IL-15 Enhances Activation and IGF-1 Production of Dendritic Epidermal T Cells to Promote Wound Healing in Diabetic Mice

Immune cells in skin inflammation, wound healing, and skin cancer

Given the self-evident importance of cutaneous immunity in the maintenance of body-surface homeostasis, disturbance of the steady-state skin is inextricably intertwined with dysfunction in cutaneous immunity. It is often overlooked by people that skin, well-known as a solid physical barrier, is also a strong immunological barrier, considering the abundant presence of immune cells including lymphocytes, granulocytes, dendritic cells, and macrophages. What's more, humoral immune components including cytokines, immunoglobulins, and antimicrobial peptides are also rich in the skin. This review centers on skin inflammation (acute and chronic, infection and aseptic inflammation), wound healing, and skin cancer to elucidate the elaborate network of immune cells in skin diseases.

Spatiotemporal orchestration of macrophage activation trajectories by Vγ4 T cells during skin wound healing

Dysregulated macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotypes underlies impaired cutaneous wound healing. This study reveals Vγ4+ γδ T cells spatiotemporally calibrate macrophage trajectories during skin repair via sophisticated interferon-γ (IFN-γ) conditioning across multiple interconnected tissues. Locally within wound beds, infiltrating Vγ4+ γδ T cells directly potentiate M1 activation and suppress M2 polarization thereby prolonging local inflammation. In draining lymph nodes, infiltrated Vγ4+ γδ T cells expand populations of IFN-γ-competent lymphocytes which disseminate systemically and infiltrate into wound tissues, further enforcing M1 macrophages programming. Moreover, Vγ4+γδ T cells flushed into bone marrow stimulate increased IFN-γ production, which elevates the output of pro-inflammatory Ly6C+monocytes. Mobilization of these monocytes continually replenishes the M1 macrophage pool in wounds, preventing phenotypic conversion to M2 activation. Thus, multi-axis coordination of macrophage activation trajectories by trafficking Vγ4+ γδ T cells provides a sophisticated immunological mechanism regulating inflammation timing and resolution during skin repair.

Skin Homeostasis and Repair: A T Lymphocyte Perspective

Chronic, nonhealing wounds remain a clinical challenge and a significant burden for the healthcare system. Skin-resident and infiltrating T cells that recognize pathogens, microbiota, or self-antigens participate in wound healing. A precise balance between proinflammatory T cells and regulatory T cells is required for the stages of wound repair to proceed efficiently. When diseases such as diabetes disrupt the skin microenvironment, T cell activation and function are altered, and wound repair is hindered. Recent studies have used cutting-edge technology to further define the cellular makeup of the skin prior to and during tissue repair. In this review, we discuss key advances that highlight mechanisms used by T cell subsets to populate the epidermis and dermis, maintain skin homeostasis, and regulate wound repair. Advances in our understanding of how skin cells communicate in the skin pave the way for therapeutics that modulate regulatory versus effector functions to improve nonhealing wound treatment.

Widespread and dynamic expression of granzyme C by skin-resident antiviral T cells

After recognition of cognate antigen (Ag), effector CD8+ T cells secrete serine proteases called granzymes in conjunction with perforin, allowing granzymes to enter and kill target cells. While the roles for some granzymes during antiviral immune responses are well characterized, the function of others, such as granzyme C and its human ortholog granzyme H, is still unclear. Granzyme C is constitutively expressed by mature, cytolytic innate lymphoid 1 cells (ILC1s). Whether other antiviral effector cells also produce granzyme C and whether it is continually expressed or responsive to the environment is unknown. To explore this, we analyzed granzyme C expression in different murine skin-resident antiviral lymphocytes. At steady-state, dendritic epidermal T cells (DETCs) expressed granzyme C while dermal γδ T cells did not. CD8+ tissue-resident memory T cells (TRM) generated in response to cutaneous viral infection with the poxvirus vaccinia virus (VACV) also expressed granzyme C. Both DETCs and virus-specific CD8+ TRM upregulated granzyme C upon local VACV infection. Continual Ag exposure was not required for maintained TRM expression of granzyme C, although re-encounter with cognate Ag boosted expression. Additionally, IL-15 treatment increased granzyme C expression in both DETCs and TRM. Together, our data demonstrate that granzyme C is widely expressed by antiviral T cells in the skin and that expression is responsive to both environmental stimuli and TCR engagement. These data suggest that granzyme C may have functions other than killing in tissue-resident lymphocytes.

