Acute downregulation of miR-155 at wound sites leads to a reduced fibrosis through attenuating inflammatory response

NLRP3 inflammasome and its role in autoimmune diseases: A promising therapeutic target

The NOD-like receptor protein 3 (NLRP3) inflammasome is a protein complex that regulates innate immune responses by activating caspase-1 and the inflammatory cytokines IL-1β and IL-18. Numerous studies have highlighted its crucial role in the pathogenesis and development of inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, autoimmune thyroid diseases, and other autoimmune diseases. Therefore, investigating the underlying mechanisms of NLRP3 in disease and targeted drug therapies holds clinical significance. This review summarizes the structure, assembly, and activation mechanisms of the NLRP3 inflammasome, focusing on its role and involvement in various autoimmune diseases. This review also identifies studies where the involvement of the NLRP3 inflammasome in the disease mechanism within the same disease appears contradictory, as well as differences in NLRP3-related gene polymorphisms among different ethnic groups. Additionally, the latest therapeutic advances in targeting the NLRP3 inflammasome for autoimmune diseases are outlined, and novel clinical perspectives are discussed. Conclusively, this review provides a consolidated source of information on the NLRP3 inflammasome and may guide future research efforts that have the potential to positively impact patient outcomes.

Novel Biotherapeutics Targeting Biomolecular and Cellular Approaches in Diabetic Wound Healing

Wound healing responses play a major role in chronic inflammation, which affects millions of people around the world. One of the daunting tasks of creating a wound-healing drug is finding equilibrium in the inflammatory cascade. In this study, the molecular and cellular mechanisms to regulate wound healing are explained, and recent research is addressed that demonstrates the molecular and cellular events during diabetic wound healing. Moreover, a range of factors or agents that facilitate wound healing have also been investigated as possible targets for successful treatment. It also summarises the various advances in research findings that have revealed promising molecular targets in the fields of therapy and diagnosis of cellular physiology and pathology of wound healing, such as neuropeptides, substance P, T cell immune response cDNA 7, miRNA, and treprostinil growth factors such as fibroblast growth factor, including thymosin beta 4, and immunomodulators as major therapeutic targets.

Coinfection of Dermal Fibroblasts by Human Cytomegalovirus and Human Herpesvirus 6 Can Boost the Expression of Fibrosis-Associated MicroRNAs

Tissue fibrosis can affect every type of tissue or organ, often leading to organ malfunction; however, the mechanisms involved in this process are not yet clarified. A role has been hypothesized for Human Cytomegalovirus (HCMV) and Human Herpesvirus 6 (HHV-6) infections as triggers of systemic sclerosis (SSc), a severe autoimmune disease causing progressive tissue fibrosis, since both viruses and antiviral immune responses toward them have been detected in patients. Moreover, HCMV or HHV-6A infection was reported to increase the expression of fibrosis-associated transcriptional factors and miRNAs in human dermal fibroblasts. However, it is unlikely that they have separate effects in the infected host, as both viruses are highly prevalent in the human population. Thus, our study aimed to investigate, by quantitative real-time PCR microarray, the impact of HCMV/HHV-6A coinfection on the expression of pro-fibrotic miRNAs in coinfected cells, compared to the effect of single viruses. The results showed a possible synergistic effect of the two viruses on pro-fibrotic miRNA expression, thus suggesting that HCMV and HHV-6 may enhance each other and cooperate at inducing enhanced miRNA-driven fibrosis. These data may also suggest a possible use of virus-induced miRNAs as novel diagnostic or prognostic biomarkers for SSc and its clinical treatment.

miRNA-encapsulated abiotic materials and biovectors for cutaneous and oral wound healing: Biogenesis, mechanisms, and delivery nanocarriers

MicroRNAs (miRNAs) as therapeutic agents have attracted increasing interest in the past decade owing to their significant effectiveness in treating a wide array of ailments. These polymerases II-derived noncoding RNAs act through post-transcriptional controlling of different proteins and their allied pathways. Like other areas of medicine, researchers have utilized miRNAs for managing acute and chronic wounds. The increase in the number of patients suffering from either under-healing or over-healing wound demonstrates the limited efficacy of the current wound healing strategies and dictates the demands for simpler approaches with greater efficacy. Various miRNA can be designed to induce pathway beneficial for wound healing. However, the proper design of miRNA and its delivery system for wound healing applications are still challenging due to their limited stability and intracellular delivery. Therefore, new miRNAs are required to be identified and their delivery strategy needs to be optimized. In this review, we discuss the diverse roles of miRNAs in various stages of wound healing and provide an insight on the most recent findings in the nanotechnology and biomaterials field, which might offer opportunities for the development of new strategies for this chronic condition. We also highlight the advances in biomaterials and delivery systems, emphasizing their challenges and resolutions for miRNA-based wound healing. We further review various biovectors (e.g., adenovirus and lentivirus) and abiotic materials such as organic and inorganic nanomaterials, along with dendrimers and scaffolds, as the delivery systems for miRNA-based wound healing. Finally, challenges and opportunities for translation of miRNA-based strategies into clinical applications are discussed.

