Altered TGF-β signaling in fetal fibroblasts: what is known about the underlying mechanisms?

USC-Derived Small Extracellular Vesicles-Functionalized Scaffolds Promote Scarless Vaginal Defect Repair via Delivery of Decorin and DUSP3 Proteins

Background

Scar formation following large-area vaginal defects post-vaginoplasty is a major clinical challenge. Compared to skin scars, vaginal scars can lead to pain during intercourse and urinary difficulties, severely impacting quality of life. Small extracellular vesicles (sEVs) encapsulate diverse bioactive components, making them potential therapeutic agents. Designing functional scaffolds that incorporate sEVs is a promising approach for scarless vaginal defect repair.

Methods

sEVs-loaded scaffolds were developed through electrostatic interactions between negatively charged sEVs secreted by urine-derived stem cells (USC-sEVs) and positively charged human acellular amniotic membranes. The efficacy of sEVs-loaded scaffolds in the treatment of vaginal defects in rabbits was assessed by histological analysis. Immunofluorescence staining, Western blot, qRT-PCR and collagen gel contraction analyses were conducted to evaluate the antifibrotic effects of USC-sEVs. RNA sequencing was employed to elucidate the underlying mechanisms involved. LC‒MS/MS analysis was used to identify candidate upstream proteins in USC-sEVs.

Results

In vivo experiments demonstrated that the sEVs-loaded scaffolds promoted scarless healing of vaginal defects in rabbits by modulating collagen deposition, reducing fibrosis, and diminishing inflammation. In vitro experiments revealed that USC-sEVs significantly inhibited the proliferation, collagen production, and activation of fibroblasts with a fibrotic phenotype, indicating the antifibrotic properties of USC-sEVs. Transcriptome and Western blot analyses revealed that USC-sEVs treatment inhibited fibrosis by downregulating the TGF-β and p38 MAPK signaling pathways. LC‒MS/MS analysis identified 2653 proteins encapsulated in USC-sEVs. Western blot analysis revealed that decorin, an inhibitor of the TGF-β signaling pathway, and DUSP3, a negative regulator of p38 phosphorylation, were enriched in USC-sEVs and could be transferred to fibroblasts.

Conclusion

USC-sEVs inhibited fibrosis and promoted scarless healing by delivering decorin and DUSP3 proteins, which regulate the TGF-β and p38 MAPK signaling pathways, respectively. This study highlights the potential of sEVs-loaded scaffolds as a promising strategy for scarless vaginal repair following vaginoplasty, offering a novel approach for regenerative medicine with significant translational potential for clinical application.

Recent advances in the role of neuroregulation in skin wound healing

Neuroregulation during skin wound healing involves complex interactions between the nervous system and intricate tissue repair processes. The skin, the largest organ, depends on a complex system of nerves to manage responses to injury. Recent research has emphasized the crucial role of neuroregulation in maximizing wound healing outcomes. Recently, researchers have also explained the interactive contact between the peripheral nervous system and skin cells during the different phases of wound healing. Neurotransmitters and neuropeptides, once observed as simple signalling molecules, have since been recognized as effective regulators of inflammation, angiogenesis, and cell proliferation. The significance of skin innervation and neuromodulators is underscored by the delayed wound healing observed in patients with diabetes and the regenerative capabilities of foetal skin. Foetal skin regeneration is influenced by the neuroregulatory environment, immature immune system, abundant growth factors, and increased pluripotency of cells. Foetal skin cells exhibit greater flexibility and specialized cell types, and the extracellular matrix composition promotes regeneration. The extracellular matrix composition of foetal skin promotes regeneration, making it more capable than adult skin because neuroregulatory signals affect skin regeneration. The understanding of these systems can facilitate the development of therapeutic strategies to alter the nerve supply to the skin to enhance the process of wound healing. Neuroregulation is being explored as a potential therapeutic strategy for enhancing skin wound repair. Bioelectronic strategies and neuromodulation techniques can manipulate neural signalling, optimize the neuroimmune axis, and modulate inflammation. This review describes the function of skin innervation in wound healing, emphasizing the importance of neuropeptides released by sensory and autonomic nerve fibres. This article discusses significant discoveries related to neuroregulation and its impact on skin wound healing.

Improvement in Early Scar Maturation by Nanofat Infiltration: Histological and Spectrophotometric Preliminary Results From a Split Scar-Controlled, Randomized, Double-Blinded Clinical Trial

Background

The regenerative properties of stromal vascular fraction (SVF) in wound healing and scar formation are a subject of increasing clinical interest.

Objectives

Although preclinical studies have confirmed the angiogenetic, proliferative, and antifibrotic properties of SVF, there is limited clinical evidence from randomized controlled clinical trials.

Methods

Twelve patients who underwent abdominoplasty were included in this clinical study. Nanofat was mechanically obtained intraoperatively and infiltrated intradermally in the sutured surgical wound, randomly assigned to either the left or the right side. The abdominal scar was evaluated with the Patient and Observer Scar Assessment Scale, whereas erythema and pigmentation were measured with a reflectance spectrophotometry device (Mexameter, Courage + Khazaka electronic GmbH, Köln,Germany). Histological analysis and electron scan microscopy of tissue biopsies were performed at 8 months.

Results

The treated side of the scar showed significantly less erythema at 3- and 6-month follow-ups, but this difference reduced after 12 months. Patients reported better scar scores at the 6-month follow-up with a significantly better color at the treated side. Observers reported better overall scar scores at the treated side at 3-, 6-, and 12-month follow-ups, with better vascularization, pigmentation, and thickness. There was no statistically significant difference in terms of histological analysis between the 2 groups. There was no difference in the occurrence of adverse events between both sides.

Conclusions

Infiltration of nanofat exhibited promising results in surgical scar maturation characterized by less erythema and better texture. More clinical trials with a larger sample size are warranted to better elucidate the possible benefits of SVF on surgical scar formation.

Level of Evidence 5

HUC-MSCs combined with platelet lysate treat diabetic chronic cutaneous ulcers in Bama miniature pig

Human umbilical cord mesenchymal stem cells (HUC-MSCs) and platelet lysate (PL) shows potential of wound healing. However, MSCs in combination with PL for wound healing is still lacking. In this study, we presented high glucose cultured wound related cells to mimic diabetic chronic ulcers (DCU) cells, wound healing indicators and the TGFβ/Smad signaling pathway were detected by PL cultured HUC-MSC supernatant (MSC-Sp) in vitro. In vivo study, diabetes was induced in pigs feeding a high-energy diet and multiple injections of streptozotocin (125 mg/kg). Chronic wounds were created on both sides of the backs of seven pigs by surgical creation and foreign body compression for eight weeks before treatment. The wounds were treated with saline control (N = 11), PL (N = 11), HUC- MSCs (N = 18, 6 × 106/mL/cm2), and PL + HUC-MSCs (N = 18, 6 × 106/mL/cm2) respectively. Tissue samples were collected to observe new collagen, neovascularization, wound healing factors, and the TGFβ/Smad signaling pathway. The resulting PL-cultured MSC-Sp promoted the proliferation of keratinocytes, fibroblasts, and vascular endothelial cells and inhibited the TGFβ1/TGFβ3 ratio, upregulated VEGF-α and PDGF-BB production by keratinocytes and fibroblasts, and downregulated the expression of CD86, IL-6, and TNF-α in RAW264.7 cells. PL + HUC-MSCs had the best wound healing rate in vivo, and promoted collagen formation, neovascularization, and inflammation, regulated the balance between IL-6/TGFβ1 and IL-6/Arg-1 and upregulated the expression of VEGF-α and TGFβ1. In summary, PL + HUC-MSCs had a better wound healing effect than HUC-MSCs or PL treatment alone by regulating the IL-6/Arg-1 and IL-6/TGFβ1 balance and upregulating TGFβ1, VEGF-α, Col1, and α-SMA.