Wounds under diabetic milieu: The role of immune cellar components and signaling pathways

A major challenge in the field of diabetic wound healing is to confirm the body's intrinsic mechanism that could sense the immune system damage promptly and protect the wound from non-healing. Accumulating literature indicates that macrophage, a contributor to prolonged inflammation occurring at the wound site, might play such a role in hindering wound healing. Likewise, other immune cell dysfunctions, such as persistent neutrophils and T cell infection, may also lead to persistent oxidative stress and inflammatory reaction during diabetic wound healing. In this article, we discuss recent advances in the immune cellular components in wounds under the diabetic milieu, and the role of key signaling mechanisms that compromise the function of immune cells leading to persistent wound non-healing.

Diminished schwann cell repair responses play a role in delayed diabetes-associated wound healing

Diabetes mellitus is the most common metabolic disease associated with impaired wound healing. Recently, Schwann cells (SCs), the glia of the peripheral nervous system, have been suggested to accelerate normal skin wound healing. However, the roles of SCs in diabetic wound healing are not fully understood. In this study, Full-thickness wounds were made in the dorsal skin of C57/B6 mice and db/db (diabetic) mice. Tissue samples were collected at different time points, and immunohistochemical and immunofluorescence analyses were performed to detect markers of de-differentiated SCs, including myelin basic protein, Sox 10, p75, c-Jun, and Ki67. In addition, in vitro experiments were performed using rat SC (RSC96) and murine fibroblast (L929) cell lines to examine the effects of high glucose conditions (50 mM) on the de-differentiation of SCs and the paracrine effects of SCs on myofibroblast formation. Here, we found that, compared with that in normal mice, wound healing was delayed and SCs failed to rapidly activate a repair program after skin wound injury in diabetic mice. Furthermore, we found that SCs from diabetic mice displayed functional impairments in cell de-differentiation, cell-cycle re-entry, and cell migration. In vitro, hyperglycemia impaired RSC 96 cell de-differentiation, cell-cycle re-entry, and cell migration, as well as their paracrine effects on myofibroblast formation, including the secretion of TGF-β and Timp1. These results suggest that delayed wound healing in diabetes is due in part to a diminished SC repair response and attenuated paracrine effects on myofibroblast formation.

IL-1β/NF-κB signaling inhibits IGF-1 production via let-7f-5p in dendritic epidermal T cells

Dendritic epidermal T cells (DETCs) are the main source of insulin-like growth factor-1 (IGF-1) in epidermal tissue, which promote re-epithelialization and wound healing. In refractory wounds, IL-1β has been shown to activate NF-κB and suppress IGF-1 expression in DETCs. Nevertheless, the underlying mechanisms remain unclear. In this study, chromatin immunoprecipitation analysis revealed that IL-1β did not inhibit NF-κB binding to IGF-1 promoter, indicating that IL-1β/NF-κB may suppress IGF-1 expression by alternative mechanisms. MiRNAs negatively regulate gene expression predominantly by base pairing to the 3' untranslation region (UTR) of target mRNAs. Let-7f-5p, miR-1a-3p, and miR-98-5p have been identified as IGF-1-specific miRNAs that can bind directly to the 3'UTR of IGF-1 mRNA and dysregulate IGF-1 mRNA and protein levels. In IL-1β-treated epidermis around wounds or DETCs in vitro, NF-κB promoted the expression of let-7f-5p, and IGF-1 expression was impeded via NF-κB/let-7f-5p pathway. As pre-let-7f-5p, let-7f-1 is located in the 3'UTR of LOC118568094, and let-7f-2 is located in the intron of HUWE1. We discovered that NF-κB p65 bound to the promoters of LOC118568094 and HUWE1 to accelerate let-7f-5p expression, but NF-κB p65 did not affect the methylation levels of LOC118568094 and HUWE1 CpG islands. Injections of Let-7f-5p antagomir into IL-1β-treated and ischemic wound margins restored IGF-1 secretion in DETCs and promoted wound healing. In conclusion, we demonstrated that NF-κB signaling pathway activated by IL-1β could increase let-7f-5p expression to inhibit IGF-1 production in DETCs and delay wound healing. And let-7f-5p antagomir utilized in wound margin could effectively promote refractory wound healing.

