Regulation Of Tissue Repair Research Articles

Cell Death in the Tumor Microenvironment: Implications for Cancer Immunotherapy.

The physiological fate of cells that die by apoptosis is their prompt and efficient removal by efferocytosis. During these processes, apoptotic cells release intracellular constituents that include purine nucleotides, lysophosphatidylcholine (LPC), and Sphingosine-1-phosphate (S1P) that induce migration and chemo-attraction of phagocytes as well as mitogens and extracellular membrane-bound vesicles that contribute to apoptosis-induced compensatory proliferation and alteration of the extracellular matrix and the vascular network. Additionally, during efferocytosis, phagocytic cells produce a number of anti-inflammatory and resolving factors, and, together with apoptotic cells, efferocytic events have a homeostatic function that regulates tissue repair. These homeostatic functions are dysregulated in cancers, where, aforementioned events, if not properly controlled, can lead to cancer progression and immune escape. Here, we summarize evidence that apoptosis and efferocytosis are exploited in cancer, as well as discuss current translation and clinical efforts to harness signals from dying cells into therapeutic strategies.

Pathogenic Activation of Mesenchymal Stem Cells Is Induced by the Disease Microenvironment in Systemic Sclerosis.

In systemic sclerosis (SSc), a persistent tissue repair process leads to progressive fibrosis of the skin and internal organs. The role of mesenchymal stem cells (MSCs), which characteristically initiate and regulate tissue repair, has not been fully evaluated. We undertook this study to investigate whether dividing metakaryotic MSCs are present in SSc skin and to examine whether exposure to the disease microenvironment activates MSCs and leads to transdifferentiation. Skin biopsy material from patients with recent-onset diffuse SSc was examined by collagenase spread of 1-mm-thick surface-parallel sections, in order to identify dividing metakaryotic stem cells in each tissue plane. Adipose-derived MSCs from healthy controls were treated with dermal blister fluid (BF) from patients with diffuse SSc and profiled by next-generation sequencing, or they were evaluated for phenotypic changes relevant to SSc. Differential responses of dermal fibroblasts were studied in parallel. MSC-like cells undergoing active metakaryotic division were identified in SSc sections (but not control sections) most prominently in the deep dermis and adjacent to damaged microvessels, in both clinically involved and uninvolved skin. Furthermore, exposure to SSc BF caused selective MSC activation, inducing a myofibroblast signature, while reducing signatures of vascular repair and adipogenesis and enhancing migration and contractility. Microenvironmental factors implicated in inducing transdifferentiation included the profibrotic transforming growth factor β, the presence of lactate, and mechanosensing, while the microenvironment Th2 cytokine, interleukin-31, enhanced osteogenic commitment (calcinosis). Dividing MSC-like cells are present in the SSc disease microenvironment where multiple factors, likely acting in concert, promote transdifferentiation and lead to a complex and resistant disease state.

PDGFRα ablation leads to alteration of ECM and immune cell composition in the lung

Abstract Fibroblasts are the major cells responsible for tissue homeostasis, repair, and remodeling. In particular, PDGFRα is expressed by mesenchymal progenitors in the lung that constitute the myofibroblast population which transiently express α-SMA during alveologenesis. In the fibrotic lungs, PDGFRα+ lineages can differentiate into subpopulation of myofibroblasts which regulate tissue repair and remodeling. Although the contribution of PDGFRα+lineage to lung development and fibrosis are particularly well-known, their roles in the lung parenchyma at baseline are less characterized. To explore how PDGFRα+ fibroblasts affect extracellular matrix in baseline lung, we used genetic ablation of PDGFRα+ fibroblasts using Pdgfrα-CreERT2-driven expression of diphtheria toxin A. Histologically, thin mesenchyme was observed in fibroblast-ablated adult lungs. A majority of PDGFRα+ lineages are Col1a1-GFP+ cells, but PDGFRα-ablated lungs showed a significant decrease in the number of PDGFRα lineage and Col1a1-GFP+ cells. In addition, decreased expressions of ECM genes, such as Col1a1, Col1a2, and fibronectin-1 were observed in PDGFRα-ablated lungs. These data indicated that PDGFRα+ cells are a major source of extracellular proteins and PDGFRα ablation leads to alteration of ECM homeostasis in the baseline lung. Flow cytometry analysis of the lung tissues revealed that PDGFRα ablation resulted in elevated numbers of leukocytes and neutrophils. However, fibroblast loss did not affect macrophage numbers. These data suggested that fewer PDGFRα+ cells or loss of ECM or both can affect the recruitment of immune cells in the lung. In summary, changes in ECM environment by PDGFRα ablation leads to altered immune cell composition in the lung.