Machine learning and single-cell transcriptome profiling reveal regulation of fibroblast activation through THBS2/TGFβ1/P-Smad2/3 signalling pathway in hypertrophic scar

Hypertrophic scar (HS) is a chronic inflammatory skin disorder characterized by excessive deposition of extracellular matrix, and the mechanisms underlying their formation remain poorly understood. We analysed scRNA-seq data from samples of normal skin and HS. Using the hdWGCNA method, key gene modules of fibroblasts in HS were identified. Non-negative matrix factorization was employed to perform subtype analysis of HS patients using these gene modules. Multiple machine learning algorithms were applied to screen and validate accurate gene signatures for identifying and predicting HS, and a convolutional neural network (CNN) based on deep learning was established and validated. Quantitative reverse transcription-polymerase chain reaction and western blotting were performed to measure mRNA and protein expression. Immunofluorescence was used for gene localization analysis, and biological features were assessed through CCK8 and wound healing assay. Single-cell sequencing revealed distinct subpopulations of fibroblasts in HS. HdWGCNA identified key gene characteristics of this population, and pseudotime analysis was conducted to investigate gene variation during fibroblast differentiation. By employing various machine learning algorithms, the gene range was narrowed down to three key genes. A CNN was trained using the expression of these key genes and immune cell infiltration, enabling diagnosis and prediction of HS. Functional experiments demonstrated that THBS2 is associated with fibroblast proliferation and migration in HS and affects the formation and development of HS through the TGFβ1/P-Smad2/3 pathway. Our study identifies unique fibroblast subpopulations closely associated with HS and provides biomarkers for the diagnosis and treatment of HS.

Potential Role of AGR2 for Mammalian Skin Wound Healing

The limited ability of mammals to regenerate has garnered significant attention, particularly in regard to skin wound healing (WH), which is a critical step for regeneration. In human adults, skin WH results in the formation of scars following injury or trauma, regardless of severity. This differs significantly from the scarless WH observed in the fetal skin of mammals or anamniotes. This review investigates the role of molecular players involved in scarless WH, which are lost or repressed in adult mammalian WH systems. Specifically, we analyze the physiological role of Anterior Gradient (AGR) family proteins at different stages of the WH regulatory network. AGR is activated in the regeneration of lower vertebrates at the stage of wound closure and, accordingly, is important for WH. Mammalian AGR2 is expressed during scarless WH in embryonic skin, while in adults, the activity of this gene is normally inhibited and is observed only in the mucous epithelium of the digestive tract, which is capable of full regeneration. The combination of AGR2 unique potencies in postnatal mammals makes it possible to consider it as a promising candidate for enhancing WH processes.

Polyphenol-driven facile assembly of a nanosized acid fibroblast growth factor-containing coacervate accelerates the healing of diabetic wounds

Diabetic wounds are challenging to heal due to complex pathogenic abnormalities. Routine treatment with acid fibroblast growth factor (aFGF) is widely used for diabetic wounds but hardly offers a satisfying outcome due to its instability. Despite the emergence of various nanoparticle-based protein delivery approaches, it remains challenging to engineer a versatile delivery system capable of enhancing protein stability without the need for complex preparation. Herein, a polyphenol-driven facile assembly of nanosized coacervates (AE-NPs) composed of aFGF and Epigallocatechin-3-gallate (EGCG) was constructed and applied in the healing of diabetic wounds. First, the binding patterns of EGCG and aFGF were predicted by molecular docking analysis. Then, the characterizations demonstrated that AE-NPs displayed higher stability in hostile conditions than free aFGF by enhancing the binding activity of aFGF to cell surface receptors. Meanwhile, the AE-NPs also had a powerful ability to scavenge reactive oxygen species (ROS) and promote angiogenesis, which significantly accelerated full-thickness excisional wound healing in diabetic mice. Besides, the AE-NPs suppressed the early scar formation by improving collagen remodeling and the mechanism was associated with the TGF-β/Smad signaling pathway. Conclusively, AE-NPs might be a potential and facile strategy for stabilizing protein drugs and achieving the scar-free healing of diabetic wounds. STATEMENT OF SIGNIFICANCE: Diabetic chronic wound is among the serious complications of diabetes that eventually cause the amputation of limbs. Herein, a polyphenol-driven facile assembly of nanosized coacervates (AE-NPs) composed of aFGF and EGCG was constructed. The EGCG not only acted as a carrier but also possessed a therapeutic effect of ROS scavenging. The AE-NPs enhanced the binding activity of aFGF to cell surface receptors on the cell surface, which improved the stability of aFGF in hostile conditions. Moreover, AE-NPs significantly accelerated wound healing and improved collagen remodeling by regulating the TGF-β/Smad signaling pathway. Our results bring new insights into the field of polyphenol-containing nanoparticles, showing their potential as drug delivery systems of macromolecules to treat diabetic wounds.

USP15 Enhances the Proliferation, Migration, and Collagen Deposition of Hypertrophic Scar-Derived Fibroblasts by Deubiquitinating TGF-βR1 In Vitro

BACKGROUND

Hypertrophic scar is a fibroproliferative disorder caused by skin injury. The incidence of hypertrophic scar following trauma or burns is 40 to 70 percent or 70 percent, respectively. It has been shown that transforming growth factor (TGF) β1/Smad signaling plays a crucial role in hypertrophic scar, and that USP15 can regulate the activity of TGFβ1/Smad signaling to affect the progression of the disease. However, the underlying mechanism of USP15 in hypertrophic scar remains unclear. The authors hypothesized that USP15 was up-regulated and enhanced the proliferation, migration, invasion, and collagen deposition of hypertrophic scar-derived fibroblasts by deubiquitinating TGF-β receptor I (TβRI) in vitro.

METHODS

Fibroblasts were isolated from human hypertrophic scars in vitro. The knockdown and overexpression of USP15 in hypertrophic scar-derived fibroblasts were performed using lentivirus infection. The effect of USP15 on hypertrophic scar-derived fibroblast proliferation, migration, and invasion, and the expression of TβRI, Smad2, Smad3, α-SMA, COL1, and COL3, were detected by Cell Counting Kit-8, scratch, invasion, quantitative real-time polymerase chain reaction, and Western blot assays. The interaction between USP15 and TβRI was detected by co-immunoprecipitation and ubiquitination assays.

RESULTS

The authors demonstrated that USP15 knockdown significantly inhibited the proliferation, migration, and invasion of hypertrophic scar-derived fibroblasts in vitro and down-regulated the expression of TβRI, Smad2, Smad3, α-SMA, COL1, and COL3; in addition, USP15 overexpression showed the opposite trends (p < 0.05). Co-immunoprecipitation and ubiquitination assays revealed that USP15 interacted with TβRI and deubiquitinated TβRI.

CONCLUSION

USP15 enhances the proliferation, migration, invasion, and collagen deposition of hypertrophic scar-derived fibroblasts by deubiquitinating TβRI in vitro.

Finding Solutions for Fibrosis: Understanding the Innate Mechanisms Used by Super-Regenerator Vertebrates to Combat Scarring

Soft tissue fibrosis and cutaneous scarring represent massive clinical burdens to millions of patients per year and the therapeutic options available are currently quite limited. Despite what is known about the process of fibrosis in mammals, novel approaches for combating fibrosis and scarring are necessary. It is hypothesized that scarring has evolved as a solution to maximize healing speed to reduce fluid loss and infection. This hypothesis, however, is complicated by regenerative animals, which have arguably the most remarkable healing abilities and are capable of scar-free healing. This review explores the differences observed between adult mammalian healing that typically results in fibrosis versus healing in regenerative animals that heal scarlessly. Each stage of wound healing is surveyed in depth from the perspective of many regenerative and fibrotic healers so as to identify the most important molecular and physiological variances along the way to disparate injury repair outcomes. Understanding how these powerful model systems accomplish the feat of scar-free healing may provide critical therapeutic approaches to the treatment or prevention of fibrosis.

