Characterization of In Vitro Reconstructed Human Normotrophic, Hypertrophic, and Keloid Scar Models

Cytokines, chemokines and growth factors involved in keloids pathogenesis

Keloid is a common fibrotic disease, which is difficult to treat. It often causes itching and pain, which greatly disturbs patients in their work and daily life and causing difficulties in social interaction. Its pathogenesis is not clear, but may be related to several aspects: genetic susceptibility, environmental, immunological and endocrine factors, trauma and tension. The central point of its pathogenesis is the excessive proliferation of fibroblasts, with excessive synthesis and secretion of extracellular matrix such as collagen. However, the cause of fibroblast excessive proliferation and differentiation is not clear. Immune abnormalities may play an important role, with cytokines, chemokines, growth factors, and other important immune molecules acting on fibroblasts. This paper presents a detailed and comprehensive literature review on this subject.

Zinc-Alpha-2-Glycoprotein Peptide Downregulates Type I and III Collagen Expression via Suppression of TGF-β and p-Smad 2/3 Pathway in Keloid Fibroblasts and Rat Incisional Model

BACKGROUND

Keloids and hypertrophic scars result from abnormal collagen accumulation and the inhibition of its degradation. Although the pathogenesis remains unclear, excessive accumulation of the extracellular matrix (ECM) is believed to be associated with the TGF-β/SMAD pathway. Zinc-alpha-2-glycoprotein (ZAG) inhibits TGF-β-mediated epithelial-to-mesenchymal transdifferentiation and impacts skin barrier functions. In this study, we investigated the potential of a small ZAG-derived peptide against hypertrophic scars and keloids.

METHODS

The study examined cell proliferation and mRNA expression of collagen types I and III in human dermal fibroblast (HDF) cell lines and keloid-derived fibroblasts (KF) following ZAG peptide treatment. A rat incisional wound model was used to evaluate the effect of ZAG peptide in scar tissue.

RESULTS

Significantly lower mRNA levels of collagen types I and III were observed in ZAG-treated fibroblasts, whereas matrix metalloproteinase (MMP)-1 and MMP-3 mRNA levels were significantly increased in HDFs and KFs. Furthermore, ZAG peptide significantly reduced protein expression of collagen type I and III, TGF-β1, and p-Smad2/3 complex in KFs. Rat incisional scar models treated with ZAG peptide presented narrower scar areas and reduced immature collagen deposition, along with decreased expression of collagen type I, α-SMA, and p-Smad2/3.

CONCLUSION

ZAG peptide effectively suppresses the TGF-β and p-Smad2/3 pathway and inhibits excessive cell proliferation during scar formation, suggesting its potential therapeutic implications against keloids and hypertrophic scars.

Angiogenesis and full thickness wound repair in a cell sheet-based vascularized skin substitute

Skin tissue engineering is undergoing tremendous expansion as a result from clinical needs, mandatory replacement of animal models and development of new technologies. Many approaches have been used to produce vascularized skin substitutes for grafting purposes showing the presence of capillary-like structures but with limited analysis of their in vitro maturation and plasticity. Such knowledge is however important for the development of tissue substitutes with improved implantation success as well as for validation of vascularization in vitro models, including as a readout in pharmacological analyses. For optimal interactions of cells with microenvironment and vasculature, we here used a cell sheet approach consisting in the sole production of matrix by the cells. In this context, we limited the density of endothelial cells seeded for self-assembly and rather relied on the stimulation of angiogenesis for the development of an extensive connected microvascular-like network. After detailed characterization of this network, we challenged its plasticity both during and after establishment of the skin substitute. We show that fine tuning of VEGF concentration and time of application differentially affects formation of capillary-like structures and their perivascular coverage. Furthermore, we performed a deep wound assay that displayed tissue repair and angiogenesis with unique characteristics of the physiological process. These studies demonstrate the importance of cell-derived microenvironment for the establishment of mature yet dynamic vascularized skin models allowing a wide range of pharmacological and basic investigations. STATEMENT OF SIGNIFICANCE: The significant advancements in organ-on-chips and tissue engineering call for more relevant models including microvascularization with remodeling potential. While vascularized skin substitutes have been developed for years, focus has primarily been on the impact of microvascularization on implantation rather than on its in vitro characterization. We here developed a cell sheet-based vascularized skin substitute relying on angiogenesis, i.e. growth of vessel-like structures within the 3D model, rather than solely on endothelial cell self-assembly. We then characterized :1/ vascularization after modulation of angiogenic factor VEGF during the substitute construction; -2/ angiogenesis associated to tissue repair after deep mechanical wounding. These studies establish a solid physiologically relevant model for further investigation of skin cell interactions and in vitro wound healing.

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

STAT3-induced lncRNA GNAS-AS1 accelerates keloid formation by mediating the miR-196a-5p/CXCL12/STAT3 axis in a feedback loop

Keloids are pathological scar tissue resulting from skin trauma or spontaneous formation, often accompanied by itching and pain. Although GNAS antisense RNA 1 (GNAS-AS1) shows abnormal upregulation in keloids, the underlying molecular mechanism is unclear. The levels of genes and proteins in clinical tissues from patients with keloids and human keloid fibroblasts (HKFs) were measured using quantitative reverse transcription PCR, western blot and enzyme-linked immunosorbent assay. The features of HKFs, including proliferation and migration, were evaluated using cell counting kit 8 and a wound healing assay. The colocalization of GNAS-AS1 and miR-196a-5p in HKFs was measured using fluorescence in situ hybridization. The relationships among GNAS-AS1, miR-196a-5p and C-X-C motif chemokine ligand 12 (CXCL12) in samples from patients with keloids were analysed by Pearson correlation analysis. Gene interactions were validated by chromatin immunoprecipitation and luciferase reporter assays. GNAS-AS1 and CXCL12 expression were upregulated and miR-196a-5p expression was downregulated in clinical tissues from patients with keloids. GNAS-AS1 knockdown inhibited proliferation, migration, and extracellular matrix (ECM) accumulation of HKFs, all of which were reversed by miR-196a-5p downregulation. Signal transducer and activator of transcription 3 (STAT3) induced GNAS-AS1 transcription through GNAS-AS1 promoter interaction, and niclosamide, a STAT3 inhibitor, decreased GNAS-AS1 expression. GNAS-AS1 positively regulated CXCL12 by sponging miR-196-5p. Furthermore, CXCL12 knockdown restrained STAT3 phosphorylation in HKFs. Our findings revealed a feedback loop of STAT3/GNAS-AS1/miR-196a-5p/CXCL12/STAT3 that promoted HKF proliferation, migration and ECM accumulation and affected keloid progression.

