Advances in scarless foetal wound healing and prospects for scar reduction in adults

Enhanced myofibroblast differentiation of eMSCs in intrauterine adhesions

BACKGROUND

Intrauterine adhesions (IUA) is one of the most common gynecological diseases and main causes of uterine infertility. Among proposed hypotheses on IUA development, the reduced endometrial regeneration resulting from loss of functional stem cells has been proposed as the key factor affecting the IUA prognosis. However, the underlying mechanisms mostly remain unclear. Because the eMSCs (endometrial mesenchymal stem/stromal cells) play a critical role in both supporting the gland development and also preparing the environment for embryo implantation through decidualization, the characteristics and functions were compared between the eMSCs derived from IUA and non-IUA patients, to uncover the important roles of eMSCs in IUA and also the underlying mechanisms.

METHODS

Endometrium biopsies were collected from IUA patients and controls. The fibrosis features and eMSC distributions were investigated with IHC (immunohistochemistry). Then the eMSCs were isolated and their functions and characteristics were analyzed in vitro.

RESULTS

Our results indicate that the scar tissues in IUA are characterized with hyper-activation of pro-fibrotic fibroblast and myo-differentiation, along with reduced number of eMSCs. The isolated eMSCs from IUA and controls show similar functions from the perspectives of cell morphology, proliferation, colony formation, exosome secretion, positive ratio of eMSC markers and conventional MSC markers, tri-differentiation efficiency, the ability of suppressing lymphocyte proliferation, cell aging, and promoting vascular tube formation. However, the eMSCs from IUA have reduced levels of decidualization and higher levels of cell migration, invasion, and also myofibroblast differentiation. Further investigations indicate that the TGF-β pathway, which is the major inducer of myofibroblast differentiation, is up-regulated and responsible for the enhanced myofibroblast differentiation potential of eMSCs from IUA.

CONCLUSIONS

In conclusion, we have demonstrated here that the scar tissues in IUA biopsy are characterized with enhanced differentiation of pro-fibrotic fibroblast and myofibroblast. The number of eMSCs is reduced in IUA tissues, and their myofibroblast differentiation capability is increased.

Polysaccharide-Based Injectable Hydrogel Loaded with Quercetin Promotes Scarless Healing of Burn Wounds by Reducing Inflammation

Moisture loss, infection, and severe inflammatory reactions are the primary factors affecting burn wound healing and leading to scar formation. Herein, we developed a quercetin-loaded polysaccharide-based injectable hydrogel (named PECE). The PECE consists of oxidized sodium alginate (OAlg) coupled with chitosan (CS) via Schiff bases and electrostatic interactions, while Que is incorporated via hydrogen bonding. Benefiting from the hydroxyl and carboxyl groups, PECE features distinguished moisturizing ability. Additionally, the sustained release of Que imparts remarkable antibacterial activity against Escherichia coli and Staphylococcus aureus. Likewise, PECE demonstrates favorable in vitro anti-inflammatory capacity as released Que significantly downregulates pro-inflammatory factors (IL-6 and TNF-α) secreted by RAW 264.7 macrophages. More importantly, in a rat model of deep second-degree burn wounds, PECE effectively inhibits wound infection, reduces inflammation, and promotes angiogenesis and collagen deposition, ultimately minimizing scar formation. Overall, this work presents a promising strategy for scarless healing of burn wounds.

Melatonin's Impact on Wound Healing

Melatonin (5-methoxy-N-acetyltryptamine) is an indoleamine compound that plays a critical role in the regulation of circadian rhythms. While melatonin is primarily synthesized from the amino acid tryptophan in the pineal gland of the brain, it can also be produced locally in various tissues, such as the skin and intestines. Melatonin's effects in target tissues can be mediated through receptor-dependent mechanisms. Additionally, melatonin exerts various actions via receptor-independent pathways. In biological systems, melatonin and its endogenous metabolites often produce similar effects. While injuries are common in daily life, promoting optimal wound healing is essential for patient well-being and healthcare outcomes. Beyond regulating circadian rhythms as a neuroendocrine hormone, melatonin may enhance wound healing through (1) potent antioxidant properties, (2) anti-inflammatory actions, (3) infection control, (4) regulation of vascular reactivity and angiogenesis, (5) analgesic (pain-relieving) effects, and (6) anti-pruritic (anti-itch) effects. This review aims to provide a comprehensive overview of scientific studies that demonstrate melatonin's potential roles in supporting effective wound healing.