Macromolecular Crowding as a Tool to Screen Anti-fibrotic Drugs: The Scar-in-a-Jar System Revisited

An unsolved therapeutic problem in fibrosis is the overproduction of collagen. In order to screen the effect of anti-fibrotic drugs on collagen deposition, the Scar-in-a-Jar approach has been introduced about a decade ago. With macromolecular crowding a rapid deposition of collagen is seen, resulting in a substantial decrease in culture time, but the system has never been tested in an adequate way. We therefore have compared six different macromolecular crowders [Ficoll PM 70 (Fc70), Ficoll PM 400 (Fc400), a mixture of Ficoll 70 and 400 (Fc70/400), polyvinylpyrrolidone 40 (PVP40), polyvinylpyrrolidone 360 (PVP360), neutral dextran 670 (ND670), dextran sulfate 500 (DxS500), and carrageenan (CR)] under profibrotic conditions (addition of TGFβ1) with primary human adult dermal fibroblasts in the presence of 0.5 and 10% FBS. We found that (1) collagen deposition and myofibroblast formation was superior with 0.5% FBS, (2) DxS500 and CR results in an aberrant collagen deposition pattern, (3) ND670 does not increase collagen deposition, and (4) CR, DxS500, and Fc40/700 affected important phenotypical properties of the cells when cultured under pro-fibrotic conditions, whereas PVP40 and PVP360 did less or not. Because of viscosity problems with PVP360, we conclude that PVP40 is the most optimal crowder for the screening of anti-fibrotic drugs. Finally, the effect of various concentrations of Imatinib, Galunisertib, Omipalisib or Nintedanib on collagen deposition and myofibroblast formation was tested with PVP40 as the crowder.

Stem cells and growth factors-based delivery approaches for chronic wound repair and regeneration: A promise to heal from within

The sophisticated chain of cellular and molecular episodes during wound healing includes cell migration, cell proliferation, deposition of extracellular matrix, and remodelling and are onerous to replicate. Encapsulation of growth factors (GFs) and Stem cell-based (SCs) has been proclaimed to accelerate healing by transforming every phase associated with wound healing to enhance skin regeneration. Therapeutic application of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (PSCs) provides aid in wound fixing, tissue integrity restoration and function of impaired tissue. Several scientific studies have established the essential role GFs in wound healing and their reduced degree in the chronic wound. The overall limitation includes half-life, unfriendly microhabitat abundant with protease, and inadequate delivery approaches results in decreased delivery of effective amounts in a suitable time-based fashion. Advancements in the area of reformative medicine as well as tissue engineering have offered techniques competent of dispensing SCs and GFs in site-oriented manner. The progress in nanotechnology-based approaches attracts researcher to study and evaluate the potential of this SCs and GFs based therapy in chronic wounds. These techniques embrace the polymeric regime viz., nano-formulations, hydrogels, liposomes, scaffolds, nanofibers, metallic nanoparticles, lipid-based nanoparticles and dendrimers that have established better retort through targeting tissues when GFs and SCs are transported via these humans made devices. Assumed the current problems, improvements in delivery approaches and difficulties offered by chronic wounds, we hope to show that encapsulation of SCs and GFs loaded nanoformulations therapies is the rational next step in improving wound care.

Erythroid differentiation regulator 1 promotes wound healing by inducing the production of C‑C motif chemokine ligand 2 via the activation of MAP kinases in vitro and in vivo

The erythroid differentiation regulator 1 (Erdr1) protein has been studied for its role in various inflammatory skin diseases, including skin cancer, actinic keratosis and psoriasis. However, the therapeutic effects of Erdr1 on wound repair and its underlying mechanisms remain unknown. The present study aimed to investigate the effects of Erdr1 on wound healing in vitro and in vivo. The results demonstrated that treatment with recombinant Erdr1 enhanced wound healing in vivo and in vitro. In addition, Erdr1 increased the proliferation and migration of human dermal fibroblasts (HDFs). Notably, Erdr1 significantly induced the production of the chemoattractant C-C motif chemokine ligand 2 (CCL2) and recruited immune cells involved in wound healing. Treatment with recombinant Erdr1 induced the activation of the ERK1/1, p38 and JNK1/2 mitogen-activated protein (MAP) kinases. Treatment with specific inhibitors for MAP kinase inhibitors markedly suppressed cell proliferation and migration, and inhibited the production of CCL2 in HDFs. Furthermore, the inhibition of CCL2 with a neutralizing antibody significantly suppressed the recombinant Erdr1-induced proliferation and migration of HDFs. The wound healing activity of Erdr1 was comparable to that of epidermal growth factor. Taken together, these results demonstrated that Erdr1 promoted the proliferation and migration of HDFs and exhibited potent wound healing properties mediated by CCL2. Therefore, the results of the present study suggested that Erdr1 may be a potential therapeutic target for promoting wound healing.

Smad‑binding decoy reduces extracellular matrix expression in human hypertrophic scar fibroblasts

The exact mechanisms underlying hypertrophic scarring is yet to be fully understood. However, excessive collagen deposition by fibroblasts has been demonstrated to result in hypertrophic scar formation, and collagen synthesis in dermal fibroblasts is regulated by the transforming growth factor-β1/Smad signaling pathway. In view of this, a Smad-binding decoy was designed and its effects on hypertrophic scar-derived human skin fibroblasts was evaluated. The results of the present study revealed that the Smad decoy attenuates the total amount of collagen, collagen I and Smad2/3 expression in scar fibroblasts. Data from RNA sequencing indicated that the Smad decoy induced more than 4-fold change in 178 genes, primarily associated with to the extracellular matrix, compared with the untreated control. In addition, results from quantitative real-time polymerase chain reaction further confirmed that the Smad decoy significantly attenuated the expression of extracellular matrix-related genes, including COL1A1, COL1A2 and COL3A1. Furthermore, the Smad decoy reduced transforming growth factor-β1-induced collagen deposition in scar fibroblasts. Data generated from the present study provide evidence supporting the use of the Smad decoy as a potential hypertrophic scar treatment.

Human bone marrow mesenchymal stem cell-derived exosomes stimulate cutaneous wound healing mediates through TGF-β/Smad signaling pathway

BACKGROUND

Cutaneous wound healing represents a morphogenetic response to injury and is designed to restore anatomic and physiological function. Human bone marrow mesenchymal stem cell-derived exosomes (hBM-MSC-Ex) are a promising source for cell-free therapy and skin regeneration.

METHODS

In this study, we investigated the cell regeneration effects and its underlying mechanism of hBM-MSC-Ex on cutaneous wound healing in rats. In vitro studies, we evaluated the role of hBM-MSC-Ex in the two types of skin cells: human keratinocytes (HaCaT) and human dermal fibroblasts (HDFs) for the proliferation. For in vivo studies, we used a full-thickness skin wound model to evaluate the effects of hBM-MSC-Ex on cutaneous wound healing in vivo.

RESULTS

The results demonstrated that hBM-MSC-Ex promote both two types of skin cells' growth effectively and accelerate the cutaneous wound healing. Interestingly, we found that hBM-MSC-Ex significantly downregulated TGF-β1, Smad2, Smad3, and Smad4 expression, while upregulated TGF-β3 and Smad7 expression in the TGF-β/Smad signaling pathway.

CONCLUSIONS

Our findings indicated that hBM-MSC-Ex effectively promote the cutaneous wound healing through inhibiting the TGF-β/Smad signal pathway. The current results provided a new sight for the therapeutic strategy for the treatment of cutaneous wounds.

Silencing of p53 reduces cell migration in human Tenon's fibroblasts induced by TGF-β

PURPOSE

Growth factors are considered as key molecules that participating in fibrosis formation. This research aimed to clarify potential effects of p53 on regulation of transforming growth factor β (TGF-β) and fibrosis formation and investigate the associated mechanisms.

METHODS

Vimentin was examined to identify human Tenon's fibroblasts (HTFs). p53-targeting small interfere RNA (siRNA) was synthesis and transfected into HTFs. Real-time PCR assay was utilized to evaluate p53 and microRNA-29b (miR-29b) expression. Immunocytochemical assay was used to observe TGF-β expression. The wound healing assay was conducted to evaluate migration of HTFs. Dual-luciferase assay was employed to identify interaction between p53 and miR-29b in HTFs.

