Re-epithelialization rate and protein expression in the suction-induced wound model: comparison between intact blisters, open wounds and calcipotriol-pretreated open wounds

Image-based non-invasive assessment of suction blister wounds for clinical safety and efficacy

Recognising the need for objective imaging-based technologies to assess wound healing in clinical studies, the suction blister wound model offers an easily accessible wound model that creates reproducible epidermal wounds that heal without scarring. This study provides a comprehensive methodology for implementing and evaluating photography-based imaging techniques utilising the suction blister wound model. Our method encompasses a protocol for capturing consistent, high-quality photographs and procedures for quantifying these images via a visual wound healing score and a computer-assisted colour analysis of wound exudation and wound redness. We employed this methodology on 16 suction blister wounds used as controls in a clinical phase-1 trial. Our method enabled us to discern and quantify subtle differences between individual wounds concerning healing progress, erythema and wound exudation. The wound healing score exhibited a high inter-rater agreement. There was a robust correlation between the spectrophotometer-measured erythema index and photography-based wound redness, as well as between dressing protein content and photography-based dressing yellowness. In conclusion, this study equips researchers conducting clinical wound studies with reproducible methods that may support future wound research and aid in the development of new treatments.

Microneedle-based glucose monitoring: a review from sampling methods to wearable biosensors

Blood glucose (BG) monitoring is critical for diabetes management. In recent years, microneedle (MN)-based technology has attracted emerging attention in glucose sensing and detection. In this review, we summarized MN-based sampling for glucose collection and glucose analysis in detail. First, different principles of MN-based biofluid extraction were elaborated, including external negative pressure, capillary force, swelling force and iontophoresis, which would guide the shape design and material optimization of MNs. Second, MNs coupled with different analysis approaches, including Raman methods, colorimetry, fluorescence, and electrochemical sensing, were emphasized to exhibit the trend towards highly integrated wearable sensors. Finally, the future development prospects of MN-based devices were discussed.

Gene Expression Linked to Reepithelialization of Human Skin Wounds

Our understanding of the regulatory processes of reepithelialization during wound healing is incomplete. In an attempt to map the genes involved in epidermal regeneration and differentiation, we measured gene expression in formalin-fixed, paraffin-embedded standardized epidermal wounds induced by the suction-blister technique with associated nonwounded skin using NanoString technology. The transcripts of 139 selected genes involved in clotting, immune response to tissue injury, signaling pathways, cell adhesion and proliferation, extracellular matrix remodeling, zinc transport and keratinocyte differentiation were evaluated. We identified 22 upregulated differentially expressed genes (DEGs) in descending order of fold change (MMP1, MMP3, IL6, CXCL8, SERPINE1, IL1B, PTGS2, HBEGF, CXCL5, CXCL2, TIMP1, CYR61, CXCL1, MMP12, MMP9, HGF, CTGF, ITGB3, MT2A, FGF7, COL4A1 and PLAUR). The expression of the most upregulated gene, MMP1, correlated strongly with MMP3 followed by IL6 and IL1B. rhIL-1β, but not rhIL-6, exposure of cultured normal human epidermal keratinocytes and normal human dermal fibroblasts increased both MMP1 mRNA and MMP-1 protein levels, as well as TIMP1 mRNA levels. The increased TIMP1 in wounds was validated by immunohistochemistry. The six downregulated DEGs (COL7A1, MMP28, SLC39A2, FLG1, KRT10 and FLG2) were associated with epidermal maturation. KLK8 showed the strongest correlation with MKI67 mRNA levels and is a potential biomarker for keratinocyte proliferation. The observed gene expression changes correlate well with the current knowledge of physiological reepithelialization. Thus, the gene expression panel described in this paper could be used in patients with impaired healing to identify possible therapeutic targets.