From Histopathology to High-Resolution Ultrasound Imaging of Skin Scars

Nowadays, modern ultrasound machines and high-frequency transducers allow us to accurately assess the superficial soft tissues of the human body. In this sense, sonographic evaluation of the skin and related pathologies is progressively growing in the pertinent literature. To the best of our knowledge, a standardized sonographic protocol focused on the assessment of pathological skin scars is still lacking. As such, the main purpose of the present study was to propose a technical guide to sonographically assess skin scars in the daily practice of clinicians-starting from knowledge on their histopathological features. In order to standardize the ultrasound examination, a superficial-to-deep, layer-by-layer approach has been proposed to optimize its reproducibility and to promote a common language among the different healthcare providers.

Evaluation of Facial Trauma Scars After Treating by Refining Plastic Surgery Techniques: A Follow-Up Study

BACKGROUND

Although early debridement and refining plastic surgery techniques have been shown to be effective in the treatment of facial scars after trauma, their postoperative outcomes have not been quantitatively evaluated by the relevant Scar Cosmesis Assessment and Rating (SCAR) Scale. This study was designed to provide a fair assessment of the appearance and local symptoms of scars after treatment by refining plastic surgery techniques and to share the operational skills of surgical repairs.

PATIENTS AND METHODS

Patients who received refining plastic surgery techniques were followed up, and facial scars were taken as high-definition photos, which were presented to 6 professional observers, 6 lay observers, and patients themselves to score the facial scars, including: scar spread, erythema, dyspigmentation, track marks or suture marks, hypertrophy/atrophy, itch and pain according to the SCAR.

RESULTS

There were 56 patients who met the inclusion criteria and 25 agreed to participate in the study. No hypertrophic scar was found, and all patients were satisfied with the scar control effect. The scores showed that the treatment was achieved good results in scar spread (pro group: 0.85±0.55, lay group: 0.96±0.68, patients: 0.92±0.64), erythema (pro group: 0.34±0.26, lay group: 0.45±0.37, patients: 0.32±0.48), hypertrophy/atrophy (pro group: 0.21±0.27, lay group: 0.21±0.31, patients: 0.32±0.48), and there was no significant difference in the scores of the 3 observation groups ( P >0.05). However, it is difficult to eliminate dyspigmentation (pro group: 0.29±0.26, lay group: 0.30±0.30, patients: 0.40±0.50), track marks or suture marks (pro group: 0.45±0.33, lay group: 0.59±0.30, patients: 0.36±0.49). Two (8%) patients complained of itch and 1 (4%) patient complained of both itch and pain in the past 24 hours.

CONCLUSIONS

The appearance of facial scars is satisfactory, the local symptoms are mild, and the evaluation among different aesthetics is affirmative after receiving refining plastic surgery techniques, which is just in line with the purpose of seeking beauty for the patients, and meanwhile can provide a good foundation for the comprehensive treatment of late scars, so that the treatment plan should be promoted.

A Reconstructed Human Melanoma-in-Skin Model to Study Immune Modulatory and Angiogenic Mechanisms Facilitating Initial Melanoma Growth and Invasion

Invasion, immune modulation, and angiogenesis are crucial in melanoma progression. Studies based on animals or two-dimensional cultures poorly recapitulate the tumor-microenvironmental cross-talk found in humans. This highlights a need for more physiological human models to better study melanoma features. Here, six melanoma cell lines (A375, COLO829, G361, MeWo, RPMI-7951, and SK-MEL-28) were used to generate an in vitro three-dimensional human melanoma-in-skin (Mel-RhS) model and were compared in terms of dermal invasion and immune modulatory and pro-angiogenic capabilities. A375 displayed the most invasive phenotype by clearly expanding into the dermal compartment, whereas COLO829, G361, MeWo, and SK-MEL-28 recapitulated to different extent the initial stages of melanoma invasion. No nest formation was observed for RPMI-7951. Notably, the integration of A375 and SK-MEL-28 cells into the model resulted in an increased secretion of immune modulatory factors (e.g., M-CSF, IL-10, and TGFβ) and pro-angiogenic factors (e.g., Flt-1 and VEGF). Mel-RhS-derived supernatants induced endothelial cell sprouting in vitro. In addition, observed A375-RhS tissue contraction was correlated to increased TGFβ release and α-SMA expression, all indicative of differentiation of fibroblasts into cancer-associated fibroblast-like cells and reminiscent of epithelial-to-mesenchymal transition, consistent with A375's most prominent invasive behavior. In conclusion, we successfully generated several Mel-RhS models mimicking different stages of melanoma progression, which can be further tailored for future studies to investigate individual aspects of the disease and serve as three-dimensional models to assess efficacy of therapeutic strategies.

Human In Vitro Skin Models for Wound Healing and Wound Healing Disorders

Skin wound healing is essential to health and survival. Consequently, high amounts of research effort have been put into investigating the cellular and molecular components involved in the wound healing process. The use of animal experiments has contributed greatly to the knowledge of wound healing, skin diseases, and the exploration of treatment options. However, in addition to ethical concerns, anatomical and physiological inter-species differences often influence the translatability of animal-based studies. Human in vitro skin models, which include essential cellular and structural components for wound healing analyses, would improve the translatability of results and reduce animal experiments during the preclinical evaluation of novel therapy approaches. In this review, we summarize in vitro approaches, which are used to study wound healing as well as wound healing-pathologies such as chronic wounds, keloids, and hypertrophic scars in a human setting.