Landscape of the epigenetic regulation in wound healing

Wound healing after skin injury is a dynamic and highly coordinated process involving a well-orchestrated series of phases, including hemostasis, inflammation, proliferation, and tissue remodeling. Epigenetic regulation refers to genome-wide molecular events, including DNA methylation, histone modification, and non-coding RNA regulation, represented by microRNA (miRNA), long noncoding RNA (lncRNA), and circular RNA (circRNA). Epigenetic regulation is pervasively occurred in the genome and emerges as a new role in gene expression at the post-transcriptional level. Currently, it is well-recognized that epigenetic factors are determinants in regulating gene expression patterns, and may provide evolutionary mechanisms that influence the wound microenvironments and the entire healing course. Therefore, this review aims to comprehensively summarize the emerging roles and mechanisms of epigenetic remodeling in wound healing. Moreover, we also pose the challenges and future perspectives related to epigenetic modifications in wound healing, which would bring novel insights to accelerated wound healing.

Progress toward molecular therapy for diabetes mellitus: A focus on targeting inflammatory factors

Diabetes mellitus (DM) has been the most prevalent global metabolic disease, turning into a serious risk for human health. Several researches have recorded a role for inflammation and immunity in the pathogenesis of both in T1DM and in T2DM. Lots of chemical agents are available to control and to cure diabetic patients, which are not always sufficient for euglycemia maintenance and late stage diabetic complications avoidance. Therefore, newborn therapeutic methods to refine clinical outcomes in DM are required. Nucleic-acid-based therapy also known as gene expression level regulator within the target cells has been calculated to be promising in various diseases. Thus, pronounced attempts have been dedicated to develop new targeted molecular therapy aimed at improving insulin resistance in DM. This review mainly focuses on recent progress in DM molecular therapy and whether, has potential efficacy against inflammatory mediators involved in DM.

Mesenchymal Stem Cell-Derived Exosomes Loaded with miR-155 Inhibitor Ameliorate Diabetic Wound Healing

Diabetic wounds are one of the debilitating complications that affect up to 20% of diabetic patients. Despite the advent of extensive therapies, the recovery rate is unsatisfactory, and approximately, 25% of patients undergo amputation, thereby demanding alternative therapeutic strategies. On the basis of the individual therapeutic roles of the miR-155 inhibitor and mesenchymal stem cells (MSC)-derived exosomes, we conjectured that the combination of the miR-155 inhibitor and MSC-derived exosomes would have synergy in diabetic wound healing. Herein, miR-155-inhibitor-loaded MSC-derived exosomes showed synergistic effects in keratinocyte migration, restoration of FGF-7 levels, and anti-inflammatory action, leading to accelerated wound healing mediated by negative regulation of miR-155, using an in vitro co-culture model and in vivo mouse model of the diabetic wound. Furthermore, treatment with miR-155-inhibitor-loaded MSC-derived exosomes led to enhanced collagen deposition, angiogenesis, and re-epithelialization in diabetic wounds. This study revealed the therapeutic potential of miR-155-inhibitor-loaded MSC-derived exosomes in diabetic wound healing and opened the doors for encapsulating miRNAs along with antibiotics within the MSC-derived exosomes toward improved management of chronic, nonhealing diabetic wounds.

Targeting microRNA for improved skin health

BACKGROUND

In human skin, miRNAs have important regulatory roles and are involved in the development, morphogenesis, and maintenance by influencing cell proliferation, differentiation, immune regulation, and wound healing. MiRNAs have been investigated for many years in various skin disorders such as atopic dermatitis, psoriasis, as well as malignant tumors. Only during recent times, cosmeceutical use of molecules/natural active ingredients to regulate miRNA expression for significant advances in skin health/care product development was recognized.

AIM

To review miRNAs with the potential to maintain and boost skin health and avoid premature aging by improving barrier function, preventing photoaging, hyperpigmentation, and chronological aging/senescence.

METHODS

Most of the cited articles were found through literature search on PubMed. The main search criteria was a keyword "skin" in combination with the following words: miRNA, photoaging, UV, barrier, aging, exposome, acne, wound healing, pigmentation, pollution, and senescence. Most of the articles reviewed for relevancy were published during the past 10 years.

RESULTS

All results are summarized in Figure 1, and they are based on cited references.

CONCLUSIONS

Thus, regulating miRNAs expression is a promising approach for novel therapy not only for targeting skin diseases but also for cosmeceutical interventions aiming to boost skin health.

NLRP3 Inflammasome: Checkpoint Connecting Innate and Adaptive Immunity in Autoimmune Diseases

Autoimmune diseases are a broad spectrum of human diseases that are characterized by the breakdown of immune tolerance and the production of autoantibodies. Recently, dysfunction of innate and adaptive immunity is considered to be a key step in the initiation and maintenance of autoimmune diseases. NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a multimeric protein complex, which can detect exogenous pathogen irritants and endogenous danger signals. The main function of NLRP3 inflammasome is to promote secretion of interleukin (IL)-1β and IL-18, and pyroptosis mediated by caspase-1. Served as a checkpoint in innate and adaptive immunity, aberrant activation and regulation of NLRP3 inflammasome plays an important role in the pathogenesis of autoimmune diseases. This paper reviewed the roles of NLRP3 inflammasome in autoimmune diseases, which shows NLRP3 inflammasome may be a potential target for autoimmune diseases deserved further study.

