Dermal fibroblasts—A heterogeneous population with regulatory function in wound healing

Dermal Fibroblast Heterogeneity and Its Contribution to the Skin Repair and Regeneration

Significance: Dermal fibroblasts are the major cell type in the skin's dermal layer. These cells originate from distinct locations of the embryo and reside in unique niches in the dermis. Different dermal fibroblasts exhibit distinct roles in skin development, homeostasis, and wound healing. Therefore, these cells are becoming attractive candidates for cell-based therapies in wound healing. Recent Advances: Human skin dermis comprises multiple fibroblast subtypes, including papillary, reticular, and hair follicle-associated fibroblasts, and myofibroblasts after wounding. Recent studies reveal that these cells play distinct roles in wound healing and contribute to diverse healing outcomes, including nonhealing chronic wound or excessive scar formation, such as hypertrophic scars (HTS) and keloids, with papillary fibroblasts having antiscarring and reticular fibroblast scar-forming properties. Critical Issues: The identities and functions of dermal fibroblast subpopulations in many respects remain unknown. In this review, we summarize the current understanding of dermal fibroblast heterogeneity, including their defined cell markers and dermal niches, dynamic changes, and contributions to skin wound healing, with the emphasis on scarless healing, healing with excessive scars (HTS and keloids), chronic wounds, and the potential application of this heterogeneity for developing cell-based therapies that allow wounds to heal faster with less scarring. Future Directions: Heterogeneous dermal fibroblast populations and their functions are poorly characterized. Refining and advancing our understanding of dermal fibroblast heterogeneity and their participation in skin homeostasis and wound healing may create potential therapeutic applications for nonhealing chronic wounds or wounds that heal with excessive scarring.

The role of CXCL8 in chronic nonhealing diabetic foot ulcers and phenotypic changes in fibroblasts: a molecular perspective

INTRODUCTION

A persistent inflammation is perpetuated by infiltrating immune cells and cytokines secreted from these immune cells. Additionally, apoptotic keratinocytes and adipocytes in diabetes causes diabetic foot ulcer (DFU) to arrest in an inflammatory phase without progressing to the resolution phase. This leads to a nonhealing DFU and, despite advanced treatments consisting of wound debridement, off-loading the ulcer of necrotic tissue, wound dressings to keep it moist and control exudate, medication, and preventing infection, DFUs remain a clinical problem. Nonhealing DFUs pose not only an economic burden but also increased morbidity and mortality in the form of psychological stress with and increased chance of amputation, and even death. Thus, investigating the complicated underlying molecular mechanism responsible for nonhealing patterns and designing better therapeutics is warranted. This review article focuses on the role of IL-8-mediated persistent inflammation and phenotypic change of fibroblasts due to this inflammatory cascade. We have discussed various sources of interleukin (IL)-8 secretion and the possible association of IL8-fibroblast plasticity as a cause of nonhealing DFUs.

MATERIAL AND METHODS

A literature search on PubMed, Google Scholar, and PMC was done including the terms diabetic foot ulcer, diabetes, diabetic ulcer, chronic inflammation, interleukin 8, diabetic wound, and nonhealing diabetic foot ulcers. The articles in the English language and published in last 10 years were selected. From the pool of these, the articles describing the relationship between IL-8 and nonhealing diabetic foot ulcer and diabetic ulcer were used sorted out and used for this review article following PRISMA guidelines.

CONCLUSION

Increased infiltration of inflammatory immune cells, secretion of pro-inflammatory cytokines, altered keratinocyte-fibroblast function, and phenotypic changes of fibroblasts in DFUs seem to be critical to the nonhealing of DFUs. Thus, inhibiting IL-8 secretion and downstream signaling seems to be a goal of potential therapeutics.

Is the future scarless? - Fibroblasts as targets for scarless wound healing: a narrative review

Introduction: Scarless healing is the ideal outcome of wound healing and is exhibited in some species. This narrative review assembles the current understanding of fibroblast heterogenicity along with the latest fibroblast-related targets for scar reduction therapies. Human regenerative wound healing is deemed possible due to the wound regeneration already seen in the early gestation foetus. Methods: This literature narrative review was undertaken by searching PubMed and Web of Science databases and Google Scholar to find articles concerning the fibroblast involvement in wound healing. We evaluated and collated these articles to form a consensus of the current understanding of the field. Discussion: This article describes current understanding of fibroblast heterogenicity and involvement in wound healing, focusing on the role of fibroblasts during physiological scarring. We also present the current most promising targets involving fibroblasts in the reduction of scarring and how we can manipulate the behaviour of fibroblasts to mimic the wound regeneration models in the human foetus. These targets include the pro-fibrotic EN1 positive fibroblast lineage, TGFβ1 inhibition, and genetic therapies utilising miRNAs and siRNAs. Conclusion: No therapies are currently available to eradicate scarring; however, treatment options are available to reduce the appearance of scarring. Further research into the heterogenicity and interactions of fibroblasts in both the foetus and adult is needed, and this may lead to the development of novel treatments against scarring.

Cellular Interaction of Human Skin Cells towards Natural Bioink via 3D-Bioprinting Technologies for Chronic Wound: A Comprehensive Review

Skin substitutes can provide a temporary or permanent treatment option for chronic wounds. The selection of skin substitutes depends on several factors, including the type of wound and its severity. Full-thickness skin grafts (SGs) require a well-vascularised bed and sometimes will lead to contraction and scarring formation. Besides, donor sites for full-thickness skin grafts are very limited if the wound area is big, and it has been proven to have the lowest survival rate compared to thick- and thin-split thickness. Tissue engineering technology has introduced new advanced strategies since the last decades to fabricate the composite scaffold via the 3D-bioprinting approach as a tissue replacement strategy. Considering the current global donor shortage for autologous split-thickness skin graft (ASSG), skin 3D-bioprinting has emerged as a potential alternative to replace the ASSG treatment. The three-dimensional (3D)-bioprinting technique yields scaffold fabrication with the combination of biomaterials and cells to form bioinks. Thus, the essential key factor for success in 3D-bioprinting is selecting and developing suitable bioinks to maintain the mechanisms of cellular activity. This crucial stage is vital to mimic the native extracellular matrix (ECM) for the sustainability of cell viability before tissue regeneration. This comprehensive review outlined the application of the 3D-bioprinting technique to develop skin tissue regeneration. The cell viability of human skin cells, dermal fibroblasts (DFs), and keratinocytes (KCs) during in vitro testing has been further discussed prior to in vivo application. It is essential to ensure the printed tissue/organ constantly allows cellular activities, including cell proliferation rate and migration capacity. Therefore, 3D-bioprinting plays a vital role in developing a complex skin tissue structure for tissue replacement approach in future precision medicine.

miR-24-3p obstructs the proliferation and migration of HSFs after thermal injury by targeting PPAR-β and positively regulated by NF-κB

Thermal injury repair is a complex process during which the maintenance of the proliferation and migration of human skin fibroblasts (HSFs) exert a crucial role. MicroRNAs have been proven to exert an essential function in repairing skin burns. This study delves into the regulatory effects of miR-24-3p on the migration and proliferation of HSFs that have sustained a thermal injury; thereby, providing deeper insight into thermal injury repair pathogenesis. The PPAR-β protein expression level progressively increased in a time-dependent manner on the 12^th , 24^th , and 48^th hour following the thermal injury of the HSFs. The knockdown of PPAR-β markedly suppressed the proliferation of and migration of HSF. Following thermal injury, the knockdown also promoted the inflammatory cytokine IL-6, TNF-, PTGS-2, and P65 expression. PPAR-β contrastingly exhibited an opposite trend. A targeted relationship between PPAR-β and miR-24-3p was predicted and verified. miR-24-3p inhibited thermal injured-HSFs proliferation and migration and facilitated inflammatory cytokine expression through the regulation of PPAR-β. p65 directly targeted the transcriptional precursor of miR-24 and promoted miR-24 expression. A negative correlation between miR-24-3p expression level and PPAR-β expression level in rats burnt dermal tissues was observed. Our findings reveal that miR-24-3p is conducive to rehabilitating the denatured dermis, which may be beneficial in providing effective therapy of skin burns.

A novel multifunctional bilayer scaffold based on chitosan nanofiber/alginate-gelatin methacrylate hydrogel for full-thickness wound healing

Due to their lack of multifunctionality, the majority of traditional wound dressings do not support all the clinical requirements. Bilayer wound dressings with multifunctional properties can be attractive for effective skin regeneration. In the present study, we designed a multifunctional bilayer scaffold containing Chitosan-Polycaprolactone (PC) nanofiber and tannic acid (TA) reinforced methacrylate gelatin (GM)/alginate (Al) hydrogel (GM/Al/TA). PC nanofibers were coated with GM/Al/TA hydrogel to obtain a bilayer nanocomposite scaffold (Bi-TA). The GM/Al/TA hydrogel layer of Bi-TA showed antibacterial, free radical scavenging, and biocompatibility properties. Also, PC nanofiber acted as a barrier for preventing bacterial invasion and moisture loss of the hydrogel layer. The wound healing performance of the Bi-TA scaffold was investigated via a full-thickness wound model. In addition, the histopathological and immunohistochemical (IHC) stainings of transforming growth factor-β1(TGF-β1) and tumor necrosis factor-α (TNF-α) were assessed. The results indicated an enhanced wound closure rate, effective collagen deposition, quick re-epithelialization, more skin appendages, and replacement of defect area with normal skin tissue by Bi-TA scaffold compared to other groups. Additionally, the regulation of TGF-β1 and TNF-α was observed by Bi-TA dressing. Overall, the Bi-TA with appropriate structural and multifunctional properties can be an excellent candidate for developing effective dressings for wound healing applications.