IL-13 promotes precancerous epithelial cell changes during autoimmune gastritis

Abstract Individuals with chronic autoimmune diseases have an increased risk of cancer development in the affected organ. Cytokines released during chronic inflammation regulate tissue repair processes and can contribute to an increased risk of carcinogenesis. However, the identities and mechanisms by which cytokines regulate cancer development is poorly understood. In these studies, a TCR transgenic mouse model of autoimmune gastritis (AIG) was used to determine the cellular sources of IL-13 and the molecular mechanisms by which IL-13 promotes precancerous epithelial cell changes in a setting of chronic inflammation. Using this model, we identified IL-13 secreting CD4+ T cells, ILC2s, and mast cells present in the mucosa of chronically inflamed stomachs. The use of both murine and human 3D gastric organoid cultures established that IL-13 acted directly on the gastric epithelium and regulated epithelial cell survival, growth, and differentiation. Neutralizing IL-13 in mice with AIG prevented many of the precancerous cellular changes associated with gastric carcinogenesis. Finally, single-cell RNA sequencing of gastric epithelial cells with and without IL-13 receptors identified the transcriptional responses of mucosal epithelium to IL-13 during chronic autoimmunity. These studies have identified that tissue-specific IL-13 production during autoimmunity acts directly on the gastric epithelium to induce cellular changes associated with gastric cancer.

Nitric Oxide in Dental Pulp Tissue: From Molecular Understanding to Clinical Application in Regenerative Endodontic Procedures.

Nitric oxide (NO), which is synthesized by the enzyme NO synthase (NOS), is a versatile endogenous molecule with multiple biological effects on many tissues and organs. In dental pulp tissue, NO has been found to play multifaceted roles in regulating physiological activities, inflammation processes, and tissue repair events, such as cell proliferation, neuronal degeneration, angiogenesis, and odontoblastic differentiation. However, there is a deficiency of detailed discussion on the NO-mediated interactions between inflammation and reparative/regenerative responses in wounded dental pulp tissue, which is a central determinant of ultimate clinical outcomes. Thus, the purpose of this review is to outline the current molecular understanding on the roles of Janus-faced molecule NO in dental pulp physiology, inflammation, and reparative activities. Based on this knowledge, advanced physicochemical techniques designed to manipulate the therapeutic potential of NOS and NO production in endodontic regeneration procedures are further discussed. Impact statement The interaction between inflammation and reparative/regenerative responses is very important for regenerative endodontic procedures, which are biologically based approaches intended to replace damaged tissues. Inside dental pulp tissue, endogenous nitric oxide (NO) is generated mainly by immunocompetent cells and dental pulp cells and mediates not only inflammatory/immune activities but also signaling cascades that regulate tissue repair and reconstruction, indicating its involvement in both tissue destruction and regeneration. Thus, it is feasible that NO acts as one of the indicators and modulators in dental pulp repair or regeneration under physiological and pathological conditions.