In Vitro, Ex Vivo, and In Vivo Approaches for Investigation of Skin Scarring: Human and Animal Models

Significance: The cutaneous repair process naturally results in different types of scarring that are classified as normal or pathological. Affected individuals are often affected from an esthetic, physical (functional), and psychosocial perspective. The distinct nature of scarring in humans, particularly the formation of pathological scars, makes the study of skin scarring a challenge for researchers in this area. Several established experimental models exist for studying scar formation. However, the increasing development and validation of newly emerging models have made it possible to carry out studies focused on different variables that influence this unique process. Recent Advances: Experimental models such as in vitro, ex vivo, and in vivo models have obtained different degrees of success in the reproduction of the scar formation in its native milieu and true environment. These models also differ in their ability to elucidate the molecular, cellular, and structural mechanisms involved in scarring, as well as for testing new agents and approaches for therapies. The models reviewed here, including cells derived from human skin and in vivo animal models, have contributed to the advancement of skin scarring research. Critical Issues and Future Directions: The absence of experimental models that faithfully reproduce the typical characteristics of the different types of human skin scars makes the improvement of validated models and the establishment of new ones a critical unmet need. The fields of wound healing research combined with tissue engineering have offered newer alternatives for experimental studies with the potential to provide clinically useful knowledge about scar formation.

The JAK-STAT pathway in keloid pathogenesis: a systematic review with qualitative synthesis

Keloid tissues contain inflammatory cells and upregulated pro-inflammatory cytokines. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway mediate cellular responses to these cytokines. We performed a systematic review on the role of the JAK-STAT pathway in keloid pathogenesis and the evidence for JAK-STAT inhibitors in keloid treatment. The search combined the terms (1) keloid and (2) JAK or TYK or STAT and included MeSH terms and synonyms. Two reviewers screened the articles and assessed the full texts on eligibility. Data were collected on the tested drugs and molecules, the type of cells and tissues used in the experiments, and study findings on the association between the JAK-STAT pathway and keloid cells and tissues. A total of twenty preclinical studies were included. Eleven preclinical studies proved that STAT3 expression and phosphorylation are enhanced in keloid tissue and keloid fibroblasts. Thirteen different JAK and/or STAT inhibitors were investigated. Tested drugs inhibited keloid progression as demonstrated by different processes, including reduced collagen production, cell proliferation and migration, increased cell cycle arrest and apoptosis, enhanced antioxidant responses, decreased (paracrine) signalling, and decreased profibrotic gene expression. No clinical studies have been published to date. Preclinical studies indicate a role for the JAK-STAT pathway in keloid pathogenesis and a potential role for JAK-STAT inhibitors in keloid treatment. The effect of these drugs should be further investigated on relevant biomarkers in a human keloid skin model, preferably including immune cells besides keloid fibroblasts and keratinocytes and in clinical studies.

Effect of Mortalin on Scar Formation in Human Dermal Fibroblasts and a Rat Incisional Scar Model

Wound healing is a complicated cascading process; disequilibrium among reparative processes leads to the formation of pathologic scars. Herein, we explored the role of mortalin in scar formation and its association with the interleukin-1α receptor using in vitro and in vivo models. To investigate the effects of mortalin, we performed an MTT cell viability assay, qRT-PCR, and Western blot analyses, in addition to immunofluorescence and immunoprecipitation studies using cultured fibroblasts. A rat incisional wound model was used to evaluate the effect of a mortalin-specific shRNA (dE1-RGD/GFP/shMot) Ad vector in scar tissue. In vitro, the mortalin-treated human dermal fibroblast displayed a significant increase in proliferation of type I collagen, α-smooth muscle actin, transforming growth factor-β, phospho-Smad2/3-complex, and NF-κB levels. Immunofluorescence staining revealed markedly increased mortalin and interleukin-1α receptor protein in keloid tissue compared to those in normal tissue, suggesting that the association between mortalin and IL-1α receptor was responsible for the fibrogenic effect. In vivo, mortalin-specific shRNA-expressing Ad vectors significantly decreased the scar size and type-I-collagen, α-SMA, and phospho-Smad2/3-complex expression in rat incisional scar tissue. Thus, dE1-RGD/GEP/shMot can inhibit the TGF-β/α-SMA axis and NF-κB signal pathways in scar formation, and blocking endogenous mortalin could be a potential therapeutic target for keloids.

Effectiveness of artesunate combined with fractional CO2 laser in a hypertrophic scar model with underlying mechanism

BACKGROUND AND OBJECTIVES

Both artesunate and fractional CO2 laser have been proved effective in the treatment of hypertrophic scars, yet little data are available for the efficacy of artesunate combined with fractional CO2 laser. In order to assess the pre-clinical significance and the underlying mechanism of this combined treatment profile, we attempted to observe the effectiveness of this therapy in rabbit models through determining the expression of BMP-7 and Fas.

MATERIALS AND METHODS

Twenty-Four New Zealand white rabbits with established hypertrophic scar samples were randomly divided into control group and three treatment groups. Artesunate (20 μl/cm2) was injected into the rat's scar of artesunate and combination groups, while fractional CO2 laser (Combo mode, deep energy:10 mJ, super energy: 50 mJ) was applied to rats in fractional CO2 laser and combination groups at week 4 after model establishment. All rabbits underwent a total of 3 sessions of treatment once every 2 weeks. Histological and immunohistochemistry study, Western blot assay, cell viability, ELISA and RT-QPCR were performed at week 10 to observe the aspects of hypertrophic scar sample changes and expression of BMP-7 and Fas in the scar tissues.

RESULTS

Compared with control group, hypertrophic scars and the collagen fibers were significantly inhibited after treatment, and higher inhibition was seen in the samples in combination group compared to that in artesunate and fractional CO2 laser groups (P < 0.01). Meanwhile, BMP-7 and Fas expressions were both notably increased in all treatment groups, and upregulation of the two proteins was dominant in combination group (P < 0.01).