From local to global matrix organization by fibroblasts: a 4D laser-assisted bioprinting approach

Fibroblasts and myofibroblasts play a central role in skin homeostasis through dermal organization and maintenance. Nonetheless, the dynamic interactions between (myo)fibroblasts and the extracellular matrix (ECM) remain poorly exploited in skin repair strategies. Indeed, there is still an unmet need for soft tissue models allowing to study the spatial-temporal remodeling properties of (myo)fibroblasts. In vivo, wound healing studies in animals are limited by species specificity. In vitro, most models rely on collagen gels reorganized by randomly distributed fibroblasts. But biofabrication technologies have significantly evolved over the past ten years. High-resolution bioprinting now allows to investigate various cellular micropatterns and the emergent tissue organizations over time. In order to harness the full dynamic properties of cells and active biomaterials, it is essential to consider "time" as the 4th dimension in soft tissue design. Following this 4D bioprinting approach, we aimed to develop a novel model that could replicate fibroblast dynamic remodeling in vitro. For this purpose, (myo)fibroblasts were patterned on collagen gels with laser-assisted bioprinting (LAB) to study the generated matrix deformations and reorganizations. First, distinct populations, mainly composed of fibroblasts or myofibroblasts, were established in vitro to account for the variety of fibroblastic remodeling properties. Then, LAB was used to organize both populations on collagen gels in even isotropic patterns with high resolution, high density and high viability. With maturation, bioprinted patterns of fibroblasts and myofibroblasts reorganized into dispersed or aggregated cells, respectively. Stress-release contraction assays revealed that these phenotype-specific pattern maturations were associated with distinct lattice tension states. The two populations were then patterned in anisotropic rows in order to direct the cell-generated deformations and to orient global matrix remodeling. Only maturation of anisotropic fibroblast patterns, but not myofibroblasts, resulted in collagen anisotropic reorganizations both at tissue-scale, with lattice contraction, and at microscale, with embedded microbead displacements. Following a 4D bioprinting approach, LAB patterning enabled to elicit and orient the dynamic matrix remodeling mechanisms of distinct fibroblastic populations and organizations on collagen. For future studies, this method provides a new versatile tool to investigate in vitro dermal organizations and properties, processes of remodeling in healing, and new treatment opportunities.

Evaluation of Immunomodulatory Responses and Changed Wound Healing in Type 2 Diabetes-A Study Exploiting Dermal Fibroblasts from Diabetic and Non-Diabetic Human Donors

The dermis is the connective layer between the epidermis and subcutis and harbours nerve endings, glands, blood vessels, and hair follicles. The most abundant cell type is the fibroblast. Dermal fibroblasts have a versatile portfolio of functions within the dermis that correspond with different types of cells by either direct contact or by autocrine and paracrine signalling. Diabetic skin is characterized by itching, numbness, ulcers, eczema, and other pathophysiological changes. These pathogenic phenotypes have been associated with the effects of the reactive glucose metabolite methylglyoxal (MGO) on dermal cells. In this study, dermal fibroblasts were isolated from diabetic and non-diabetic human donors. Cultured dermal fibroblasts from diabetic donors exhibited reduced insulin-induced glucose uptake and reduced expression of the insulin receptor. This diabetic phenotype persists under cell culture conditions. Secretion of IL-6 was increased in fibroblasts from diabetic donors. Increased secretion of IL-6 and MIF was also observed upon the treatment of dermal fibroblasts with MGO, suggesting that MGO is sufficient for triggering these immunomodulatory responses. Remarkably, MIF treatment resulted in decreased activity of MGO-detoxifying glyoxalase-1. Given that reduced glyoxalase activity results in increased MGO levels, these findings suggested a positive-feedback loop for MGO generation, in which MIF, evoked by MGO, in turn blocks MGO-degrading glyoxalase activity. Finally, secretion of procollagen Type I C-Peptide (PICP), a marker of collagen production, was reduced in fibroblast from diabetic donors. Remarkably, treatment of fibroblasts with either MGO or MIF was sufficient for inducing reduced PICP levels. The observations of this study unravel a signalling network in human dermal fibroblasts with the metabolite MGO being sufficient for inflammation and delayed wound healing, hallmarks of T2D.

An overview on the manufacturing of functional and mature cellular skin substitutes

There are different types of skin diseases due to chronic injuries that impede the natural healing process of the skin. Tissue engineering (TE) has focused on the development of bioengineered skin or skin substitutes that cover the wound, providing the necessary care to restore the functionality of injured skin. There are two types of substitutes: acellular skin substitutes (ASSs), which offer a low response of the body, and cellular skin substitutes (CSSs), which incorporate living cells and appear as a great alternative in the treatment of skin injuries due to them presenting a greater interaction and integration with the rest of the body. For the development of a CSS, it is necessary to select the most suitable biomaterials, cell components, and methodology of biofabrication for the wound to be treated. Moreover, these CSSs are immature substitutes that must undergo a maturing process in specific bioreactors, guaranteeing their functionality. The bioreactor simulates the natural state of maturation of the skin by controlling parameters such as temperature, pressure, or humidity, allowing a homogeneous maturation of the CSSs in an aseptic environment. The use of bioreactors not only contributes to the maturation of the CSSs, but also offers a new way of obtaining large sections of skin substitutes or natural skin from small portions acquired from the patient, donor, or substitute. Based on the innovation of this technology and the need to develop efficient CSSs, this work offers an update on bioreactor technology in the field of skin regeneration.

Vascularization in skin wound healing: where do we stand and where do we go?

Cutaneous healing is a highly complex process that, if altered due to, for example, impaired vascularization, results in chronic wounds or repaired neotissue of poor quality. Significant progress has been achieved in promoting neotissue vascularization during tissue repair/regeneration. In this review, we discuss the strategies that have been explored and how each one of them contributes to regulate vascularization in the context of cutaneous wound healing from two different perspectives - biomaterial-based and a cell-based approaches. Finally, we discuss the implications of these findings on the development of the 'next generation' approaches to target vascularization in wound healing highlighting the importance of going beyond its contribution to regulate vascularization and take into consideration the temporal features of the healing process and of different types of wounds.

Controlling cell elongation and orientation by using microstructural nanofibre scaffolds for accelerating tissue regeneration

The topographic surface conditions of scaffolds can regulate cellular behaviours, such as by stimulating cellular migration and morphological changes to wound sites and have the potential to promote tissue regeneration. In this research, four types of engineered topographic surfaces, including arrays of hemisphere, pyramid, semi-cylinder, and triangle prism microstructures, were patterned on silicon moulds using microfabrication processes. The microstructural patterns were transferred onto the surface of polycaprolactone membranes and nanofibrous scaffolds by combining with the moulding approach and electrospinning technique, respectively. In vitro experimental results demonstrated that the triangular microstructural nanofibre provided a strong guiding performance to the filopodia of cultured C2C12 myoblast cells, thus inducing cellular elongation and alignment in the longitudinal direction and forming an elongated cell morphology. The cultured cells rapidly transitioned into an elongated morphology at an aspect ratio of 17.33 after 24 h of incubation, with 70% of the cell elongates aligning with the direction of triangular microstructural patterns. The cells cultured on the triangular microstructural nanofibre elongated four-fold compared with those in the flat nanofibre scaffold. Moreover, an in vivo study showed that wounds treated with the triangular microstructural nanofibre scaffold achieved 95.04% wound closure after 14 days and completed the reepithelialisation with an ordered collagen arrangement. Therefore, we believe that the engineered triangular nanofibrous scaffold may accelerate tissue regeneration and has potential for wound healing applications.

Physically crosslinked PVA/graphene-based materials/aloe vera hydrogel with antibacterial activity

Burn is a major skin injury that occurs worldwide. For second-degree burns, special treatment should be given for creating a suitable wound healing environment. Hydrogel wound dressing as the primary care should possess extra properties that include antibacterial activity and cytocompatibility to enhance the treatment effectiveness. Additional therapy such as electrical stimulation can be applied as well promote wound healing. Herein, we used the tissue engineering concept to create a novel antibacterial and cytocompatible hydrogel made of polyvinyl alcohol (PVA), graphene-based material (GBM), and aloe vera extract (Av) through the freeze-thaw process. We prepared the PVA/GBM/Av hydrogel and examined its potential as a wound dressing. We found that it exhibited excellent hydrophilicity with a contact angle between 15 and 31 degrees and electrical conductivity within the range of 0.0102-0.0154 S m-1, which is comparable to that of the human skin tissue and possesses tensile strength up to 1.5 MPa with elongation of 405%. It also demonstrated good stability in phosphate buffer saline with a weight ratio of 73-80% after 14 days of immersion. We presented that the addition of graphene and graphene oxide (GO) inhibited the growth of Gram-positive Staphylococcus aureus ATCC 6538 with the lowest bacterial population observed in PVA/GO, which is 1.74 × 107 cfu mL-1 after 1 day incubation and 99.94% bacterial reduction. Furthermore, our PVA/GBM/Av showed no toxicity to 3T3 fibroblast cells after 48 h with viability up to 295% for PVA/GO/Av. In summary, our fabricated hydrogels have shown their potential as wound dressing with antibacterial and non-cytotoxic properties.

