Lumican alleviates hypertrophic scarring by suppressing integrin-FAK signaling

Biomimetic strategies for the deputization of proteoglycan functions

Proteoglycans (PGs), which have glycosaminoglycan chains attached to their protein cores, are essential for maintaining the morphology and function of healthy body tissues. Extracellular PGs perform various functions, classified into the following four categories: i) the modulation of tissue mechanical properties; ii) the regulation and protection of the extracellular matrix; iii) protein sequestration; and iv) the regulation of cell signaling. The depletion of PGs may significantly impair tissue function, encompassing compromised mechanical characteristics and unregulated inflammatory responses. Since PGs play critical roles in the function of healthy tissues and their synthesis is complex, the development of PG mimetic molecules that recapitulate PG functions for tissue engineering and therapeutic applications has attracted the interest of researchers for more than 20 years. These approaches have ranged from semisynthetic graft copolymers to recombinant PG domains produced by cells that have undergone genetic modifications. This review discusses some essential extracellular PG functions and approaches to mimicking these functions.

Integrative Analysis of Lactylome and Proteome of Hypertrophic Scar To Identify Pathways or Proteins Associated with Disease Development

Lactylation (Kla), a recently discovered post-translational modification derived from lactate, plays crucial roles in various cellular processes. However, the specific influence of lactylation on the biological processes underlying hypertrophic scar formation remains unclear. In this study, we present a comprehensive profiling of the lactylome and proteome in both hypertrophic scars and adjacent normal skin tissues. A total of 1023 Kla sites originating from 338 nonhistone proteins were identified based on lactylome analysis. Proteome analysis in hypertrophic scar and adjacent skin samples revealed the identification of 2008 proteins. It is worth noting that Kla exhibits a preference for genes associated with ribosome function as well as glycolysis/gluconeogenesis in both normal skin and hypertrophic scar tissues. Furthermore, the functional enrichment analysis demonstrated that differentially lactyled proteins are primarily involved in proteoglycans, HIF-1, and AMPK signaling pathways. The combined analysis of the lactylome and proteome data highlighted a significant upregulation of 14 lactylation sites in hypertrophic scar tissues. Overall, our investigation unveiled the significant involvement of protein lactylation in the regulation of ribosome function as well as glycolysis/gluconeogenesis, potentially contributing to the formation of hypertrophic scars.

Lumican, a Multifunctional Cell Instructive Biomarker Proteoglycan Has Novel Roles as a Marker of the Hypercoagulative State of Long Covid Disease

This study has reviewed the many roles of lumican as a biomarker of tissue pathology in health and disease. Lumican is a structure regulatory proteoglycan of collagen-rich tissues, with cell instructive properties through interactions with a number of cell surface receptors in tissue repair, thereby regulating cell proliferation, differentiation, inflammation and the innate and humoral immune systems to combat infection. The exponential increase in publications in the last decade dealing with lumican testify to its role as a pleiotropic biomarker regulatory protein. Recent findings show lumican has novel roles as a biomarker of the hypercoagulative state that occurs in SARS CoV-2 infections; thus, it may also prove useful in the delineation of the complex tissue changes that characterize COVID-19 disease. Lumican may be useful as a prognostic and diagnostic biomarker of long COVID disease and its sequelae.

Impaired healing in an incision wound in corneal stroma in a lumican-null mouse

PURPOSE

We investigated healing pattern of an incisional wound in corneal stroma of lumican-null (KO) mice.

METHODS

C57BL/6 mice (wild-type, WT) and lumican-null (knockout, KO) mice were used. A linear full-thickness incision was produced in one cornea of each mouse. After intervals of healing, the corneas were processed for the following analyses. Histology was employed to measure the distance between each edge of the disrupted Descemet's membrane at the center of the cornea. Immunohistochemistry and real-time RT-PCR were employed to evaluate the expression of wound healing-related components in the tissue. Cultured ocular fibroblasts were obtained from cornea and sclera of WT and KO postnatal day 1 pups. The cells were subjected to examination for cell proliferation and expression of wound healing-related gene products. In vitro gel contraction assay was used to asses cell contractile activity of WT and KO cells.

RESULTS

At day 5 of incision, the distance between the disrupted Descemet's membrane was larger in a KO mouse as compared with a WT mouse. Myofibroblast appearance in the wound was suppressed by the loss of lumican. The loss of lumican downregulated TGFβ1's effects on mRNA expression of α-smooth muscle actin and collagen Ia1 in cultured ocular fibroblasts. Cell proliferation rate increased in injured stroma, which was further supported by in vitro datum of cell proliferation augmentation by the loss of lumican. Loss of lumican suppressed cell-mediated gel contraction.

