Pathogenesis Of Wound Healing Research Articles

MicroRNA-146a Deficiency Delays Wound Healing in Normal and Diabetic Mice.

Objective: MiRNAs are important regulators of inflammation and wound healing. However, the mechanisms through which miRNAs regulate wound healing under normal and diabetic conditions are poorly understood. We aimed to determine the effects of miR-146a on the pathogenesis of wound healing in normal and streptozotocin (STZ)-induced diabetic mice. Approach: Wild-type (WT) and miR-146a knockout (KO) mice were induced to develop diabetes with STZ. Next, skin and corneal wounds were produced and measured. Percent wound closure and histology were evaluated. Inflammation at wound sites was analyzed using flow cytometry, reverse-transcription PCR, and western blot. Results: Healing of wounded skin was significantly delayed in miR-146a KO compared with WT mice. However, corneal epithelial wound healing did not differ significantly in the mice with normal blood glucose, whereas corneal and skin wound healing was significantly delayed in KO mice with diabetes. Neutrophil infiltration increased in skin wounds of KO compared with normal mice. The potential mechanisms were associated with dysregulated interleukin 1β, tumor necrosis factor alpha (TNF-α), IRAK1 (interleukin-1 receptor-associated kinase 1), TRAF6 (TNF receptor-associated factor 6), and nuclear factor kappa B (NF-κB) signaling induced by miR-146a KO. Innovation: Skin wound healing was delayed in miR-146a KO mice and enhanced inflammatory responses were mediated by the NF-κB signaling pathway. Conclusions: Deficiency in miR-146a delayed skin wound healing by enhancing inflammatory responses in normal and diabetic mice. Therefore, miR-146a may be a potential target for modulation to accelerate skin wound healing.

Identification of potential hub genes associated with skin wound healing based on time course bioinformatic analyses

BackgroundThe skin is the largest organ of the body and has multiple functions. Wounds remain a significant healthcare problem due to the large number of traumatic and pathophysiological conditions patients suffer.MethodsGene expression profiles of 37 biopsies collected from patients undergoing split-thickness skin grafts at five different time points were downloaded from two datasets (GSE28914 and GSE50425) in the Gene Expression Omnibus (GEO) database. Principal component analysis (PCA) was applied to classify samples into different phases. Subsequently, differentially expressed genes (DEGs) analysis, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway functional enrichment analyses were performed, and protein–protein interaction (PPI) networks created for each phase. Furthermore, based on the results of the PPI, hub genes in each phase were identified by molecular complex detection combined with the ClueGO algorithm.ResultsUsing principal component analysis, the collected samples were divided into four phases, namely intact phase, acute wound phase, inflammatory and proliferation phase, and remodeling phase. Intact samples were used as control group. In the acute wound phase, a total of 1 upregulated and 100 downregulated DEGs were identified. Tyrosinase (TYR), tyrosinase Related Protein 1 (TYRP1) and dopachrome tautomerase (DCT) were considered as hub genes and enriched in tyrosine metabolism which dominate the process of melanogenesis. In the inflammatory and proliferation phase, a total of 85 upregulated and 164 downregulated DEGs were identified. CHEK1, CCNB1 and CDK1 were considered as hub genes and enriched in cell cycle and P53 signaling pathway. In the remodeling phase, a total of 121 upregulated and 49 downregulated DEGs were identified. COL4A1, COL4A2, and COL6A1 were considered as hub genes and enriched in protein digestion and absorption, and ECM-receptor interaction.ConclusionThis comprehensive bioinformatic re-analysis of GEO data provides new insights into the molecular pathogenesis of wound healing and the potential identification of therapeutic targets for the treatment of wounds.

Aberrant Wound Healing in an Epidermal Interleukin-4 Transgenic Mouse Model of Atopic Dermatitis.

Wound healing in a pre-existing Th2-dominated skin milieu was assessed by using an epidermal specific interleukin-4 (IL-4) transgenic (Tg) mouse model, which develops a pruritic inflammatory skin condition resembling human atopic dermatitis. Our results demonstrated that IL-4 Tg mice had delayed wound closure and re-epithelialization even though these mice exhibited higher degrees of epithelial cell proliferation. Wounds in IL-4 Tg mice also showed a marked enhancement in expression of inflammatory cytokines/chemokines, elevated infiltration of inflammatory cells including neutrophils, macrophages, CD3+ lymphocytes, and epidermal dendritic T lymphocytes. In addition, these mice exhibited a significantly higher level of angiogenesis as compared to wild type mice. Furthermore, wounds in IL-4 Tg mice presented with larger amounts of granulation tissue, but had less expression and deposition of collagen. Taken together, an inflamed skin condition induced by IL-4 has a pronounced negative influence on the healing process. Understanding more about the pathogenesis of wound healing in a Th2- dominated environment may help investigators explore new potential therapeutic strategies.