MicroRNAs in shaping the resolution phase of inflammation

Inflammation is a host defense mechanism orchestrated through imperative factors - acute inflammatory responses mediated by cellular and molecular events leading to activation of defensive immune subsets - to marginalize detrimental injury, pathogenic agents and infected cells. These potent inflammatory events, if uncontrolled, may cause tissue damage by perturbing homeostasis towards immune dysregulation. A parallel host mechanism operates to contain inflammatory pathways and facilitate tissue regeneration. Thus, resolution of inflammation is an effective moratorium on the pro-inflammatory pathway to avoid the tissue damage inside the host and leads to reestablishment of tissue homeostasis. Dysregulation of the resolution pathway can have a detrimental impact on tissue functionality and contribute to the diseased state. Multiple reports have suggested peculiar dynamics of miRNA expression during various pro- and anti-inflammatory events. The roles of miRNAs in the regulation of immune responses are well-established. However, understanding of miRNA regulation of the resolution phase of events in infection or wound healing models, which is sometimes misconstrued as anti-inflammatory signaling, remains limited. Due to the deterministic role of miRNAs in pro-inflammatory and anti-inflammatory pathways, in this review we have provided a broad perspective on the putative role of miRNAs in the resolution of inflammation and explored their imminent role in therapeutics.

The role of miRNAs in the inflammatory phase of skin wound healing

<abstract> <p>Wound healing (WH) is a fundamental physiological process to keep the integrity of the skin, therefore impaired and chronic WH is a common and severe medical problem and represent one of the biggest challenges of public health. The resolution of the WH inflammatory phase is characterized by a complex series of events that involves many cellular types, especially neutrophils, macrophages and inflammatory mediators, which are crucial for a correct wound closure. MicroRNAs (miRNAs) play essential roles in wound repair. In fact, miR-142 is linked to inflammation modulating neutrophils' chemotaxis and polarization, while the polarization of M1 toward the M2 phenotype is driven by miR-223 and miR-132 is linked to chemokines and cytokines that activate endothelial cells and attract leukocytes and peripheral cells to the damage site. Thus, understanding the dysregulation of miRNAs in WH will be decisive for the development of new and more effective therapies for the management of chronic wounds.</p> </abstract>

miR‑155 modulates high glucose‑induced cardiac fibrosis via the Nrf2/HO‑1 signaling pathway

Cardiac fibrosis is a major pathological manifestation of diabetic cardiomyopathy, which is a leading cause of mortality in patients with diabetes. MicroRNA (miR)‑155 is upregulated in cardiomyocytes in cardiac fibrosis, and the aim of the present study was to investigate if the inhibition of miR‑155 was able to ameliorate cardiac fibrosis by targeting the nuclear factor erythroid‑2‑related factor 2 (Nrf2)/heme oxygenase‑1 (HO‑1) signaling pathway. H9C2 rat cardiomyocytes were cultured with high glucose (HG; 30 mM) to establish an in vitro cardiac fibrosis model that mimicked diabetic conditions; a miR‑155 inhibitor and a miR‑155 mimic were transfected into H9C2 cells. Following HG treatment, H9C2 cells exhibited increased expression levels of miR‑155 and the fibrosis markers collagen I and α‑smooth muscle actin (α‑SMA). In addition, the expression levels of endonuclear Nrf2 and HO‑1 were decreased, but the expression level of cytoplasmic Nrf2 was increased. Moreover, oxidative stress, mitochondrial damage and cell apoptosis were significantly increased, as indicated by elevated reactive oxygen species, malonaldehyde and monomeric JC‑1 expression levels. In addition, superoxide dismutase expression was attenuated and there was an increased expression level of released cytochrome‑c following HG treatment. Furthermore, it was demonstrated that expression levels of Bcl‑2 and uncleaved Poly (ADP‑ribose) polymerase were downregulated, whereas Bax, cleaved caspase‑3 and caspase‑9 were upregulated after HG treatment. However, the miR‑155 inhibitor significantly restored Nrf2 and HO‑1 expression levels, and reduced oxidative stress levels, the extent of mitochondrial damage and the number of cells undergoing apoptosis. Additionally, the miR‑155 inhibitor significantly reversed the expression levels of collagen I and α‑SMA, thus ameliorating fibrosis. Furthermore, the knockdown of Nrf2 reversed the above effects induced by the miR‑155 inhibitor. In conclusion, the miR‑155 inhibitor may ameliorate diabetic cardiac fibrosis by reducing the accumulation of oxidative stress‑related molecules, and preventing mitochondrial damage and cardiomyocyte apoptosis by enhancing the Nrf2/HO‑1 signaling pathway. This mechanism may facilitate the development of novel targets to prevent cardiac fibrosis in patients with diabetes.

Role of TRPV4 in matrix stiffness-induced expression of EMT-specific LncRNA

Long non-coding RNAs (LncRNAs) are long (> 200 bases), non-coding, single-stranded RNAs that have emerged as major regulators of gene expression, cell differentiation, development, and oncogenesis. In view of the fact that matrix stiffness plays a role in cellular functions associated with these processes, it is important to ask what role matrix stiffness plays in regulating expression of LncRNAs. In this report, we show that (i) matrix stiffness causes differential expression of epithelial-mesenchymal transition (EMT)-related LncRNAs and mRNAs in primary mouse normal epidermal keratinocytes, (ii) differential expression of EMT-related LncRNAs and mRNAs occurs in response to combined stimulation of transforming growth factor β1 and matrix stiffness, and (iii) transient receptor potential (TRP) channel of the vanilloid subfamily, TRPV4, a matrix stiffness-sensitive ion channel, plays a role in differential expression of EMT-related LncRNAs and mRNAs in response to combined stimulation by TGFβ1 and matrix stiffness. These data identify TRPV4 as a candidate plasma membrane mechanosensor that transmits matrix-sensing signals essential to LncRNA expression. Our results also show that we have established and validated an assay system capable of discovering novel LncRNAs and mRNAs sensitive to matrix stiffening.