The Emerging Role of Immune Cells and Targeted Therapeutic Strategies in Diabetic Wounds Healing

Poor wound healing in individuals with diabetes has long plagued clinicians, and immune cells play key roles in the inflammation, proliferation and remodeling that occur in wound healing. When skin integrity is damaged, immune cells migrate to the wound bed through the actions of chemokines and jointly restore tissue homeostasis and barrier function by exerting their respective biological functions. An imbalance of immune cells often leads to ineffective and disordered inflammatory responses. Due to the maladjusted microenvironment, the wound is unable to smoothly transition to the proliferation and remodeling stage, causing it to develop into a chronic refractory wound. However, chronic refractory wounds consistently lead to negative outcomes, such as long treatment cycles, high hospitalization rates, high medical costs, high disability rates, high mortality rates, and many adverse consequences. Therefore, strategies that promote the rational distribution and coordinated development of immune cells during wound healing are very important for the treatment of diabetic wounds (DW). Here, we explored the following aspects by performing a literature review: 1) the current situation of DW and an introduction to the biological functions of immune cells; 2) the role of immune cells in DW; and 3) existing (or undeveloped) therapies targeting immune cells to promote wound healing to provide new ideas for basic research, clinical treatment and nursing of DW.

Dendritic epidermal T cells secreting exosomes promote the proliferation of epidermal stem cells to enhance wound re-epithelialization

Background

Efficient re-epithelialization is important for successful skin wound healing. The proportion of epidermal stem cells (EpSCs) and dendritic epidermal T cells (DETCs) determines the extent of wound re-epithelialization, especially in large areas of skin tissue loss. However, it remains unknown whether and how DETCs regulate the status of EpSCs to impact wound re-epithelialization.

Methods

To investigate how DETCs regulate EpSCs in skin re-epithelialization, we utilized normal or full-thickness skin deficient wide type (WT) mice and Tcrσ knockout (Tcrσ^−/−) mice with DETCs or DETCs-derived exosomes (Exos) treatment. Flow cytometry analysis (FCAS), BrdU labelled experiments, immunofluorescence and immunohistochemical assays were performed to detect the proportion of EpSCs in the epidermis. Wound closure rate and re-epithelialization were assayed by a macroscopical view and hematoxylin–eosin (H&E) staining. EpSCs in vitro were co-cultured with DETCs in a transwell-dependent or -independent manner, or supplement with GW4869 or Exos (5 µg/mL, 15 µg/mL and 45 µg/mL), and the proliferation of EpSCs was detected by means of FCAS and CFSE.

Results

Our data showed that the proportion of CD49f^briCD71^dim cells, K15⁺ cells and BrdU⁺ cells in the normal epidermis of Tcrδ^−/− mice had no significant difference compared to WT mice. For wounded Tcrδ^−/− mice, DETCs treatment increase the proportion of CD49f^briCD71^dim cells, K15⁺ cells and BrdU⁺ cells in the epidermis around the wound in comparison to PBS treatment. DETCs significantly increased the number of CD49f^briCD7^dim cells and K15⁺ cells through transwell-dependent or -independent manners relative to control group. Furthermore, Exos stimuli remarkedly promote the proliferation of EpSCs compared to control group, while the increasement was suppressed when DETCs were interfered with GW4869. Gross observation and H&E staining showed that Exos significantly accelerated wound closure and increased re-epithelialization length in Tcrδ^−/− mice when compared to control mice. Additionally, we found in vivo that Exos observably facilitated the proliferation of CD49f^briCD7^dim cells and K15⁺ cells.

Conclusions

We revealed that DETCs enhanced the proliferation of EpSCs in the epidermis around the wounds to accelerate re-epithelialization in which Exos played important roles in the remote regulation of EpSCs proliferation. Together, these findings suggest a mechanistic link among DETC-derived exosomes, the proliferation of EpSCs, and wound re-epithelialization in the skin.

Construction of heparin-based hydrogel incorporated with Cu5.4O ultrasmall nanozymes for wound healing and inflammation inhibition

Excessive production of inflammatory chemokines and reactive oxygen species (ROS) can cause a feedback cycle of inflammation response that has a negative effect on cutaneous wound healing. The use of wound-dressing materials that simultaneously absorb chemokines and scavenge ROS constitutes a novel 'weeding and uprooting' treatment strategy for inflammatory conditions. In the present study, a composite hydrogel comprising an amine-functionalized star-shaped polyethylene glycol (starPEG) and heparin for chemokine sequestration as well as Cu5.4O ultrasmall nanozymes for ROS scavenging (Cu5.4O@Hep-PEG) was developed. The material effectively adsorbs the inflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, decreasing the migratory activity of macrophages and neutrophils. Furthermore, it scavenges the ROS in wound fluids to mitigate oxidative stress, and the sustained release of Cu5.4O promotes angiogenesis. In acute wounds and impaired-healing wounds (diabetic wounds), Cu5.4O@Hep-PEG hydrogels outperform the standard-of-care product Promogram® in terms of inflammation reduction, increased epidermis regeneration, vascularization, and wound closure.