The bright side of fibroblasts: molecular signature and regenerative cues in major organs

Fibrosis is a pathologic process characterized by the replacement of parenchymal tissue by large amounts of extracellular matrix, which may lead to organ dysfunction and even death. Fibroblasts are classically associated to fibrosis and tissue repair, and seldom to regeneration. However, accumulating evidence supports a pro-regenerative role of fibroblasts in different organs. While some organs rely on fibroblasts for maintaining stem cell niches, others depend on fibroblast activity, particularly on secreted molecules that promote cell adhesion, migration, and proliferation, to guide the regenerative process. Herein we provide an up-to-date overview of fibroblast-derived regenerative signaling across different organs and discuss how this capacity may become compromised with aging. We further introduce a new paradigm for regenerative therapies based on reverting adult fibroblasts to a fetal/neonatal-like phenotype.

ZFP36 family members regulate the pro-inflammatory features of psoriatic dermal fibroblasts

Dermal fibroblasts are strategically positioned underneath the basal epidermis layer to support keratinocyte proliferation and extracellular matrix production. In inflammatory conditions, these fibroblasts produce cytokines and chemokines that promote the chemoattraction of immune cells into the dermis and the hyperplasia of the epidermis, two characteristic hallmarks of Psoriasis (Pso). However, how dermal fibroblasts specifically contribute to Pso development remains largely uncharacterized. Here we investigated through which cytokines and signaling pathways dermal fibroblasts contribute to the inflammatory features of psoriatic skin. We show that dermal fibroblasts from lesional Pso skin are important producers of inflammatory mediators, including IL6, CXCL8 and CXCL2. This increased cytokine production was found to be regulated by ZFP36 family members ZFP36, ZFP36L1 and ZPF36L2, RNA-binding proteins with mRNA-degrading properties. Additionally, the expression of ZFP36 family proteins was found reduced in chronic inflammatory conditions that mimic psoriatic lesional skin. Collectively, these results indicate that dermal fibroblasts are important producers of cytokines in psoriatic skin, and that reduced expression of ZFP36 members in Pso dermal fibroblasts contributes to their inflammatory phenotype.

Inflammation-Responsive Drug-Loaded Hydrogels with Sequential Hemostasis, Antibacterial, and Anti-Inflammatory Behavior for Chronically Infected Diabetic Wound Treatment

Stimuli-responsive hydrogels possess unique advantages in drug delivery due to their variable performance and status based on the external environment. In the present study, a dual-responsive (pH and reactive oxygen species (ROS)) hydrogel was prepared to realize drug release properties under inflammatory stimulation. By grafting 3-carboxy-phenylboronic acid to the gelatin molecular backbone and cross-linking with poly(vinyl alcohol), we successfully synthesized the inflammation-responsive drug-loaded hydrogels after encapsulation with vancomycin-conjugated silver nanoclusters (VAN-AgNCs) and pH-sensitive micelles loaded with nimesulide (NIM). This novel design not only retained the dynamic functions of hydrogels, such as injectability, self-healing, and remodeling, but also realized sequential and on-demand drug delivery at diabetic-infected wound sites. In this work, we found that the hydrogel exhibited excellent biocompatibility and hemostasis properties owing to the enhanced cell-adhesive property of the gelatin component. The significant antibacterial and anti-inflammatory effect of the hydrogel was demonstrated in an in vitro experiment. Moreover, in the in vivo experiment, the hydrogel was found to play a role in promoting infected wound healing through sequential hemostasis and antibacterial and anti-inflammatory processes. Collectively, this inflammation-responsive hydrogel design containing VAN-AgNCs and NIM-loaded micelles has great potential in the application of chronically infected diabetic wound treatment, as well as in other inflammatory diseases.

Fibroblasts: Heterogeneous Cells With Potential in Regenerative Therapy for Scarless Wound Healing

In recent years, research on wound healing has become increasingly in-depth, but therapeutic effects are still not satisfactory. Occasionally, pathological tissue repair occurs. Influencing factors have been proposed, but finding the turning point between normal and pathological tissue repair is difficult. Therefore, we focused our attention on the most basic level of tissue repair: fibroblasts. Fibroblasts were once considered terminally differentiated cells that represent a single cell type, and their heterogeneity was not studied until recently. We believe that subpopulations of fibroblasts play different roles in tissue repair, resulting in different repair results, such as the formation of normal scars in physiological tissue repair and fibrosis or ulcers in pathological tissue repair. It is also proposed that scarless healing can be achieved by regulating fibroblast subpopulations.

Adipose Tissue-Derived Mesenchymal Stem Cells (ADMSCs) and ADMSC-Derived Secretome Expedited Wound Healing in a Rodent Model - A Preliminary Study

Introduction

The biological role of mesenchymal stem cells (MSCs) in wound healing has been demonstrated. However, there were limited studies on the healing effect of secretome which consists of many biological factors secreted by MSCs. In this study, we aimed to compare the therapeutic effects of secretome with MSCs on facilitating wound healing.

Methods

Green fluorescent protein labelled adipose-derived MSCs (GFP-ADMSCs) or secretome was injected in the full-thickness skin excision model on SD rats. The wound healing process was evaluated by calculating the healing rate and the histological examinations on skin biopsy. The cell viability, proliferation and mobility of the rat dermal fibroblasts were compared after different treatments. The inflammatory response in macrophages was indicated by the level of nitric oxide (NO) and inflammatory cytokines through NO assay and ELISA.

Results

On day 5 and day 14, both MSCs and secretome accelerated the wound healing, secretome further enhanced the process. GFP-MSCs were detected 10 days after transplantation. The level of IL-6 and TNF-α in blood was reduced after MSCs and secretome treatments. The expressions of VEGF and PCNA were increased after treatment, higher intensity of VEGF was observed in secretome-injected tissue. The concentrations of total protein and VEGF in secretome were 2.2 ± 0.5 mg/mL and 882.0 ± 72.7 pg/mL, respectively. The cell viability and proliferation of FR were promoted significantly after the treatment. The scratch test showed that secretome accelerated the wound healing speed. Secretome reduced the metabolism of macrophages remarkably, but it did not decrease the level of macrophage-secreted NO. The expression of the pro-inflammatory cytokines (IL-6, MCP-1 and TNF-α) was downregulated significantly.

Conclusion

Our study indicated both MSCs and MSCs-derived secretome enhanced the wound healing process in early phase. Secretome further promoted the healing effects through promoting the fibroblast proliferation and migration and suppressing the inflammatory response.

Diabetic wound healing: The impact of diabetes on myofibroblast activity and its potential therapeutic treatments

Diabetes is a systemic disease in which the body cannot regulate the amount of sugar, namely glucose, in the blood. High glucose toxicity has been implicated in the dysfunction of diabetic wound healing, following insufficient production (Type 1) or inadequate usage (Type 2) of insulin. Chronic non-healing diabetic wounds are one of the major complications of both types of diabetes, which are serious concerns for public health and can impact the life quality of patients significantly. In general, diabetic wounds are characterized by deficient chemokine production, an unusual inflammatory response, lack of angiogenesis and epithelialization, and dysfunction of fibroblasts. Increasing scientific evidence from available experimental studies on animal and cell models strongly associates impaired wound healing in diabetes with dysregulated fibroblast differentiation to myofibroblasts, interrupted myofibroblast activity, and inadequate extracellular matrix production. Myofibroblasts play an important role in tissue repair by producing and organizing extracellular matrix and subsequently promoting wound contraction. Based on these studies, hyperglycaemic conditions can interfere with cytokine signalling pathways (such as growth factor-β pathway) affecting fibroblast differentiation, alter fibroblast apoptosis, dysregulate dermal lipolysis, and enhance hypoxia damage, thus leading to damaged microenvironment for myofibroblast formation, inappropriate extracellular matrix modulation, and weakened wound contraction. In this review, we will focus on the current available studies on the impact of diabetes on fibroblast differentiation and myofibroblast function, as well as potential treatments related to the affected pathways.

Application of biomaterials in periodontal tissue repair and reconstruction in the presence of inflammation under periodontitis through the foreign body response: Recent progress and perspectives

Periodontitis would cause dental tissue damage locally. Biomaterials substantially affect the surrounding immune microenvironment through treatment-oriented local inflammatory remodeling in dental periodontitis. This remodeling process is conducive to wound healing and periodontal tissue regeneration. Recent progress in understanding the foreign body response (FBR) and immune regulation, including cell heterogeneity, and cell-cell and cell-material interactions, has provided new insights into the design criteria for biomaterials applied in treatment of periodontitis. This review discusses recent progress and perspectives in the immune regulation effects of biomaterials to augment or reconstruct soft and hard tissue in an inflammatory microenvironment of periodontitis.