Effects of magnetic fields on immune system, tissue repair and fibrosis

Tissue repair and regeneration are vital biological processes that involve three intertwined stages of inflammation, proliferation, and remodeling. The immune system plays an important role in each stage to regulate the processes of tissue repair, mainly by a complex network consisting of immune cells and the secreted cytokines. In recent years, with the popularity of electronic devices and magnetic materials, the biological effects of magnetic fields (MFs) have received widespread attention, and research on the effects of MFs on biological tissue repair and fibrosis has made a series of advantages. Using different types of MFs of varying strengths, researchers have found that MFs modulate the body’s immune system in various disease models. MFs affect the process of tissue repair and scarring by changing the number, function and phenotype of immune cells. Macrophages have two distinct functions in the processes of wound healing and these functions are closely related to their phenotypic changes in different physiological states. Inflammatory macrophages (M1 type) disrupt the normal metabolism of cells, induce apoptosis, or exacerbate ischemia and hypoxia. Anti-inflammatory macrophages (M2 type) bridge the processes of tissue repair by activating and supporting the function of stem cells/progenitor cells, and remodeling extracellular matrix components to provide scaffold for tissue regeneration and angiogenesis. MFs thus change the phenotype and function of macrophages through various mechanisms, thereby regulate the repair processes of damage. Mesenchymal stem cells (MSCs) are a group of multifunctional cells that have the ability to differentiate into bone cells, adipocytes, and chondrocytes. They are recruited to the site of injury and can interact directly with other immune cells, thus inhibit inflammation and promote tissue repair. Some studies suggest that MFs could not only improve the differentiation potential of MSCs, but also promote MSCs accumulation in the target tissue. Myeloid-derived suppressor cells (MDSCs) are a group of cells with immunosuppressive functions. The phenotype and number of MDSCs can be changed by MFs, therefore MFs may exert the function of regulating tissue repair via changing the state of MDSCs, thus, participating in pathological processes such as immune regulation and inflammatory response of tumorigenesis. Researchers also reported that MFs influence tissue repair though neutrophils and keratinocyte, and enhance the therapy efficacy of antibiotics. Fibrotic scar is a structure formed by excessive extracellular matrix deposition during tissue repairing process, and differs from normal tissue morphology. As the function of macrophages, MSCs and fibroblasts can be affected by MFs, MFs have the ability to regulate fibrosis formation. This review article focuses on the effect of MFs on tissue repairing and regeneration. Further exploration of the role of MFs in tissue repairing and fibrosis formation will lead to new ideas for using MFs in disease treating.

CXCL-10/CXCR3 in macrophages regulates tissue repair by controlling the expression of Arg1, VEGFa and TNFα.

Macrophages have been reported to participate in inflammation, tissue homeostasis and tissue repair. The detailed mechanism of macrophage-mediated tissue repair is not clear. CXCL-10, secreted by monocytes, endothelial cells and fibroblasts, mediates immune response and angiogenesis by binding to CXCR3. In this study, the expression of CXCL-10 and CXCR3 in porcine lung injury induced by porcine reproductive and respiratory syndrome virus (PRRSV) infection was firstly examined. The results showed that the expression of both CXCL-10 and CXCR3 increased in the infected pig lungs. In addition, the increased expression of CXCL-10 and CXCR3 in macrophage treated by poly (I:C) was also observed, suggesting the autocrine system existed in macrophages. Furthermore, CXCL-10 treatment induced upregulation of Arg1 and VEGFa, and downregulation of TNFα in macrophage, and CXCR3 antagonist AMG487 treatment presented the contrary effects on the expression of Arg1, VEGFa, and TNFα. CXCL- 10-stimulated effects were dependent on PI3K/Akt signaling pathway. Wound-healing assay showed that CXCL-10 treatment macrophage conditioned medium promoted the healing process of endothelial cells. Our results suggested that CXCL-10/CXCR3 in macrophage may mediate tissue repair by regulating the macrophage expression of Arg1, VEGFa and TNFα. Modulation of CXCL-10/CXCR3 axis in macrophage may be a potential therapeutic strategy for tissue injury and repair.

An emerging role of regulatory T-cells in cardiovascular repair and regeneration.

Accumulating evidence has demonstrated that immune cells play an important role in the regulation of tissue repair and regeneration. After injury, danger signals released by the damaged tissue trigger the initial pro-inflammatory phase essential for removing pathogens or cellular debris that is later replaced by the anti-inflammatory phase responsible for tissue healing. On the other hand, impaired immune regulation can lead to excessive scarring and fibrosis that could be detrimental for the restoration of organ function. Regulatory T-cells (Treg) have been revealed as the master regulator of the immune system that have both the immune and regenerative functions. In this review, we will summarize their immune role in the induction and maintenance of self-tolerance; as well as their regenerative role in directing tissue specific response for repair and regeneration. The latter is clearly demonstrated when Treg enhance the differentiation of stem or progenitor cells such as satellite cells to replace the damaged skeletal muscle, as well as the proliferation of parenchymal cells including neonatal cardiomyocytes for functional regeneration. Moreover, we will also discuss the reparative and regenerative role of Treg with a particular focus on blood vessels and cardiac tissues. Last but not least, we will describe the ongoing clinical trials with Treg in the treatment of autoimmune diseases that could give clinically relevant insights into the development of Treg therapy targeting tissue repair and regeneration.