Knockout of MicroRNA-155 Ameliorates the Th17/Th9 Immune Response and Promotes Wound Healing

MiRNAs are integral for maintaining immune homeostasis and self-tolerance. In this study, qPCR analyses were performed to determine which miRNAs play an important role in wound healing. Next, an experiment in a model of wound healing was performed, and histology, mRNA expression and T-cell subpopulations in wound tissue were analyzed. The accelerated experiments were performed by local injection of either rIL-17A and/or rIL-9 after wound healing. In vitro, the differentiation of Th17/Th9 in miR-155^+/+ or miR-155^-/- mice was investigated, and the target genes of miR155 were analyzed. From our findings, miR-155^-/- in mice promoted wound healing and weakened T cell-mediated inflammation, especially in IL-17/IL-9, and less severe skin fibrosis developed in the mice. rIL-17A and/or rIL-9 could exacerbate inflammatory injury and delay wound healing. We also demonstrated that miR-155^-/- led to a defect in the differentiation of Th17/Th9 in vitro, and this effect of IL-17/IL-9 might be related to the expression of C-maf, which is a target gene of miR155. MiR-155 regulated IL-17/IL-9-related inflammation in wound healing and might be a potential therapeutic target to attenuate the inflammatory response in wound tissue and promote the closure of wound injuries.

The extensive role of miR-155 in malignant and non-malignant diseases

MicroRNAs (miRNAs) have rapidly emerged as key molecules in cancer initiation and development, showing the capability to regulate pivotal oncogenic pathways. MiR-155 has gathered an increased attention especially in oncology, but also in non-malignanat pathologies. Nowadays, this noncoding RNA is one of the most important miRNAs in cancer, due to the extensive signaling network associated with it, implication in immune system regulation and also deregulation in disease states. Therefore, numerous research protocols are focused on preclinical modulation of miR-155 for therapeutic purposes, or investigation of its dynamic expression for diagnostic/prognostic assessments, with the final intention of bringing this miRNA into the clinical setting. This review comprehensively presents the extended role of miR-155 in cancer and other pathologies, where its expression is dysregulated. Finally, we assess the future steps toward miR-155 based therapeutics.

The role of microRNAs in the healing of diabetic ulcers

MicroRNAs (miRNAs) are small protected molecules with a length of 18 to 25 nucleotides. Many studies have recently been conducted on miRNAs, illustrating their role in regulating many biological, physiological, and pathological activities, such as maintaining cellular signalling and regulating cellular pathways. The main role of miRNAs is to regulate the expression of genes after translation, which can lead to the destruction or suppression of translation by binding to mRNAs. As any change in the regulation of miRNAs is associated with several physiological abnormalities, such as type 2 diabetes and its complications, these molecules can be used for therapeutic purposes or as biomarkers for the diagnosis of diseases such as diabetes and its complications. In this review article, we will discuss important findings about the miRNAs and the role of these molecules in different phases of the wound-healing process of chronic wounds, especially diabetic ulcer.

MicroRNA 155 Downregulation by Vitamin C–Loaded Human Serum Albumin Nanoparticles During Cutaneous Wound Healing in Mice

This study focused on potential of vitamin C loaded human serum albumin (HSA) nanoparticles for treatment of wound. Nanocarrier were prepared and assessed for their effect on growth of 3T3 fibroblast cells, cell migration, wound healing rate and expression of miR-155, TGF-β1 and SMAD 1,2 genes. Wound healing assay was done and wounds were treated with vitamin C loaded HSA nanoparticles. Nanoparticles were prepared with size and zeta potential of 180±6 and -29 mV, respectively. Vitamin C loaded HSA nanoparticles showed controlled release of vitamin C into the buffer solution. Also, yield and encapsulation efficacy of loaded nanoparticles were obtained as 70.6 and 52.1 %, respectively. MTT results showed that the growth of 3T3 fibroblast cells was promoted in culture medium with 20 µg/ml of vitamin C loaded HSA nanoparticles. Cell migration assay indicated the positive effect of loaded nanoparticles on wound healing. The in-vivo results showed that the rate of wound healing was increased after treatment with 20 µg/ml of vitamin C loaded HSA nanoparticles. The wounds were healed faster when treated with vitamin C loaded HSA nanoparticles in comparison with control group. The expression of miR-155 was downregulated after treatment. Furthermore, expression of TGF-β1 and SMAD 1,2 were increased while the wounds were treated with these nanoparticles. In conclusion, these results showed for the first time that wounds were healed after treatment with albumin nanocarrier loaded with vitamin C. This nanocarrier changed expression of miR-155 and TGF-β1 towards faster healing of wounds.

microRNA-155 inhibition restores Fibroblast Growth Factor 7 expression in diabetic skin and decreases wound inflammation

Treatment for chronic diabetic foot ulcers is limited by the inability to simultaneously address the excessive inflammation and impaired re-epithelization and remodeling. Impaired re-epithelization leads to significantly delayed wound closure and excessive inflammation causes tissue destruction, both enhancing wound pathogen colonization. Among many differentially expressed microRNAs, miR-155 is significantly upregulated and fibroblast growth factor 7 (FGF7) mRNA (target of miR-155) and protein are suppressed in diabetic skin, when compared to controls, leading us to hypothesize that topical miR-155 inhibition would improve diabetic wound healing by restoring FGF7 expression. In vitro inhibition of miR-155 increased human keratinocyte scratch closure and topical inhibition of miR-155 in vivo in wounds increased murine FGF7 protein expression and significantly enhanced diabetic wound healing. Moreover, we show that miR-155 inhibition leads to a reduction in wound inflammation, in accordance with known pro-inflammatory actions of miR-155. Our results demonstrate, for the first time, that topical miR-155 inhibition increases diabetic wound fibroblast growth factor 7 expression in diabetic wounds, which, in turn, increases re-epithelization and, consequently, accelerates wound closure. Topical miR-155 inhibition targets both excessive inflammation and impaired re-epithelization and remodeling, being a potentially new and effective treatment for chronic diabetic foot ulcers.