CONCLUSION

Loss of lumican perturbs the healing of penetrating incision in mouse corneal stroma in association with suppression of myofibroblast generation.

The endothelial-to-mesenchymal transition changes the focal adhesion site proteins levels and the SLRP-lumican level in HMEC-1 cell line

Scleroderma, the chronic autoimmune disease is a consequence of inflammation in the connective tissue. Prolonged duration affects formation of compact connective tissue strands (scarring) within the target organ. Endothelial cells undergoing endothelial-to-mesenchymal transition (EndMT) are the source of fibroblast phenotype-resembling cells. EndMT contributes to reorganization of the focal adhesion proteins (FA), including integrins, and intensive extracellular matrix (ECM) remodelling. However, in endothelial cells, the relationship between EndMT and the interaction of integrin receptors with lumican - a component of ECM, is still unclear. Our findings indicate that at the early stages of EndMT caused by Snail-1 transcription factor overexpression, the level of the β1 integrin subunit and its phosphorylation are elevated. Simultaneously, the changes in the level of proteins that build FAs and promote activation of integrin receptors as well as a decrease in lumican quantity were observed. These modulations contributed to increased migration of human microvascular endothelial cells, HMEC-1. Our findings were achieved by WB, ELISA and wound healing assay. Taken altogether, transfection of HMEC-1 cells with Snail-1 plasmids inducing the early stages of EndMT results in the increase of total FAK and integrin β1 phosphorylation as well as cell migration: phenomena which are modulated by interaction with lumican.

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.

The Biology of Extracellular Matrix Proteins in Hypertrophic Scarring

Significance: Hypertrophic scars (HTS) are a fibroproliferative disorder that occur following deep dermal injury and affect up to 72% of burn patients. These scars result in discomfort, impaired mobility, disruption of normal function and cosmesis, and significant psychological distress. Currently, there are no satisfactory methods to treat or prevent HTS, as the cellular and molecular mechanisms are complex and incompletely understood. This review summarizes the biology of proteins in the dermal extracellular matrix (ECM), which are involved in wound healing and hypertrophic scarring. Recent Advances: New basic research continues toward understanding the diversity of cellular and molecular mechanisms of normal wound healing and hypertrophic scarring. Broadening the understanding of these mechanisms creates insight into novel methods for preventing and treating HTS. Critical Issues: Although there is an abundance of research conducted on collagen in the ECM and its relationship to HTS, there is a significant gap in understanding the role of proteoglycans and their specific isoforms in dermal fibrosis. Future Directions: Exploring the biological roles of ECM proteins and their unique isoforms in HTS, mature scars, and normal skin will further the understanding of abnormal wound healing and create a more robust understanding of what constitutes dermal fibrosis. Research into the biological roles of ECM protein isoforms and their regulation during wound healing warrants a more extensive investigation to identify their distinct biological functions in cellular processes and outcomes.

Recent Advances in Experimental Burn Models

Experimental burn models are essential tools for simulating human burn injuries and exploring the consequences of burns or new treatment strategies. Unlike clinical studies, experimental models allow a direct comparison of different aspects of burns under controlled conditions and thereby provide relevant information on the molecular mechanisms of tissue damage and wound healing, as well as potential therapeutic targets. While most comparative burn studies are performed in animal models, a few human or humanized models have been successfully employed to study local events at the injury site. However, the consensus between animal and human studies regarding the cellular and molecular nature of systemic inflammatory response syndrome (SIRS), scarring, and neovascularization is limited. The many interspecies differences prohibit the outcomes of animal model studies from being fully translated into the human system. Thus, the development of more targeted, individualized treatments for burn injuries remains a major challenge in this field. This review focuses on the latest progress in experimental burn models achieved since 2016, and summarizes the outcomes regarding potential methodological improvements, assessments of molecular responses to injury, and therapeutic advances.