CONCLUSIONS

Artesunate combined with fractional CO2 laser is effective in hypertrophic scarring in this rabbit model. Our findings can serve as a potential alternative strategy to treatment of hypertrophic scar in clinical practice.

The Epidermis in Microgravity and Unloading Conditions and Their Effects on Wound Healing

The future objectives of human space flight are changing from low-term permanence in the International Space Station to missions beyond low Earth orbit to explore other planets. This implies that astronauts would remain exposed for long time to a micro-gravity environment with limited medical support available. This has sparkled medical research to investigate how tissues may adapt to such conditions and how wound repair may be influenced. This mini-review is focused on the effects of microgravity and unloading conditions on the epidermis and its keratinocytes. Previous studies, originally aimed at improving the in vitro protocols to generate skin substitutes for plastic surgery purposes, showed that epidermal stem cells cultured in simulated microgravity underwent enhanced proliferation and viability and reduced terminal differentiation than under normal gravity. In the meantime, microgravity also triggered epithelial-mesenchymal transition of keratinocytes, promoting a migratory behavior. The molecular mechanisms, only partially understood, involve mechano-trasduction signals and pathways whereby specific target genes are activated, i.e., those presiding to circadian rhythms, migration, and immune suppression, or inhibited, i.e., those involved in stress responses. However, despite the above in vitro studies suggest that microgravity would accelerate keratinocyte growth rate and migration, in vivo findings on animals in experimental set-ups to simulate low gravity rather suggest that prolonged mechanical unloading contributes to delayed and impaired epidermal repair. This is in keeping with the finding that microgravity interferes at multiple levels with the regulatory signals which coordinate the different cell types involved in the repair process, thereby negatively influencing skin wound healing.

Verifying the outcomes of artesunate plus 595-nm PDL in hypertrophic scars via determining BMP-7 and Fas level in model rabbits

BACKGROUND AND OBJECTIVES

Single-use of artesunate (ART) or 595-nm pulsed-dye laser (PDL) has proven clinical efficacy in the treatment of hypertrophic scars (HSs), yet little research has been done on the combined use of ART and PDL. Bone morphogenetic protein-7 (BMP-7) and Fas are recognized to be two important proteins in reducing scar formation. This study was designed to observe the effect of ART combined with 595-nm PDL in the treatment of HS in rabbit models, and investigate the effect of such protocol on the expression of BMP-7 and Fas in rabbit models.

STUDY DESIGN/MATERIALS AND METHODS

Twenty-four New Zealand white rabbits were randomly divided into the control group, ART group, PDL group, and combined treatment (ART + PDL) group. ART was respectively applied to the ART group and combined treatment group. Treatment was once every 2-week for a total of three sessions for both groups. Animals in the PDL group were simply treated with 595-nm PDL. Then, hematoxylin & eosin and Van Gieson straining, immunohistochemical study, enzyme-linked immunosorbent assay (ELISA), Cell counting kit-8 test, western blot assay, and real-time polymerase chain reaction (RT-PCR) were carried out to observe the development of HS samples and expression of BMP-7 and Fas proteins in the sample tissues.

RESULTS

After treatment, the scar samples grew lower and flatter, which was particularly evident in the combined treatment group, with notably inhibited fibroblast and collagen compared to other groups (p < 0.001). Western blot assay and RT-PCR demonstrated that the expression of BMP-7 was most increased in scar samples treated by ART + PDL. BMP-7 level was correspondingly and notably upregulated in treatment groups, especially in the ART + PDL group. In addition, relevant expression of Fas was also higher after treatment, especially in the ART + PDL group compared to either ART or 595-nm PDL group. The difference was significant among groups (p < 0.001).

CONCLUSIONS

Combined use of ART and 595-nm PDL can inhibit HSs in rabbit models via inhibiting extra fibroblast and collagens. The potential mechanism may be involved in enhanced BMP-7 and Fas expression. Our observations may create an alternative therapeutic strategy for HSs in the clinic.

Single-Cell and Bulk Transcriptome Data Integration Reveals Dysfunctional Cell Types and Aberrantly Expressed Genes in Hypertrophic Scar

Hypertrophic scar (HS) is a common skin disorder characterized by excessive extracellular matrix (ECM) deposition. However, it is still unclear how the cellular composition, cell-cell communications, and crucial transcriptionally regulatory network were changed in HS. In the present study, we found that FB-1, which was identified a major type of fibroblast and had the characteristics of myofibroblast, was significantly expanded in HS by integrative analysis of the single-cell and bulk RNA sequencing (RNA-seq) data. Moreover, the proportion of KC-2, which might be a differentiated type of keratinocyte (KC), was reduced in HS. To decipher the intercellular signaling, we conducted the cell-cell communication analysis between the cell types, and found the autocrine signaling of HB-1 through COL1A1/2-CD44 and CD99-CD99 and the intercellular contacts between FB-1/FB-5 and KC-2 through COL1A1/COL1A2/COL6A1/COL6A2-SDC4. Almost all the ligands and receptors involved in the autocrine signaling of HB-1 were upregulated in HS by both scRNA-seq and bulk RNA-seq data. In contrast, the receptor of KC-2, SDC4, which could bind to multiple ligands, was downregulated in HS, suggesting that the reduced proportion of KC-2 and apoptotic phenotype of KC-2 might be associated with the downregulation of SDC4. Furthermore, we also investigated the transcriptionally regulatory network involved in HS formation. The integrative analysis of the scRNA-seq and bulk RNA-seq data identified CREB3L1 and TWIST2 as the critical TFs involved in the myofibroblast of HS. In summary, the integrative analysis of the single-cell RNA sequencing (scRNA-seq) and bulk RNA-seq data greatly improved our understanding of the biological characteristics during the HS formation.