RESULTS

Vimentin was extensively distributed in HTFs cells. HTFs at density of 5 × 10⁴ cells/ml and 6 days exhibited the best growth. The p53 level in TGF-β treatment group was significantly higher compared to that in blank group (p < 0.01). miR-29b level in siRNA targeting p53 group was significantly increased compared to that in blank group (p < 0.01). siRNA targeting p53 could significantly inhibit HTFs migration compared to that in single TGF-β treating HTFs group (p < 0.01). Relative luciferase activity was significantly increased in p53 overexpressed HTFs compared to that in cells transfected with empty pcDNA3.0 plasmid (p < 0.01).

CONCLUSIONS

p53 inhibited expression of TGF-β, suppressed HTFs migration and inhibited HTFs growth, by reducing miR-29b expression and interacting with miR29b gene in HTFs.

Impaired Neovascularization in Aging

Significance: The skin undergoes an inevitable degeneration as an individual ages. As intrinsic and extrinsic factors degrade the structural integrity of the skin, it experiences a critical loss of function and homeostatic stability. Thus, aged skin becomes increasingly susceptible to injury and displays a prolonged healing process. Recent Advances: Several studies have found significant differences during wound healing between younger and older individuals. The hypoxia-inducible factor 1-alpha (HIF-1α) signaling pathway has recently been identified as a major player in wound healing. Hypoxia-inducible factors (HIFs) are pleiotropic key regulators of oxygen homeostasis. HIF-1α is essential to neovascularization through its regulation of cytokines, such as SDF-1α (stromal cell-derived factor 1-alpha) and has been shown to upregulate the expression of genes important for a hypoxic response. Prolyl hydroxylase domain proteins (PHDs) and factor inhibiting HIF effectively block HIF-1α signaling in normoxia through hydroxylation, preventing the signaling cascade from activating, leading to impaired tissue survival. Critical Issues: Aged wounds are a major clinical burden, resisting modern treatment and costing millions in health care each year. At the molecular level, aging has been shown to interfere with PHD regulation, which in turn prevents HIF-1α from activating gene expression, ultimately leading to impaired healing. Other studies have identified loss of function in cells during aging, impeding processes such as angiogenesis. Future Directions: An improved understanding of the regulation of molecular mediators, such as HIF-1α and PHD, will allow for manipulation of the various factors underlying delayed wound healing in the aged. The findings highlighted in this may facilitate the development of potential therapeutic approaches involved in the alteration of cellular dynamics and aging.

Growth Factors in Regeneration and Regenerative Medicine: "the Cure and the Cause"

The potential rapid advance of regenerative medicine was obstructed by findings that stimulation of human body regeneration is a much tougher mission than expected after the first cultures of stem and progenitor cells were established. In this mini review, we focus on the ambiguous role of growth factors in regeneration, discuss their evolutionary importance, and highlight them as the "cure and the cause" for successful or failed attempts to drive human body regeneration. We draw the reader's attention to evolutionary changes that occurred in growth factors and their receptor tyrosine kinases (RTKs) and how they established and shaped response to injury in metazoans. Discussing the well-known pleiotropy of growth factors, we propose an evolutionary rationale for their functioning in this specific way and focus on growth factors and RTKs as an amazing system that defines the multicellular nature of animals and highlight their participation in regeneration. We pinpoint potential bottlenecks in their application for human tissue regeneration and show their role in fibrosis/regeneration balance. This communication invites the reader to re-evaluate the functions of growth factors as keepers of natively existing communications between elements of tissue, which makes them a fundamental component of a successful regenerative strategy. Finally, we draw attention to the epigenetic landscape that may facilitate or block regeneration and give a brief insight into how it may define the outcome of injury.

Human fetal skin-derived stem cell secretome enhances radiation-induced skin injury therapeutic effects by promoting angiogenesis

Background

Radiation dermatitis is a refractory skin injury caused by radiotherapy. Human fetal skin-derived stem cell (hFSSC) is a preferable source for cell therapy and skin tissue regeneration. In the present study, we investigated the repair effect of using hFSSC secretome on a radiation skin injury model in rats.

Methods

We prepared the hFSSC secretome and studied its effects on the proliferation and tube formation of human umbilical vein endothelial cell (HUVEC) in vitro. Furthermore, we used a Sr-90 radiation-induced skin injury model of rats and evaluated the effects of hFSSC secretome on radiation skin injury in vivo.

Results

The results showed that hFSSC secretome significantly promoted the proliferation and tube formation of HUVEC in vitro; in addition, hFSSC secretome-treated rats exhibited higher healing quality and faster healing rate than the other two control groups; the expression level of collagen type III α 1 (Col3A1), transforming growth factor β3 (TGF-β3), angiotensin 1 (Ang-1), angiotensin 2 (Ang-2), vascular endothelial growth factor (VEGF), and placental growth factor (PLGF) was significantly increased, while collagen type I α 2 (Col1A2) and transforming growth factor β1 (TGF-β1) were decreased in hFSSC secretome group.

Conclusions

In conclusion, our results provided the first evidence on the effects of hFSSC secretome towards radiation-induced skin injury. We found that hFSSC secretome significantly enhanced radiation dermatitis angiogenesis, and the therapeutic effects could match with the characteristics of fetal skin. It may act as a kind of novel cell-free therapeutic approach for radiation-induced cutaneous wound healing.

Antler stem cell-conditioned medium stimulates regenerative wound healing in rats

Background

When the deer antler is cast, it leaves a cutaneous wound that can achieve scarless healing due to the presence of antler stem cells (ASCs). This provides an opportunity to study regenerative wound healing.

Methods

In this study, we investigated the therapeutic effects and mechanism of antler stem cell-conditioned medium (ASC-CM) on cutaneous wound healing in rats. In vitro, we investigated the effects of the ASC-CM on proliferation of HUVEC and NIH-3T3 cell lines. In vivo, we evaluated the effects of ASC-CM on cutaneous wound healing using full-thickness skin punch-cut wounds in rats.

Results

The results showed that ASC-CM significantly stimulated proliferation of the HUVEC and NIH-3T3 cells in vitro. In vivo, completion of healing of the rat wounds treated with ASC-CM was on day 16 (± 3 days), 9 days (± 2 days) earlier than the control group (DMEM); the area of the wounds treated with ASC-CM was significantly smaller (p < 0.05) than the two control groups. Further molecular characterization showed that the ratios of Col3A1/Col1A2, TGF-β3/TGF-β1, MMP1/TIMP1, and MMP3/TIMP1 significantly increased (p < 0.01) in the healed tissue in the ASC-CM group.

Conclusions

In conclusion, ASC-CM effectively accelerated the wound closure rate and enhanced the quality of healing, which might be through transforming wound dermal fibroblasts into the fetal counterparts. Therefore, the ASC-CM may have potential to be developed as a novel cell-free therapeutic for scarless wound healing.

Direct and Indirect Roles of Macrophages in Hypertrophic Scar Formation

Hypertrophic scars are pathological scars that result from abnormal responses to trauma, and could cause serious functional and cosmetic disability. To date, no optimal treatment method has been established. A variety of cell types are involved in hypertrophic scar formation after wound healing, but the underlying molecular mechanisms and cellular origins of hypertrophic scars are not fully understood. Macrophages are major effector cells in the immune response after tissue injury that orchestrates the process of wound healing. Depending on the local microenvironment, macrophages undergo marked phenotypic and functional changes at different stages during scar pathogenesis. This review intends to summarize the direct and indirect roles of macrophages during hypertrophic scar formation. The in vivo depletion of macrophages or blocking their signaling reduces scar formation in experimental models, thereby establishing macrophages as positive regulatory cells in the skin scar formation. In the future, a significant amount of attention should be given to molecular and cellular mechanisms that cause the phenotypic switch of wound macrophages, which may provide novel therapeutic targets for hypertrophic scars.

Scarless wound healing: From development to senescence

An essential element of tissue homeostasis is the response to injuries, cutaneous wound healing being the most studied example. In the adults, wound healing aims at quickly restoring the barrier function of the skin, leading however to scar, a dysfunctional fibrotic tissue. On the other hand, in fetuses a scarless tissue regeneration takes place. During ageing, the wound healing capacity declines; however, in the absence of comorbidities a higher quality in tissue repair is observed. Senescent cells have been found to accumulate in chronic unhealed wounds, but more recent reports indicate that their transient presence may be beneficial for tissue repair. In this review data on skin wound healing and scarring are presented, covering the whole spectrum from early embryonic development to adulthood, and furthermore until ageing of the organism.