Repair and regeneration: ferroptosis in the process of remodeling and fibrosis in impaired organs

As common clinical-pathological processes, wound healing and tissue remodelling following injury or stimulation are essential topics in medical research. Promoting the effective healing of prolonged wounds, improving tissue repair and regeneration, and preventing fibrosis are important and challenging issues in clinical practice. Ferroptosis, which is characterized by iron overload and lipid peroxidation, is a nontraditional form of regulated cell death. Emerging evidence indicates that dysregulated metabolic pathways and impaired iron homeostasis play important roles in various healing and regeneration processes via ferroptosis. Thus, we review the intrinsic mechanisms of tissue repair and remodeling via ferroptosis in different organs and systems under various conditions, including the inflammatory response in skin wounds, remodeling of joints and cartilage, and fibrosis in multiple organs. Additionally, we summarize the common underlying mechanisms, key molecules, and targeted drugs for ferroptosis in repair and regeneration. Finally, we discuss the potential of therapeutic agents, small molecules, and novel materials emerging for targeting ferroptosis to promote wound healing and tissue repair and attenuate fibrosis.

Loss of the ability to regenerate body appendages in vertebrates: from side effects of evolutionary innovations to gene loss

The ability to regenerate large body appendages is an ancestral trait of vertebrates, which varies across different animal groups. While anamniotes (fish and amphibians) commonly possess this ability, it is notably restricted in amniotes (reptiles, birds, and mammals). In this review, we explore the factors contributing to the loss of regenerative capabilities in amniotes. First, we analyse the potential negative impacts on appendage regeneration caused by four evolutionary innovations: advanced immunity, skin keratinization, whole-body endothermy, and increased body size. These innovations emerged as amniotes transitioned to terrestrial habitats and were correlated with a decline in regeneration capability. Second, we examine the role played by the loss of regeneration-related enhancers and genes initiated by these innovations in the fixation of an inability to regenerate body appendages at the genomic level. We propose that following the cessation of regenerative capacity, the loss of highly specific regeneration enhancers could represent an evolutionarily neutral event. Consequently, the loss of such enhancers might promptly follow the suppression of regeneration as a side effect of evolutionary innovations. By contrast, the loss of regeneration-related genes, due to their pleiotropic functions, would only take place if such loss was accompanied by additional evolutionary innovations that compensated for the loss of pleiotropic functions unrelated to regeneration, which would remain even after participation of these genes in regeneration was lost. Through a review of the literature, we provide evidence that, in many cases, the loss in amniotes of genes associated with body appendage regeneration in anamniotes was significantly delayed relative to the time when regenerative capability was lost. We hypothesise that this delay may be attributed to the necessity for evolutionary restructuring of developmental mechanisms to create conditions where the loss of these genes was a beneficial innovation for the organism. Experimental investigation of the downregulation of genes involved in the regeneration of body appendages in anamniotes but absent in amniotes offers a promising avenue to uncover evolutionary innovations that emerged from the loss of these genes. We propose that the vast majority of regeneration-related genes lost in amniotes (about 150 in humans) may be involved in regulating the early stages of limb and tail regeneration in anamniotes. Disruption of this stage, rather than the late stage, may not interfere with the mechanisms of limb and tail bud development during embryogenesis, as these mechanisms share similarities with those operating in the late stage of regeneration. Consequently, the most promising approach to restoring regeneration in humans may involve creating analogs of embryonic limb buds using stem cell-based tissue-engineering methods, followed by their transfer to the amputation stump. Due to the loss of many genes required specifically during the early stage of regeneration, this approach may be more effective than attempting to induce both early and late stages of regeneration directly in the stump itself.