595-nm pulsed dye laser combined with fractional CO2 laser reduces hypertrophic scar through down-regulating TGFβ1 and PCNA

595-nm pulsed dye laser and fractional CO2 laser have been demonstrated effective to treat hypertrophic scar. The underlying mechanism may involve transforming growth factor-beta1 (TGFβ1) and proliferating cell nuclear antigen (PCNA), but remains to be clarified. Our study was performed to investigate how 595-nm pulsed dye laser combined with fractional CO2 laser treats hypertrophic scars in a rabbit model through regulating the expression of TGFβ1 and PCNA. Twenty-four New Zealand white rabbits were randomly divided into control group, pulsed dye laser group, fractional CO2 laser group, and pulsed dye laser + fractional CO2 laser (combination) group. Surgical wounds were made and allowed to grow into hypertrophic scars at day 28. Next, 595-nm pulsed dye laser (fluence: 15 J/cm2; square: 7 mm; pulse duration: 10 ms) was used in pulsed dye laser and combination group, while fractional CO2 laser (combo mode, deep energy: 12.5 mJ; super energy: 90 mJ) in fractional CO2 laser and combination groups, once every 4 weeks for 3 times. The appearance and thickness of hypertrophic scar samples were measured with hematoxylin-eosin and Van Gieson's straining. The expressions of TGFβ1 and PCNA were evaluated by immunohistochemical and western blot analysis. A significant improvement was noted in the thickness, size, hardness, and histopathology of hypertrophic scar samples after laser treatment, especially in combination group. Scar Elevation Index (SEI), fiber density (NA), and collagen fiber content (AA) decreased most significantly in combination group (2.10 ± 0.14; 2506 ± 383.00; 22.98 ± 2.80%) compared to 595-nm pulsed dye laser group (3.35 ± 0.28; 4857 ± 209.40; 42.83 ± 1.71%) and fractional CO2 laser group (2.60 ± 0.25; 3995 ± 224.20; 38.33 ± 3.01%) (P < 0.001). Furthermore, TGFβ1 and PCNA expressions were more suppressed in combination group (8.78 ± 1.03; 7.81 ± 1.51) than in 595-nm pulsed dye laser (14.91 ± 1.68; 15.73 ± 2.53) and fractional CO2 laser alone group (15.96 ± 1.56; 16.13 ± 1.72) (P < 0.001). The combination of 595-nm pulsed dye laser with fractional CO2 laser can improve the morphology and histology of hypertrophic scars in a rabbit model through inhibiting the expression of TGFβ1 and PCNA protein. Our findings can pave the way for new clinical treatment strategies for hypertrophic scars.

Protein tyrosine phosphatase 1B regulates fibroblasts proliferation, motility and extracellular matrix synthesis via the MAPK/ERK signalling pathway in keloid

Keloid is a fibroproliferative disorder resulting from trauma, characterized by abnormal activation of keloid fibroblasts and excessive deposition of extracellular matrix (ECM). It affects life quality of patients and lacks of effective therapeutic targets. Protein tyrosine phosphatase 1B (PTP1B) belongs to the protein tyrosine phosphatases and participates in many cellular processes such as metabolism, proliferation and motility. It has been reported that PTP1B negatively regulated diabetic wound healing and tumor progression. However, its effects in keloid remain unclear. Here, we aimed to evaluate the effects of PTP1B on keloid fibroblasts which play essential roles in keloids pathogenesis. Our results revealed that PTP1B expression was decreased both in keloid tissues and in keloid fibroblasts compared to healthy controls. Keloid fibroblasts (KFs) showed higher cell proliferation, motility, ECM production and ERK activity than normal fibroblasts (NFs). Overexpression of PTP1B in KFs and NFs inhibited cell proliferation, motility, ECM synthesis and the MAPK/ERK signalling pathway while knockdown of PTP1B showed converse effects. The rescue experiments with ERK inhibitor further verified that MAPK/ERK signalling pathway involved in PTP1B regulatory network. Taken together, our findings indicated that overexpression of PTP1B suppressed keloid fibroblasts bio-behaviours and promoted their phenotype switch to normal cells via inhibiting the MAPK/ERK signalling pathway, suggesting it may be a potential anti-keloid therapy.

Effect of Artesunate Combined With Fractional CO2 Laser on the Hypertrophic Scar in a Rabbit Model

BACKGROUND AND OBJECTIVES

Hypertrophic scar (HS), a common complication in wound healing, is characterized by the disarrangement of collagen, fibers, and extracellular matrix. Artesunate (ART) can inhibit the abnormal formation of fibroblasts and collagens. Fractional CO2 laser (FCO2 L) can facilitate tissue remodeling and the absorption of drugs into ablative microthermal columns in HS. So far, no research has investigated the efficacy of ART combined with an FCO2 L in treating HS. To investigate the theoretical basis and clinical significance of this combination, we established a rabbit model of HS to observe the change in the expression of transforming growth factor β1 (TGF-β1) and proliferating cell nuclear antigen (PCNA).

STUDY DESIGN/MATERIALS AND METHODS

Forty New Zealand white rabbits were randomly divided into four groups: control group, ART group, FCO2 L group, and ART + FCO2 L (combination) group. Four wounds were surgically established in the ear of each rabbit and allowed to develop into HS. ART (20 μL/cm2 ) was injected in ART and combination groups, and FCO2 L (combo mode, deep energy:10m J, super energy: 50 mJ) in FCO2 L and combination groups on the 28th day after HS occurred. Three rounds of treatment were applied (once every 14 days). HS samples were measured by hematoxylin and eosin staining, Van Gieson staining, immunohistochemistry, and Western blot analysis on the 70th day.

RESULTS

The morphological and histopathological changes in HS were significant. HSs were smoother and smaller and the collagen fibers were thinner and less disordered in the combination group than those in ART and FCO2 L groups. Meanwhile, the hypertrophic index (HI), fiber density (NA), and collagen fiber content (AA) were lower in the combination group (1.54 ± 0.15, 3.30 ± 0.22, 30.37 ± 1.41%) than in the ART group (2.51 ± 0.22, 4.69 ± 0.16, 44.68 ± 2.30%) and FCO2 L group (1.99 ± 0.14, 4.13 ± 0.12, 37.74 ± 1.38%) (P < 0.01). Additionally, the expressions of TGF-β1 and PCNA protein were suppressed in the ART group (0.30 ± 0.03, 0.25 ± 0.03) and FCO2 L group (0.35 ± 0.03, 0.32 ± 0.05), and the suppression was more significant in the combination group(0.07 ± 0.02, 0.07 ± 0.02) (P < 0.01).