Tissue engineering strategies combining molecular targets against inflammation and fibrosis, and umbilical cord blood stem cells to improve hampered muscle and skin regeneration following cleft repair

Cleft lip with or without cleft palate is a congenital deformity that occurs in about 1 of 700 newborns, affecting the dentition, bone, skin, muscles and mucosa in the orofacial region. A cleft can give rise to problems with maxillofacial growth, dental development, speech, and eating, and can also cause hearing impairment. Surgical repair of the lip may lead to impaired regeneration of muscle and skin, fibrosis, and scar formation. This may result in hampered facial growth and dental development affecting oral function and lip and nose esthetics. Therefore, secondary surgery to correct the scar is often indicated. We will discuss the molecular and cellular pathways involved in facial and lip myogenesis, muscle anatomy in the normal and cleft lip, and complications following surgery. The aim of this review is to outline a novel molecular and cellular strategy to improve musculature and skin regeneration and to reduce scar formation following cleft repair. Orofacial clefting can be diagnosed in the fetus through prenatal ultrasound screening and allows planning for the harvesting of umbilical cord blood stem cells upon birth. Tissue engineering techniques using these cord blood stem cells and molecular targeting of inflammation and fibrosis during surgery may promote tissue regeneration. We expect that this novel strategy improves both muscle and skin regeneration, resulting in better function and esthetics after cleft repair.

Skin tissue regeneration for burn injury

The skin is the largest organ of the body, which meets the environment most directly. Thus, the skin is vulnerable to various damages, particularly burn injury. Skin wound healing is a serious interaction between cell types, cytokines, mediators, the neurovascular system, and matrix remodeling. Tissue regeneration technology remarkably enhances skin repair via re-epidermalization, epidermal-stromal cell interactions, angiogenesis, and inhabitation of hypertrophic scars and keloids. The success rates of skin healing for burn injuries have significantly increased with the use of various skin substitutes. In this review, we discuss skin replacement with cells, growth factors, scaffolds, or cell-seeded scaffolds for skin tissue reconstruction and also compare the high efficacy and cost-effectiveness of each therapy. We describe the essentials, achievements, and challenges of cell-based therapy in reducing scar formation and improving burn injury treatment.

Genetically-modified bone mesenchymal stem cells with TGF-β3 improve wound healing and reduce scar tissue formation in a rabbit model

Extensive scar tissue formation often occurs after severe burn injury, trauma, or as one of complications after surgical intervention. Despite significant therapeutic advances, it is still a significant challenge to manage massive scar tissue formation while also promoting normal wound healing. The goal of this study was to investigate the therapeutic effect of bone mesenchymal stem cells (BMSCs) that were genetically modified to overexpress transforming growth factor-beta 3 (TGF-β₃), an inhibitor of myofibroblast proliferation and collagen type I deposition, on full-thickness cutaneous wound healing in a rabbit model. Twenty-four rabbits with surgically-induced full-thickness cutaneous wounds created on the external ear (1.5 × 1.5 cm, two wounds/ear) were randomized into four groups: (G1), wounds with no special treatment but common serum-free culture medium as negative controls; (G2), topically-applied recombinant adenovirus, expressing TGF-β₃/GFP; (G3), topically-applied BMSCs alone; (G4), topically-applied BMSCs transfected with Ad-TGF-β₃/GFP (BMSCs^TGF-β3); and (G5), an additional normal control (n = 2) with neither wound nor treatment on the external ear skin. The sizes of wounds on the ear tissues were grossly examined, and the scar depth and density of wounds were histologically evaluated 21, 45, and 90 days after surgical wound creation. Our results demonstrated that G4 significantly reduced the wound scar depth and density, compared to G1~3. Numbers of cells expressing GFP significantly increased in G4, compared to G2. The protein expression of TGF-β₃ and type III collagen in G4 significantly increased, while the ratio of type I to type III collagen was also significantly reduced, which is similar to the tissue architecture found in G5, as compared the other treatment groups. In conclusion, transplantation of BMSCs^TGF-β3 remarkably improves wound healing and reduces skin scar tissue formation in an animal model, which may potentially provide an alternative in the treatment of extensive scar tissue formation after soft tissue injury.

Learning from regeneration research organisms: The circuitous road to scar free wound healing

The skin is the largest organ in the body and plays multiple essential roles ranging from regulating temperature, preventing infection and ultimately defining who we are physically. It is a highly dynamic organ that constantly replaces the outermost cells throughout life. However, when faced with a major injury, human skin cannot restore a significant lesion to its original functionality, instead a reparative scar is formed. In contrast to this, many other species have the unique ability to regenerate full thickness skin without formation of scar tissue. Here we review recent advances in the field that shed light on how the skin cells in regenerative species react to injury to prevent scar formation versus scar forming humans.

Scar management in burn injuries using drug delivery and molecular signaling: Current treatments and future directions

In recent decades, there have been tremendous improvements in burn care that have allowed patients to survive severe burn injuries that were once fatal. However, a major limitation of burn care currently is the development of hypertrophic scars in approximately 70% of patients. This significantly decreases the quality of life for patients due to the physical and psychosocial symptoms associated with scarring. Current approaches to manage scarring include surgical techniques and non-surgical methods such as laser therapy, steroid injections, and compression therapy. These treatments are limited in their effectiveness and regularly fail to manage symptoms. As a result, the development of novel treatments that aim to improve outcomes and quality of life is imperative. Drug delivery that targets the molecular cascades of wound healing to attenuate or prevent hypertrophic scarring is a promising approach that has therapeutic potential. In this review, we discuss current treatments for scar management after burn injury, and how drug delivery targeting molecular signaling can lead to new therapeutic strategies.

Mast cell chymase promotes hypertrophic scar fibroblast proliferation and collagen synthesis by activating TGF-β1/Smads signaling pathway

The present study assessed the existence of mast cell chymase in hypertrophic scars and determined whether chymase promotes fibrosis via the transforming growth factor (TGF)-β1/Smads signaling pathway. Five patients with hypertrophic scars and another five patients subjected to repair and reconstruction of other tissue defects were included in the present study. To detect the existence of mast cells and mast cell chymase in hypertrophic scars, immunohistochemistry was employed. To test the effect of chymase on TGF-β1, angiotensin, and type I and III collagen mRNA expression in isolated hypertrophic scar fibroblasts in vitro, reverse-transcription quantitative PCR was performed. To investigate how chymase affects TGF-β1, phosphorylated (P)-Smad2/3 as well as Smad4 and Smad7 protein expression, western blot analysis was used. Mast cell chymase was identified to promote the mRNA expression of TGF-β1, angiotensin, and type I and III collagen in hypertrophic scar fibroblasts in a time- and dose-dependent manner. Furthermore, treatment with 60 ng/ml mast cell chymase for 12 h led to the upregulation of TGF-β1, P-Smad2/3, Smad4 and Smad7 in hypertrophic scar fibroblasts. The present study demonstrated that mast cells and chymase are present in hypertrophic scars, and chymase promotes hypertrophic scar fibroblast proliferation and collagen synthesis by activating the TGF-β1/Smads signaling pathway.

The Contractile Phenotype of Dermal Fetal Fibroblasts in Scarless Wound Healing

PURPOSE OF REVIEW

Injured skin in the mammalian fetus can heal regeneratively due to the ability of fetal fibroblasts to effectively reorganize the extracellular matrix (ECM). This process occurs without fetal fibroblasts differentiating into highly contractile myofibroblasts which cause scarring and fibrosis in adult wounds. Here, we provide a brief review of fetal wound healing and the evidence supporting a unique contractile phenotype in fetal fibroblasts. Furthermore, we discuss the biomechanical role of the ECM in driving myofibroblast differentiation in wound healing and the implications for new clinical modalities based on the biophysical properties of fetal fibroblasts.