Kaempferia galanga L. sebagai Anti-Inflamasi dan Analgetik

Galangal ( Kaempferia galanga l ) is an herb that is often used in everyday life and widely used as a spice, food flavoring, and local tonic ingredients called ‘Jamu’. Galangal is a source of zinc, starch, ethyl ester, paraeumarin, borneaol, minerals, cinnamic acid, and other nutrients that are widely used in traditional medicine applications for a long time, especially in Southeast Asia. Besides that, it has medical functions, one of which is anti-inflammatory. Inflammation is a normal protective response to tissue injuries caused by physical trauma, damaging chemicals or microbiological substances. Inflammation can also be interpreted as the body's effort to activate or damage organisms that attack, eliminate irritants and regulate tissue repair. Signs of inflammation are redness, swelling, heat, and pain. Many chemical drugs are used to prevent inflammation, one of which is that modern drugs commonly used as anti-inflammatory drugs are NSAIDs (Non-Steroid Anti-inflammatory) Mechanism as an anti-inflammatory activity by elevating anti-inflammatory production IL-10, reducing pro-inflammatory IL-6 or TNF-a production, reducing the expression of iNOS and COX-2, inhibition of PG synthesis, Kaempferia galanga L also inhibits several inflammatory mediators TNF-α, IL-1β, and Nitric Oxide (NO) and angiogenesis.

Single-cell transcriptomics of the naked mole-rat reveals unexpected features of mammalian immunity.

The immune system comprises a complex network of specialized cells that protects against infection, eliminates cancerous cells, and regulates tissue repair, thus serving a critical role in homeostasis, health span, and life span. The subterranean-dwelling naked mole-rat (NM-R; Heterocephalus glaber) exhibits prolonged life span relative to its body size, is unusually cancer resistant, and manifests few physiological or molecular changes with advancing age. We therefore hypothesized that the immune system of NM-Rs evolved unique features that confer enhanced cancer immunosurveillance and prevent the age-associated decline in homeostasis. Using single-cell RNA-sequencing (scRNA-seq) we mapped the immune system of the NM-R and compared it to that of the short-lived, cancer-prone mouse. In contrast to the mouse, we find that the NM-R immune system is characterized by a high myeloid-to-lymphoid cell ratio that includes a novel, lipopolysaccharide (LPS)-responsive, granulocyte cell subset. Surprisingly, we also find that NM-Rs lack canonical natural killer (NK) cells. Our comparative genomics analyses support this finding, showing that the NM-R genome lacks an expanded gene family that controls NK cell function in several other species. Furthermore, we reconstructed the evolutionary history that likely led to this genomic state. The NM-R thus challenges our current understanding of mammalian immunity, favoring an atypical, myeloid-biased mode of innate immunosurveillance, which may contribute to its remarkable health span.

Shape-dependent regulation of differentiation lineages of bone marrow-derived cells under cyclic stretch

Multipotent stem cells are considered as a key material in regenerative medicine, and the understanding of the heterogeneity in the differentiation potentials of bone marrow-derived cells is important in the successful regenerative tissue repair. Therefore, the present study has been performed to investigate how the differentiation of post-harvest, native bone marrow-derived cells is regulated by cyclic stretch in vitro. Bone marrow-derived cells were obtained from mouse femur of both hind limbs and categorized into the following five categories: amebocytes, round cells, spindle cells, stellate cells and others. The cells were seeded on a silicone-made stretch chamber, and subjected to cyclic stretch with an amplitude of 10% at a frequency of 1 Hz for 7 days for cell shape analysis and for 3 days for the analysis of the expression of marker proteins of osteogenic (osteocalcin), vascular smooth muscle (α-smooth muscle actin and smooth muscle myosin heavy chain) and neurogenic (neurofilament) differentiation. When disregarding the differences in the cell shapes, there was an overall trend that the application of 10% cyclic stretch inhibited osteogenic and neurogenic differentiation, but enhanced smooth muscle differentiation. Close examinations revealed that round cells were influenced the most by cyclic stretch (significant up- or down-regulation in all the four marker protein expressions) while amebocytes and spindle cells were only influenced by cyclic stretch for vascular smooth muscle and/or neurogenic differentiation. As far as the authors know, this is the first study reporting the shape-related differences in the fate decision criteria for mechanical strain in bone marrow-derived cells.

