates that porcine ADM induced down-regulation of miR-124-3p.1/139-5p in wounds and up-regulation of JAG1/Notch1 in ESCs, thus enhancing cutaneous wound healing.

From Inflammation to Cutaneous Repair: Topical Application of Lupeol Improves Skin Wound Healing in Rats by Modulating the Cytokine Levels, NF-κB, Ki-67, Growth Factor Expression, and Distribution of Collagen Fibers.

Skin wound healing is a highly complex event that involves different mediators at the cellular and molecular level. Lupeol has been reported to possess different biological activities, such as anti-inflammatory, antioxidant, antidiabetic, and in vitro wound healing properties, which motivated us to proceed with in vivo studies. We aimed to investigate the wound healing effect of lupeol-based cream for 3, 7, and 14 days. Wound excisions were induced on the thoraco-lumbar region of rats and topically treated immediately after injury induction. Macroscopic, histopathological, and immunohistochemical analyses were performed. Cytokine levels were measured by ELISA and gene expression was evaluated by real-time RT-qPCR. Our results showed a strong wound-healing effect of lupeol-based cream after 7 and 14 days. Lupeol treatment caused a reduction in proinflammatory cytokines (TNF-a, IL-1ß, and IL-6) and gene and protein NF-κB expression, and positively altered IL-10 levels, showing anti-inflammatory effects in the three treatment periods. Lupeol treatment showed involvement in the proliferative phase by stimulating the formation of new blood vessels, increasing the immunostaining of Ki-67 and gene expression, and immunolabeling of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF), and increasing gene expression of transforming growth factor beta-1 (TGF-ß1) after seven days of treatment. Lupeol was also involved in the tissue regeneration phase by increasing the synthesis of collagen fibers noted in the three treatment periods analyzed. Our findings suggest that lupeol may serve as a novel therapeutic option to treat cutaneous wounds by regulating mechanisms involved in the inflammatory, proliferative, and tissue-remodeling phases.

Participation of Somatic Stem Cells, Labeled by a Unique Antibody (A3) Recognizing both N-glycan and Peptide, to Hair Follicle Cycle and Cutaneous Wound Healing in Rats.

A monoclonal antibody (A3) was generated by using rat malignant fibrous histiocytoma (MFH) cells as the antigen. Generally, MFH is considered to be a sarcoma derived from undifferentiated mesenchymal cells. Molecular biological analyses using the lysate of rat MFH cells revealed that A3 is a conformation specific antibody recognizing both N-glycan and peptide. A3-labeled cells in bone marrow were regarded as somatic stem cells, because the cells partly coexpressed CD90 and CD105 (both immature mesenchymal markers). In the hair follicle cycle, particularly the anagen, the immature epithelial cells (suprabasal cells) near the bulge and some immature mesenchymal cells in the disassembling dermal papilla and regenerating connective tissue sheath/hair papilla reacted to A3. In the cutaneous wound-healing process, A3-labeled epithelial cells participated in re-epithelialization in the wound bed, and apparently, the labeled cells were derived from the hair bulge; in addition, A3-labeled immature mesenchymal cells in the connective tissue sheath of hair follicles at the wound edge showed the expansion of the A3 immunolabeling. A3-labeled immature epithelial and mesenchymal cells contributed to morphogenesis in the hair cycle and tissue repair after a cutaneous wound. A3 could become a unique antibody to identify somatic stem cells capable of differentiating both epithelial and mesenchymal cells in rat tissues.

Live imaging of angiogenesis during cutaneous wound healing in adult zebrafish.