Influence of TGFBR2, TGFB3, DNMT1, and DNMT3A Knockdowns on CTGF, TGFBR2, and DNMT3A in Neonatal and Adult Human Dermal Fibroblasts Cell Lines

Dermal fibroblasts are responsible for the production of the extracellular matrix that undergoes significant changes during the skin aging process. These changes are partially controlled by the TGF-β signaling, which regulates tissue homeostasis dependently on several genes, including CTGF and DNA methyltransferases. To investigate the potential differences in the regulation of the TGF-β signaling and related molecular pathways at distinct developmental stages, we silenced the expression of TGFB1, TGFB3, TGFBR2, CTGF, DNMT1, and DNMT3A in the neonatal (HDF-N) and adult (HDF-A) human dermal fibroblasts using the RNAi method. Through Western blot, we analyzed the effects of the knockdowns of these genes on the level of the CTGF, TGFBR2, and DNMT3A proteins in both cell lines. In the in vitro assays, we observed that CTGF level was decreased after knockdown of DNMT1 in HDF-N but not in HDF-A. Similarly, the level of DNMT3A was decreased only in HDF-N after silencing of TGFBR2, TGFB3, or DNMT1. TGFBR2 level was lower in HDF-N after knockdown of TGFB3, DNMT1, or DNMT3A, but it was higher in HDF-A after TGFB1 silencing. The reduction of TGFBR2 after silencing of DNMT3A and vice versa in neonatal cells only suggests the developmental stage-specific interactions between these two genes. However, additional studies are needed to explain the dependencies between analyzed proteins.

The differences in the number of fibroblasts and blood vessels after the topical and systemic administration of Lactobacillus casei Shirota probiotics for the treatment of traumatic ulcers in Wistar rats (Rattus norvegicus)

Background and Aim

The use of drugs as a therapy for traumatic ulcers may lead to drug resistance and other side effects. Lactobacillus casei Shirota can affect the number of fibroblasts and blood vessels in wound healing. The aim of this study was to investigate the difference in the number of fibroblast cells and blood vessels after the topical and systemic administration of L. casei Shirota probiotics in Wistar rats with traumatic ulcer.

Materials and Methods

Overall, 36 healthy male Wistar rats aged 2-3 months old and weighing 175-250 g in body weight were used as a sample. Traumatic ulcer was made on the labial fornix incisive inferior. The subject rats were divided into groups: (1) A control group over 3 days, (2) a group that used distilled water over 7 days, (3) a group that underwent topical treatment over 3 days, (4) a group that used probiotics administered topically over 7 days, (5) a group that underwent systemic treatment over 3 days, and (6) a group that took oral probiotics for the traumatic ulcers over 7 days. The number of fibroblasts and blood vessels was observed through a hematoxylin-eosin examination.

Results

Based on the results of the study, a significant difference was observed in the number of fibroblasts (p=0.00) and blood vessels (p=0.018) in the 3-day topical group that underwent a 3-day systemic administration of probiotics compared with the number of fibroblast cells in the 7-day topical group and 7-day systemic group (p=0.00).

Conclusion

Overall, significant differences were observed in the number of fibroblasts and blood vessels in Wistar rats with traumatic ulcer after undergoing the topical and systemic administration of L. casei Shirota probiotics.

Synergistic Effect of Biomaterial and Stem Cell for Skin Tissue Engineering in Cutaneous Wound Healing: A Concise Review

Skin tissue engineering has made remarkable progress in wound healing treatment with the advent of newer fabrication strategies using natural/synthetic polymers and stem cells. Stem cell therapy is used to treat a wide range of injuries and degenerative diseases of the skin. Nevertheless, many related studies demonstrated modest improvement in organ functions due to the low survival rate of transplanted cells at the targeted injured area. Thus, incorporating stem cells into biomaterial offer niches to transplanted stem cells, enhancing their delivery and therapeutic effects. Currently, through the skin tissue engineering approach, many attempts have employed biomaterials as a platform to improve the engraftment of implanted cells and facilitate the function of exogenous cells by mimicking the tissue microenvironment. This review aims to identify the limitations of stem cell therapy in wound healing treatment and potentially highlight how the use of various biomaterials can enhance the therapeutic efficiency of stem cells in tissue regeneration post-implantation. Moreover, the review discusses the combined effects of stem cells and biomaterials in in vitro and in vivo settings followed by identifying the key factors contributing to the treatment outcomes. Apart from stem cells and biomaterials, the role of growth factors and other cellular substitutes used in effective wound healing treatment has been mentioned. In conclusion, the synergistic effect of biomaterials and stem cells provided significant effectiveness in therapeutic outcomes mainly in wound healing improvement.

Antioxidant Properties of Plant-Derived Phenolic Compounds and Their Effect on Skin Fibroblast Cells

Plants are rich sources of a diverse range of chemicals, many of which have significant metabolic activity. One large group of secondary compounds are the phenolics, which act as inter alia potent reactive oxygen scavengers in cells, including fibroblasts. These common dermis residue cells play a crucial role in the production of extracellular matrix components, such as collagen, and maintaining the integrity of connective tissue. Chronic wounds or skin exposure to UV-irradiation disrupt fibroblast function by the generation of reactive oxygen species, which may damage cell components and modify various signaling pathways. The resulting imbalance may be reversed by the antioxidant activity of plant-derived phenolic compounds. This paper reviews the current state of knowledge on the impact of phenolics on fibroblast functionality under oxidative stress conditions. It examines a range of compounds in extracts from various species, as well as single specific plant-derived compounds. Phenolics are a good candidate for eliminating the causes of skin damage including wounds and aging and acting as skin care agents.

Bioactive Ibuprofen-Loaded PLGA Coatings for Multifunctional Surface Modification of Medical Devices

To modulate the biofunctionality of implantable medical devices commonly used in clinical practice, their surface modification with bioactive polymeric coatings is an attractive and successful emerging strategy. Biodegradable coatings based on poly(lactic acid-co-glycolic acid), PLGA, represent versatile and safe candidates for surface modification of implantable biomaterials and devices, providing additional tunable ability for topical delivery of desired therapeutic agents. In the present study, Ibuprofen-loaded PLGA coatings (PLGA/IBUP) were obtained by using the dip-coating and drop-casting combined protocol. The composite materials demonstrated long-term drug release under biologically simulated dynamic conditions. Reversible swelling phenomena of polymeric coatings occurred in the first two weeks of testing, accompanied by the gradual matrix degradation and slow release of the therapeutic agent. Irreversible degradation of PLGA coatings occurred after one month, due to copolymer's hydrolysis (evidenced by chemical and structural modifications). After 30 days of dynamic testing, the cumulative release of IBUP was ~250 µg/mL. Excellent cytocompatibility was revealed on human-derived macrophages, fibroblasts and keratinocytes. The results herein evidence the promising potential of PLGA/IBUP coatings to be used for surface modification of medical devices, such as metallic implants and wound dressings.

Dielectrophoresis Prototypic Polystyrene Particle Synchronization toward Alive Keratinocyte Cells for Rapid Chronic Wound Healing

Diabetes patients are at risk of having chronic wounds, which would take months to years to resolve naturally. Chronic wounds can be countered using the electrical stimulation technique (EST) by dielectrophoresis (DEP), which is label-free, highly sensitive, and selective for particle trajectory. In this study, we focus on the validation of polystyrene particles of 3.2 and 4.8 μm to predict the behavior of keratinocytes to estimate their crossover frequency (fXO) using the DEP force (FDEP) for particle manipulation. MyDEP is a piece of java-based stand-alone software used to consider the dielectric particle response to AC electric fields and analyzes the electrical properties of biological cells. The prototypic 3.2 and 4.8 μm polystyrene particles have fXO values from MyDEP of 425.02 and 275.37 kHz, respectively. Fibroblast cells were also subjected to numerical analysis because the interaction of keratinocytes and fibroblast cells is essential for wound healing. Consequently, the predicted fXO from the MyDEP plot for keratinocyte and fibroblast cells are 510.53 and 28.10 MHz, respectively. The finite element method (FEM) is utilized to compute the electric field intensity and particle trajectory based on DEP and drag forces. Moreover, the particle trajectories are quantified in a high and low conductive medium. To justify the simulation, further DEP experiments are carried out by applying a non-uniform electric field to a mixture of different sizes of polystyrene particles and keratinocyte cells, and these results are well agreed. The alive keratinocyte cells exhibit NDEP force in a highly conductive medium from 100 kHz to 25 MHz. 2D/3D motion analysis software (DIPP-MotionV) can also perform image analysis of keratinocyte cells and evaluate the average speed, acceleration, and trajectory position. The resultant NDEP force can align the keratinocyte cells in the wound site upon suitable applied frequency. Thus, MyDEP estimates the Clausius-Mossotti factors (CMF), FEM computes the cell trajectory, and the experimental results of prototypic polystyrene particles are well correlated and provide an optimistic response towards keratinocyte cells for rapid wound healing applications.