αβ T cells replacing dermal and epidermal γδ T cells in Tcrd-/- mice express an MHC-independent TCR repertoire

The epidermis of mouse skin is usually populated by dendritic epidermal T cells (γδDETC) expressing an invariant Vγ5Vδ1⁺ TCR. In Tcrd^-/- mice, skin-resident γδDETC are replaced by αβDETC carrying polyclonal αβ TCRs. Although they exhibit a dendritic morphology, αβDETC were reported to be less functional than genuine γδDETC, likely because their TCR is unable to interact with the original TCR ligands of γδDETC. However, the TCR repertoire of those replacement DETC in Tcrd^-/- mice might provide clues for understanding the development and selection of canonical γδDETC. Here, we compare the phenotype and TCR repertoires of wild-type and Tcrd^-/- mouse skin T cells. Our data reveal that αβDETC are CD4/CD8 double negative and express an MHC-independent TCR repertoire. Furthermore, we identify a second MHC-independent population of CD103^hi CD4/ CD8 double-negative αβ T cells in the dermis of Tcrd^-/- mice.

The molecular mechanisms supporting the homeostasis and activation of dendritic epidermal T cell and its role in promoting wound healing

The epidermis is the outermost layer of skin and the first barrier against invasion. Dendritic epidermal T cells (DETCs) are a subset of γδ T cells and an important component of the epidermal immune microenvironment. DETCs are involved in skin wound healing, malignancy and autoimmune diseases. DETCs secrete insulin-like growth factor-1 and keratinocyte growth factor for skin homeostasis and re-epithelization and release inflammatory factors to adjust the inflammatory microenvironment of wound healing. Therefore, an understanding of their development, activation and correlative signalling pathways is indispensable for the regulation of DETCs to accelerate wound healing. Our review focuses on the above-mentioned molecular mechanisms to provide a general research framework to regulate and control the function of DETCs.

The G protein-coupled receptor 15 (GPR15) regulates cutaneous immunology by maintaining dendritic epidermal T cells and regulating the skin microbiome

The G protein-coupled receptor 15 (GPR15) regulates homing of different T-cell populations into the gut, thus, preserving tissue homeostasis. Its potential role in the preservation of homeostasis on other body interfaces, including the skin, is less well understood. We addressed the impact of GPR15 on cutaneous T-cell populations and the skin microbiome under steady-state conditions. Genetic deficiency in GPR15 substantially altered the composition of skin-resident T-cell populations. Precisely, dendritic epidermal T cells were almost absent in the epidermis of Gpr15^-/- mice. The niche of dendritic epidermal T cells in the epidermis was, instead, populated by αβ TCR⁺ T cells. These changes were associated with shifts in the skin microbiota in Gpr15^-/- mice. Collectively, our results uncover a role of GPR15 in the regulation of the cutaneous immune system and, thus, highlight the receptor as important general regulator of tissue homeostasis of exterior body interfaces.

Epidermal resident γδ T cell development and function in skin

Epidermal resident γδ T cells, or dendritic epidermal T cells (DETCs) in mice, are a unique and conserved population of γδ T cells enriched in the epidermis, where they serve as the regulators of immune responses and sense skin injury. Despite the great advances in the understanding of the development, homeostasis, and function of DETCs in the past decades, the origin and the underlying molecular mechanisms remain elusive. Here, we reviewed the recent research progress on DETCs, including their origin and homeostasis in the skin, especially at transcriptional and epigenetic levels, and discuss the involvement of DETCs in skin diseases.