The MicroRNA miR-155 Is Essential in Fibrosis

The function of microRNAs (miRNAs) during fibrosis and the downstream regulation of gene expression by these miRNAs have become of great biological interest. miR-155 is consistently upregulated in fibrotic disorders, and its ablation downregulates collagen synthesis. Studies demonstrate the integral role of miR-155 in fibrosis, as it mediates TGF-β1 signaling to drive collagen synthesis. In this review, we summarize recent findings on the association between miR-155 and fibrotic disorders. We discuss the cross-signaling between macrophages and fibroblasts that orchestrates the upregulation of collagen synthesis mediated by miR-155. As miR-155 is involved in the activation of the innate and adaptive immune systems, specific targeting of miR-155 in pathologic cells that make excessive collagen could be a viable option before the depletion of miR-155 becomes an attractive antifibrotic approach.

miR-96 promotes collagen deposition in keloids by targeting Smad7

The abnormal upregulation of transforming growth factor-β (TGF-β) signaling has been demonstrated to initiate keloid formation and progression. Keloid is a type of benign skin tumor that may occur following sustaining skin injury. microRNA-96 (miR-96) serves an important role in the progression of various malignant diseases. Using reverse transcription quantitative polymerase chain reaction (RT-qPCR), the present study demonstrated that miR-96 was overexpressed in keloid-derived fibroblasts (KFs). Luciferase reporter assay revealed mothers against decapentaplegic homolog (Smad)7, which is one of the important inhibitory factors in the TGF-β pathway, as a direct target of miR-96. miR-96 was initially observed to be correlated with the deposition of type I collagen in KFs in vitro. The miR-96 antagomir, was directly added into the keloid organ culture (OC) to find its significant antifibrotic potential, such as keloid OC shrinkage, exhibited by its dry weight loss and improved dermis architecture, exhibited by Masson's staining. Following miR-96 antagomir treatment, a reduction in the mRNA and protein expression levels of collagen type I α 1 chain and collagen type 3 α 1 chain within keloid OC tissues was observed. The present study revealed that miR-96 serves an important role in pathogenic keloid formation, suggesting that miR-96 antagomir has the potential to prevent keloid progression.

Identification and functional analysis of inflammation-related miRNAs in skin wound repair

Inflammation at a wound site is essential for preventing infection. However, misregulated inflammation leads to pathologies of the healing process, including chronic non-healing wounds and scarring. MicroRNAs (miRNAs) are key regulators of the inflammatory response and tissue repair, acting by translational processing of target mRNAs. In the final step of miRNA processing, Argonaute 2 (Ago2)-bound mature miRNA complexes bind to target mRNAs and inhibit their translation. A variety of wound healing-related miRNAs have been identified and their misregulation likely contributes to wound pathologies, including scarring and chronic healing. Recently, we have developed an Ago2-bound mature miRNA purification system that uses Ago2 antibody to analyze the expression of miRNAs from wound tissues by microarray and next generation sequencing. We have identified several wound inflammation-related miRNAs via Ago2-target immunoprecipitation assays and next generation sequencing of wound tissues from wild-type and PU.1 knockout mice, which exhibit no inflammatory response because of a lack of immune cell lineages. We demonstrated that miR-142, an identified inflammation-related miRNA, is essential role for neutrophilic chemotaxis via inhibition of small GTPase translation; its misregulation leads to susceptibility to infection against Staphylococcus aureus at skin wound sites. In this review, we summarize recent advances of miRNA studies in skin wound healing, introduce our miRNA purification system using an immunoprecipitation assay method, and discuss the function of miR-142 in skin wound healing.

Insights into the key roles of epigenetics in matrix macromolecules-associated wound healing

Extracellular matrix (ECM) is a dynamic network of macromolecules, playing a regulatory role in cell functions, tissue regeneration and remodeling. Wound healing is a tissue repair process necessary for the maintenance of the functionality of tissues and organs. This highly orchestrated process is divided into four temporally overlapping phases, including hemostasis, inflammation, proliferation and tissue remodeling. The dynamic interplay between ECM and resident cells exerts its critical role in many aspects of wound healing, including cell proliferation, migration, differentiation, survival, matrix degradation and biosynthesis. Several epigenetic regulatory factors, such as the endogenous non-coding microRNAs (miRNAs), are the drivers of the wound healing response. microRNAs have pivotal roles in regulating ECM composition during wound healing and dermal regeneration. Their expression is associated with the distinct phases of wound healing and they serve as target biomarkers and targets for systematic regulation of wound repair. In this article we critically present the importance of epigenetics with particular emphasis on miRNAs regulating ECM components (i.e. glycoproteins, proteoglycans and matrix proteases) that are key players in wound healing. The clinical relevance of miRNA targeting as well as the delivery strategies designed for clinical applications are also presented and discussed.

miRNA delivery for skin wound healing

The wound healing has remained a worldwide challenge as one of significant public health problems. Pathological scars and chronic wounds caused by injury, aging or diabetes lead to impaired tissue repair and regeneration. Due to the unique biological wound environment, the wound healing is a highly complicated process, efficient and targeted treatments are still lacking. Hence, research-driven to discover more efficient therapeutics is a highly urgent demand. Recently, the research results have revealed that microRNA (miRNA) is a promising tool in therapeutic and diagnostic fields because miRNA is an essential regulator in cellular physiology and pathology. Therefore, new technologies for wound healing based on miRNA have been developed and miRNA delivery has become a significant research topic in the field of gene delivery.