NF-κB and COX-2 repression with topical application of hesperidin and naringin hydrogels augments repair and regeneration of deep dermal wounds

INTRODUCTION

Wound injury is common and causes serious complications if not treated properly. The moist dressing heals wounds faster than other dressings. Therefore, we sought to study the effect of hesperidin/naringin hydrogel wound dressing or their combinations on the deep dermal wounds in mice.

METHODS

A rectangular full thickness skin flap of 2.5 × 1.5 cm was excised from depilated mice dorsum and the wound was fully covered with 5% hesperidin/5% naringin hydrogel or both in the ratio of 1:1, 2:1, or 1:2, respectively once daily until complete healing of the wound. Data were collected on wound contraction, mean wound healing time, collagen, DNA, and nitric oxide syntheses, glutathione concentration, superoxide dismutase activity, and lipid peroxidation throughout healing. Expression of NF-κB and COX-2 were also estimated in the regenerating granulation tissue using Western blot.

FINDINGS

Dressing of wounds with 5% hesperidin hydrogel led to a higher and early wound contraction and significantly reduced mean wound healing time by 5.7 days than 5% naringin or combination of hesperidin and naringin hydrogels in the ratio of 1:1, 2:1, or 1:2. Hesperidin hydrogel wound dressing caused higher collagen and DNA syntheses than other groups at all times after injury. Glutathione concentration and superoxide dismutase activity increased followed by a decline in lipid peroxidation in regenerating wounds after hesperidin/naringin hydrogel application and a maximum effect was observed for hesperidin alone. The hesperidin/naringin hydrogel suppressed NF-κB and COX-2 expression on days 6 and 12.

CONCLUSIONS

Application of 5% hesperidin hydrogel was more effective than 5% naringin or combination of hesperidin and naringin gels (1:1, 2:1 or 1:2) indicated by a greater wound contraction, reduced mean wound healing time, elevated collagen and DNA syntheses, rise in glutathione concentration, and superoxide dismutase activity followed by reduced lipid peroxidation, and NF-κB, and COX-2 expression.

Autocrine and Paracrine Effects of Vascular Endothelial Cells Promote Cutaneous Wound Healing

Background

When vascular endothelial cells are subjected to external stimuli, paracrine hormones and cytokines act on adjacent cells. The regulation of the biological behaviour of cells is closely related to the maintenance of organ function and the occurrence and development of disease. However, it is unclear whether vascular endothelial cells affect the biological behaviour of cells involved in wound repair through autocrine and paracrine mechanisms and ultimately play a role in wound healing. We aimed to verify the effect of the autocrine and paracrine functions of vascular endothelial cells on wound healing.

Materials and Methods

ELISA was used to detect platelet-derived growth factor, basic fibroblast growth factor, epidermal growth factor, and vascular endothelial growth factor in human umbilical vascular endothelial cell-conditioned medium (HUVEC-CM). Different concentrations of HUVEC-CM were used to treat different stem cells. CCK-8 and scratch assays were used to detect the proliferation and migration ability of each cell. A full-thickness dorsal skin defect model was established in mice, and skin wound healing was observed after the local injection of HUVEC-CM, endothelial cell medium (ECM), or normal saline. H&E staining and immunofluorescence were used to observe the gross morphology of the wound tissue, the epithelial cell migration distance, and the expression of CD3 and CD31.

Results

HUVEC-CM promotes the proliferation and migration of epidermal stem cells, skin fibroblasts, bone marrow mesenchymal stem cells, and HUVECs themselves. Furthermore, HUVEC-CM can promote angiogenesis in mouse skin wounds and granulation tissue formation and can accelerate wound surface epithelialization and collagen synthesis, thereby promoting wound healing.

Conclusion

Our results clearly suggest that it is practicable and effective to promote wound healing with cytokines secreted by vascular endothelial cells in a mouse model.

Nanofibrillar Hydrogel Recapitulates Changes Occurring in the Fibrotic Extracellular Matrix

Fibrosis is a pathological condition that leads to excessive deposition of collagen and increased tissue stiffness. Understanding the mechanobiology of fibrotic tissue necessitates the development of effective in vitro models that recapitulate its properties and structure; however, hydrogels that are currently used for this purpose fail to mimic the filamentous structure and mechanical properties of the fibrotic extracellular matrix (ECM). Here, we report a nanofibrillar hydrogel composed of cellulose nanocrystals and gelatin, which addresses this challenge. By altering the composition of the hydrogel, we mimicked the changes in structure, mechanical properties, and chemistry of fibrotic ECM. Furthermore, we decoupled the variations in hydrogel structure, properties, and ligand concentration. We demonstrate that this biocompatible hydrogel supports the three-dimensional culture of cells relevant to fibrotic diseases. This versatile hydrogel can be used for in vitro studies of fibrosis of different tissues, thus enabling the development of novel treatments for fibrotic diseases.

Effect of dermal fibroblasts and mesenchymal stem cells seeded on an amniotic membrane scaffold in skin regeneration: A case series

BACKGROUND

Skin wound healing has always been a challenging subject as it involves the coordinated functioning of various cells and molecules. Any disorder in wound healing can cause healing failure and result in chronic wounds. In this study, we hypothesized that co-cultured dermal fibroblasts (DFs) and Wharton's jelly mesenchymal stem cells (WJ-MSCs) seeded on an acellular amniotic membrane scaffold could be used to promote skin regeneration in chronic ulcers.

MATERIALS AND METHODS

In this case series, the chronic wounds of five diabetic patients aged between 30 and 60 years were treated with co-cultured WJ-MSCs and DFs seeded on an acellular amniotic membrane. Treatment was applied and the wound healing process was evaluated every three days for nine days, with the patients being subsequently followed up for one month. The wound healing percentage, time taken for the wound to heal, and wound size were monitored.

RESULTS

The mean wound healing rate (WHR) increased progressively in all lesions. The mean percentage of wound healing after transplantation of the biological scaffold enriched with WJ-MSCs and autologous DFs after treatment was 93.92%, respectively. The healing percentage significantly increased after three days; significant decreases in wound size and healing time were recorded after six and nine days of treatment, respectively (p < 0.002); and total skin regeneration and re-epithelialization were achieved by the ninth day of treatment. There were no side effects or complications.

CONCLUSION

Given the current problems and complications presented by chronic wounds, Novel Clinical approaches involving cell therapy and tissue engineering can be regarded as an attractive therapeutic option for the treatment of chronic and difficult-to-heal wounds.

Chitosan-based nanoparticles as delivery-carrier for promising antimicrobial glycolipid biosurfactant to improve the eradication rate of Helicobacter pylori biofilm

Driven by the need to find alternatives to control H. pylori infections, this work describes the development of chitosan-PMLA nanoparticulate systems as carriers for antimicrobial glycolipid. By using a simple ionic gelation method stable nanoparticle was obtained showing an encapsulation efficiency of 73.1 ± 1.3% and an average size of 217.0 ± 15.6 nm for rhamnolipids chitosan-PMLA nanoparticles (RL-CS-NPs). Glycolipid incorporation and particle size were correspondingly corroborated by FT-IR and TEM analysis. Rhamnolipids chitosan nanoparticles (RL-CS-NPs) presented the highest antimicrobial effect towards H. pylori (ATCC 26695) exhibiting a minimal inhibitory concentration of 132 µg/mL and a biofilm inhibition ability of 99%. Additionally, RL-CS-NPs did not interfere with human fibroblasts viability and proliferation under the tested conditions. The results revealed that the RL-CS-NPs were able to inhibit bacterial growth showing adequate cytocompatibility and might become, after additional studies, a valuable approach to fight H. pylori biofilm related-infections.

Engineering a Chemically Defined Hydrogel Bioink for Direct Bioprinting of Microvasculature

Vascularizing printed tissues is a critical challenge in bioprinting. While protein-based hydrogel bioinks have been successfully used to bioprint microvasculature, their compositions are ill-defined and subject to batch variation. Few studies have focused on engineering proangiogenic bioinks with defined properties to direct endogenous microvascular network formation after printing. Here, a peptide-functionalized alginate hydrogel bioink with defined mechanical, rheological, and biochemical properties is developed for direct bioprinting of microvascularized tissues. An integrin-binding peptide (RGD) and a vascular endothelial growth factor-mimetic peptide with a protease-sensitive linker are conjugated onto a biodegradable alginate to synergistically promote vascular morphogenesis and capillary-scale endothelial tube formation. Partial ionic crosslinking before printing converts the otherwise unprintable hydrogel into a viscoelastic bioink with excellent printability and cytocompatibility. We use the bioink to fabricate a compartmentalized vascularized tissue construct, wherein we observe pericyte-endothelial cell colocalization and angiogenic sprouting across a tissue interface, accompanied by deposition of fibronectin and collagen in vascular and tissue components, respectively. This study provides a tunable and translational "off-the-shelf" hydrogel bioink with defined composition for vascularized bioprinting.