Promotion of collagen deposition during skin healing through Smad3/mTOR pathway by parathyroid hormone-loaded microneedle

Skin wounds are associated with huge economic and emotional burdens for millions of people annually and are a challenge for health workers worldwide. At present, for skin defects after traumatic accidents, especially large-area skin defects, newly developed strategies such as the use of emerging biomaterials and cell therapy could be considered as options besides classic skin grafts. However, the new strategies have to deal with problems such as immune rejection and high costs for patients. An insufficient understanding of the mechanisms of skin wound healing further hinders the development of innovative treatment approaches. In this study, we developed a parathyroid hormone (PTH)-loaded phase-transition microneedle (PTMN) patch to deliver PTH subcutaneously in an efficient manner and change microneedle patch daily to achieve intermittent and systematic drug administration. By evaluating wound closure, re-epithelialization, collagen deposition, and extracellular matrix (ECM) expression in a Sprague-Dawley rat model of traumatic skin wounds, we demonstrated that intermittent systemic administration of PTH using our PTMN patches accelerated skin wound healing. Further, we demonstrated that the use of the patch may accelerate skin wound healing depending on the activation of the transforming growth factor (TGF)-β/Smad3/mammalian target of rapamycin (mTOR) cascade pathway. Our results suggest that the PTH-loaded PTMN patch may be a novel therapeutic strategy for treating skin wounds.

Skin Resident γδ T Cell Function and Regulation in Wound Repair

The skin is a critical barrier that protects against damage and infection. Within the epidermis and dermis reside γδ T cells that play a variety of key roles in wound healing and tissue homeostasis. Skin-resident γδ T cells require T cell receptor (TCR) ligation, costimulation, and cytokine reception to mediate keratinocyte activity and inflammatory responses at the wound site for proper wound repair. While both epidermal and dermal γδ T cells regulate inflammatory responses in wound healing, the timing and factors produced are distinct. In the absence of growth factors, cytokines, and chemokines produced by γδ T cells, wound repair is negatively impacted. This disruption in γδ T cell function is apparent in metabolic diseases such as obesity and type 2 diabetes. This review provides the current state of knowledge on skin γδ T cell activation, regulation, and function in skin homeostasis and repair in mice and humans. As we uncover more about the complex roles played by γδ T cells in wound healing, novel targets can be discovered for future clinical therapies.

Get in Touch With Dendritic Epithelial T Cells!

Innate and adaptive immune systems continuously interchange information and orchestrate their immune responses to protect the host. γδT cells play crucial roles, as they incorporate both innate and adaptive immune characteristics. Dendritic epidermal T cells (DETC) are specialized γδT cells, which are uniquely positioned to rapidly respond to skin wounds and infections. Their elongated dendrite morphology allows them to be in continuous contact with multiple neighboring keratinocytes and Langerhans cells. Cellular interactions are fundamental to the formation, activation and maintenance of immune cell functions during steady state and pathology. Recent technological advances, especially in the field of cellular imaging, have contributed greatly to the characterization of complex cellular interactions in a spatiotemporally resolved manner. In this review, we will highlight the often-underappreciated function of DETC and other γδT cells during steady state and an ongoing immune response. More specifically, we discuss how DETC-precursors are shaped in the fetal thymus during embryogenesis as well as how direct cell-cell interactions of DETC with neighboring epidermal cells shape skin homeostasis and effector functions. Furthermore, we will discuss seminal work and recent discoveries made in the γδT cell field, which have highlighted the importance of γδT cells in the skin, both in humans and mice.

Immune Cell Therapies to Improve Regeneration and Revascularization of Non-Healing Wounds

With the increased prevalence of chronic diseases, non-healing wounds place a significant burden on the health system and the quality of life of affected patients. Non-healing wounds are full-thickness skin lesions that persist for months or years. While several factors contribute to their pathogenesis, all non-healing wounds consistently demonstrate inadequate vascularization, resulting in the poor supply of oxygen, nutrients, and growth factors at the level of the lesion. Most existing therapies rely on the use of dermal substitutes, which help the re-epithelialization of the lesion by mimicking a pro-regenerative extracellular matrix. However, in most patients, this approach is not efficient, as non-healing wounds principally affect individuals afflicted with vascular disorders, such as peripheral artery disease and/or diabetes. Over the last 25 years, innovative therapies have been proposed with the aim of fostering the regenerative potential of multiple immune cell types. This can be achieved by promoting cell mobilization into the circulation, their recruitment to the wound site, modulation of their local activity, or their direct injection into the wound. In this review, we summarize preclinical and clinical studies that have explored the potential of various populations of immune cells to promote skin regeneration in non-healing wounds and critically discuss the current limitations that prevent the adoption of these therapies in the clinics.