Hair follicle stem cell progeny heal blisters while pausing skin development

Injury in adult tissue generally reactivates developmental programs to foster regeneration, but it is not known whether this paradigm applies to growing tissue. Here, by employing blisters, we show that epidermal wounds heal at the expense of skin development. The regenerated epidermis suppresses the expression of tissue morphogenesis genes accompanied by delayed hair follicle (HF) growth. Lineage tracing experiments, cell proliferation dynamics, and mathematical modeling reveal that the progeny of HF junctional zone stem cells, which undergo a morphological transformation, repair the blisters while not promoting HF development. In contrast, the contribution of interfollicular stem cell progeny to blister healing is small. These findings demonstrate that HF development can be sacrificed for the sake of epidermal wound regeneration. Our study elucidates the key cellular mechanism of wound healing in skin blistering diseases.

Endogenous Antioxidant Cocktail Loaded Hydrogel for Topical Wound Healing of Burns

The main goal of this work is the study of the skin wound healing efficacy of an antioxidant cocktail consisting of vitamins A, D, E and the endogenous pineal hormone melatonin (MLT), with all of these loaded into a thermosensitive hydrogel delivery system. The resulting formulation was characterized by scanning electron microscopy. The antioxidant efficacy and microbiological activity against Gram positive and Gram negative strains were also assayed. The skin healing efficacy was tested using an in vivo model which included histological evaluation. Furthermore, atomic force microscopy was employed to evaluate the wound healing efficacy of rat skin burns through the determination of its elasticity at the nanoscale using force spectroscopy analysis. The resulting hydrogel exhibited sol state at low temperature and turned into a gel at 30 ± 0.2 °C. The hydrogel containing the antioxidant cocktail showed higher scavenging activity than the hydrogel containing vitamins or MLT, separately. The formulation showed optimal antimicrobial activity. It was comparable to a commercial reference. It was also evidenced that the hydrogel containing the antioxidant cocktail exhibited the strongest healing process in the skin burns of rats, similar to the assayed commercial reference containing silver sulfadiazine. Histological studies confirmed the observed results. Finally, atomic force microscopy demonstrated a similar distribution of Young's modulus values between burned skin treated with the commercial reference and burned skin treated with hydrogel containing the antioxidant cocktail, and all these with healthy skin. The use of an antioxidant cocktail of vitamins and MLT might be a promising treatment for skin wounds for future clinical studies.

Design and evaluation of a multifunctional thermosensitive poloxamer-chitosan-hyaluronic acid gel for the treatment of skin burns

The main goal of this study was the design, development and characterization of a poloxamer/chitosan/hyaluronic based vehicle including three biological antioxidant molecules such as vitamins A, D and E aimed at improving the treatment of skin burns. The physical characterization of hydrogel, its mechanical and rheological properties as well as internal structure were investigated. Furthermore, biological characteristics such as ex vivo antimicrobial properties and in vivo wound healing were also accomplished and compared with a commercial reference. Results showed optimal physicochemical properties with biocompatible pH value of 4.6 ± 0.1 and zeta potential dependent on pH. The swelling rate was around 350% with optimal wettability, adhesion and leakage properties, as well as thermosensitive gelation processes. The microbiological assay demonstrated similar antimicrobial activity to that of commercial reference. In vivo tolerance study revealed no skin reactions. Finally, the wound healing efficacy of hydrogel in skin burn model showed dermal appendages and similar epidermis, dermis and stratum corneum to the commercial reference. These findings indicated that our hydrogel loading vitamins could be considered an outstanding candidate for further clinical studies.

The spectrum of histopathologic findings in pemphigoid: Avoiding diagnostic pitfalls

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune vesiculobullous dermatitis that primarily affects the elderly and presents with tense, fluid-filled blisters. The histological hallmark on routine hematoxylin & eosin (H&E)-stained specimens is a subepidermal blister with luminal eosinophils. However, there are histologic variants than can produce diagnostic confusion.