The Role of MicroRNA in Adipose-derived Stem Cells for Skin Wound Healing

Wound healing is an intricate process whereby the skin, or similar tissues, repairs itself after injury. Impaired wound healing with loss of temporospatial orchestration of processes remains challenging and can be highly debilitating to patients. Recently, the novel strategy of administering mesenchymal stem cells (MSCs) derived from bone marrow, adipose tissues and other sources, has achieved high therapeutic efficiency in healing wounds. Adipose-derived stem cells (ASCs) are pluripotent stem cells with the ability to differentiate into different lineages and to secrete paracrine factors to initiate tissue regeneration. However, the exact molecular mechanism by which ASCs exert their function is not well characterized. MicroRNAs (MiRNAs) are important regulators of diverse cell functions and the cytokine network is necessary for endothelial cell migration, capillary formation, matrix metalloproteinase production, collagen synthesis and degradation. This review will focus on the significant role of MicroRNA within ASCs and how these are interlinked to the pathogenesis of wound healing.

Impaired wound healing in bleomycin-induced murine scleroderma: a new model of wound retardation.

Bleomycin-induced scleroderma in mice is an established model for human scleroderma. Making use of this, we have established a new model for wound retardation. After inducing dermal sclerosis by local bleomycin treatment in nude mice, a full-thickness wound was made by punch excision on the bleomycin application site. Mice pretreated with bleomycin showed a significant delay in wound closure, as compared with mice pretreated with phosphate-buffered saline. Proliferation of keratinocytes was significantly inhibited and the number of Ki-67-positive keratinocytes was significantly lower in the bleomycin-pretreated skin. Also, the number of CD31-positive blood vessels was markedly reduced in the bleomycin-treated skin. The topical daily application of basic fibroblast growth factor (bFGF) significantly promoted wound closure, while increasing blood vessel formation and reducing transforming growth factor-β and alpha-smooth muscle actin mRNA levels. Furthermore, only two applications of PG-FGF1, a fusion protein of FGF1 with heparan sulfate proteoglycan, overcame the delay in wound closure. Wound delay in this model mainly occurred as a result of decreased vessel formation and keratinocyte migration following bleomycin treatment. It is expected that this model will provide novel insights into the pathogenesis of wound healing and the exploration of possible candidate drugs for refractory or chronic wounds in the clinical setting.

Atherosclerosis, Cancer, Wound Healing, and Inflammation - Shared or Parallel Evolution

Wound healing is a complex process involving inflammatory cell activation and invasion as well as scar tissue deposition (in the form of fibrotic tissue and collagen matrix). With tissue repair there is active cell proliferation designed to heal the damaged tissues. Recent work has suggested that cancer is a form of dysregulated wound healing where inflammatory responses and cellular proliferation goes awry. Additionally other diseases such as the highly prevalent atherosclerotic coronary plaque are hypothesized to be a form of unregulated wound healing. The ‘Response to Injury’ hypothesis was first presented by Russell Ross as an explanation for atherosclerosis. The basic premise for this theory on the etiology of atherosclerotic arterial disease is that all forms of damage to the arterial wall, whether hypertension, hyperlipidemia, angioplasty injury or transplantation, cause an accelerated injury response with aggressive inflammatory cell responses and cell proliferation, in short an unchecked form of wound healing. Prior to Dr Ross’ theory, Earl Benditt postulated that human atheromata were benign intimal tumors. He demonstrated that many atherosclerotic plaques were derived from individual smooth muscle cells using X chromosome inactivation patterns with results that were highly suggestive of a proliferating monoclonal tumour cell. More recent work has now linked excess inflammation with growth and instability of atherosclerotic plaque and with progression of invasive cancers. There are thus now many parallels in developing cancer and atherosclerosis and many close associations between cancer, atheroma and wound healing. These findings raise one basic question – Are carcinogenesis and atherogenesis manifestations of the same initiating disease generating events or simply parallel manifestations of similar pathogenic disease mechanisms, e.g. are these shared or parallel evolutions. The history of our understanding of the pathogenesis of wound healing and inflammation helps in understanding these disorders and the underlying mechanisms of disease. Ilya Ilyich Mechnikov (18451916), a Russian biologist and zoologist who moved to work at the Institute Pasteur in Paris, was the first to discover the existence of innate immunity, also termed inflammation. Although the innate immune system is now known to cure the majority of infections and drives wound healing after injury long before the adaptive immune response becomes active, Mechnikov’s initial discovery of this more ancient defense system was viewed with some suspicion and he shared

Nonsteroidal Anti-Inflammatory Drugs for Wounds: Pain Relief or Excessive Scar Formation?