Nanofiber-reinforced decellularized amniotic membrane improves limbal stem cell transplantation in a rabbit model of corneal epithelial defect

Human amniotic membrane (AM) offers unique advantages as a matrix to support the transplantation of limbal stem cells (LSCs) due to its inherent pro-regenerative and anti-inflammatory properties. However, the widespread use of AM in clinical treatments of ocular surface disorders is limited by its weak mechanical strength and fast degradation, and high cost associated with preserving freshly isolated AM. Here we constructed a composite membrane consisting of an electrospun bioabsorbable poly(ε-caprolactone) (PCL) nanofiber mesh to significantly improve the ultimate tensile strength, toughness, and suture retention strength by 4–10-fold in comparison with decellularized AM sheet. The composite membrane showed extended stability and conferred longer-lasting coverage on wounded cornea surface compared with dAM. The composite membrane maintained the pro-regenerative and immunomodulatory properties of dAM, promoted LSC survival, retention, and organization, improved re-epithelialization of the defect area, and reduced inflammation and neovascularization. This study demonstrates the translational potential of our composite membrane for stem cell-based treatment of ocular surface damage. Statement of SignificanceHuman decellularized amniotic membrane (dAM) has been widely shown as a biodegradable and bioactive matrix for regenerative tissue repair. However, the weak mechanical property has limited its widespread use in the clinic. Here we constructed a composite membrane using a layer of electrospun poly(ε-caprolactone) (PCL) nanofiber mesh to reinforce the dAM sheet through covalent interfacial bonding, while retaining the unique bioactivity of dAM. In a rabbit model of limbal stem cell (LSC) deficiency induced by alkaline burn, we demonstrated the superior property of this PCL-dAM composite membrane for repairing damaged cornea through promoting LSC transplantation, improving re-epithelialization, and reducing inflammation and neovascularization. This new composite membrane offers great translational potential in supporting stem cell-based treatment of ocular surface damage.

Long Pentraxin 3 (PTX3) Regulates IL-17A Mediated Immunity to Primary and Secondary Leishmania major Infection

Abstract Resolution of cutaneous leishmaniasis (CL), caused by the protozoan parasite Leishmania (L) major, relies on the nature of the host immune response. The long pentraxin 3 (PTX3), a soluble pattern recognition molecule, is critical for wound healing by regulating tissue repair and also in innate and adaptive responses during infection and inflammation. Here, we show that PTX3 regulates disease pathogenesis and immunity to CL. PTX3 expression is increased in active skin lesions in patients and mice during CL, with higher levels being expressed in individuals with severe disease. PTX3−/− mice were highly resistant to primary and secondary L. major infection. Interestingly, the enhanced resistance of PTX3−/− mice to primary or secondary L. major infection was not associated with enhanced IFN-γ or decreased IL-10 response. Instead, L. major-infected PTX3−/− mice displayed strong IL-17 response and in vivo neutralization of IL-17A abolished their enhanced resistance. Naïve CD4+ T cells from PTX3−/− mice displayed increased differentiation into Th17 cells and this was associated with increased expression of Th17-specific transcription factors including RORγt, AhR and STAT3. Addition of recombinant PTX3 significantly inhibited the expression of Th17-specific transcription factors and the frequency of Th17 cells in Th17 polarizing cultures of PTX3−/− CD4+ T cells. Similarly, healed PTX3−/− mice had higher frequencies of effector memory CD4+ T cells that rapidly proliferate and differentiate into IL-17A-producing CD4+ T cells upon secondary challenge. Collectively, our results show that PTX3 contributes to pathogenesis of CL by negatively regulating protective Th17 and IL-17 responses.