METHODS

All immunofluorescence reports from an independent certified dermatopathology laboratory (2006-2015) were inspected, and those with findings consistent with an autoimmune subepidermal blistering process were selected. Seventy-seven cases were identified, and the corresponding H&E-stained specimens were reviewed by two dermatopathologists who tabulated the histopathologic findings.

RESULTS

Just over half of biopsies showed subepidermal clefting (54%). The histologic variants included: urticarial or eczematous findings (17%), partial or complete re-epithelialization (28%), and epidermal necrosis (7%).

CONCLUSION

While re-epithelialization of subepidermal blisters is a commonly accepted phenomenon, there are no published data demonstrating its incidence. Because only half of the biopsies showed the classic subepidermal blister, it is important to be aware of the spectrum of histopathologic findings that occur in this disease. Specifically, the presence of an intraepidermal blister and/or epidermal necrosis on routine H&E-stained specimens does not preclude the diagnosis of pemphigoid.

Reduced fibulin-2 contributes to loss of basement membrane integrity and skin blistering in mice lacking integrin α3β1 in the epidermis

Deficient epidermal adhesion is a hallmark of blistering skin disorders and chronic wounds, implicating integrins as potential therapeutic targets. Integrin α3β1, a major receptor in the epidermis for adhesion to laminin-332 (LN-332), has critical roles in basement membrane (BM) organization during skin development. In the current study we identify a role for α3β1 in promoting stability of nascent epidermal BMs through induction of fibulin-2, a matrix-associated protein that binds LN-332. We demonstrate that mice lacking α3β1 in the epidermis display ruptured BM beneath neo-epidermis of wounds, characterized by extensive blistering. This junctional blistering phenocopies defects reported in newborn α3-null mice, as well as in human patients with α3 gene mutations, indicating that the developmental role of α3β1 in BM organization is recapitulated during wound healing. Mice lacking epidermal α3β1 also have reduced fibulin-2 expression, and fibulin-2-null mice display perinatal skin blisters similar to those in α3β1-deficient mice. Interestingly, α3-null wound epidermis or keratinocytes also show impaired processing of the LN-332 γ2 chain, although this defect was independent of reduced fibulin-2 and did not appear to cause blistering. Our findings indicate a role for integrin α3β1 in BM stability through fibulin-2 induction, both in neonatal skin and in adult wounds.

Transmembrane collagen XVII modulates integrin dependent keratinocyte migration via PI3K/Rac1 signaling

The hemidesmosomal transmembrane component collagen XVII (ColXVII) plays an important role in the anchorage of the epidermis to the underlying basement membrane. However, this adhesion protein seems to be also involved in the regulation of keratinocyte migration, since its expression in these cells is strongly elevated during reepithelialization of acute wounds and in the invasive front of squamous cell carcinoma, while its absence in ColXVII-deficient keratinocytes leads to altered cell motility. Using a genetic model of murine Col17a1⁻/⁻ keratinocytes we elucidated ColXVII mediated signaling pathways in cell adhesion and migration. Col17a1⁻/⁻ keratinocytes exhibited increased spreading on laminin 332 and accelerated, but less directed cell motility. These effects were accompanied by increased expression of the integrin subunits β4 and β1. The migratory phenotype, as evidenced by formation of multiple unstable lamellipodia, was associated with enhanced phosphoinositide 3-kinase (PI3K) activity. Dissection of the signaling pathway uncovered enhanced phosphorylation of the β4 integrin subunit and the focal adhesion kinase (FAK) as activators of PI3K. This resulted in elevated Rac1 activity as a downstream consequence. These results provide mechanistic evidence that ColXVII coordinates keratinocyte adhesion and directed motility by interfering integrin dependent PI3K activation and by stabilizing lamellipodia at the leading edge of reepithelializing wounds and in invasive squamous cell carcinoma.