Acute downregulation of miR-155 leads to a reduced collagen synthesis through attenuating macrophages inflammatory factor secretion by targeting SHIP1

Fibrosis, tightly associated with fibroblasts collagen synthesis, is related closely with inflammatory response. Our previously study found that acute downregulation of miR-155 at wound sites leads to a reduced fibrosis, however its particular mechanism is unclear. Herein, we aimed to explore the mechanism of miR-155 in reducing fibrosis. We first found that down-regulation of miR-155 inhibited macrophages transforming growth factor-β1 (TGF-β1) and IL-1β secretion. Next, we found that co-cultured with macrophages increased the proliferation and collagen synthesis of fibroblasts, and downregulation of miR-155 in macrophages could effectively attenuate the accelerative effects. We further identified SH2 domain containing inositol-5-phosphatase 1 (SHIP1) as a direct target of miR-155 in macrophages, and the expression of SHIP1 was negatively correlated with the level of miR-155. We further confirmed that PI3K/Akt pathway was involved in this process. Last, we found that downregulation of miR-155 leads to a reduced fibrosis in sever burn rat. Taken together, these results indicate that down-regulation of miR-155 leads to a reduced fibroblasts proliferation and collagen synthesis through attenuating macrophages TGF-β1 and IL-1β secretion by targeting SHIP1 via PI3K/Akt pathway, suggesting its potential therapeutic effects on the treatment of skin fibrosis.

MicroRNAs in the skin: role in development, homoeostasis and regeneration

The skin is the largest organ of the integumentary system and possesses a vast number of functions. Due to the distinct layers of the skin and the variety of cells which populate each, a tightly regulated network of molecular signals control development and regeneration, whether due to programmed cell termination or injury. MicroRNAs (miRs) are a relatively recent discovery; they are a class of small non-coding RNAs which possess a multitude of biological functions due to their ability to regulate gene expression via post-transcriptional gene silencing. Of interest, is that a plethora of data demonstrates that a number of miRs are highly expressed within the skin, and are evidently key regulators of numerous vital processes to maintain non-aberrant functioning. Recently, miRs have been targeted as therapeutic interventions due to the ability of synthetic 'antagomiRs' to down-regulate abnormal miR expression, thereby potentiating wound healing and attenuating fibrotic processes which can contribute to disease such as systemic sclerosis (SSc). This review will provide an introduction to the structure and function of the skin and miR biogenesis, before summarizing the literature pertaining to the role of miRs. Finally, miR therapies will also be discussed, highlighting important future areas of research.

Mir-155 is overexpressed in systemic sclerosis fibroblasts and is required for NLRP3 inflammasome-mediated collagen synthesis during fibrosis

BACKGROUND

Despite the important role that microRNAs (miRNAs) play in immunity and inflammation, their involvement in systemic sclerosis (SSc) remains poorly characterized. miRNA-155 (miR-155) plays a role in pulmonary fibrosis and its expression can be induced with interleukin (IL)-1β. SSc fibroblasts have activated inflammasomes that are integrally involved in mediating the myofibroblast phenotype. In light of this, we investigated whether miR-155 played a role in SSc and if its expression was dependent on inflammasome activation.

METHODS

miR-155 expression was confirmed in SSc dermal and lung fibroblasts by quantitative polymerase chain reaction (PCR). Wild-type and NLRP3-deficient murine fibroblasts were utilized to explore the regulation of miR-155 during inflammasome activation. miR-155-deficient fibroblasts and retroviral transductions with a miR-155 expression or control vectors were used to understand the contribution of miR-155 in fibrosis.

RESULTS

miR-155 was significantly increased and the highest expressing miRNA in SSc lung fibroblasts. Its expression was dependent on inflammasome activation as miR-155 expression could be blocked when inflammasome signaling was inhibited. In the absence of miR-155, inflammasome-mediated collagen synthesis could not be induced but was restored when miR-155 was expressed in miR-155-deficient fibroblasts.

CONCLUSIONS

miR-155 is upregulated in SSc. These results suggest that the inflammasome promotes the expression of miR-155 and that miR-155 is a critical miRNA that drives fibrosis.

MicroRNA-155 Inhibition Promoted Wound Healing in Diabetic Rats

Diabetes leads to amputation in approximately 15% to 20% of patients and is associated with high morbidity and mortality. Thus, improving the quality of wound healing in this condition is essential. Diabetes is associated with acute/chronic inflammation affecting all organs especially the foot, while, inhibition of microRNA-155 (miR-155) has been reported to improve or reduce inflammatory situation. However, the role of miR-155 inhibition in promoting diabetic wound healing is not clear. To further study the potential benefit of miR-155 inhibition, a study of male Sprague-Dawley rats was conducted and diabetes was induced by injection of streptozotocin. Real-time polymerase chain reaction (PCR), hematoxylin and eosin staining and immunohistochemistry were then performed. The PCR results confirmed that miR-155 expression was lower after miR-155 inhibition on days 3, 7, and 13 (all Ps <.05). The wound healing rate between the normal glucose group (N group), diabetic PBS group (PBS group) and the topical miR-155 inhibitor group was compared. Faster healing of cutaneous wounds was observed in the miR-155 inhibitor group than in the PBS group and normal glucose group ( P < .05). In addition, downregulation of inflammatory cells, including neutrophils (MPO-positive) and macrophages (CD68-positive), and upregulation of the angiogenic protein CD31 and markers indicative of fibroblast proliferation and collagen deposition, such as collagen 1, TGF-β1, and α-SMA, were observed. These data permit the observation that miR-155 inhibition possesses the potential to reduce inflammation in acute wounds. This property may benefit the healing of diabetic foot wounds.