The effect of TGFβRI inhibition on fibroblast heterogeneity in hypertrophic scar 2D in vitro models

In burn patients, wound healing is often accompanied by hypertrophic scarring (HTS), resulting in both functional and aesthetic problems. HTSs are characterized by abundant presence of myofibroblasts (MFs) residing in the dermis. HTS development and MF persistence is primarily regulated by TGF-β signalling. A promising method to target the transforming growth factor receptor I (TGFβRI; also known as activin-like kinase 5 (ALK5)) is by making use of exon skipping through antisense oligonucleotides. In HTS the distinguishing border between the papillary dermis and the reticular dermis is completely abrogated, thus exhibiting a one layered dermis containing a heterogenous fibroblast population, consisting of papillary fibroblasts (PFs), reticular fibroblasts (RFs) and MFs. It has been proposed that PFs, as opposed to RFs, exhibit anti-fibrotic properties. Currently, it is still unclear which fibroblast subtype is most affected by exon skipping treatment. Therefore, the aim of this study was to investigate the effect of TGFβRI inhibition by exon skipping in PF, RF and HTS fibroblast monocultures. Morphological analyses revealed the presence of a PF-like population after exon skipping in the different fibroblast cultures. This observation was further confirmed by the expression of genes specific for PFs, demonstrated by qPCR analyses. Further investigations on mRNA and protein level revealed that indeed MFs and to a lesser extent RFs are targeted by exon skipping. Furthermore, collagen gel contraction analysis showed that ALK5 exon skipping reduced TGF-β- induced contraction together with decreased alpha-smooth muscle actin expression levels. In conclusion, we show for the first time that exon skipping primarily targets pro-fibrotic fibroblasts. This could be a promising step towards reduced HTS development of burn tissue.

Glycocalyx disruption enhances motility, proliferation and collagen synthesis in diabetic fibroblasts

Impaired wound healing represents one of the most debilitating side effects of Diabetes mellitus. Though the role of fibroblasts in wound healing is well-known, the extent to which their function is altered in the context of diabetes remains incompletely understood. Here, we address this question by comparing the phenotypes of healthy dermal fibroblasts (HDFs) and diabetic dermal fibroblasts (DDFs). We show that DDFs are more elongated but less motile and less contractile than HDFs. Reduced motility of DDFs is attributed to formation of larger focal adhesions stabilized by a bulky glycocalyx, associated with increased expression of the cell surface glycoprotein mucin 16 (MUC 16). Disruption of the glycocalyx not only restored DDF motility to levels comparable to that of HDFs, but also led to increased proliferation and collagen synthesis. Collectively, our results illustrate the influence of glycocalyx disruption on mechanics of diabetic fibroblasts relevant to cell motility.

Three-Dimensional Model of Hypertrophic Scar Using a Tissue-Engineering Approach

Following wound healing, skin is replaced by a specialized tissue called scar. Sometime, this scar can become pathologic, called hypertrophic scar, with a high amount of extracellular matrix, capillaries, and myofibroblast persistence. To understand the mechanisms at the origin of the fibrosis is paramount to treat patients, but despite few animal models and in vitro studies using mainly human pathological cells cultured on plastic on monolayer, the treatment of these fibrotic scars remains unsatisfactory. As in tissue, cells are most often imbedded in extracellular matrix, we have developed, using a tissue engineering method, new in vitro models to study human fibrotic skin pathologies as hypertrophic scars. Human cells isolated from hypertrophic scars are used to reconstitute a three-dimensional fibrotic skin comprising both dermal and epidermal parts. This method called the self-assembly approach is based on the cell capacity to reconstitute their own environment as in vivo. In this chapter, the described methods include extraction and culture of human scar keratinocytes and fibroblasts from cutaneous biopsies as well as the protocols to produce fibrotic skin that can be used to study pathological process.

Extracellular vesicle-based therapeutics for the regeneration of chronic wounds: current knowledge and future perspectives

Chronic wounds are still an intractable medical problem for both clinicians and researchers and cause a substantial social and medical burden. Current clinical approaches can only manage wounds but have limited capacity to promote the regeneration of chronic wounds. As a type of natural nanovesicle, extracellular vesicles (EVs) from multiple cell types (e.g., stem cells, immune cells, and skin cells) have been shown to participate in all stages of skin wound healing including inflammation, proliferation, and remodeling, and display beneficial roles in promoting wound repair. Moreover, EVs can be further re-engineered with genetic/chemical or scaffold material-based strategies for enhanced skin regeneration. In this review, we provide an overview of EV biology and discuss the current findings regarding the roles of EVs in chronic wound healing, particularly in immune regulation, cell proliferation and migration, angiogenesis, and extracellular matrix remodeling, as well as the therapeutic effects of EVs on chronic wounds by genetic modification, in combination with functionalized biomaterials, and as drug carriers. We also discuss the challenges and perspectives of translating EV-based therapies into clinical wound care in the future.

Proteomic analysis of extracellular vesicles and conditioned medium from human adipose-derived stem/stromal cells and dermal fibroblasts

Conditioned medium (CM) and extracellular vesicles (EV) from Adipose-derived Stem/stromal cells (ASC) and Dermal fibroblasts (DF) represent promising tools for therapeutic applications. Which one should be preferred is still under debate and no direct comparison of their proteome has been reported yet. Here, we apply quantitative proteomics to explore the protein composition of CM and EV from the two cell types. Data are available via ProteomeXchange (identifier PXD020219). We identified 1977 proteins by LC-MS/MS proteomic analysis. Unsupervised clustering analysis and PCA recognized CM and EV as separate groups. We identified 68 and 201 CM and EV specific factors. CM were enriched in proteins of endoplasmic reticulum, Golgi apparatus and lysosomes, whereas EV contained a large amount of GTPases, ribosome and translation factors. The analysis of ASC and DF secretomes revealed the presence of cell type-specific proteins. ASC-CM and -EV carried factors involved in ECM organization and immunological regulation, respectively. Conversely, DF-CM and -EV were enriched in epithelium development associated factors and -EV in Wnt signaling factors. In conclusion, this analysis provides evidence of a different protein composition between CM and EV and of the presence of cell type-specific bioactive mediators suggesting their specific future use as advanced therapy medicinal products. SIGNIFICANCE: The use of cell secretome presents several advantages over cell therapy such as the lower risks associated to the administration step and the avoidance of any potential risk of malignant transformation. The main secretome preparations consist in concentrated conditioned medium (CM) and extracellular vesicles (EV). Both of them showed well-documented therapeutic potentials. However, it is still not clear in which case it should be better to use one preparation over the other and an exhaustive comparison between their proteome has not been performed yet. The choice of the cell source is another relevant aspect that still needs to be addressed. In order to shed light on these questions we explored the protein composition of CM and EV obtained from Adipose-derived Stem/stromal Cells (ASC) and Dermal Fibroblasts (DF), by a comprehensive quantitative proteomics approach. The analysis showed a clear distinction between CM and EV proteome. CM were enriched in proteins of endoplasmic reticulum, Golgi apparatus and lysosomes, whereas EV contained a large amount of GTPases, ribosome and translation-related factors. Furthermore, the analysis of ASC and DF secretomes revealed specific biological processes for the different cell products. ASC secretome presented factors involved in ECM organization (hyaluronan and glycosaminoglycan metabolism) and immunological regulation (e.g. macrophage and IkB/NFkB signaling regulation), respectively. On the other hand, DF-CM and -EV were both enriched in epithelium development associated factors, whilst DF-CM in proteins involved in cellular processes regulation and -EV in Wnt signaling factors. In conclusion, our study shed a light on the different protein composition of CM and EV of two promising cell types, spanning from basic processes involved in secretion to specific pathways supporting their therapeutic potential and their possible future use as advanced therapy medicinal products.

Experimental Study on Blue Light Interaction with Human Keloid-Derived Fibroblasts

Keloids are an exuberant response to wound healing, characterized by an exaggerated synthesis of collagen, probably due to the increase of fibroblasts activity and to the reduction of their apoptosis rate: currently no standard treatments or pharmacological therapies are able to prevent keloid recurrence. To reach this goal, in recent years some physical treatments have been proposed, and among them the PhotoBioModulation therapy (PBM). This work analyses the effects of a blue LED light irradiation (410-430 nm, 0.69 W/cm² power density) on human fibroblasts, isolated from both keloids and perilesional tissues. Different light doses (3.43-6.87-13.7-20.6-30.9 and 41.2 J/cm²) were tested. Biochemical assays and specific staining were used to assess cell metabolism, proliferation and viability. Micro-Raman spectroscopy was used to explore direct effects of the blue LED light on the Cytochrome C (Cyt C) oxidase. We also investigated the effects of the irradiation on ionic membrane currents by patch-clamp recordings. Our results showed that the blue LED light can modulate cell metabolism and proliferation, with a dose-dependent behavior and that these effects persist at least till 48 h after treatment. Furthermore, we demonstrated that the highest fluence value can reduce cell viability 24 h after irradiation in keloid-derived fibroblasts, while the same effect is observed 48 h after treatment in perilesional fibroblasts. Electrophysiological recordings showed that the medium dose (20.6 J/cm²) of blue LED light induces an enhancement of voltage-dependent outward currents elicited by a depolarizing ramp protocol. Overall, these data demonstrate the potentials that PBM shows as an innovative and minimally-invasive approach in the management of hypertrophic scars and keloids, in association with current treatments.