Alternatives for animal wound model systems

In this chapter a review of animal model systems already being utilized to study normal and pathologic wound healing is provided. We also go into details on alternatives for animal wound model systems. The case is made for limitations in the various approaches. We also discuss the benefits/limitations of in vitro/ex vivo systems bringing everything up to date with our current work on developing a cell-based reporter system for diabetic wound healing.

Accelerated wound repair in ADAM-9 knockout animals

ADAM-9 belongs to a family of transmembrane, disintegrin-containing metalloproteinases (ADAMs) involved in protein ectodomain shedding and cell-cell and cell-matrix interactions. Although the functions of many ADAM family members are known, the specific biological function of ADAM-9 is still unclear. In this study, we have analyzed ADAM-9 temporal and spatial distribution during wound healing. We showed increased ADAM-9 transcript expression during the first 7 days post-wounding and, by immunolocalization, detected ADAM-9 in all migrating and proliferating keratinocytes from days 3 to 7. In older 14-day-old wounds, ADAM-9 expression was restored. We have investigated the role of this protein in the healing process following excisional wounding. Animals deficient in ADAM-9 showed accelerated wound repair compared with control littermates. No alterations in neutrophil, leukocyte, and macrophage infiltration were observed. However, re-epithelialization was significantly faster in Adam-9 -/- than control wounds. Although no differences in proliferation were observed in vivo and in vitro, increased migration of keratinocytes was responsible for this effect. These results show the previously unreported role of ADAM-9 in wound repair by regulating keratinocyte migration through modulation of collagen XVII shedding.

Role of dermal-epidermal basement membrane zone in skin, cancer, and developmental disorders

The dermal-epidermal basement membrane zone is an important epithelial and stromal interface, consisting of an intricately organized collection of intracellular, transmembrane, and extracellular matrix proteins. The basement membrane zone has several main functions including acting as a permeability barrier, forming an adhesive interface between epithelial cells and the underlying matrix, and controlling cellular organization and differentiation. This article identifies key molecular players of the dermal-epidermal membrane zone, and highlights recent research studies that have identified structural and functional roles of these components in the context of various blistering, neoplastic, and developmental syndromes.

Epidermal wound healing in severe sepsis and septic shock in humans

Introduction

The effect of sepsis on epidermal wound healing has not been previously studied. It was hypothesised that epidermal wound healing is disturbed in severe sepsis.

Methods

Blister wounds were induced in 35 patients with severe sepsis and in 15 healthy controls. The healing of the wounds was followed up by measuring transepidermal water loss and blood flow in the wound, reflecting the restoration of the epidermal barrier function and inflammation, respectively. The first set of suction blisters (early wound) was made within 48 hours of the first sepsis-induced organ failure and the second set (late wound) four days after the first wound. In addition, measurements were made on the intact skin.

Results

The average age of the whole study population was 62 years (standard deviation [SD] 12). The mean Acute Physiology and Chronic Health Evaluation II (APACHE II) score on admission was 25 (SD 8). The two most common causes of infections were peritonitis and pneumonia. Sixty-six percent of the patients developed multiple organ failure. The decrease in water evaporation from the wound during the first four days was lower in septic patients than in the control subjects (56 g/m² per hour versus 124 g/m² per hour, P = 0.004). On the fourth day, septic patients had significantly higher blood flow in the wound compared with the control subjects (septic patients 110 units versus control subjects 47 units, P = 0.001). No difference in transepidermal water loss from the intact skin was found between septic patients and controls. Septic patients had higher blood flow in the intact skin on the fourth and on the eighth day of study compared with the controls.

Conclusions

The restoration of the epidermal barrier function is delayed and wound blood flow is increased in patients with severe sepsis.

Two major 5'-untranslated regions for type XVII collagen mRNA

BACKGROUND

Type XVII collagen is an important structural component of keratinocyte hemidesmosomes and its functional loss in genetic or autoimmune disease results in blistering of the skin. In neoplastic tissue aberrant expression is seen dependent on the stage of the tumor. While the sequence of the type XVII collagen encoding gene -COL17A1 - is now completely elucidated, the sequence of the 5'-untranslated region (UTR) of the mRNA is still unknown. Since UTRs can modulate translation efficiency, the determination of the UTR sequence is indispensable for understanding the regulation of translation of type XVII collagen mRNA.