Lingo3 interacts with TFF2 to control mucosal integrity, Type 1 inflammation, and colitic tissue repair

Abstract Constant exposure of intestinal epithelial cells (IEC) to potentially damaging stimuli makes mucosal repair programs essential for gut homeostasis, immunological quiescence and resistance to colitis. Trefoil factor 2 (TFF2) is a mucus associated protein that promotes epithelial barrier integrity in the lung and intestine, but whether a bona-fide TFF2 receptor exists remains controversial. Herein, we provide evidence that leucine rich repeat nogo interacting protein 3 (LINGO3) is a transmembrane component of TFF2 signaling and proliferation within IEC. TFF2 requires LINGO3 for barrier recovery in scratch-wound assays and mice lacking LINGO3 (LINGO3KO) have impaired intestinal barrier function under steady state conditions. Interestingly, LINGO3KO mice phenocopy TFF2KO mice, with both having a significant accumulation of mucosal CD4+TH1 cells expressing IFNg+ TNFa+ under steady-state conditions and impaired recovery from DSS-induced colitis. Impaired recovery in LINGO3KO animals was marked by reduced intestinal crypt regeneration and reduced expression of the stem cell marker LGR5 compared to WT counterparts. Additionally, TFF2 agonist administration (TFF2-Fc) promoted enhanced recovery and limited inflammatory cell recruitment in WT mice during DSS-induced colitis whereas TFF2-Fc treatment was ineffective in LINGO3KO animals. Combined, these data support our contention that a TFF2-LINGO3 ligand/receptor axis regulates tissue repair and inflammation within the gastrointestinal tract through regulation of IEC function.

Single cell RNA sequencing identifies unique inflammatory airspace macrophage subsets.

Macrophages are well recognized for their dual roles in orchestrating inflammatory responses and regulating tissue repair. In almost all acutely inflamed tissues, 2 main subclasses of macrophages coexist. These include embryonically derived resident tissue macrophages and BM-derived recruited macrophages. While it is clear that macrophage subsets categorized in this fashion display distinct transcriptional and functional profiles, whether all cells within these categories and in the same inflammatory microenvironment share similar functions or whether further specialization exists has not been determined. To investigate inflammatory macrophage heterogeneity on a more granular level, we induced acute lung inflammation in mice and performed single cell RNA sequencing of macrophages isolated from the airspaces during health, peak inflammation, and resolution of inflammation. In doing so, we confirm that cell origin is the major determinant of alveolar macrophage (AM) programing, and, to our knowledge, we describe 2 previously uncharacterized, transcriptionally distinct subdivisions of AMs based on proliferative capacity and inflammatory programing.

Emerging therapeutic potential of group 2 innate lymphoid cells in acute kidney injury.

Acute kidney injury (AKI) remains a global challenge and, despite the availability of dialysis and transplantation, can be fatal. Those that survive an AKI are at increased risk of developing chronic kidney disease and end stage renal failure. Understanding the fundamental mechanisms underpinning the pathophysiology of AKI is critical for developing novel strategies for diagnosis and treatment. A growing body of evidence indicates that amplifying type 2 immunity may have therapeutic potential in kidney injury and disease. Of particular interest are the recently described subset of innate immune cells, termed group 2 innate lymphoid cells (ILCs). Group 2 ILCs are crucial tissue-resident immune cells that maintain homeostasis and regulate tissue repair at multiple organ sites, including the kidney. They are critical mediators of type 2 immune responses following infection and injury. The existing literature suggests that activation of group 2 ILCs and production of a local type 2 immune milieu is protective against renal injury and associated pathology. In this review, we describe the emerging role for group 2 ILCs in renal homeostasis and repair. We provide an in-depth discussion of the most recent literature that use preclinical models of AKI and assess the therapeutic effect of modulating group 2 ILC function. We debate the potential for targeting these cells as novel cellular therapies in AKI and discuss the implications for future studies and translation. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Eicosanoids in tissue repair.

Trauma or infection can result in tissue damage, which needs to be repaired in a well-orchestrated manner to restore tissue function and homeostasis. Lipid mediators derived from arachidonic acid (termed eicosanoids) play central and versatile roles in the regulation of tissue repair. Here, I summarize the current state-of the-art regarding the functional activities of eicosanoids in tissue repair responses during homeostasis and disease. I also describe how eicosanoids are produced during tissue damage and repair in a time-, cell- and tissue-dependent fashion. In particular, recent insights into the roles of eicosanoids in epithelial barrier repair are reviewed. Furthermore, the distinct roles of different eicosanoids in settings of pathological tissue repair such as chronic wounds, scarring or fibrosis are discussed. Finally, an outlook is provided on how eicosanoids may be targeted by future therapeutic strategies to achieve physiological tissue repair and prevent scarring and loss of tissue function in various disease contexts.