CONCLUSIONS

The combination of ART and FCO2 L can effectively reduce HS in the rabbit model. This is the first report about this combination in the treatment of HS. A novel treatment is expected to be based on our findings. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Hypertrophic scars and keloids: Overview of the evidence and practical guide for differentiating between these abnormal scars

Although hypertrophic scars and keloids both generate excessive scar tissue, keloids are characterized by their extensive growth beyond the borders of the original wound, which is not observed in hypertrophic scars. Whether or not hypertrophic scars and keloids are two sides of the same coin or in fact distinct entities remains a topic of much debate. However, proper comparison between the two ideally occurs within the same study, but this is the exception rather than the rule. For this reason, the goal of this review was to summarize and evaluate all publications in which both hypertrophic scars and keloids were studied and compared to one another within the same study. The presence of horizontal growth is the mainstay of the keloid diagnosis and remains the strongest argument in support of keloids and hypertrophic scars being distinct entities, and the histopathological distinction is less straightforward. Keloidal collagen remains the strongest keloid parameter, but dermal nodules and α-SMA immunoreactivity are not limited to hypertrophic scars alone. Ultimately, the current hypertrophic scars-keloid differences are mostly quantitative in nature rather than qualitative, and many similar abnormalities exist in both lesions. Nonetheless, the presence of similarities does not equate the absence of fundamental differences, some of which may not yet have been uncovered given how much we still have to learn about the processes involved in normal wound healing. It therefore seems pertinent to continue treating hypertrophic scars and keloids as separate entities, until such a time as new findings more decisively convinces us otherwise.

The Northwestern Abdominoplasty Scar Model: A Tool for High-Throughput Assessment of Scar Therapeutics

Significance: Scar management is an important concern in plastic surgery. Scar models that best mimic in vivo human scarring are essential for understanding scar development and progression, assessing the efficacy of therapeutics, and providing reliable and valid research outcomes. Recent Advances: In 2016, Lanier et al. proposed a new in vivo patient model, the Northwestern Abdominoplasty Scar Model, that overcomes the prior limitations of both animal and human models, with greater representativeness of the human scarring process, expedited recruitment, smaller sample requirements, and greater flexibility in the types and number of interventions that can be studied simultaneously. Critical Issues: Existing animal models suffer from limitations that impede generalization to human scars. Human scar studies are difficult to conduct and rarely used due to recruitment difficulties, ethical concerns regarding purposeful wounding, and inherent variability based on location, type of scar, and the heterogeneity of the host response between humans. Although overcoming many of these hurdles, the Northwestern Abdominoplasty Scar Model still has a few limitations. In addition, there remains a need for further study of and comparison between the Northwestern Abdominoplasty Scar Model and existing human and animal models, to inspire more widespread acceptance of a standardized human scar model. Future Directions: The Northwestern Abdominoplasty Scar Model is a critical stepping stone toward better human scar models. This model hopefully will inspire other in vivo patient models utilizing elective surgery to overcome recruitment and ethical concerns.

The Keloid Disorder: Heterogeneity, Histopathology, Mechanisms and Models

Keloids constitute an abnormal fibroproliferative wound healing response in which raised scar tissue grows excessively and invasively beyond the original wound borders. This review provides a comprehensive overview of several important themes in keloid research: namely keloid histopathology, heterogeneity, pathogenesis, and model systems. Although keloidal collagen versus nodules and α-SMA-immunoreactivity have been considered pathognomonic for keloids versus hypertrophic scars, conflicting results have been reported which will be discussed together with other histopathological keloid characteristics. Importantly, histopathological keloid abnormalities are also present in the keloid epidermis. Heterogeneity between and within keloids exists which is often not considered when interpreting results and may explain discrepancies between studies. At least two distinct keloid phenotypes exist, the superficial-spreading/flat keloids and the bulging/raised keloids. Within keloids, the periphery is often seen as the actively growing margin compared to the more quiescent center, although the opposite has also been reported. Interestingly, the normal skin directly surrounding keloids also shows partial keloid characteristics. Keloids are most likely to occur after an inciting stimulus such as (minor and disproportionate) dermal injury or an inflammatory process (environmental factors) at a keloid-prone anatomical site (topological factors) in a genetically predisposed individual (patient-related factors). The specific cellular abnormalities these various patient, topological and environmental factors generate to ultimately result in keloid scar formation are discussed. Existing keloid models can largely be divided into in vivo and in vitro systems including a number of subdivisions: human/animal, explant/culture, homotypic/heterotypic culture, direct/indirect co-culture, and 3D/monolayer culture. As skin physiology, immunology and wound healing is markedly different in animals and since keloids are exclusive to humans, there is a need for relevant human in vitro models. Of these, the direct co-culture systems that generate full thickness keloid equivalents appear the most promising and will be key to further advance keloid research on its pathogenesis and thereby ultimately advance keloid treatment. Finally, the recent change in keloid nomenclature will be discussed, which has moved away from identifying keloids solely as abnormal scars with a purely cosmetic association toward understanding keloids for the fibroproliferative disorder that they are.