RECENT FINDINGS

We and others have found that fetal fibroblasts are refractory to the environmental stimuli necessary for myofibroblast differentiation in adult wound healing including mechanical stress.

SUMMARY

Understanding the biomechanical mechanisms that regulate the contractile phenotype of fetal fibroblasts may unlock new avenues for anti-scarring therapies that target myofibroblast differentiation of adult fibroblasts.

Theoretical and practical aspects of using fetal fibroblasts for skin regeneration

Cutaneous wounding in late-gestational fetal or postnatal humans results in scar formation without any skin appendages. Early or mid- gestational skin healing in humans is characterized by the absence of scaring in a process resembling regeneration. Tremendous cellular and molecular mechanisms contribute to this distinction, and fibroblasts play critical roles in scar or scarless wound healing. This review discussed the different repair mechanisms involved in wound healing of fibroblasts at different developmental stages and further confirmed that fetal fibroblast transplantation resulted in reduced scar healing in vivo. We also discussed the possible problem in fetal fibroblast transplantation for wound repair. We proposed the use of small molecules to improve the regenerative potential of repairing cells in the wound given that remodeling of the wound microenvironment into a regenerative microenvironment in adults might improve skin regeneration.

Polymeric Nanofibre Scaffold for the Delivery of a Transforming Growth Factor β1 Inhibitor

Skin scarring is a highly prevalent and inevitable outcome of adult mammalian wound healing. Scar tissue is both pathologically and aesthetically inferior to the normal skin owing to elevated concentration of highly orientated collagen I architecture in the innate repaired tissue. With highly invasive surgery being the main treatment modality, there is a great need for alternative strategies to mitigate the problem of scar formation. Tissue engineering approaches using polymeric scaffolds have shown tremendous promise in various disease models including skin wound healing; however, the problem of skin scarring has been greatly overlooked. Herein, we developed an electrospun poly(glycidyl methacrylate) (ES-PGMA) scaffold incorporating a small-molecule antiscarring agent, PXS64. PXS64, a lipophilic neutral analogue of mannose-6-phosphate, has been shown to inhibit the activation of transforming growth factor β1 (TGFβ1). TGFβ1 is a primary protein cytokine regulating the expression of collagen I during wound healing and therefore governs the formation of scar tissue. The nanofibres were tested for biocompatibility as a tissue engineering scaffold and for their efficacy to inhibit TGFβ1 activation in human dermal skin fibroblasts.

In vitro cultured fetal fibroblasts have myofibroblast-associated characteristics and produce a fibrotic-like environment upon stimulation with TGF-β1: Is there a thin line between fetal scarless healing and fibrosis?

Transforming growth factor-β (TGF-β) is a cytokine occurring in three isoforms with an important function in development and wound healing. In wound healing, prolonged TGF-β signaling results in myofibroblast differentiation and fibrosis. In contrast, the developing second-trimester fetal skin contains high levels of all three TGF-β isoforms but still has the intrinsic capacity to heal without scarring. Insight into TGF-β signal transduction during fetal wound healing might lead to methods to control the signaling pathway during adult wound healing. In this study, we imitated wound healing in vitro by stimulating fibroblasts with TGF-β1 and examining myofibroblast differentiation. The aim was to gain insight into TGF-β signaling in human fibroblasts from fetal and adult dermis. First, TGF-β1 stimulation resulted in similar or even more severe upregulation of myofibroblast-associated genes in fetal fibroblasts compared to adult fibroblasts. Second, fetal fibroblasts also had higher protein levels of myofibroblast-marker α-smooth muscle actin (α-SMA). Third, stimulated fetal fibroblasts in collagen matrices had higher protein levels of α-SMA, produced more of the fibrotic protein fibronectin splice-variant extra domain A (FnEDA), and showed enhanced contraction. Finally, fetal fibroblasts also produced significant higher levels of TGF-β1. Altogether, these data show that in vitro cultured fetal fibroblasts have myofibroblast-associated characteristics and do produce a fibrotic environment. As healthy fetal skin has high levels of TGF-β1, FnEDA, and collagen-III as well, these findings correlate with the in vivo situation. Therefore, our study demonstrates that there are similarities between fetal skin development and fibrosis and shows the necessity to discriminate between these processes.

Skin Wound Healing: An Update on the Current Knowledge and Concepts

BACKGROUND

The integrity of healthy skin plays a crucial role in maintaining physiological homeostasis of the human body. The skin is the largest organ system of the body. As such, it plays pivotal roles in the protection against mechanical forces and infections, fluid imbalance, and thermal dysregulation. At the same time, it allows for flexibility to enable joint function in some areas of the body and more rigid fixation to hinder shifting of the palm or foot sole. Many instances lead to inadequate wound healing which necessitates medical intervention. Chronic conditions such as diabetes mellitus or peripheral vascular disease can lead to impaired wound healing. Acute trauma such as degloving or large-scale thermal injuries are followed by a loss of skin organ function rendering the organism vulnerable to infections, thermal dysregulation, and fluid loss.

METHODS

For this update article, we have reviewed the actual literature on skin wound healing purposes focusing on the main phases of wound healing, i.e., inflammation, proliferation, epithelialization, angiogenesis, remodeling, and scarring.

RESULTS

The reader will get briefed on new insights and up-to-date concepts in skin wound healing. The macrophage as a key player in the inflammatory phase will be highlighted. During the epithelialization process, we will present the different concepts of how the wound will get closed, e.g., leapfrogging, lamellipodial crawling, shuffling, and the stem cell niche. The neovascularization represents an essential component in wound healing due to its fundamental impact from the very beginning after skin injury until the end of the wound remodeling. Here, the distinct pattern of the neovascularization process and the special new functions of the pericyte will be underscored. At the end, this update will present 3 topics of high interest in skin wound healing issues, dealing with scarring, tissue engineering, and plasma application.

CONCLUSION

Although wound healing mechanisms and specific cell functions in wound repair have been delineated in part, many underlying pathophysiological processes are still unknown. The purpose of the following update on skin wound healing is to focus on the different phases and to brief the reader on the current knowledge and new insights. Skin wound healing is a complex process, which is dependent on many cell types and mediators interacting in a highly sophisticated temporal sequence. Although some interactions during the healing process are crucial, redundancy is high and other cells or mediators can adopt functions or signaling without major complications.

Neuronal Protein 3.1 Deficiency Leads to Reduced Cutaneous Scar Collagen Deposition and Tensile Strength due to Impaired Transforming Growth Factor-β1 to -β3 Translation

Neuronal protein 3.1 (P311), a conserved RNA-binding protein, represents the first documented protein known to stimulate transforming growth factor (TGF)-β1 to -β3 translation in vitro and in vivo. Because TGF-βs play critical roles in fibrogenesis, we initiated efforts to define the role of P311 in skin scar formation. Here, we show that P311 is up-regulated in skin wounds and in normal and hypertrophic scars. Genetic ablation of p311 resulted in a significant decrease in skin scar collagen deposition. Lentiviral transfer of P311 corrected the deficits, whereas down-regulation of P311 levels by lentiviral RNA interference reproduced the deficits seen in P311^-/- mice. The decrease in collagen deposition resulted in scars with reduced stiffness but also reduced scar tensile strength. In vitro studies using murine and human dermal fibroblasts showed that P311 stimulated TGF-β1 to -β3 translation, a process that involved eukaryotic translation initiation factor 3 subunit b as a P311 binding partner. This resulted in increased TGF-β levels/activity and increased collagen production. In addition, P311 induced dermal fibroblast activation and proliferation. Finally, exogenous TGF-β1 to -β3, each restituted the normal scar phenotype. These studies demonstrate that P311 is required for the production of normal cutaneous scars and place P311 immediately up-stream of TGF-βs in the process of fibrogenesis. Conditions that decrease P311 levels could result in less tensile scars, which could potentially lead to higher incidence of dehiscence after surgery.