Natural products for the treatment of hypertrophic scars: Preclinical and clinical studies

Hypertrophic scarring (HS) is a complication of wound healing that causes physiological and psychological distress in patients. However, the possible mechanism underlying HS is not fully understood, and there is no gold standard for its treatment. Natural products are more effective, economical, convenient, and safe than existing drugs, and they have a wide application prospect. However, there is a lack of literature on this topic, so we reviewed in vivo, in vitro, and clinical studies and screened natural products showing beneficial effects on HS that can become potential therapeutic agents for HS to fill in the gaps in the field. In addition, we discussed the drug delivery systems related to these natural products and their mechanisms in the treatment of HS. Generally speaking, natural products inhibit inflammation, myofibroblast activation, angiogenesis, and collagen accumulation by targeting interleukins, tumor necrosis factor-α, vascular endothelial growth factors, platelet-derived growth factors, and matrix metalloproteinases, so as to play an anti-HS effects of natural products are attributed to their anti-inflammatory, anti-proliferative, anti-angiogenesis, and pro-apoptotic (enhancing apoptosis and autophagy) roles, thus treating HS. We also screened the potential therapeutic targets of these natural compounds for HS through network pharmacology and constructed a protein-protein interaction (PPI) network, which may provide clues for the pharmacological mechanism of natural products in treating this disease and the development and application of drugs.

Delayed Collagen Production without Myofibroblast Formation Contributes to Reduced Scarring in Adult Skin Microwounds

In adult mammals, wound healing predominantly follows a fibrotic pathway, culminating in scar formation. However, cutaneous microwounds generated through fractional photothermolysis, a modality that produces a constellation of microthermal zones, exhibit a markedly different healing trajectory. Our study delineates the cellular attributes of these microthermal zones, underscoring a temporally limited, subclinical inflammatory milieu concomitant with rapid re-epithelialization within 24 hours. This wound closure is facilitated by the activation of genes associated with keratinocyte migration and differentiation. In contrast to macrothermal wounds, which predominantly heal through a robust myofibroblast-mediated collagen deposition, microthermal zones are characterized by absence of wound contraction and feature delayed collagen remodeling, initiating 5-6 weeks after injury. This distinct wound healing is characterized by a rapid re-epithelialization process and a muted inflammatory response, which collectively serve to mitigate excessive myofibroblast activation. Furthermore, we identify an initial reparative phase characterized by a heterogeneous extracellular matrix protein composition, which precedes the delayed collagen remodeling. These findings extend our understanding of cutaneous wound healing and may have significant implications for the optimization of therapeutic strategies aimed at mitigating scar formation.

Acellular dermal matrix in urethral reconstruction

The management of severe urethral stricture has always posed a formidable challenge. Traditional approaches such as skin flaps, mucosal grafts, and urethroplasty may not be suitable for lengthy and intricate strictures. In the past two decades, tissue engineering solutions utilizing acellular dermal matrix have emerged as potential alternatives. Acellular dermal matrix (ADM) is a non-immunogenic biological collagen scaffold that has demonstrated its ability to induce layer-by-layer tissue regeneration. The application of ADM in urethral reconstruction through tissue engineering has become a practical endeavor. This article provides an overview of the preparation, characteristics, advantages, and disadvantages of ADM along with its utilization in urethral reconstruction via tissue engineering.

[Research progress on the role of adipose-derived stem cell exosomes in skin scar formation]

The adipose-derived stem cell exosomes are subcellular structures of adipose stem cells. They are nano-sized membrane vesicles that can transport various cell components and act on target cells by paracrine, and they play an important role in the exchanges of substance and information between cells. Scar healing is the commonest way of healing after skin tissue injury. Pathological scar can not only cause movement dysfunction, but also lead to deformity, which affects the appearance of patients and brings life and mental pressure to the patients. In recent years, many researches have shown that the adipose-derived stem cell exosomes contain a variety of bioactive molecules, which play an important role in reducing scar formation and scar-free wound healing, by affecting the proliferation and migration of fibroblasts and the composition of extracellular matrix. This article reviewed the recent literature on the roles and mechanisms of adipose-derived stem cell exosomes in scar formation, and prospected the future application and development of adipose-derived stem cell exosomes in scar treatment.