The Effects of the Transforming Growth Factor-β1 (TGF-β1) Signaling Pathway on Cell Proliferation and Cell Migration are Mediated by Ubiquitin Specific Protease 4 (USP4) in Hypertrophic Scar Tissue and Primary Fibroblast Cultures

BACKGROUND Hypertrophic scar results from an abnormal repair response to trauma in the skin and involves fibroblasts proliferation with increased collagen deposition. Transforming growth factor-ß1 (TGF-ß1) and TGF-ß receptor type I (TGF-ßR1) are involved in tissue repair and are increased by ubiquitin-specific protease 4 (USP4). This study aimed to investigate the effects of TGF-ßR1 and USP4 in human tissue samples of hypertrophic scar and on cell proliferation and cell migration in primary fibroblast cultures in vitro. MATERIAL AND METHODS Skin excision tissue samples with adjacent normal skin were obtained from 15 patients with hypertrophic scar, which provided tissue sections and primary fibroblast culture for analysis. Immunohistochemistry detected the expression of USP4 and TGF-ßR1 in tissue sections. MicroRNA (miRNAs) expression levels were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to measure protein expression levels. Cultured skin fibroblasts were investigated using immunofluorescence staining. Fibroblast proliferation, apoptosis, and migration were measured with the Cell Counting Kit-8 (CCK-8) assay, flow cytometry, and a wound-healing assay, respectively. RESULTS The expression of USP4 and TGF-ßR1 in hypertrophic scar were increased compared with normal skin. Fibroblasts cultured from hypertrophic scar tissue showed increased expression of of USP4 and TGF-ßR1. Fibroblast transfection with USP4 short-interfering RNA (siRNA) resulted in reduced fibroblast proliferation and migration, and increased apoptosis. Downregulation of USP4 inhibited the expression of TGF-ßR1 protein and increased the expression levels of Smad7 protein. CONCLUSIONS USP4 regulated the proliferation, migration, and apoptosis of hypertrophic scar fibroblasts by regulating the TGF-ß1 signaling pathway.

Pilot Study of the Biological Properties and Vascularization of 3D Printed Bilayer Skin Grafts

The skin is the largest human organ, and defects in the skin with a diameter greater than 4 cm do not heal without treatment. Allogeneic skin transplantation has been used to allow wound healing, but many grafts do not survive after implantation, due to multiple complications in the procedure. In the present study, the vascularization of three-dimensional (3D) printed full-thickness skin grafts was investigated. Dermal-epithelial grafts were transplanted into a nude mouse model to evaluate integration with the host tissue and the extent of wound healing. To create microvessels in the skin grafts, a bilayer structure consisting of human dermal fibroblasts, keratinocytes, and microvascular endothelial cells was designed and fabricated using an extruded 3D printer. Human dermal fibroblasts and human microvascular endothelial cells were mixed with gelatin-sodium alginate composite hydrogel as the dermis, and human keratinocytes were mixed with gel as the epithelium. Confocal imaging allowed visualization of the location of the cells in the double-layer skin grafts. A full-thickness wound was created on the backs of nude mice and then covered with a double-layer skin graft. Various groups of mice were tested. Animals were euthanized and tissue samples collected after specified time points. Compared with the control group, wound contraction improved by approximately 10%. Histological analysis demonstrated that the new skin had an appearance similar to that of normal skin and with a significant degree of angiogenesis. The results of the immunohistochemical analysis demonstrated that the transplanted cells survived and participated in the healing process.

Hypertrophic and keloid scars fail to progress from the CD34- /α-smooth muscle actin (α-SMA)+ immature scar phenotype and show gradient differences in α-SMA and p16 expression

BACKGROUND

Our understanding of the pathogenesis underlying keloid scar formation is still very limited, and the morphological distinction between hypertrophic and keloid scars remains difficult.

OBJECTIVES

To test whether hypertrophic and keloid scars may reflect an inability to progress from immaturity to the desired mature normotrophic scar phenotype.

METHODS

Using whole-biopsy imaging and an objectively quantifiable way to analyse immunoreactivity, we have compared the immunohistopathological profiles of young immature scars with mature normotrophic scars, hypertrophic scars, and keloids with their surrounding-normal-skin.

RESULTS

Abnormal scars (hypertrophic scars and keloids) maintain the immature scar phenotype, characterized by a CD34^- (tumour biomarker) and α-smooth muscle actin (α-SMA)⁺ (myofibroblast) dermal region. This is in contrast to normal skin, surrounding-normal-skin and mature normotrophic scars that were CD34⁺ / α-SMA^- . Immature, hypertrophic and keloid scars showed abnormal epidermal differentiation (involucrin), but only hypertrophic scars and keloids showed increased epidermal thickness. Immature scars did show increased epidermal and dermal proliferation (Ki67), which was absent from abnormal scars, where mesenchymal hypercellularity (vimentin) and senescence (p16) were predominant. Keloidal collagen and α-SMA were previously considered to distinguish between hypertrophic scars and keloids. However, α-SMA staining was present in both abnormal scar types, while keloidal collagen was present mostly in keloids. There were no obvious signs of heterogeneity within keloid scars, and the surrounding-normal-skin resembled normal skin.

CONCLUSIONS

Both abnormal scar types showed a unique CD34^- /α-SMA⁺ /p16⁺ scar phenotype, but the differences between hypertrophic scars and keloids observed in this study were of a gradient rather than absolute nature. This suggests that scar progression to the mature normal scar phenotype is, for as yet unknown reasons, hindered in hypertrophic and keloid scars. What's already known about this topic? Hypertrophic and keloid scars both have sustained epidermal barrier dysfunction, suggesting the persistence of an immature scar phenotype. Morphological distinction between hypertrophic and keloid scars remains a topic of debate, although α-smooth muscle actin (α-SMA) and keloidal collagen have been considered distinguishing features of hypertrophic and keloid scars, respectively. It has been suggested that keloids are not simply homogeneous growths, as heterogeneity within keloid scars and possible involvement of the surrounding-normal-skin have been reported. What does this study add? An extensive whole-biopsy imaging and quantifiable immunohistochemical assessment of immature, mature normal, hypertrophic and keloid scars, including normal skin surrounding keloids. Hypertrophic and keloid scars maintain dermal characteristics of immature scars, rather than transitioning into the normal mature phenotype. Differences between hypertrophic and keloid scars were of a gradient rather than absolute nature, with keloids showing the more extreme phenotype. There was no obvious heterogeneity within keloids, and the normal skin surrounding keloids resembled normal skin. What is the translational message? Keloids remain primarily a clinical diagnosis. A raised scar with the CD34^- /α-SMA⁺ /p16⁺ phenotype with strong immunoreactivity for p16 and significant amounts of keloidal collagen, together with a thickened and strongly abnormal involucrin-stained epidermis, would sway the diagnosis towards keloid scars. A hypertrophic scar seems more likely when the CD34^- /α-SMA⁺ /p16⁺ phenotype shows very strong presence of α-SMA⁺ in large dermal nodules, with lesser p16 staining and absent or negligible keloidal collagen.