Collagen-Derived Di-Peptide, Prolylhydroxyproline (Pro-Hyp): A New Low Molecular Weight Growth-Initiating Factor for Specific Fibroblasts Associated With Wound Healing

Many cells and soluble factors are involved in the wound healing process, which can be divided into inflammatory, proliferative, and remodeling phases. Fibroblasts play a crucial role in wound healing, especially during the proliferative phase, and show heterogeneity depending on lineage, tissue distribution, and extent of differentiation. Fibroblasts from tissue stem cells rather than from healthy tissues infiltrate wounds and proliferate. Some fibroblasts in the wound healing site express the mesenchymal stem cell marker, p75NTR. In the cell culture system, fibroblasts attached to collagen fibrils stop growing, even in the presence of protein growth factors, thus mimicking the quiescent nature of fibroblasts in healthy tissues. Fibroblasts in wound healing sites proliferate and are surrounded by collagen fibrils. These facts indicate presence of new growth-initiating factor for fibroblasts attached to collagen fibrils at the wound healing site, where the collagen-derived peptide, prolyl-hydroxyproline (Pro-Hyp), is generated. Pro-Hyp triggers the growth of p75NTR-positive fibroblasts cultured on collagen gel but not p75NTR-negative fibroblasts. Thus, Pro-Hyp is a low molecular weight growth-initiating factor for specific fibroblasts that is involved in the wound healing process. Pro-Hyp is also supplied to tissues by oral administration of gelatin or collagen hydrolysate. Thus, supplementation of gelatin or collagen hydrolysate has therapeutic potential for chronic wounds. Animal studies and human clinical trials have demonstrated that the ingestion of gelatin or collagen hydrolysate enhances the healing of pressure ulcers in animals and humans and improves delayed wound healing in diabetic animals. Therefore, the low molecular weight fibroblast growth-initiating factor, Pro-Hyp, plays a significant role in wound healing and has therapeutic potential for chronic wounds.

Exploring the potential of chitosan-based particles as delivery-carriers for promising antimicrobial glycolipid biosurfactants

Driven by the need to find alternatives to control Staphylococcus aureus infections, this work describes the development of chitosan-based particulate systems as carriers for antimicrobial glycolipids. By using a simple ionic gelation method stable nanoparticles were obtained showing an encapsulation efficiency of 41.1 ± 8.8 % and 74.2 ± 1.3 % and an average size of 210.0 ± 15.7 nm and 329.6 ± 8.0 nm for sophorolipids and rhamnolipids chitosan-nanoparticles, respectively. Glycolipids incorporation and particle size was correspondingly corroborated by FTIR-ATR and TEM analysis. Rhamnolipids chitosan nanoparticles (RLs-CS_p) presented the highest antimicrobial effect towards S. aureus (ATCC 25923) exhibiting a minimal inhibitory concentration of 130 μg/mL and a biofilm inhibition ability of 99 %. Additionally, RLs-CS_p did not interfere with human dermal fibroblasts (AG22719) viability and proliferation under the tested conditions. The results revealed that the RLs-CS_p were able to inhibit bacterial growth showing adequate cytocompatibility and might become, after additional studies, a valuable approach to prevent S. aureus related infections.

Comparative Analysis of the Effectiveness of Some Biological Injected Wound Healing Stimulators and Criteria for Its Evaluation

PURPOSE

To investigate the comparative effectiveness of certain biological injectable stimulants for the healing of skin wounds and criteria for its assessment.

MATERIALS AND METHODS

A comparative study of the effectiveness of mesenchymal stem cells (SC group), collagen (Collagen group), and deproteinized calf blood hemoderivative (DCBH group) was carried out using an acute wound model. Control wounds were injected with isotonic sodium chloride solution (Control group). A total of four groups (28 wounds per group) were included in the study. Aged male Wistar rats were used as experimental animals. A dynamic assessment of the wound areas and edges, microvasculature assessment via laser Doppler flowmetry, histological and morphometric analyses to determine the quantitative and qualitative fibroblasts composition, as well as the degree of newly synthesized collagen maturity, was conducted on days 0, 3, 7, and 14.

RESULTS

The administration of SCs provided a rapid but short-lasting effect, whereas the administration of collagen resulted in a delayed but long-lasting wound-healing effect. DCBH resulted in little to no effect. An increase in the perfusion volume of the wound edges accelerated the regeneration process, while the level of microcirculation did not affect the number and activity of fibroblasts. The wound healing acceleration, as well as the new collagen and stratified epithelium formation and maturation, was associated with the presence of a sufficient pool of mature and active fibroblasts in the wound, and not with the number of fibroblasts.

CONCLUSION

The present results clarify the action mechanisms of the studied drugs. In addition, the application purposes and different effects of each drug on the different wound healing phases were demonstrated. An assumption on the multi-component treatment advisability under the wound condition objective assessment possibility was made. Findings from this study may assist clinicians in making an informed transition to personalized wound management and achieve better clinical outcomes.

Notch1 signaling determines the plasticity and function of fibroblasts in diabetic wounds

Fibroblasts play a pivotal role in wound healing. However, the molecular mechanisms determining the reparative response of fibroblasts remain unknown. Here, we identify Notch1 signaling as a molecular determinant controlling the plasticity and function of fibroblasts in modulating wound healing and angiogenesis. The Notch pathway is activated in fibroblasts of diabetic wounds but not in normal skin and non-diabetic wounds. Consistently, wound healing in the FSP-1 ^+/- ;ROSA ^LSL-N1IC+/+ mouse, in which Notch1 is activated in fibroblasts, is delayed. Increased Notch1 activity in fibroblasts suppressed their growth, migration, and differentiation into myofibroblasts. Accordingly, significantly fewer myofibroblasts and less collagen were present in granulation tissues of the FSP-1 ^+/- ;ROSA ^LSL-N1IC+/+ mice, demonstrating that high Notch1 activity inhibits fibroblast differentiation. High Notch1 activity in fibroblasts diminished their role in modulating the angiogenic response. We also identified that IL-6 is a functional Notch1 target and involved in regulating angiogenesis. These findings suggest that Notch1 signaling determines the plasticity and function of fibroblasts in wound healing and angiogenesis, unveiling intracellular Notch1 signaling in fibroblasts as potential target for therapeutic intervention in diabetic wound healing.

Bidirectional regulation of i-type lysozyme on cutaneous wound healing

OBJECTIVE

This study aimed to assess the effect and mechanism of i-type lysozyme on cutaneous wound healing animal model and Multiple cell models both in vivo and in vitro.

METHODS

Therefore, to evaluate its regenerative efficacy on wound healing process, we daily applied i-type lysozyme on murine full-thickness excisional wounds. After sacrifice on indicated days, skin tissues around surgical defects were harvested and assessed for re-epithelialization, granulation tissue formation, neovascularization and remodeling. To elucidate the underlying mechanisms, i-type lysozyme was analyzed for its tissue regenerative potency on the proliferation, invasion, migration and tube formation against keratinocytes, fibroblasts and endothelial cells. Antioxidant and antimicrobial experiments were also conducted to elucidate protective ability of i-type lysozyme to wound bed.

RESULTS

It displayed excellent bi-directional regulation in wound repair, with significant acceleration of epidermal and dermal regeneration as well as the efficient attenuation of excessive collagen deposition and fibrosis in the surgical lesion. I-type lysozyme treatment augmented the proliferation and migration of HaCaT, NIH 3T3 and HUVECs, enhanced the invasion of HaCaT and HUVECs as well as accelerated tube formation of HUVECs. Additionally, it significantly recovered the proliferation of H₂O₂-damaged cells, whereas represented no microbicidal effect under effective concentration of wound healing.

CONCLUSION

Our findings demonstrate the bi-directional regulation of i-type lysozyme in wound healing process through promoting tissue regeneration while hampering scar formation, implying that it is a promising therapeutic agent for wound repair.

Molecular Action of Hydroxytyrosol in Wound Healing: An In Vitro Evidence-Based Review

Hydroxytyrosol (HT) is an essential molecule isolated from the phenolic fraction of olive (Olea europaea). HT has been implicated for its health-stimulating effect mainly due to its antioxidative capacity. The current review summarises and discusses the available evidence, related to HT activities in wound healing enhancement. The literature search of related articles published within the year 2010 to 2020 was conducted using Medline via Ebscohost, Scopus, and Google Scholar databases. Studies were limited to in vitro research regarding the role of HT in wound closure, including anti-inflammation, antimicrobial, antioxidative, and its direct effect to the cells involved in wound healing. The literature search revealed 7136 potentially relevant records were obtained from the database search. Through the screening process, 13 relevant in vitro studies investigating the role of HT in wound repair were included. The included studies reported a proangiogenic, antioxidative, antiaging, anti-inflammatory and antimicrobial effect of HT. The current in vitro evidence-based review highlights the cellular and molecular action of HT in influencing positive outcomes toward wound healing. Based on this evidence, HT is a highly recommended bioactive compound to be used as a pharmaceutical product for wound care applications.