OBJECTIVE

To resolve the sequence of the 5'UTR of type XVII collagen mRNA and to analyse the promoter region for transcription motifs.

METHODS

5' Rapid amplification of cDNA ends (RACE) followed by sequence analysis and ribonuclease protection assays (RPA) were performed.

RESULTS

RACE and sequence analysis revealed the presence of six different 5'UTRs for the type XVII collagen mRNA. The start points of these six transcripts differ but no alternative exons are used. The longest 5'UTR starts 220 nucleotides before the open reading frame, whereas the shortest UTR is only 89 nucleotides in length. RPA confirmed the RACE results and furthermore demonstrated that the 5'UTRs with lengths of 102 and 220 nucleotides are the two major transcripts. Transcription motif analysis of the 5' region of the COL17A gene demonstrated several binding sites for transcription factors including the Sp1 and activating protein-1 (AP-1) families.

CONCLUSION

Type XVII collagen mRNA is alternatively transcribed, which may result in complex regulation of type XVII collagen.

Artificial Barrier Repair in Wounds by Semi-Occlusive Foils Reduced Wound Contraction and Enhanced Cell Migration and Reepithelization in Mouse Skin

The repair of the permeability barrier to prevent the entry of harmful substances into the body is a goal in wound healing. Semi-occlusive foils, which provide an artificial barrier, are commonly used for the treatment of wounds. We examined the effects of foils on wound contraction, cell migration, and reepithelization. Full-thickness skin wounds in mice were covered with occlusive latex foils or semi-occlusive water vapor-permeable hydrocolloid foils for either the entire, the first half, or the second half of the wound-healing period. We found that application of foils for the entire healing period initially reduced wound healing during the first week of treatment, whereas healing was enhanced during the second week. Foils were found to reduce wound contraction, but enhanced reepithelization during the second week of wound healing because of increased proliferation and migration of keratinocytes. These effects were also noted when the hydrocolloid foils were applied for the second part of the healing period, only. The fully occlusive latex foil led to irritation of the skin, whereas less irritation occurred under semi-occlusive conditions. In summary, we found that artificial barrier repair with semi-occlusive foils in wounds reduced wound contraction and enhanced cell migration and reepithelization without irritation.

Effect of jaundice and its resolution on wound re-epithelization, skin collagen synthesis, and serum collagen propeptide levels in patients with neoplastic pancreaticobiliary obstruction

BACKGROUND

Wound and anastomotic healing is considered to be delayed in patients with obstructive jaundice. The study was designed to find out whether the healing of experimental suction blister wounds, skin collagen synthesis, and serum procollagen levels are affected by obstructive jaundice, and if biliary drainage may cause any alterations in these processes.

PATIENTS AND METHODS

Suction blisters were induced on 24 patients with obstructive jaundice caused by neoplastic pancreaticobiliary obstruction and 17 control patients with the corresponding condition without jaundice, to compare healing parameters and collagen synthesis between the groups. A second set of suction blisters were induced on 13 formerly jaundiced patients after the resolution of jaundice and on 14 control patients, to find out whether drainage or time modifies healing or collagen synthesis. By using this model, it is possible to evaluate the re-epithelization and inflammation on wound healing and to assess the baseline skin collagen synthesis. The healing of suction blisters was followed up by measuring water evaporation and blood flow in the wound. Blister fluids and serum samples were collected to study collagen propeptides.

RESULTS

Healing of the blister wound was unaffected by obstructive jaundice. Drainage had no effect on healing. The baseline synthesis of type I and type III collagen in the skin was decreased in jaundiced patients. Biliary drainage improved the synthesis. Serum type III procollagen propeptide levels were elevated in jaundiced patients, but began to normalize after drainage.