Wound healing mechanisms in rats with streptozotocin-induced diabetes mellitus

Background. Wound healing disorders and formation of diabetic foot, a severe disabling complication of diabetes mellitus, are accompanied by nervous system impairment and/or ischemia.
 Objective — the study was aimed at assessing the effect of peripheral innervation disorders on the regulation of tissue repair in the streptozotocin-induced rat model of diabetes mellitus.
 Material and methods. The study was carried out in male white outbred rats (n=70). The animals were wounded 42 days after induction of diabetes by injecting streptozotocin (diabetes group; this group received insulin Levemir at a dose of 2 units/kg in saline subcutaneously to reduce mortality), or after injection of citrate buffer (CB group). Skin samples were taken on day 8, 16, and 24 after wound modeling. Pain sensitivity was assessed in all animals. The resulting skin fragments were fixed, dehydrated, and embedded in paraffin according to standard procedures. Sections were stained with hematoxylin and eosin, antibodies specific for Ki-67, α1, β1, and β2-adrenoreceptors were used for immunohistochemical staining. Intact animals were used as an additional control group.
 Results. Tail withdrawal time measured on day 56 was higher in DM group rats as compared to the control group (p=0.017). CB group demonstrated a tendency towards more rapid wounds healing than diabetic animals, although the difference was not statistically significant due to wide scatter of data in the DM group (p=0.64). The intensity of staining for Ki67 was lower in the DM group (p=0.045). Reduced density of β2-adrenoreceptors was observed at the areas remote from the wound in CB group rats.
 Conclusion The results show no correlation between altered innervation and impaired tissue repair in rats with streptozotocin-induced diabetes.

Mesenchymal Precursor Cells in Adult Nerves Contribute to Mammalian Tissue Repair and Regeneration.

Peripheral innervation plays an important role in regulating tissue repair and regeneration. Here we provide evidence that injured peripheral nerves provide a reservoir of mesenchymal precursor cells that can directly contribute to murine digit tip regeneration and skin repair. In particular, using single-cell RNA sequencing and lineage tracing, we identify transcriptionally distinct mesenchymal cell populations within the control and injured adult nerve, including neural crest-derived cells in the endoneurium with characteristics of mesenchymal precursor cells. Culture and transplantation studies show that these nerve-derived mesenchymal cells have the potential to differentiate into non-nerve lineages. Moreover, following digit tip amputation, neural crest-derived nerve mesenchymal cells contribute to the regenerative blastema and, ultimately, to the regenerated bone. Similarly, neural crest-derived nerve mesenchymal cells contribute to the dermis during skin wound healing. These findings support a model where peripheral nerves directly contribute mesenchymal precursor cells to promote repair and regeneration of injured mammalian tissues.

Dysregulation of Nrf2/Keap1 Redox Pathway in Diabetes Affects Multipotency of Stromal Cells.

The molecular and cellular level reaches of the metabolic dysregulations that characterize diabetes are yet to be fully discovered. As mechanisms underlying management of reactive oxygen species (ROS) gain interest as crucial factors in cell integrity, questions arise about the role of redox cues in the regulation and maintenance of bone marrow-derived multipotent stromal cells (BMSCs) that contribute to wound healing, particularly in diabetes. Through comparison of BMSCs from wild-type and diabetic mice, with a known redox and metabolic disorder, we found that the cytoprotective nuclear factor erythroid-related factor 2 (Nrf2)/kelch-like erythroid cell-derived protein 1 (Keap1) pathway is dysregulated and functionally insufficient in diabetic BMSCs (dBMSCs). Nrf2 is basally active, but in chronic ROS, we found irregular inhibition of Nrf2 by Keap1, altered metabolism, and limited BMSC multipotency. Forced upregulation of Nrf2-directed transcription, through knockdown of Keap1, restores redox homeostasis. Normalized Nrf2/Keap1 signaling restores multipotent cell properties in dBMSCs through Sox2 expression. These restored BMSCs can resume their role in regenerative tissue repair and promote healing of diabetic wounds. Knowledge of diabetes and hyperglycemia-induced deficits in BMSC regulation, and strategies to reverse them, offers translational promise. Our study establishes Nrf2/Keap1 as a cytoprotective pathway, as well as a metabolic rheostat, that affects cell maintenance and differentiation switches in BMSCs.