[Effects of porcine urinary bladder matrix on motility and polarization of bone marrow-derived macrophages in mice]

Objective: To explore the effects of porcine urinary bladder matrix (UBM) on the motility and polarization of bone marrow-derived macrophages in mice, so as to provide evidence for the rational selection of stent in clinical wound repair. Methods: The method of experimental research was used. The microstructure of porcine UBM and absorbable dressing was observed under scanning electron microscope. Polyacrylamide gel electrophoresis was used to observe the protein distribution of the two stent extracts. The primary macrophages were induced from bone marrow-derived cells isolated from six 6-8-week-old male C57BL/6J mice (mouse age, sex, and strain, the same below) and identified. Three batches of macrophages were divided into porcine UBM extract group and absorbable dressing extract group. The cells in each group were cultured with Dulbecco's modified Eagle medium/F12 medium containing the corresponding extracts. The cell migration rate was detected and calculated on 1, 3, and 7 d after scratching by scratch test. The number of migrated cells at 12 and 24 h of culture was detected by Transwell experiment. The percentages of CD206 and CD86 positive cells at 24 h of culture was detected by flow cytometer. The numbers of sample in the above cell experiments were all 3. An incision was prepared on the left and right back of twelve mice, respectively. The left incision of each mouse was included in porcine UBM group and the right incision was included in absorbable dressing group, and the corresponding stents were implanted into the incisions respectively. On post operation day (POD) 7 and 14, the number of inflammatory cells infiltrated in the stent was detected by hematoxylin-eosin staining; the number of F4/80, transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), and matrix metalloprotein-9 (MMP-9) positive cells and type Ⅰ collagen deposition in stents were observed by immunohistochemistry; the percentages of F4/80, CD86, and CD206 positive cells were observed by immunofluorescence staining. The numbers of sample in the above animal experiments were all 6. Data were statistically analyzed with analysis of variance for factorial design, analysis of variance for repeated measurement, and independent sample t test. Results: Porcine UBM has a dense basement membrane structure on one side and porous propria containing a fibrous structures on the other. Both sides of the absorbable dressing had three-dimensional porous structure. In the molecular weight range of (50-70)×103, multiple non-type Ⅰ collagen bands appeared in the lanes of porcine UBM extract, while no obvious bands appeared in the lanes of absorbable dressing extract. It had been identified that mouse bone marrow-derived cells had been successfully induced into macrophages. The cell migration rates in porcine UBM extract group were significantly higher than those in absorbable dressing extract group on 1, 3, and 7 d after scratching (with t values of 15.31, 19.76, and 20.58, respectively, P<0.05). The numbers of migrated cells in porcine UBM extract group were significantly more than those in absorbable dressing extract group at 12 and 24 h of culture (with t values of 12.20 and 33.26, respectively, P<0.05). At 24 h of culture, the percentage of CD86 positive cells in porcine UBM extract group ((1.27±0.19)%) was significantly lower than (7.34±0.14)% in absorbable dressing extract group (t=17.03, P<0.05);the percentage of CD206 positive cells in porcine UBM extract group was (73.4±0.7)%, significantly higher than (32.2±0.5)% in absorbable dressing extract group (t=119.10, P<0.05). On POD 7 and 14, the numbers of inflammatory cells infiltrated in the stents in porcine UBM group was significantly more than those in absorbable dressing group (with t values of 6.58 and 10.70, respectively, P<0.05). On POD 7 and 14, the numbers of F4/80, TGF-β1, VEGF, and MMP-9 positive cells in the stents in porcine UBM group were significantly more than those in absorbable dressing group (with t values of 46.11, 40.69, 13.90, 14.15, 19.79, 32.93, 12.16, and 13.21, respectively, P<0.05); type Ⅰ collagen deposition in the stents in porcine UBM group was more pronounced than that in absorbable dressing group; the percentages of CD206 positive cells in the stents in porcine UBM group were significantly higher than those in absorbable dressing group (with t values of 5.05 and 4.13, respectively, P<0.05), while the percentages of CD86 positive cells were significantly lower than those in absorbable dressing group (with t values of 20.90 and 19.64, respectively, P<0.05), and more M2-type macrophages were seen in the stents in porcine UBM group and more M1-type macrophages were seen in the stents in absorbable dressing group. Conclusions: Porcine UBM can enhance macrophage motility, induce M2 polarization and paracrine function, create a microenvironment containing growth factors such as TGF-β1 and MMP-9 tissue remodeling molecules, and promote tissue regeneration and extracellular matrix remodeling in mice.