Alveolar Epithelial Cells Promote IGF-1 Production by Alveolar Macrophages Through TGF-β to Suppress Endogenous Inflammatory Signals

To maintain alveolar gas exchange, the alveolar surface has to limit unnecessary inflammatory responses. This involves crosstalk between alveolar epithelial cells (AECs) and alveolar macrophages (AMs) in response to damaging factors. We recently showed that insulin-like growth factor (IGF)-1 regulates the phagocytosis of AECs. AMs secrete IGF-1 into the bronchoalveolar lavage fluid (BALF) in response to inflammatory stimuli. However, whether AECs regulate the production of IGF-1 by AMs in response to inflammatory signals remains unclear, as well as the role of IGF-1 in controlling the alveolar balance in the crosstalk between AMs and AECs under inflammatory conditions. In this study, we demonstrated that IGF-1 was upregulated in BALF and lung tissues of acute lung injury (ALI) mice, and that the increased IGF-1 was mainly derived from AMs. In vitro experiments showed that the production and secretion of IGF-1 by AMs as well as the expression of TGF-β were increased in LPS-stimulated AEC-conditioned medium (AEC-CM). Pharmacological blocking of TGF-β in AECs and addition of TGF-β neutralizing antibody to AEC-CM suggested that this AEC-derived cytokine mediates the increased production and secretion of IGF-1 from AMs. Blocking TGF-β synthesis or treatment with TGF-β neutralizing antibody attenuated the increase of IGF-1 in BALF in ALI mice. TGF-β induced the production of IGF-1 by AMs through the PI3K/Akt signaling pathway. IGF-1 prevented LPS-induced p38 MAPK activation and the expression of the inflammatory factors MCP-1, TNF-α, and IL-1β in AECs. However, IGF-1 upregulated PPARγ to increase the phagocytosis of apoptotic cells by AECs. Intratracheal instillation of IGF-1 decreased the number of polymorphonuclear neutrophils in BALF of ALI model mice, reduced alveolar congestion and edema, and suppressed inflammatory cell infiltration in lung tissues. These results elucidated a mechanism by which AECs used TGF-β to regulate IGF-1 production from AMs to attenuate endogenous inflammatory signals during alveolar inflammation.

Role of Dendritic Epidermal T Cells in Cutaneous Carcinoma

Dendritic epidermal T cells (DETCs) are γδ T cells expressing invariant Vγ5Vδ1 T cell receptor (TCR) in murine epidermis. Initially, the development and the maturation of DETC progenitors are mediated by skint-1, TCR, and cytokines in the fetal thymus. Then, the DETC progenitors migrate to the epidermis with the guidance of selectins, CCR10, CCR4, etc. Eventually, mature DETCs proliferate and maintain a homeostatic population in the epidermis through IL-15 and aryl hydro-carbon receptor signaling. In “stressed” skin, DETCs are activated, exhibiting features such as a round morphology, cytotoxicity, and production of cytokines. In cutaneous carcinoma, DETCs generally inhibit tumor development directly in non-major histocompatibility complex-restricted manner, with the assistance of cytokines. DETCs also recognize and inhibit tumor via TCR, non-TCR receptors (such as 2B4 and NKG2D), or both. This study summarizes the biogenesis and the function of DETCs in cutaneous carcinoma and clarifies the essential surveillance role in the epidermis that DETCs play. As there are no DETCs in human epidermis but only human epidermis γδ T cells, we need to understand the anti-tumor pathways used by DETCs to find analogous immune pathways in human skin, which could be exploited for novel therapeutics.

Ultrasmall copper-based nanoparticles for reactive oxygen species scavenging and alleviation of inflammation related diseases

Oxidative stress is associated with many acute and chronic inflammatory diseases, yet limited treatment is currently available clinically. The development of enzyme-mimicking nanomaterials (nanozymes) with good reactive oxygen species (ROS) scavenging ability and biocompatibility is a promising way for the treatment of ROS-related inflammation. Herein we report a simple and efficient one-step development of ultrasmall Cu_5.4O nanoparticles (Cu_5.4O USNPs) with multiple enzyme-mimicking and broad-spectrum ROS scavenging ability for the treatment of ROS-related diseases. Cu_5.4O USNPs simultaneously possessing catalase-, superoxide dismutase-, and glutathione peroxidase-mimicking enzyme properties exhibit cytoprotective effects against ROS-mediated damage at extremely low dosage and significantly improve treatment outcomes in acute kidney injury, acute liver injury and wound healing. Meanwhile, the ultrasmall size of Cu_5.4O USNPs enables rapid renal clearance of the nanomaterial, guaranteeing the biocompatibility. The protective effect and good biocompatibility of Cu_5.4O USNPs will facilitate clinical treatment of ROS-related diseases and enable the development of next-generation nanozymes.