Overview of Current Advances in Extrusion Bioprinting for Skin Applications

Bioprinting technologies, which have the ability to combine various human cell phenotypes, signaling proteins, extracellular matrix components, and other scaffold-like biomaterials, are currently being exploited for the fabrication of human skin in regenerative medicine. We performed a systematic review to appraise the latest advances in 3D bioprinting for skin applications, describing the main cell phenotypes, signaling proteins, and bioinks used in extrusion platforms. To understand the current limitations of this technology for skin bioprinting, we briefly address the relevant aspects of skin biology. This field is in the early stage of development, and reported research on extrusion bioprinting for skin applications has shown moderate progress. We have identified two major trends. First, the biomimetic approach uses cell-laden natural polymers, including fibrinogen, decellularized extracellular matrix, and collagen. Second, the material engineering line of research, which is focused on the optimization of printable biomaterials that expedite the manufacturing process, mainly involves chemically functionalized polymers and reinforcement strategies through molecular blending and postprinting interventions, i.e., ionic, covalent, or light entanglement, to enhance the mechanical properties of the construct and facilitate layer-by-layer deposition. Skin constructs manufactured using the biomimetic approach have reached a higher level of complexity in biological terms, including up to five different cell phenotypes and mirroring the epidermis, dermis and hypodermis. The confluence of the two perspectives, representing interdisciplinary inputs, is required for further advancement toward the future translation of extrusion bioprinting and to meet the urgent clinical demand for skin equivalents.

The immunologic changes during different phases of intestinal anastomotic healing

Intestinal anatomosis is a complex and multicellular process that involving three overlapped phases: exudative phase, proliferative phase, and reparative phase. Undisturbed anastomotic healings are crucial for the recovery of patients after operations but unsuccessful healings are linked with a considerable mortality. This time, we concentrate on the immunologic changes during different phases of intestinal anastomotic healing and select several major immune cells and cytokines of each phase to get a better understanding of these immunologic changes in different phases, which will be significant for more precise therapy strategies in anastomoses.

PLGF-1 contained in normal wound myofibroblast-derived microvesicles stimulated collagen production by dermal fibroblasts

During the last stages of wound healing, myofibroblasts differentiate mainly from fibroblasts. Myofibroblasts from normal skin wounds (Wmyo) can communicate with its surrounding using secreted factors. They also have the capacity to produce microvesicles (MVs), a type of extracellular vesicles, as mediators of intercellular communication. MVs cargo are potentially capable of regulating the behavior of targeted cells and tissues. The aim of this study is to evaluate the effect of Wmyo-derived MVs on dermal fibroblasts and to determine the responsible signaling molecule. Microvesicles were obtained from culture media of myofibroblasts and characterized using protein quantification, dynamic light scattering and transmission electron microscopy. Uptake of fluorescent MVs in fibroblasts was assessed by flow cytometry. Cytokines concentrations were quantified in MV samples by a multiplex ELISA. Different concentration of MVs or a selected cytokine were used as treatments over fibroblasts culture for 5 days. Following the treatments, parameters linked to the extracellular matrix were studied. Lastly, the selected cytokine was neutralized within MVs before evaluating collagen production. We showed that Wmyo derived-MVs were internalized by dermal fibroblasts. Cytokine array analysis revealed that a large amount of placental growth factor 1 (PLGF-1) (0.88 ± 0.63 pg/μg proteins in MVs) could be detected in MVs samples. Cutaneous fibroblasts treated with MVs or PLGF-1 showed significantly stimulated procollagen I level production (Fold change of 1.80 ± 0.18 and 2.07 ± 0.18, respectively). Finally, the neutralization of PLGF-1 in MVs significantly inhibited the production of procollagen I by fibroblasts. Our study shows that Wmyo derived-MVs are involved in intercellular communication by stimulating collagen production by fibroblasts during wound healing. This effect is possibly attained through PLGF-1 signalling. These findings represent a promising opportunity to gain insight into how MVs and Wmyo may mediate the healing of a skin wound.

Pholiota nameko Polysaccharides Promotes Cell Proliferation and Migration and Reduces ROS Content in H2O2-Induced L929 Cells

Pholiota nameko, a type of edible and medicinal fungus, is currently grown extensively for food and traditional medicine in China and Japan. It possesses various biological activities, such as anti-inflammatory, anti-hyperlipidemia and antitumor activities. However, P. nameko has rarely been discussed in the field of dermatology; identifying its biological activities could be beneficial in development of a new natural ingredient used in wound care. To evaluate its in vitro wound healing activities, the present study assessed the antioxidant and anti-collagenase activities of P. nameko polysaccharides (PNPs) prepared through fractional precipitation (40%, 60% and 80% (v/v)); the assessments were conducted using reducing power, hydroxyl radical scavenging activity, dichloro-dihydro-fluorescein diacetate and collagenase activity assays. The ability of PNPs to facilitate L929 fibroblast cell proliferation and migration was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and scratch assays. The findings indicated that, among all fractions, PNP-80 showed the best antioxidant and anti-collagenase activity, as measured by their reducing power (IC₅₀ of PNP-80 was 2.43 ± 0.17 mg/mL), the hydroxyl radical scavenging (IC₅₀ of PNP-80 was 2.74 ± 0.11 mg/mL) and collagenase activity assay, and significantly reduced cellular ROS content, compared with that of H₂O₂-induced L929 cells. Moreover, PNP-80 significantly promoted L929 fibroblast proliferation and migration, compared with the control group. Overall, we suggested that PNP-80 could be a promising candidate for further evaluation of its potential application on wound healing.

Cellular Senescence as the Pathogenic Hub of Diabetes-Related Wound Chronicity

Diabetes is constantly increasing at a rate that outpaces genetic variation and approaches to pandemic magnitude. Skin cells physiology and the cutaneous healing response are progressively undermined in diabetes which predisposes to lower limb ulceration, recidivism, and subsequent lower extremities amputation as a frightened complication. The molecular operators whereby diabetes reduces tissues resilience and hampers the repair mechanisms remain elusive. We have accrued the notion that diabetic environment embraces preconditioning factors that definitively propel premature cellular senescence, and that ulcer cells senescence impair the healing response. Hyperglycemia/oxidative stress/mitochondrial and DNA damage may act as major drivers sculpturing the senescent phenotype. We review here historical and recent evidences that substantiate the hypothesis that diabetic foot ulcers healing trajectory, is definitively impinged by a self-expanding and self-perpetuative senescent cells society that drives wound chronicity. This society may be fostered by a diabetic archetypal secretome that induces replicative senescence in dermal fibroblasts, endothelial cells, and keratinocytes. Mesenchymal stem cells are also susceptible to major diabetic senescence drivers, which accounts for the inability of these cells to appropriately assist in diabetics wound healing. Thus, the use of autologous stem cells has not translated in significant clinical outcomes. Novel and multifaceted therapeutic approaches are required to pharmacologically mitigate the diabetic cellular senescence operators and reduce the secondary multi-organs complications. The senescent cells society and its adjunctive secretome could be an ideal local target to manipulate diabetic ulcers and prevent wound chronification and acute recidivism. This futuristic goal demands harnessing the diabetic wound chronicity epigenomic signature.

Topical application of Cinnamomum hydroethanolic extract improves wound healing by enhancing re-epithelialization and keratin biosynthesis in streptozotocin-induced diabetic mice

Context: Cinnamomum verum J. Presl. (Lauraceae) has a high number of polyphenols with insulin-like activity, increases glucose utilization in animal muscle, and might be beneficial for diabetic patients.Objective: This study evaluated the effectiveness of an ointment prepared from Cinnamomum verum hydroethanolic extract on wound healing in diabetic mice.Materials and methods: A total of 54 male BALB/c mice were divided into three groups: (1) diabetic non-treated group mice that were treated with soft yellow paraffin, (2 and 3) mice that were treated with 5 and 10% C. verum. Two circular full-thickness excisional wounds were created in each mouse, and the trial lasted for 16 d following induction of the wound. Further evaluation was made on the wound contraction ratio, histopathology parameters and mRNA levels of cyclin D1, insulin-like growth factor 1 (IGF-1), glucose transporter-1 (GLUT-1), total antioxidant capacity, and malondialdehyde of granulation tissue contents. HPLC apparatus was utilized to identify the compounds.Results: The HPLC data for cinnamon hydroethanolic extract identified cinnamaldehyde (11.26%) and 2-hydroxyl cinnamaldehyde (6.7%) as the major components. A significant increase was observed in wound contraction ratio, fibroblast proliferation, collagen deposition, re-epithelialization and keratin biosynthesis in the C. verum-treated groups in comparison to the diabetic non-treated group (p < 0.05). The expression level of cyclin D1, IGF1, GLUT 1 and antioxidant capacity increased in the C. verum-treated groups in comparison to the diabetic non-treated group (p < 0.05).Conclusions: Topical administration of C. verum accelerated wound healing and can possibly be employed in treating the wounds of diabetic patients.