Structure and Function of a Prostate Cancer Dissemination-Permissive Extracellular Matrix

Purpose: The poor prognosis of metastatic prostate cancer continues to present a major challenge in prostate cancer treatment. The tumor extracellular matrix (ECM) plays an important role in facilitating metastasis. Here, we investigated the structure and function of an ECM that facilitates prostate cancer metastasis by comparing orthotopic tumors that frequently metastasize to poorly metastatic subcutaneous tumors.Experimental Design: Both tumors were derived from a human prostate cancer PC3 cell line engineered to fluoresce under hypoxia. Second harmonic generation (SHG) microscopy was used to characterize collagen 1 (Col1) fiber patterns in the xenografts as well as in human samples. MRI was used to determine albumin-Gd-diethylenetriaminepenta-acetate (alb-GdDTPA) transport through the ECM using a saturation recovery MR method combined with fast T₁ SNAPSHOT-FLASH imaging. Cancer-associated fibroblasts (CAF) were also quantified in these tumors.Results: Significant structural and functional differences were identified in the prometastatic orthotopic tumor ECM compared to the less metastatic subcutaneous tumor ECM. The significantly higher number of CAFs in orthotopic tumors may explain the higher Col1 fiber volumes in these tumors. In vivo, alb-GdDTPA pooling was significantly elevated in metastatic orthotopic tumors, consistent with the increased Col1 fibers.Conclusions: Developing noninvasive MRI indices of macromolecular transport, together with characterization of Col1 fiber patterns and CAFs can assist in stratifying prostate cancers for aggressive treatments or active surveillance. These results highlight the role of CAFs in supporting or creating aggressive cancers, and the importance of depleting CAFs to prevent metastatic dissemination in prostate cancer. Clin Cancer Res; 23(9); 2245-54. ©2016 AACR.

The Effect of Adipose-Derived Stem Cells on Full-Thickness Skin Grafts

Background. The purpose of this study was to evaluate the effects of ASCs on full-thickness skin grafts. Specifically, we investigated the anti-inflammatory effects of ASCs that are mediated via regulation of the phenotypes of activated macrophages. Methods. ASCs were isolated, cultured, and injected under full-thickness skin grafts in 15 rats (ASC group). An additional 15 rats served as controls (PBS group). Skin graft survival assessment and vascularization detection were assessed with H&E staining and laser Doppler blood flowmetry (LDF). The effects of ASCs on angiogenesis, anti-inflammation, collagen accumulation-promoting, and antiscarring were assessed. Results. We found that the skin graft survival rate was significantly increased in the ASC group. The neovascularization, collagen deposition, collagen type I to type III ratio, and levels of VEGF and TGF-β3 in the ASC group were markedly higher than those in the PBS group at day 14. Additionally, in the ASC group, the levels of iNOS, IL-1β, and TNF-α were remarkably decreased, whereas the levels of IL-10 and Arg-1 were substantially increased. Conclusions. Our results confirm that ASCs transplantation can effectively improve full-thickness skin graft survival. Additionally, the anti-inflammatory role of ASCs may indirectly contribute to skin graft survival via its effect on macrophage polarization.

Distinct iris gene expression profiles of primary angle closure glaucoma and primary open angle glaucoma and their interaction with ocular biometric parameters

Background

This study aimed to evaluate differences in iris gene expression profiles between primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG) and their interaction with biometric characteristics.

Design

Prospective study.

Participants

Thirty‐five subjects with PACG and thirty‐three subjects with POAG who required trabeculectomy were enrolled at the Singapore National Eye Centre, Singapore.

Methods

Iris specimens, obtained by iridectomy, were analysed by real‐time polymerase chain reaction for expression of type I collagen, vascular endothelial growth factor (VEGF)‐A, ‐B and ‐C, as well as VEGF receptors (VEGFRs) 1 and 2. Anterior segment optical coherence tomography (ASOCT) imaging for biometric parameters, including anterior chamber depth (ACD), anterior chamber volume (ACV) and lens vault (LV), was also performed pre‐operatively.

Main Outcome Measures

Relative mRNA levels between PACG and POAG irises, biometric measurements, discriminant analyses using genes and biometric parameters.

Results

COL1A1, VEGFB, VEGFC and VEGFR2 mRNA expression was higher in PACG compared to POAG irises. LV, ACD and ACV were significantly different between the two subgroups. Discriminant analyses based on gene expression, biometric parameters or a combination of both gene expression and biometrics (LV and ACV), correctly classified 94.1%, 85.3% and 94.1% of the original PACG and POAG cases, respectively. The discriminant function combining genes and biometrics demonstrated the highest accuracy in cross‐validated classification of the two glaucoma subtypes.

Conclusions

Distinct iris gene expression supports the pathophysiological differences that exist between PACG and POAG. Biometric parameters can combine with iris gene expression to more accurately define PACG from POAG.

Healthy human second-trimester fetal skin is deficient in leukocytes and associated homing chemokines

The lack of immune cells in mid-gestational fetal skin is often mentioned as a key factor underlying scarless healing. However, the scarless healing ability is conserved until long after the immune system in the fetus is fully developed. Therefore, we studied human second-trimester fetal skin and compared the numbers of immune cells and chemokine levels from fetal skin with adult skin. By using immunohistochemistry, we show that healthy fetal skin contains significant lower numbers of CD68(+) -macrophages, Tryptase(+) -mast cells, Langerin(+) -Langerhans cells, CD1a(+) -dendritic cells, and CD3(+) -T cells compared to adult skin. Staining with an early lineage leukocyte marker, i.e., CD45, verified that the number of CD45(+) -immune cells was indeed significantly lower in fetal skin but that sufficient numbers of immune cells were present in the fetal lymph node. No differences in the vascular network were observed between fetal and adult skin. Moreover, significant lower levels of lymphocyte chemokines CCL17, CCL21, and CCL27 were observed in fetal skin. However, levels of inflammatory interleukins such as IL-6, IL-8, and IL-10 were undetectable and levels of CCL2 were similar in healthy fetal and adult skin. In conclusion, this study shows that second-trimester fetal skin contains low levels of immune cells and leukocyte chemokines compared to adult skin. This immune cell deficiency includes CD45(+) leukocytes, despite the abundant presence of these cells in the lymph node. The immune deficiency in healthy second-trimester fetal skin may result in reduced inflammation during wound healing, and could underlie the scarless healing capacities of the fetal skin.

Mesenchymal stem cell-conditioned medium accelerates wound healing with fewer scars

Mesenchymal stem cells (MSCs) derived from umbilical cords (UC-MSCs) have been shown to enhance cutaneous wound healing by means of the paracrine activity. Fibroblasts are the primary cells involved in wound repair. The paracrine effects of UC-MSCs on dermal fibroblasts have not been fully explored in vitro or in vivo. Dermal fibroblasts were treated with conditioned media from UC-MSCs (UC-MSC-CM). In this model, UC-MSC-CM increased the proliferation and migration of dermal fibroblasts. Moreover, adult dermal fibroblasts transitioned into a phenotype with a low myofibroblast formation capacity, a decreased ratio of transforming growth factor-β1,3 (TGF-β1/3) and an increased ratio of matrix metalloproteinase/tissue inhibitor of metalloproteinases (MMP/TIMP). Additionally, UC-MSC-CM-treated wounds showed accelerated healing with fewer scars compared with control groups. These observations suggest that UC-MSC-CM may be a feasible strategy to promote cutaneous repair and a potential means to realise scarless healing.

Nucleolin enhances the proliferation and migration of heat-denatured human dermal fibroblasts

Denatured dermis, a part of dermis in burned skin, has the ability to restore its normal morphology and functions after their surrounding microenvironment is improved. However, the cellular and molecular mechanisms by which the denatured dermis could improve wound healing are still unclear. This study aimed to investigate the role of nucleolin during the recovery of heat-denatured human dermal fibroblasts. Nucleolin mRNA and protein expression were significantly increased time-dependently during the recovery of heat-denatured human dermal fibroblasts (52 °C, 30 seconds). Heat-denaturation promoted a time-dependent cell proliferation, migration, chemotaxis, and scratched wound healing during the recovery of human dermal fibroblasts. These effects were prevented by knockdown of nucleolin expression with small interference RNA (siRNA), whereas overexpression of nucleolin enhanced cell proliferation, migration, and chemotaxis of human dermal fibroblasts with heat-denaturation. In addition, the expression of transforming growth factor-beta 1(TGF-β1) was significantly increased during the recovery of heat-denatured dermis and human dermal fibroblasts. TGF-β1 expression was up-regulated by nucleolin in human dermal fibroblasts. The results suggest that nucleolin expression is up-regulated, and play an important role in promoting cell proliferation, migration, and chemotaxis of human dermal fibroblasts during the recovery of heat-denatured dermis with a mechanism probably related to TGF-β1.