Systematic review and meta-analysis of mouse models of diabetes-associated ulcers

Mouse models are frequently used to study diabetes-associated ulcers, however, whether these models accurately simulate impaired wound healing has not been thoroughly investigated. This systematic review aimed to determine whether wound healing is impaired in mouse models of diabetes and assess the quality of the past research. A systematic literature search was performed of publicly available databases to identify original articles examining wound healing in mouse models of diabetes. A meta-analysis was performed to examine the effect of diabetes on wound healing rate using random effect models. A meta-regression was performed to examine the effect of diabetes duration on wound healing impairment. The quality of the included studies was also assessed using two newly developed tools. 77 studies using eight different models of diabetes within 678 non-diabetic and 720 diabetic mice were included. Meta-analysis showed that wound healing was impaired in all eight models. Meta-regression suggested that longer duration of diabetes prior to wound induction was correlated with greater degree of wound healing impairment. Pairwise comparisons suggested that non-obese diabetic mice exhibited more severe wound healing impairment compared with db/db mice, streptozotocin-induced diabetic mice or high-fat fed mice at an intermediate stage of wound healing (p<0.01). Quality assessment suggested that the prior research frequently lacked incorporation of key clinically relevant characteristics. This systematic review suggested that impaired wound healing can be simulated in many different mouse models of diabetes but these require further refinement to become more clinically relevant.

Management of Biological Therapy Before Elective Inflammatory Bowel Disease Surgeries

Increasing uptake of biologic therapy has contributed to declining surgical rates for inflammatory bowel disease (IBD). However, a significant number of patients on biologic therapy will go on to require surgery. The literature is conflicted with regard to the preoperative management of biologic therapy before urgent or elective IBD surgery. This article reviews the available data on postoperative complications following preoperative treatment with anti-tumor necrosis factor alpha therapy, anti-integrin therapy, and anti-interleukin therapy.

Mucosal healing progression after acute colitis in mice

BACKGROUND

Mucosal healing has become a therapeutic goal to achieve stable remission in patients with inflammatory bowel diseases. To achieve this objective, overlapping actions of complex cellular processes, such as migration, proliferation, and differentiation, are required. These events are longitudinally and tightly controlled by numerous factors including a wide range of distinct regulatory proteins. However, the sequence of events associated with colon mucosal repair after colitis and the evolution of the luminal content characteristics during this process have been little studied.

AIM

To document the evolution of colon mucosal characteristics during mucosal healing using a mouse model with chemically-induced colitis.

METHODS

C57BL/6 male mice were given 3.5% dextran sodium sulfate (DSS) in drinking water for 5 d. They were euthanized 2 (day 7), 5 (day 10), 8 (day 13), and 23 (day 28) d after DSS removal. The colonic luminal environment and epithelial repair processes during the inflammatory flare and colitis resolution were analyzed with reference to a non-DSS treated control group, euthanized at day 0. Epithelial repair events were assessed histo-morphologically in combination with functional permeability tests, expression of key inflammatory and repairing factors, and evaluation of colon mucosa-adherent microbiota composition by 16S rRNA sequencing.

RESULTS

The maximal intensity of colitis was concomitant with maximal alterations of intestinal barrier function and histological damage associated with goblet cell depletion in colon mucosa. It was recorded 2 d after termination of the DSS-treatment, followed by a progressive return to values similar to those of control mice. Although signs of colitis were severe (inflammatory cell infiltrate, crypt disarray, increased permeability) and associated with colonic luminal alterations (hyperosmolarity, dysbiosis, decrease in short-chain fatty acid content), epithelial healing processes were launched early during the inflammatory flare with increased gene expression of certain key epithelial repair modulators, including transforming growth factor-β, interleukin (Il)-15, Il-22, Il-33, and serum amyloid A. Whereas signs of inflammation progressively diminished, luminal colonic environment alterations and microscopic abnormalities of colon mucosa persisted long after colitis induction.

CONCLUSION

This study shows that colon repair can be initiated in the context of inflamed mucosa associated with alterations of the luminal environment and highlights the longitudinal involvement of key modulators.