Time-dependent conformational analysis of ALK5-lumican complex in presence of graphene and graphene oxide employing molecular dynamics and MMPBSA calculation

Lumican, an extracellular matrix protein avails wound healing by binding to ALK5 membrane receptor (TGF-beta receptor I). Their interaction enables epithelialization and substantiates rejuvenation of injured tissue. To enrich permanence of ALK5-lumican interaction, we employed graphene and graphene oxide co-factors. Herein, this study explicates concomitancy of graphene and graphene oxide with ALK5-lumican. We performed an in silico approach involving molecular modelling, molecular docking, molecular dynamics for 200 ns, DSSP analysis and MMPBSA calculations. Results of molecular dynamics indicate cofactors influential in altering bioactive site of lumican than ALK5. Similarly, MMPBSA calculations unveiled binding energy of apoenzyme as -108.09 kcal/mol, holoenzyme (G) as -79.20 kcal/mol and holoenzyme (GO) as -114.33 kcal/mol. This concludes graphene oxide lucrative in enhancing binding energy of ALK5-lumican in holoenzyme (GO) via coil formation of Lum C₁₃ domain. In contrast, graphene reduced binding energy of ALK5-lumican in holoenzyme (G) modifying Lum C₁₃ into beta sheets. MMPBSA residual contribution analysis of Lum C₁₃ residues revealed binding energy of -13.9 kcal/mol for apoenzyme, -6.8 kcal/mol for holoenzyme (G) and -19.5 kcal/mol for holoenzyme (GO). This supports coil formation propitious for better ALK5-Lum interaction. Highest SASA energy of -21.05 kcal/mol of holoenzyme (G) assures graphene reasonable for improved ALK5-lumican hydrophobicity. As per the motive of the study, graphene oxide enriches permanence of ALK5-lumican. This provides counsel for plausible exploitation of lumican and graphene oxide as targeted/nano drug delivery system to reinstate acute wounds, chronic wounds, corneal wounds, hypertrophic scars and keloids in near future. Communicated by Ramaswamy H. Sarma.

Scar-reducing effects of gambogenic acid on skin wounds in rabbit ears

Hypertrophic scar (HS) is a dermal fibroproliferative disease that often occurs following abnormal wound healing. To date, there is no satisfied treatment strategies for improvement of scar formation with few side effects. The effects of gambogenic acid (GNA) on scar hypertrophy has not been studied previously. The present study was undertaken to find out the scar-reducing effects of GNA (0.48, 0.96 or 1.92 mg/ml) on skin wounds in rabbit ears. Scar evaluation index (SEI), collagen I (Col1) and collagen III (Col3), microvascular density (MVD), CD4+T cells and macrophages, vascular endothelial growth factor receptor 2 (VEGFR2), fibroblast growth factor receptor 1 (FGFR1), phospho-VEGFR 2 (p-VEGFR2) and p-FGFR1, interleukin (IL)-1β, IL-6, IL-10 and tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1 and connective tissue growth factor (CTGF) in scar tissue were detected using various methods, respectively. Our data showed that GNA significantly reduced SEI, and the expression of Col1 and Col3 in scar tissue in a concentration-dependent manner. Also, it decreased MVD, the infiltration of CD4+T cells and macrophages, and the levels of VEGFR2, p-VEGFR2, FGFR1, p-FGFR1, TGF-β1, CTGF, IL-1β, IL-6, TNF-α, in addition to upregulated IL-10 in scar tissue. As a result, this study revealed that GNA reduced HS formation, which was associated with the inhibition of neoangiogenesis, local inflammatory response and growth factor expression in scar tissue during wound healing. These findings suggested that GNA may be considered as a preventive and therapeutic candidate for HS.

Proteoglycans in Biomedicine: Resurgence of an Underexploited Class of ECM Molecules

Proteoglycans have emerged as biomacromolecules with important roles in matrix remodeling, homeostasis, and signaling in the past two decades. Due to their negatively charged glycosaminoglycan chains as well as distinct core protein structures, they interact with a variety of molecules, including matrix proteins, growth factors, cytokines and chemokines, pathogens, and enzymes. This led to the dawn of glycan therapies in the 20^th century, but this research was quickly overshadowed by readily available DNA and protein-based therapies. The recent development of recombinant technology and advances in our understanding of proteoglycan function have led to a resurgence of these molecules as potential therapeutics. This review focuses on the recent preclinical efforts that are bringing proteoglycan research and therapies back to the forefront. Examples of studies using proteoglycan cores and mimetics have also been included to give the readers a perspective on the wide-ranging and extensive applications of these versatile molecules. Collectively, these advances are opening new avenues for targeting diseases at a molecular level, and providing avenues for the development of new and exciting treatments in regenerative medicine.