The inflammatory process has direct effects on normal and abnormal wound healing. Hypertrophic scar formation is an aberrant form of wound healing and is an indication of an exaggerated function of fibroblasts and excess accumulation of extracellular matrix during wound healing. Two cytokines—transforming growth factor-β (TGF-β) and prostaglandin E2 (PGE2)—are lipid mediators of inflammation involving wound healing. Overproduction of TGF-β and suppression of PGE2 are found in excessive wound scarring compared with normal wound healing. Nonsteroidal anti-inflammatory drugs (NSAIDs) or their selective cyclooxygenase-2 (COX-2) inhibitors are frequently used as a pain-killer. However, both NSAIDs and COX-2 inhibitors inhibit PGE2 production, which might exacerbate excessive scar formation, especially when used during the later proliferative phase. Therefore, a balance between cytokines and medication in the pathogenesis of wound healing is needed. This report is a literature review pertaining to wound healing and is focused on TGF-β and PGE2.

The role of endothelial dysfunction in the pathogenesis of impaired diabetic wound healing: A novel therapeutic target?

The global burden of diabetes is attributed to its multiple associated complications including impaired wound healing which can ultimately result in amputation. Peripheral vascular disease, infection, neuropathy and abnormal local cellular and cytokine activity are some of the traditionally cited pathological instigators of defective diabetic wound repair. Despite intensive research and subsequent advances in diabetic wound care technology a single treatment with measurable clinical impact has yet to be determined. The phenomenon of endothelial dysfunction as seen in atherosclerosis and recently identified as a characteristic of diabetic vasculature may contribute to impaired cutaneous healing in this group. Indicators of endothelial dysfunction have been demonstrated in diabetic wounds by a number of investigators. Successful results are being obtained with modifiers of endothelial function in the management of cardiovascular disease. We hypothesise that endothelial dysfunction plays a substantial contributory role in the pathogenesis of wound healing impairment of diabetes and holds potential as a target for therapeutic intervention.

The Expression of Nuclear Factor κ B in Inflammation-Induced Rat Corneal Neovascularization

Purpose: To investigate the involvement of the nuclear-transfactor-κ B (NF-κ B) in the rat model of inflammation-induced corneal neovascularization (CNV). Methods: The CNV model in Sprague-Dawley rats was induced by alkaline cauterization of the central cornea. The corneas were examined by a slit lamp microscope. NF-κ B was assayed by Western blot. Vascular endothelial growth factor (VEGF) protein was evaluated by immunohistochemistry. VEGF mRNA levels were determined by reverse transcription-polymerase chain reaction (RT-PCR). Results: Morphologically, the CNV was shown on the second day after cautery. In corneas after cautery, NF-κ B protein increased 6 hours after cautery, peaked 4 days after cautery, and decreased to near baseline by day 14. VEGF protein and mRNA increased gradually in the early stage after cautery, reached the highest level on the fourth day, and then decreased to near baseline slowly after 7 days. Conclusions: The activated NF-κ B was up-regulated in the early stage of CNV of rat induced by cauterization, which suggests it may participate in the pathogenesis of wound healing, inflammation, and neovascularization processes in the cornea.

Myofibroblast phenotypes expression in experimental renal scarring.

Myofibroblasts have been implicated in the pathogenesis of wound healing and tissue fibrosis. A role has also been put forward for these cells in the development of experimental and clinical renal scarring. We examined the expression of myofibroblast phenotypes by immunohistochemistry, relying on an avidin-biotin-peroxidase method, during the course of renal scarring in rats submitted to subtotal (5/6) nephrectomy (SNx). We also attempted to identify changes in immunoreactive transforming growth factor-beta (TGF-beta) and collagen (III and IV) within remnant kidneys in order to determine their association with the expression of the myofibroblasts. In normal sham-operated rats, alpha-smooth muscle actin (alpha-SMA) was confined to the media of renal arteries and arterioles. In contrast, in rats with renal ablation we observed the early (day 7) appearance of myofibroblasts expressing alpha-SMA (A) in the interstitium of remnant kidneys particularly around vessels. Interstitial cells expressing alpha-SMA increased with time as tubulointerstitial fibrosis progressed. By day 30 some interstitial cells also expressed vimentin (V). Various interstitial myofibroblast phenotypes (A, V, VA) were expressed during the course of experimental renal scarring. Interstitial myofibroblasts appeared to be associated with TGF-beta as these cells' cytoplasm stained for both this growth factor and alpha-SMA. Interstitial fibrosis was also associated with increased interstitial expression of both collagen III and IV. Some atrophic tubular cells showed positive immunostaining for vimentin during the late stages of renal scarring (days 90-150). In the glomeruli, a segmental expression of alpha-SMA was noted from day 21 after SNx onward. Normal glomerular endothelial cells appeared to express vimentin while epithelial cells expressed both vimentin and desmin (D). The glomerular immunostain for vimentin increased with time but decreased as glomerulosclerosis progressed. In contrast, glomerular desmin and alpha-SMA immunostain continued to rise with progressive glomerulosclerosis. This was associated with the appearance of type III collagen within scarred glomeruli. Both vimentin and desmin appeared within the walls of the renal arterioles and increased with time from day 7 and 15, respectively. Vimentin was also expressed in the peritubular capillaries of remnant kidneys. By contrast, alpha-SMA, normally present in the media of arterioles, decreased as arteriolar sclerosis progressed. These changes cannot be exclusively attributed to systemic hypertension as they were absent in a group of age-matched, sham-operated, spontaneously hypertensive rats. Myofibroblasts may play a role in the pathogenesis of glomerulosclerosis, tubulointerstitial fibrosis and vascular sclerosis. Further, the acquisition of new myofibroblastic phenotypes by glomerular and tubular cells may contribute to renal fibrosis.