Dynamic Expression of Novel MiRNA Candidates and MiRNA-34 Family Members in Early- to Mid-Gestational Fetal Keratinocytes Contributes to Scarless Wound Healing by Targeting the TGF-β Pathway

Background

Early- to mid-gestational fetal mammalian skin wounds heal rapidly and without scarring. Keratinocytes (KCs) have been found to exert important effects on the regulation of fibroblasts. There may be significant differences of gestational fetal KCs at different ages. The advantages in early- to mid-gestational fetal KCs could lead to fetal scarless wound healing.

Methods

KCs from six human fetal skin samples were divided into two groups: a mid-gestation group (less than 28 weeks of gestational age) and a late-gestation group (more than 28 weeks of gestational age). RNA extracted from KCs was used to prepare a library of small RNAs for next-generation sequencing (NGS). To uncover potential novel microRNA (miRNAs), the mirTools 2.0 web server was used to identify candidate novel human miRNAs from the NGS data. Other bioinformatical analyses were used to further validate the novel miRNAs. The expression levels of the miRNAs were further confirmed by real-time quantitative RT-PCR.

Results

A total of 61.59 million reads were mapped to 1,170 known human miRNAs in miRBase. Among a total of 202 potential novel miRNAs uncovered, 106 candidates have a higher probability of being novel human miRNAs. A total of 110 miRNAs, including 22 novel miRNA candidates, were significantly differently expressed between mid- and late-gestational fetal KCs. Thirty-three differentially expressed miRNAs and miR-34 family members are correlated with the transforming growth factor-β (TGF-β) pathway.

Conclusions

Taken together, our results provide compelling evidence supporting the existence of 106 novel miRNAs and the dynamic expression of miRNAs that extensively targets the TGF-β pathway at different gestational ages in fetal KCs. MiRNAs showing altered expression at different gestational ages in fetal KCs may contribute to scarless wound healing in early- to mid-gestational fetal KCs, and thus may be new targets for potential scar prevention and reduction therapies.

The role of interleukin-10 and hyaluronan in murine fetal fibroblast function in vitro: implications for recapitulating fetal regenerative wound healing

Background

Mid-gestation fetal cutaneous wounds heal scarlessly and this has been attributed in part to abundant hyaluronan (HA) in the extracellular matrix (ECM) and a unique fibroblast phenotype. We recently reported a novel role for interleukin 10 (IL-10) as a regulator of HA synthesis in the fetal ECM, as well as the ability of the fetal fibroblast to produce an HA-rich pericellular matrix (PCM). We hypothesized that IL-10-mediated HA synthesis was essential to the fetal fibroblast functional phenotype and, moreover, that this phenotype could be recapitulated in adult fibroblasts via supplementation with IL-10 via an HA dependent process.

Methodology/Principal Findings

To evaluate the differences in functional profile, we compared metabolism (MTS assay), apoptosis (caspase-3 staining), migration (scratch wound assay) and invasion (transwell assay) between C57Bl/6J murine fetal (E14.5) and adult (8 weeks) fibroblasts. We found that fetal fibroblasts have lower rates of metabolism and apoptosis, and an increased ability to migrate and invade compared to adult fibroblasts, and that these effects were dependent on IL-10 and HA synthase activity. Further, addition of IL-10 to adult fibroblasts resulted in increased fibroblast migration and invasion and recapitulated the fetal phenotype in an HA-dependent manner.

Conclusions/Significance

Our data demonstrates the functional differences between fetal and adult fibroblasts, and that IL-10 mediated HA synthesis is essential for the fetal fibroblasts' enhanced invasion and migration properties. Moreover, IL-10 via an HA-dependent mechanism can recapitulate this aspect of the fetal phenotype in adult fibroblasts, suggesting a novel mechanism of IL-10 in regenerative wound healing.

Role of micronutrients in skin health and function

Skin is the first line of defense for protecting our bodies against external perturbations, including ultraviolet (UV) irradiation, mechanical/chemical stress, and bacterial infection. Nutrition is one of many factors required for the maintenance of overall skin health. An impaired nutritional status alters the structural integrity and biological function of skin, resulting in an abnormal skin barrier. In particular, the importance of micronutrients (such as certain vitamins and minerals) for skin health has been highlighted in cell culture, animal, and clinical studies. These micronutrients are employed not only as active compounds in therapeutic agents for treating certain skin diseases, but also as ingredients in cosmetic products. Here, the author describes the barrier function of the skin and the general nutritional requirements for skin health. The goal of this review is to discuss the potential roles and current knowledge of selected micronutrients in skin health and function.

Transforming growth factor-β (TGF-β) signaling in healthy human fetal skin: a descriptive study

BACKGROUND

TGF-β plays an important role in growth and development but is also involved in scarring and fibrosis. Differences for this growth factor are known between scarless fetal wound healing and adult wound healing. Nonetheless, most of the data in this area are from animal studies or in vitro studies and, thus, information about the human situation is incomplete and scarce.

OBJECTIVE

The aim of this study was to compare the canonical TGF-β signaling in unwounded human fetal and adult skin.

METHODS

Q-PCR, immunohistochemistry, Western Blot and Luminex assays were used to determine gene expression, protein levels and protein localization of components of this pathway in healthy skin.

RESULTS

All components of the canonical TGF-β pathway were present in unwounded fetal skin. Compared to adult skin, fetal skin had differential concentrations of the TGF-β isoforms, had high levels of phosphorylated receptor-Smads, especially in the epidermis, and had low expression of several fibrosis-associated target genes. Further, the results indicated that the processes of receptor endocytosis might also differ between fetal and adult skin.

CONCLUSION

This descriptive study showed that there are differences in gene expression, protein concentrations and protein localization for most components of the canonical TGF-β pathway between fetal and adult skin. The findings of this study can be a starting point for further research into the role of TGF-β signaling in scarless healing.

The differential proliferative response of fetal and adult human skin fibroblasts to TGF-β is retained when cultured in the presence of fibronectin or collagen

BACKGROUND

Transforming growth factor-β is a multifunctional and pleiotropic factor with decisive role in tissue repair. In this context, we have shown previously that TGF-β inhibits the proliferation of fetal human skin fibroblasts but stimulates that of adult ones. Given the dynamic reciprocity between fibroblasts, growth factors and extracellular matrix (ECM) in tissue homeostasis, the present study aims to investigate the role of fibronectin and collagen in the proliferative effects of TGF-β on fetal and adult cells.

METHODS

Human fetal and adult skin fibroblasts were grown either on plastic surfaces or on surfaces coated with fibronectin or collagen type-I, as well as, on top or within three-dimensional matrices of polymerized collagen. Their proliferative response to TGF-β was studied using tritiated thymidine incorporation, while the signaling pathways involved were investigated by Western analysis and using specific kinase inhibitors.

RESULTS

Fetal skin fibroblast-proliferation was inhibited by TGF-β, while that of adult cells was stimulated by this factor, irrespective of the presence of fibronectin or collagen. Both inhibitory and stimulatory activities of TGF-β on the proliferation of fetal and adult fibroblasts, respectively, were abrogated when the Smad pathway was blocked. Moreover, inhibition of fetal fibroblasts was mediated by PKA activation, while stimulation of adult ones was effected through the autocrine activation of FGF receptor and the MEK-ERK pathway.

CONCLUSIONS

Fetal and adult human skin fibroblasts retain their differential proliferative response to TGF-β when cultured in the presence of fibronectin and unpolymerized or polymerized collagen.

GENERAL SIGNIFICANCE

The interplay between TGF-β and ECM supports the pleiotropic nature of this growth factor, in concordance with the different repair strategies between fetuses and adults. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.