New insights into balancing wound healing and scarless skin repair

Scars caused by skin injuries after burns, wounds, abrasions and operations have serious physical and psychological effects on patients. In recent years, the research of scar free wound repair has been greatly expanded. However, understanding the complex mechanisms of wound healing, in which various cells, cytokines and mechanical force interact, is critical to developing a treatment that can achieve scarless wound healing. Therefore, this paper reviews the types of wounds, the mechanism of scar formation in the healing process, and the current research progress on the dual consideration of wound healing and scar prevention, and some strategies for the treatment of scar free wound repair.

BMP3 inhibits TGFβ2-mediated myofibroblast differentiation during wound healing of the embryonic cornea

Often acute damage to the cornea initiates drastic tissue remodeling, resulting in fibrotic scarring that disrupts light transmission and precedes vision impairment. Very little is known about the factors that can mitigate fibrosis and promote scar-free cornea wound healing. We previously described transient myofibroblast differentiation during non-fibrotic repair in an embryonic cornea injury model. Here, we sought to elucidate the mechanistic regulation of myofibroblast differentiation during embryonic cornea wound healing. We found that alpha-smooth muscle actin (αSMA)-positive myofibroblasts are superficial and their presence inversely correlates with wound closure. Expression of TGFβ2 and nuclear localization of pSMAD2 were elevated during myofibroblast induction. BMP3 and BMP7 were localized in the corneal epithelium and corresponded with pSMAD1/5/8 activation and absence of myofibroblasts in the healing stroma. In vitro analyses with corneal fibroblasts revealed that BMP3 inhibits the persistence of TGFβ2-induced myofibroblasts by promoting disassembly of focal adhesions and αSMA fibers. This was confirmed by the expression of vinculin and pFAK. Together, these data highlight a mechanism to inhibit myofibroblast persistence during cornea wound repair.

Creating an Optimal In Vivo Environment to Enhance Outcomes Using Cell Therapy to Repair/Regenerate Injured Tissues of the Musculoskeletal System

Following most injuries to a musculoskeletal tissue which function in unique mechanical environments, an inflammatory response occurs to facilitate endogenous repair. This is a process that usually yields functionally inferior scar tissue. In the case of such injuries occurring in adults, the injury environment no longer expresses the anabolic processes that contributed to growth and maturation. An injury can also contribute to the development of a degenerative process, such as osteoarthritis. Over the past several years, researchers have attempted to use cellular therapies to enhance the repair and regeneration of injured tissues, including Platelet-rich Plasma and mesenchymal stem/medicinal signaling cells (MSC) from a variety of tissue sources, either as free MSC or incorporated into tissue engineered constructs, to facilitate regeneration of such damaged tissues. The use of free MSC can sometimes affect pain symptoms associated with conditions such as OA, but regeneration of damaged tissues has been challenging, particularly as some of these tissues have very complex structures. Therefore, implanting MSC or engineered constructs into an inflammatory environment in an adult may compromise the potential of the cells to facilitate regeneration, and neutralizing the inflammatory environment and enhancing the anabolic environment may be required for MSC-based interventions to fulfill their potential. Thus, success may depend on first eliminating negative influences (e.g., inflammation) in an environment, and secondly, implanting optimally cultured MSC or tissue engineered constructs into an anabolic environment to achieve the best outcomes. Furthermore, such interventions should be considered early rather than later on in a disease process, at a time when sufficient endogenous cells remain to serve as a template for repair and regeneration. This review discusses how the interface between inflammation and cell-based regeneration of damaged tissues may be at odds, and outlines approaches to improve outcomes. In addition, other variables that could contribute to the success of cell therapies are discussed. Thus, there may be a need to adopt a Precision Medicine approach to optimize tissue repair and regeneration following injury to these important tissues.