CONCLUSION

Healing of an experimental blister wound is not disturbed by obstructive jaundice. The decreased baseline skin collagen synthesis is partly restored by the resolution of jaundice. The results indicate that cell protein synthesis is disturbed earlier than cell dynamics in obstructive jaundice. The elevated serum PIIINP levels, which are most likely to be related to early fibrosis in liver, decreased after drainage.

Laminin 10/11: an alternative adhesive ligand for epidermal keratinocytes with a functional role in promoting proliferation and migration

We have investigated the expression and function of the isoforms of laminin bearing the alpha5 chain, i.e. laminin-10/11 in neonatal and adult human skin. By immunostaining human skin derived from a variety of anatomic sites, we found that the laminin-alpha5 chain is expressed abundantly in the basement membrane underlying the interfollicular epidermis and the blood vessels in the dermis. Interestingly, while the expression level of the well-studied laminin-5 isoform did not change significantly with age, laminin-10/11 (alpha5 chain) appeared to decrease in the basement membrane underlying the epidermis, in adult skin. In contrast, the levels of laminin-10/11 in the basement membrane underlying blood vessels remained unchanged in neonatal vs. adult skin. Importantly, in vitro cell adhesion assays demonstrated that laminin-10/11 is a potent adhesive substrate for both neonatal and adult keratinocytes and that this adhesion is mediated by the alpha3beta1 and alpha6beta4 integrins. Adhesion assays performed with fractionated basal keratinocytes showed that stem cells, transit amplifying cells and early differentiating cells all adhere to purified laminin-10/11 via these receptors. Further, laminin-10/11 provided a proliferative signal for neonatal foreskin keratinocytes, adult breast skin keratinocytes, and even a human papillomavirus type-18 transformed tumorigenic keratinocyte cell line in vitro. Finally, laminin-10/11 was shown to stimulate keratinocyte migration in an in vitro wound healing assay. These results provide strong evidence for a functional role for laminin-10/11 in epidermal proliferation during homeostasis, wound healing and neoplasia.

Topical synthetic inhibitor of matrix metalloproteinases delays epidermal regeneration of human wounds

Matrix metalloproteinases (MMPs) degrade extracellular proteins during epithelialization of wounds. To evaluate the biological significance of MMPs in epidermal healing, the synthetic broad-spectrum MMP inhibitor GM 6001 (also called Galardin and Ilomastat) was applied topically to standardized human wounds. GM 6001 (10 microg/microl) or vehicle alone was applied every second day onto 4 de-roofed 6 mm suction blister wounds on the volar forearm of healthy male volunteers for 12 days. GM 6001 delayed healing by 2-4 days as assessed macroscopically and microscopically. In situ hybridization or immunohistochemistry showed that MMP-1 (interstitial collagenase) was present in and MMP-2 (gelatinase A) close to laterally migrating keratinocytes whereas MMP-9 (gelatinase B) was seen during maturation of new epidermis. MMP-1 was undetectable in blister roofs (normal epidermis) and found in low levels in normal skin. Total MMP-1 activities increased about 100-fold in wounds, independent of treatment, compared to normal skin as analyzed by specific ELISA-based activity assay. By gelatin zymography, MMP-2, but not MMP-9, was detected in blister roofs and wound healing was associated with increased active MMP-2 and latent MMP-9 levels. GM 6001 prevented activation of MMP-2 and increased latent MMP-9 levels. GM 6001 delayed re-appearance of laminin-5, the synthesis of which correlated with epidermal regeneration. Restoration of stratum corneum, measured indirectly by transepidermal water loss, was also impaired (P<0.05) in the GM 6001 group. In conclusion, pharmacological MMP inhibition delayed epidermal regeneration in vivo, suggesting that MMPs are required to restore epidermis after epidermal ablation in humans.