MicroRNA-155: a Novel Armamentarium Against Inflammatory Diseases

An increasing number of diseases are being newly closely associated with inflammation, where microRNAs seem to play a critical role in the whole disease process from initiation to development. MicroRNAs are small non-coding RNAs that govern gene expression and modulation by means of mRNA degradation or translational repression. After several profound research studies, new correlations between microRNA-155 and inflammation-related diseases are strongly emerging. Hence, we review in this paper the possible molecular mechanisms of microRNA-155 in inflammatory disorders. Furthermore, we also consider the feasibility of targeting it as a bright alternative to improve the early diagnose statistics and treatments in those diseases. MicroRNA-155 features a novel breakthrough in fine-tuning inflammatory responses and, thereby, in treating a wide spectrum of diseases with inflammation as a common denominator.

Non-Coding RNAs: New Players in Skin Wound Healing

Significance: Wound healing is a basic physiological process that is utilized to keep the integrity of the skin. Impaired wound repair, such as chronic wounds and pathological scars, presents a major health and economic burden worldwide. To date, efficient targeted treatment for these wound disorders is still lacking, which is largely due to our limited understanding of the biological mechanisms underlying these diseases. Research driven around discovering new therapies for these complications is, therefore, an urgent need. Recent Advances: The vast majority of the human genome is transcribed to RNAs that lack protein-coding capacity. Intensive research in the recent decade has revealed that these non-coding RNAs (ncRNAs) function as important regulators of cellular physiology and pathology, which makes them promising therapeutic and diagnostic entities. Critical Issues: A class of short ncRNAs, microRNAs, has been found to be indispensable for all the phases of skin wound healing and plays important roles in the pathogenesis of wound complications. The role of long ncRNAs (lncRNA) in skin wound healing remains largely unexplored. Recent studies revealed the essential role of lncRNAs in epidermal differentiation and stress response, indicating their potential importance for skin wound healing, which warrants future research. Future Directions: An investigation of ncRNAs will add new layers of complexity to our understanding of normal skin wound healing as well as to the pathogenesis of wound disorders. Development of ncRNA-based biomarkers and treatments is an interesting and important avenue for future research on wound healing.

A miRNA target network putatively involved in follicular atresia

In a previous microarray study, we identified a subset of micro RNAS (miRNAs), which expression was distinctly higher in atretic than healthy follicles of cattle. In the present study, we investigated the involvement of those miRNAs in granulosa and theca cells during atresia. Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR) confirmed that miR-21-5p/-3p, miR-150, miR-409a, miR-142-5p, miR-378, miR-222, miR-155, and miR-199a-5p were expressed at higher levels in atretic than healthy follicles (9-17 mm, classified based on steroidogenic capacity). All miRNAs except miR-21-3p and miR-378 were expressed at higher levels in theca than granulosa cells. The expression of 13 predicted miRNA targets was determined in follicular cells by RT-qPCR, revealing downregulation of HIF1A, ETS1, JAG1, VEGFA, and MSH2 in either or both cell types during atresia. Based on increases in miRNA levels simultaneous with decreases in target levels in follicular cells, several predicted miRNA target interactions were confirmed that are putatively involved in follicular atresia, namely miR-199a-5p/miR-155-HIF1A in granulosa cells, miR-155/miR-222-ETS1 in theca cells, miR-199a-5p-JAG1 in theca cells, miR-199a-5p/miR-150/miR-378-VEGFA in granulosa and theca cells, and miR-155-MSH2 in theca cells. These results offer novel insight on the involvement of miRNAs in follicle development by identifying a miRNA target network that is putatively involved in follicle atresia.

Anti-Inflammatory Activity of Tanshinone IIA in LPS-Stimulated RAW264.7 Macrophages via miRNAs and TLR4-NF-κB Pathway

Inflammation is a physiological response to infection or injury and involves the innate and adaptive immune system. Tanshinone IIA (Tan IIA) is a well-known flavonoid that elicits an important therapeutic effect by inhibiting inflammatory response. In this study, we examined whether Tan IIA exerts anti-inflammatory activity and investigated the possible mechanisms, including Toll-like receptor 4 (TLR4)-MyD88-nuclear factor kappa B (NF-κB) signaling pathway and microRNA expression in lipopolysaccharide (LPS)-induced RAW264.7 cells. Tan IIA could attenuate the inflammatory reaction via decreasing cytokine, chemokine, and acute-phase protein production, including GM-CSF, sICAM-1, cxcl-1, MIP-1α, and tumor necrosis factor alpha (TNF-α), analyzed by Proteome profile array in LPS-induced RAW264.7 cells. Concurrently, the messenger RNA (mRNA) expressions of IL-1β, TNF-α, and COX-2 were also significantly reduced by Tan IIA. Additionally, Tan IIA decreased LPS-induced NF-κB activation and downregulated TLR4 and MyD88 protein expression levels. We also observed reduced microRNA-155, miR-147, miR-184, miR-29b, and miR-34c expression levels, while LPS-induced microRNA-105, miR-145a, miR-194, miR-383, miR-132, and miR-451a expression levels were upregulated using microRNA (miRNA) qPCR array. Our results indicate that Tan IIA could exert an anti-inflammatory effect on LPS-induced RAW264.7 cells by decreasing TLR4-MyD88-NF-κB signaling pathway and regulating a series of cytokine production and miRNA expression.