Angiogenesis, the growth of new blood vessels from pre-existing vessels, is critical for cutaneous wound healing. However, it remains elusive how endothelial cells (ECs) and pericytes (PCs) establish new blood vessels during cutaneous angiogenesis. We set up a live-imaging system to analyze cutaneous angiogenesis in adult zebrafish. First, we characterized basic structures of cutaneous vasculature. In normal skin tissues, ECs and PCs remained dormant to maintain quiescent blood vessels, whereas cutaneous injury immediately induced angiogenesis through the vascular endothelial growth factor signaling pathway. Tortuous and disorganized vessel networks formed within a few weeks after the injury and subsequently normalized through vessel regression in a few months. Analyses of the repair process of injured single blood vessels revealed that severed vessels elongated upon injury and anastomosed with each other. Thereafter, repaired vessels and adjacent uninjured vessels became tortuous by increasing the number of ECs. In parallel, PCs divided and migrated to cover the tortuous blood vessels. ECs sprouted from the PC-covered tortuous vessels, suggesting that EC sprouting does not require PC detachment from the vessel wall. Thus, live imaging of cutaneous angiogenesis in adult zebrafish enables us to clarify how ECs and PCs develop new blood vessels during cutaneous angiogenesis.

Are melanocortin peptides future therapeutics for cutaneous wound healing?

Cutaneous wound healing is a complex process divided into different phases, that is an inflammatory, proliferative and remodelling phase. During these phases, a variety of resident skin cell types but also cells of the immune system orchestrate the healing process. In the last year, it has been shown that the majority of cutaneous cell types express the melanocortin 1 receptor (MC1R) that binds α-melanocyte-stimulating hormone (α-MSH) with high affinity and elicits pleiotropic biological effects, for example modulation of inflammation and immune responses, cytoprotection, antioxidative defense and collagen turnover. Truncated α-MSH peptides such as Lys-Pro-Val (KPV) as well as derivatives like Lys-d-Pro-Thr (KdPT), the latter containing the amino acid sequence 193-195 of interleukin-1ß, have been found to possess anti-inflammatory effects but to lack the pigment-inducing activity of α-MSH. We propose here that such peptides are promising future candidates for the treatment of cutaneous wounds and skin ulcers. Experimental approaches in silico, in vitro, ex vivo and in animal models are outlined. This is followed by an unbiased discussion of the pro and contra arguments of such peptides as future candidates for the therapeutic management of cutaneous wounds and a review of the so-far available data on melanocortin peptides and derivatives in wound healing.

Bone Marrow-Derived Mesenchymal Stem Cells Promoted Cutaneous Wound Healing by Regulating Keratinocyte Migration via ß2-Adrenergic Receptor Signaling.

Mesenchymal stem cells (MSCs) play an important role in cutaneous wound healing; however, the functional mechanisms involved in the healing process are poorly understood. A series of studies indicate that keratinocytes that migrate into the wound bed rely on an epithelial-mesenchymal transition (EMT)-like process to initiate re-epithelialization. We therefore examined whether bone marrow-derived MSCs (BMSCs) could affect biological behavior and induce EMT-like characteristics in the human epidermal keratinocytes (HEKs) and in the immortalized human keratinocyte cell line HaCaT cells, and we investigated the signaling pathways of BMSC-mediated phenotypic changes. By assessing the expression of EMT-related markers including E-cadherin, α-SMA, and Snail family transcription factors by ß2-adrenergic receptor (ß2-AR) blockage using ICI-118,551, a ß2-AR selective antagonist, or ß2-AR small interfering RNA (siRNA), we showed an involvement of ß2-AR signaling in the induction of EMT-like alterations in human keratinocytes in vitro. ß2-AR signaling also affected collective and individual cell migration in human keratinocyte cell lines, which was attenuated by administration of ICI-118,551. Treating the cells with BMSC-conditioned media (BMSC-CM) not only recapitulated the effect of isoproterenol (ISO) on cell migration but also induced the expression of ß2-AR and a panel of proteins associated with mesenchymal phenotype in HEKs and HaCaT cells. Similarly, a blockade of the ß2-AR by either ICI-118,551 or ß2-AR siRNAs reversed both responses of the epidermal keratinocyte cell lines relative to BMSC-CM exposure. These results were further verified in our vivo findings and indicated that the exogenous application of MSCs promoted cutaneous wound healing and endowed the keratinocytes surrounding the wound area with an increased migratory phenotype through activation of ß2-AR signaling. Our findings suggest a biochemical mechanism underlying the function of MSCs in wound re-epithelization, which provides a reliable theoretical basis for the wide application of MSCs in the treatment of chronic wounds.