Liquid Dermal Scaffold With Adipose-Derived Stem Cells Improve Tissue Quality in a Murine Model of Impaired Wound Healing

Wound repair and regeneration is a multidisciplinary field of research with considerable potential value to the management of deep and large burn injuries. These injuries lack an appropriate tissue scaffold and pro-healing cells making them difficult to heal. An alternative to the often limited autologous skin is a therapy that would restore the essential matrix and cellular components for rapid healing. In this study, they use a novel liquid dermal scaffold capable of gelation in vivo to show that it is biocompatible with adipose-derived stem cells. Using a validated method of wound splinting in a delayed-healing murine model, we show that wounds treated with the scaffold and stem cells had a significant reduction in wound size and had accelerated healing compared with control. The wounds treated with stem cells had increased capillary formation, collagen content, epidermal thickness, and essential growth factor expression in the healed tissue compared with control and liquid scaffold alone. This liquid dermal scaffold combined with cells is a feasible treatment strategy for complex or large burn wounds that are otherwise lacking the appropriate cellular matrix necessary for healing.

Monocytes co-cultured with reconstructed keloid and normal skin models skew towards M2 macrophage phenotype

Several abnormalities have been reported in the peripheral blood mononuclear cells of keloid-forming patients and particularly in the monocyte cell fraction. The goal of this in vitro study was to determine whether monocytes from keloid-prone patients contribute to the keloid phenotype in early developing keloids, and whether monocyte differentiation is affected by the keloid microenvironment. Therefore, keloid-derived keratinocytes and fibroblasts were used to reconstruct a full thickness, human, in vitro keloid scar model. The reconstructed keloid was co-cultured with monocytes from keloid-forming patients and compared to reconstructed normal skin co-cultured with monocytes from non-keloid-formers. The reconstructed keloid showed increased contraction, dermal thickness (trend) and α-SMA+ staining, but co-culture with monocytes did not further enhance the keloid phenotype. After 2-week culture, all monocytes switched from a CD11c^high/CD14^high/CD68^low to a CD11c^high/CD14^low/CD68^high phenotype. However, only monocytes co-cultured with either reconstructed keloid scar or normal skin models skewed towards the more fibrotic M2-macrophage phenotype. There was negligible fibroblast and fibrocyte differentiation in mono- and co-cultured monocytes. These results indicate that monocytes differentiate into M2 macrophages when in the vicinity of early regenerating and repairing tissue, independent of whether the individual is prone to normal or keloid scar formation.

Topical essential fatty acid oil on wounds: Local and systemic effects

BACKGROUND

The use of medicinal plants and their derivatives is increasing, and approximately one-third of all traditional herbal medicines are intended for wound treatment. Natural products used in these treatments include vegetable oils, which are rich in essential fatty acids. Once in contact with an ulcerative surface, the oil reaches the blood and lymphatic vessels, thus eliciting systemic effects.

OBJECTIVE

This study evaluated the local and possible systemic effects of essential fatty acids (sunflower oil) applied topically to rat wounds.

METHODS

Cutaneous punch wounds (6 mm) were produced on the dorsa of 30 rats. Saline (SS), mineral oil (MO) or essential fatty acid (EFA) solutions were applied topically. Healing was evaluated after 2, 4 and 10 days (n = 5 per group) by visual and histological/morphometric examination, second harmonic generation (SHG) microscopy, and cytokine and growth factor quantification in the scar tissue (real-time PCR) and in serum (ELISA).

RESULTS

MO/EFA-treated animals had higher IGF-1, leptin, IL-6 and IFN-γ mRNA expression and lower serum IL-6 levels than the control (SS/MO) animals. SHG analysis showed no difference in collagen density between the animals treated with MO and EFA.

CONCLUSION

EFA treatment induces topical (observed by local IGF-1, leptin, IL-6 and IFN-γ production) and systemic effects, lowering IL-6 levels in the serum. As the oil is widely used to shorten ulcer healing time, studies are needed to evaluate the treatment safety and possible undesired effects.

Reconstructed human keloid models show heterogeneity within keloid scars

Keloid scars are often described as having an actively growing peripheral margin with a regressing centre. The aim of this study was to examine the possible heterogeneity within keloids and the involvement of different regions within and around keloid scars in the pathogenesis, using an in vitro keloid scar model. In vitro skin models were constructed from keratinocytes and fibroblasts from normal skin and different regions within and around keloid scars: periphery, centre, and (adjacent) surrounding-normal-skin regions. Additionally, fibroblasts were isolated from the superficial-central and deep-central regions of the keloid and combined with central keratinocytes. All keloid regions showed increased contraction compared to normal skin models, particularly in central regions. Myofibroblasts were present in all keloid regions but were more abundant in models containing central-deep keloid fibroblasts. Secretion of anti-fibrotic HGF and extracellular matrix collagen IV gene expression was reduced in the central deep keloid compared to normal skin. No significant differences between peripheral and central regions within keloids were observed for inflammatory cytokine CCL20, CCL27, CXCL8, IL-6 and IL-18 secretion. Parameters for surrounding-normal-skin showed similarities to both non-lesional normal skin and keloids. In conclusion, a simple but elegant method of culturing keloid-derived keratinocytes and fibroblasts in an organotypic 3D scar model was developed, for the dual purpose of studying the underlying pathology and ultimately testing new therapeutics. In this study, these tissue engineered scar models show that the central keloid region shows a more aggressive keloid scar phenotype than the periphery and that the surrounding-normal-skin also shares certain abnormalities characteristic for keloids.