Role of microRNA-155 in the liver

MicroRNAs (miRNAs) are a class of endogenous non-coding small RNAs of 22 nucleotides in length that are found in most eukaryotes. Although miRNAs are highly evolutionally conserved, they show temporal and tissue specificity. They transcriptionally and posttranscriptionally regulate gene expression by completely or imperfectly base pairing with the 3' untranslated region (3'-UTR) of target mRNAs and modulate cell proliferation, apoptosis and differentiation. MicroRNA-155 (miR-155) is a typical representative miRNA, and abnormal expression or dysfunction of miR-155 function not only affects the development of inflammation and autoimmune diseases, but also plays an important role in tumor proliferation and apoptosis. In recent years, it has been found that miR-155 plays an important role in the differentiation, morphology and function of the liver, and is associated with the development, diagnosis and treatment of liver diseases.

Biochemical and Biophysical Cues in Matrix Design for Chronic and Diabetic Wound Treatment

Progress in biomaterial science and engineering and increasing knowledge in cell biology have enabled us to develop functional biomaterials providing appropriate biochemical and biophysical cues for tissue regeneration applications. Tissue regeneration is particularly important to treat chronic wounds of people with diabetes. Understanding and controlling the cellular microenvironment of the wound tissue are important to improve the wound healing process. In this study, we review different biochemical (e.g., growth factors, peptides, DNA, and RNA) and biophysical (e.g., topographical guidance, pressure, electrical stimulation, and pulsed electromagnetic field) cues providing a functional and instructive acellular matrix to heal diabetic chronic wounds. The biochemical and biophysical signals generally regulate cell-matrix interactions and cell behavior and function inducing the tissue regeneration for chronic wounds. Some technologies and devices have already been developed and used in the clinic employing biochemical and biophysical cues for wound healing applications. These technologies can be integrated with smart biomaterials to deliver therapeutic agents to the wound tissue in a precise and controllable manner. This review provides useful guidance in understanding molecular mechanisms and signals in the healing of diabetic chronic wounds and in designing instructive biomaterials to treat them.

Transition from inflammation to proliferation: a critical step during wound healing

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

MiR-155 Knockout in Fibroblasts Improves Cardiac Remodeling by Targeting Tumor Protein p53-Inducible Nuclear Protein 1

Cardiac remodeling caused by acute myocardial infarction (AMI) represents a major challenge for heart failure research. MiR-155 has been identified as a key mediator of cardiac inflammation and hypertrophy. In this study, we investigate the role of miR-155 in cardiac remodeling induced by AMI. We demonstrate that miR-155 expressed in cardiac fibroblasts is a potent contributor to cardiac remodeling. We reveal that in vivo, miR-155 knockout improves left ventricular function, reduces infarct size, and attenuates collagen deposition, whereas overexpression of miR-155 produces the opposite effects. MiR-155 knockout also inhibits cardiac fibroblast proliferation and differentiation into myofibroblasts. In addition, downregulation of tumor protein p53-inducible nuclear protein 1 (TP53INP1) by small interfering RNA reverses the effects of miR-155 knockout on cardiac fibroblasts. Our data reveal that knockout of miR-155 in cardiac fibroblasts improves cardiac remodeling by targeting TP53INP1, which may be a novel treatment strategy for cardiac remodeling.

MicroRNA-155 Deficiency Attenuates Liver Steatosis and Fibrosis without Reducing Inflammation in a Mouse Model of Steatohepatitis

BACKGROUND & AIM

MicroRNAs (miRs) regulate hepatic steatosis, inflammation and fibrosis. Fibrosis is the consequence of chronic tissue damage and inflammation. We hypothesized that deficiency of miR-155, a master regulator of inflammation, attenuates steatohepatitis and fibrosis.

METHODS

Wild type (WT) and miR-155-deficient (KO) mice were fed methionine-choline-deficient (MCD) or -supplemented (MCS) control diet for 5 weeks. Liver injury, inflammation, steatosis and fibrosis were assessed.

RESULTS

MCD diet resulted in steatohepatitis and increased miR-155 expression in total liver, hepatocytes and Kupffer cells. Steatosis and expression of genes involved in fatty acid metabolism were attenuated in miR-155 KO mice after MCD feeding. In contrast, miR-155 deficiency failed to attenuate inflammatory cell infiltration, nuclear factor κ beta (NF-κB) activation and enhanced the expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNFα) and monocyte chemoattractant protein-1 (MCP1) in MCD diet-fed mice. We found a significant attenuation of apoptosis (cleaved caspase-3) and reduction in collagen and α smooth muscle actin (αSMA) levels in miR-155 KO mice compared to WTs on MCD diet. In addition, we found attenuation of platelet derived growth factor (PDGF), a pro-fibrotic cytokine; SMAD family member 3 (Smad3), a protein involved in transforming growth factor-β (TGFβ) signal transduction and vimentin, a mesenchymal marker and indirect indicator of epithelial-to-mesenchymal transition (EMT) in miR-155 KO mice. Nuclear binding of CCAAT enhancer binding protein β (C/EBPβ) a miR-155 target involved in EMT was significantly increased in miR-155 KO compared to WT mice.

CONCLUSIONS

Our novel data demonstrate that miR-155 deficiency can reduce steatosis and fibrosis without decreasing inflammation in steatohepatitis.