Endothelin antagonism in experimental hepatic fibrosis. Implications for endothelin in the pathogenesis of wound healing.

The liver's response to chronic injury is fibrosis, which is analogous to wound healing in other organs. Hepatic wounding is characterized by the "activation" of resident stellate cells (lipocytes, Ito cells) to myofibroblast-like cells that produce increased amounts of smooth muscle alpha-actin and extracellular matrix. Stellate cells possess abundant endothelin (ET) receptors (ETA/B) and, therefore, are subject to the effects of ET-1 and 3. In this study, we investigated whether ETs contribute to the activation of stellate cells and consequently, fibrogenesis. In cultured stellate cells, ET-1 and sarafotoxin S6C (a potent ETB receptor agonist) stimulated stellate cell activation, as assessed by expression of smooth muscle alpha-actin. Furthermore, the mixed ETA/B receptor antagonist, bosentan, blocked this process. Next, we administered bosentan during the induction of liver injury in two mechanistically distinct forms of hepatic wounding. Bosentan reduced levels of type I collagen and cellular fibronectin mRNAs in whole-liver tissue extracts in both models. In freshly isolated stellate cells from injured livers, bosentan reduced expression of activation markers, including smooth muscle alpha-actin and extracellular matrix mRNAs. We further demonstrate that endothelin antagonism after establishment of fibrosing injury reduced stellate cell activation and matrix production. These data indicate that ET contributes to stellate cell activation and fibrogenesis. Because ET is upregulated in diverse forms of parenchymal injury, we speculate that ET may play an important role in the wound-healing response.

Endotelin (ET) antagonism in experimental hepatic fibrosis: Implications for endothelin in the pathogenesis of wound healing: [formula omitted]. Liver Center Laboratory, University of California, San Francisco

Endotelin (ET) antagonism in experimental hepatic fibrosis: Implications for endothelin in the pathogenesis of wound healing: [formula omitted]. Liver Center Laboratory, University of California, San Francisco

Regulation of transforming growth factor-beta 1 and its receptor by cyclosporine in human T lymphocytes.

Scarring, fibrosis, and immunosuppression occurs with chronic cyclosporine (CsA) administration. We postulated that CsA may induce transforming growth factor (TGF)-beta 1 secretion from human T lymphocytes, a cytokine with immunoregulatory effects that has been implicated in the pathogenesis of wound healing and scarring. TGF-beta 1 was measured in serum-free supernatants harvested from T lymphocytes stimulated in the presence of CsA by a specific sandwich ELISA. CsA (10-1000 ng/ml) enhanced TGF-beta 1 secretion by approximately 40-80% in a dose-dependent manner. Increased TGF-beta 1 secretion in the presence of CsA was accompanied by a 2- to 4-fold increase in TGF-beta 1 mRNA levels due to both enhancement of its nuclear transcription as well as prolongation of TGF-beta 1 mRNA half-life. To determine whether the increase in TGF-beta 1 secretion was also accompanied by a concomitant change in its receptor, TGF-beta 1 receptor expression was analyzed by cross-linking of radioiodinated TGF-beta 1. Unactivated T lymphocytes expressed both a 105-kDa and a 65-kDa TGF-beta receptor. Upon stimulation, a transient increase in receptor density was seen at 12 hr, followed by a decline at later time points. Cells treated with CsA exhibited at least 2-fold higher levels of TGF-beta receptors in a dose-dependent manner. Thus, CsA enhances the production of TGF-beta 1 protein as well as the expression of its receptor in activated T lymphocytes. Enhanced TGF-beta 1 production and binding may contribute to the immunosuppressive and fibrosis-promoting effects of CsA therapy.