Small Leucine-Rich Proteoglycans in Skin Wound Healing

Healing of cutaneous wounds is a complex and well-coordinated process requiring cooperation among multiple cells from different lineages and delicately orchestrated signaling transduction of a diversity of growth factors, cytokines, and extracellular matrix (ECM) at the wound site. Most skin wound healing in adults is imperfect, characterized by scar formation which results in significant functional and psychological sequelae. Thus, the reconstruction of the damaged skin to its original state is of concern to doctors and scientists. Beyond the traditional treatments such as corticosteroid injection and radiation therapy, several growth factors or cytokines-based anti-scarring products are being or have been tested in clinical trials to optimize skin wound healing. Unfortunately, all have been unsatisfactory to date. Currently, accumulating evidence suggests that the ECM not only functions as the structural component of the tissue but also actively modulates signal transduction and regulates cellular behaviors, and thus, ECM should be considered as an alternative target for wound management pharmacotherapy. Of particular interest are small leucine-rich proteoglycans (SLRPs), a group of the ECM, which exist in a wide range of connecting tissues, including the skin. This manuscript summarizes the most current knowledge of SLRPs regarding their spatial-temporal expression in the skin, as well as lessons learned from the genetically modified animal models simulating human skin pathologies. In this review, particular focus is given on the diverse roles of SLRP in skin wound healing, such as anti-inflammation, pro-angiogenesis, pro-migration, pro-contraction, and orchestrate transforming growth factor (TGF)β signal transduction, since cumulative investigations have indicated their therapeutic potential on reducing scar formation in cutaneous wounds. By conducting this review, we intend to gain insight into the potential application of SLRPs in cutaneous wound healing management which may pave the way for the development of a new generation of pharmaceuticals to benefit the patients suffering from skin wounds and their sequelae.

Apigenin inhibits growth and migration of fibroblasts by suppressing FAK signaling

The naturally occurring compound apigenin has many biological effects, including anti-inflammatory, antioxidative and anticancer effects. Although hypertrophic scar formation is a common surgical complication, there is still no good treatment for it. In the present study, we examined the effect of apigenin on hypertrophic scar. After isolating fibroblasts from human hypertrophic scars, we assess the effects of apigenin on fibroblast cell survival, apoptosis and migration. The results showed that apigenin dose-dependently inhibited the growth and migration of hypertrophic scar fibroblasts. By inhibiting FAK kinase activity and FAK phosphorylation, apigenin also inhibited activation of the FAK signaling pathway. Apigenin thus appears to inhibit the growth and migration of hypertrophic scar fibroblasts by inhibiting FAK signaling. This suggests apigenin could potentially provide a new option for the treatment of hypertrophic scars.

Lumican as a multivalent effector in wound healing

Wound healing, a complex physiological process, is responsible for tissue repair after exposure to destructive stimuli, without resulting in complete functional regeneration. Injuries can be stromal or epithelial, and most cases of wound repair have been studied in the skin and cornea. Lumican, a small leucine-rich proteoglycan, is expressed in the extracellular matrices of several tissues, such as the cornea, cartilage, and skin. This molecule has been shown to regulate collagen fibrillogenesis, keratinocyte phenotypes, and corneal transparency modulation. Lumican is also involved in the extravasation of inflammatory cells and angiogenesis, which are both critical in stromal wound healing. Lumican is the only member of the small leucine-rich proteoglycan family expressed by the epithelia during wound healing. This review summarizes the importance of lumican in wound healing and potential methods of lumican drug delivery to target wound repair are discussed. The involvement of lumican in corneal wound healing is described based on in vitro and in vivo models, with critical emphasis on its underlying mechanisms of action. Similarly, the expression and role of lumican in the healing of other tissues are presented, with emphasis on skin wound healing. Overall, lumican promotes normal wound repair and broadens new therapeutic perspectives for impaired wound healing.

Scarless wound healing: Transitioning from fetal research to regenerative healing

Since the discovery of scarless fetal skin wound healing, research in the field has expanded significantly with the hopes of advancing the finding to adult human patients. There are several differences between fetal and adult skin that have been exploited to facilitate scarless healing in adults including growth factors, cytokines, and extracellular matrix substitutes. However, no one therapy, pathway, or cell subtype is sufficient to support scarless wound healing in adult skin. More recently, products that contain or mimic fetal and adult uninjured dermis were introduced to the wound healing market with promising clinical outcomes. Through our review of the major experimental targets of fetal wound healing, we hope to encourage research in areas that may have a significant clinical impact. Additionally, we will investigate therapies currently in clinical use and evaluate whether they represent a legitimate advance in regenerative medicine or a vulnerary agent. WIREs Dev Biol 2018, 7:e309. doi: 10.1002/wdev.309 This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Plant Development > Cell Growth and Differentiation Adult Stem Cells, Tissue Renewal, and Regeneration > Environmental Control of Stem Cells.