Mechanisms of Scarless Repair at Time of Menstruation: Insights From Mouse Models

The human endometrium is a remarkable tissue which may experience up to 400 cycles of hormone-driven proliferation, differentiation and breakdown during a woman's reproductive lifetime. During menstruation, when the luminal portion of tissue breaks down, it resembles a bloody wound with piecemeal shedding, exposure of underlying stroma and a strong inflammatory reaction. In the absence of pathology within a few days the integrity of the tissue is restored without formation of a scar and the endometrium is able to respond appropriately to subsequent endocrine signals in preparation for establishment of pregnancy if fertilization occurs. Understanding mechanisms regulating scarless repair of the endometrium is important both for design of therapies which can treat conditions where this is aberrant (heavy menstrual bleeding, fibroids, endometriosis, Asherman's syndrome) as well as to provide new information that might allow us to reduce fibrosis and scar formation in other tissues. Menstruation only occurs naturally in species that exhibit spontaneous stromal cell decidualization during the fertile cycle such as primates (including women) and the Spiny mouse. To take advantage of genetic models and detailed time course analysis, mouse models of endometrial shedding/repair involving hormonal manipulation, artificial induction of decidualization and hormone withdrawal have been developed and refined. These models are useful in modeling dynamic changes across the time course of repair and have recapitulated key features of endometrial repair in women including local hypoxia and immune cell recruitment. In this review we will consider the evidence that scarless repair of endometrial tissue involves changes in stromal cell function including mesenchyme to epithelial transition, epithelial cell proliferation and multiple populations of immune cells. Processes contributing to endometrial fibrosis (Asherman's syndrome) as well as scarless repair of other tissues including skin and oral mucosa are compared to that of menstrual repair.

A hybrid hydrogel composed of chitin and β-glucan for effectively management of wound healing and scarring

Non-functional scar commonly forms after the skin injury. At present, most of the clinical treatments for scar eradication are typically with long treatment courses, low curative effects and expensive. In...

Cutting into wound repair

The skin is home to an assortment of fibroblastic lineages that shape the wound repair response toward scars or regeneration. In this review, we discuss the distinct embryonic origins, anatomic locations, and functions of fibroblastic lineages, and how these distinct lineages of fibroblasts dictate the skin's wound response across injury depths, anatomic locations, and embryonic development to promote either scarring or regeneration. We highlight the supportive role of the fascia in dictating scarring outcomes; we then discuss recent findings that indicate fascia mobilization by its resident fibroblasts supersede the classical de novo deposition program of wound matrix formation. These recent findings reconfigure our traditional view of wound repair and present exciting new therapeutic avenues to treat scarring and fibrosis across a range of medical settings.

COVID-19 and pulmonary fibrosis: therapeutics in clinical trials, repurposing, and potential development

In 2019, an unprecedented disease named coronavirus disease 2019 (COVID-19) emerged and spread across the globe. Although the rapid transmission of COVID-19 has resulted in thousands of deaths and severe lung damage, conclusive treatment is not available. However, three COVID-19 vaccines have been authorized, and two more will be approved soon, according to a World Health Organization report on December 12, 2020. Many COVID-19 patients show symptoms of acute lung injury that eventually leads to pulmonary fibrosis. Our aim in this article is to present the relationship between pulmonary fibrosis and COVID-19, with a focus on angiotensin converting enzyme-2. We also evaluate the radiological imaging methods computed tomography (CT) and chest X-ray (CXR) for visualization of patient lung condition. Moreover, we review possible therapeutics for COVID-19 using four categories: treatments related and unrelated to lung disease and treatments that have and have not entered clinical trials. Although many treatments have started clinical trials, they have some drawbacks, such as short-term and small-group testing, that need to be addressed as soon as possible.

Advances in scarless foetal wound healing and prospects for scar reduction in adults

Healing after mammalian skin injury involves the interaction between numerous cellular constituents and regulatory factors, which together form three overlapping phases: an inflammatory response, a proliferation phase and a remodelling phase. Any slight variation in these three stages can substantially alter the healing process and resultant production of scars. Of particular significance are the mechanisms responsible for the scar‐free phenomenon observed in the foetus. Uncovering such mechanisms would offer great expectations in the treatment of scars and therefore represents an important area of investigation. In this review, we provide a comprehensive summary of studies on injury‐induced skin regeneration within the foetus. The information contained in these studies provides an opportunity for new insights into the treatment of clinical scars based on the cellular and molecular processes involved.