Insulin‑like growth factor 1 inhibits phagocytosis of alveolar epithelial cells in asthmatic mice

The phagocytosis of apoptotic cells by alveolar epithelial cells helps to eliminate airway inflammation. Insulin‑like growth factor 1 (IGF‑1) regulates cell metabolism and proliferation, and promotes cell survival, while it may also promote the proliferation and differentiation of alveolar epithelial cells during the repair of lung injury. The present study investigated the effect of IGF‑1 on the phagocytic activity of alveolar epithelial cells, a nonprofessional phagocyte. IGF‑1 was elevated in lung tissue and bronchoalveolar lavage fluid obtained from mice with ovalbumin‑induced asthma. IGF‑1 was reduced by 50% in the lung tissue and by nearly 100% in the bronchoalveolar lavage fluid in asthmatic mice established by depletion of alveolar macrophages using 2‑chloroadenosine. In addition, interleukin‑33 induced IGF‑1 production in primary alveolar macrophages. It was also observed that IGF‑1 inhibited the phagocytosis of fluorescent microspheres and apoptotic cells by MLE‑12 alveolar epithelial cells. Antibody blocking of IGF‑1 enhanced the phagocytosis of fluorescent microspheres and apoptotic cells, and significantly reduced inflammatory cell infiltration in airway and perivascular tissues. The elevated IGF‑1 level in the lungs of asthma model mice was mainly produced in alveolar macrophages. Taken together, the current study demonstrated that IGF‑1 inhibited phagocytosis by alveolar epithelial cells, and that IGF‑1 blockade enhanced the phagocytic activity and alleviated airway inflammation. These results support the potential use of IGF‑1 as a target in the treatment of asthma.

Upregulated IGF‑1 in the lungs of asthmatic mice originates from alveolar macrophages

Asthma is characterized by inflammation and remodeling of the airways. Insulin‑like growth factor-1 (IGF‑1) serves an important role in the repair of lung tissue injury and airway remodeling by elevating collagen and elastin content, increasing the thickness of smooth muscle and promoting the proliferation of lung epithelial and interstitial cells, as well as fibroblasts; however, the content of IGF‑1 and its cellular origin in the lungs of patients with asthma remain unknown. In the present study, a mouse model of asthma was constructed. Following isolation of alveolar macrophages (AMs), the content of IGF‑1 in lung tissue and bronchoalveolar lavage fluid (BALF) was detected by ELISA. The proliferation and phagocytosis of alveolar epithelial cells (AECs) stimulated by IGF‑1 were detected by Cell Counting Kit‑8 method and flow cytometry, respectively. In the present study, IGF‑1 was upregulated in the lung tissues of asthmatic mice, and the content of IGF‑1 in BALF was also elevated. Depletion of AMs by treating mice with 2‑chloroadenosine via nose dripping reversed the increase of IGF‑1 by 80% in lung tissues and by ~100% in BALF of asthmatic mice, suggesting that elevated IGF‑1 in asthmatic mice predominantly originated from AMs. As IGF‑1 promotes the proliferation and phagocytosis of AECs, AM‑derived IGF‑1 may serve an important role in the regulation of airway inflammation and remodeling in asthmatic mice.

Functions of Vγ4 T Cells and Dendritic Epidermal T Cells on Skin Wound Healing

Wound healing is a complex and dynamic process that progresses through the distinct phases of hemostasis, inflammation, proliferation, and remodeling. Both inflammation and re-epithelialization, in which skin γδ T cells are heavily involved, are required for efficient skin wound healing. Dendritic epidermal T cells (DETCs), which reside in murine epidermis, are activated to secrete epidermal cell growth factors, such as IGF-1 and KGF-1/2, to promote re-epithelialization after skin injury. Epidermal IL-15 is not only required for DETC homeostasis in the intact epidermis but it also facilitates the activation and IGF-1 production of DETC after skin injury. Further, the epidermal expression of IL-15 and IGF-1 constitutes a feedback regulatory loop to promote wound repair. Dermis-resident Vγ4 T cells infiltrate into the epidermis at the wound edges through the CCR6-CCL20 pathway after skin injury and provide a major source of IL-17A, which enhances the production of IL-1β and IL-23 in the epidermis to form a positive feedback loop for the initiation and amplification of local inflammation at the early stages of wound healing. IL-1β and IL-23 suppress the production of IGF-1 by DETCs and, therefore, impede wound healing. A functional loop may exist among Vγ4 T cells, epidermal cells, and DETCs to regulate wound repair.