An analysis of replicative senescence in dermal fibroblasts derived from chronic leg wounds predicts that telomerase therapy would fail to reverse their disease-specific cellular and proteolytic phenotype

The accumulation of senescent fibroblasts within tissues has been suggested to play an important role in mediating impaired dermal wound healing, which is a major clinical problem in the aged population. The concept that replicative senescence in wound fibroblasts results in reduced proliferation and the failure of refractory wounds to respond to treatment has therefore been proposed. However, in the chronic wounds of aged patients the precise relationship between the observed alteration in cellular responses with aging and replicative senescence remains to be determined. Using assays to assess cellular proliferation, senescence-associated staining beta-galactosidase, telomere length, and extracellular matrix reorganizational ability, chronic wound fibroblasts demonstrated no evidence of senescence. Furthermore, analysis of in vitro senesced fibroblasts demonstrated cellular responses that were distinct and, in many cases, diametrically opposed from those exhibited by chronic wound fibroblasts. Forced expression of telomerase within senescent fibroblasts reversed the senescent cellular phenotype, inhibiting extracellular matrix reorganizational ability, attachment, and matrix metalloproteinase production and thus produced cells with impaired key wound healing properties. It would appear therefore that the distinct phenotype of chronic wound fibroblasts is not simply due to the aging process, mediated through replicative senescence, but instead reflects disease-specific cellular alterations of the fibroblasts themselves.     

Connexins in wound healing; perspectives in diabetic patients

Skin lesions are common events and we have evolved to rapidly heal them in order to maintain homeostasis and prevent infection and sepsis. Most acute wounds heal without issue, but as we get older our bodies become compromised by poor blood circulation and conditions such as diabetes, leading to slower healing. This can result in stalled or hard-to-heal chronic wounds. Currently about 2% of the Western population develop a chronic wound and this figure will rise as the population ages and diabetes becomes more prevalent [1]. Patient morbidity and quality of life are profoundly altered by chronic wounds [2]. Unfortunately a significant proportion of these chronic wounds fail to respond to conventional treatment and can result in amputation of the lower limb. Life quality and expectancy following amputation is severely reduced. These hard to heal wounds also represent a growing economic burden on Western society with published estimates of costs to healthcare services in the region of $25B annually [3]. There exists a growing need for specific and effective therapeutic agents to improve healing in these wounds. In recent years the gap junction protein Cx43 has been shown to play a pivotal role early on in the acute wound healing process at a number of different levels [4-7]. Conversely, abnormal expression of Cx43 in wound edge keratinocytes was shown to underlie the poor rate of healing in diabetic rats, and targeting its expression with an antisense gel restored normal healing rates [8]. The presence of Cx43 in the wound edge keratinocytes of human chronic wounds has also been reported [9]. Abnormal Cx43 biology may underlie the poor healing of human chronic wounds and be amenable therapeutic intervention [7]. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.     

The role of oxidised regenerated cellulose/collagen in wound repair: effects in vitro on fibroblast biology and in vivo in a model of compromised healing

Irrespective of underlying chronic wound pathology, delayed wound healing is normally characterised by impaired new tissue formation at the site of injury. It is thought that this impairment reflects both a reduced capacity to synthesize new tissue and the antagonistic activities of high levels of proteinases within the chronic wound environment. Historically, wound dressings have largely been passive devices that offer the wound interim barrier function and establish a moist healing environment. A new generation of devices, designed to interact with the wound and promote new tissue formation, is currently being developed and tested. This study considers one such device, oxidised regenerated cellulose (ORC) /collagen, in terms of its ability to promote fibroblast migration and proliferation in vitro and to accelerate wound repair in the diabetic mouse, a model of delayed wound healing. ORC/collagen was found to promote both human dermal fibroblasts proliferation and cell migration. In vivo studies considered the closure and histological characteristics of diabetic wounds treated with ORC/collagen compared to those of wounds given standard treatment on both diabetic and non-diabetic mice. ORC/collagen was found to significantly accelerate diabetic wound closure and result in a measurable improvement in the histological appearance of wound tissues. As the diabetic mouse is a recognised model of impaired healing, which may share some characteristics of human chronic wounds, the results of this in vivo study, taken together with those relating the positive effects of ORC/collagen in vitro, may predict the beneficial use of this device in the clinical setting.     

Senescent cells: A new Achilles’ heel to exploit for cancer medicine?

Cellular senescence is a typical tumor‐suppressive mechanism that restricts the proliferation of premalignant cells. However, mounting evidence suggests that senescent cells, which also persist in vivo, can promote the incidence of aging‐related disorders principally via the senescence‐associated secretory phenotype (SASP), among which cancer is particularly devastating. Despite the beneficial effects of the SASP on certain physiological events such as wound healing and tissue repair, more studies have demonstrated that senescent cells can substantially contribute to pathological conditions and accelerate disease exacerbation, particularly cancer resistance, relapse and metastasis. To limit the detrimental properties while retaining the beneficial aspects of senescent cells, research advancements that support screening, design and optimization of anti‐aging therapeutic agents are in rapid progress in the setting of prospective development of clinical strategies, which together represent a new wave of efforts to control human malignancies or mitigate degenerative complications.     

Soft tissue fibroblasts from well healing and chronic human wounds show different rates of myofibroblasts in vitro

Due to an increasing life expectancy in western countries, chronic wound treatment will be an emerging challenge in the next decades. Because therapies are improving slowly appropriate diagnostic tools enabling the early prediction of the healing success remain to be developed. We used a well-established in vitro assay in combination with the analysis of 27 cytokines to discriminate between fibroblasts from chronic (n = 6) and well healing (n = 8) human wounds. Proliferation and migration of the cells as well as their response to hypoxia and their behaviour in co-culture with microvascular endothelial cells were analyzed. Myofibroblast differentiation, a time-limited essential process of regular wound healing, was also quantified. Besides weaker proliferation and migration significantly higher rates of myofibroblasts were detected in chronic wounds. With respect to the cytokine release, there was a clear trend within the group of chronic wound fibroblasts, which were releasing interferon-γ, monocyte chemotactic protein-1, granulocyte–macrophage colony stimulating factor and basic fibroblast growth factor in higher amounts than fibroblasts from healing wounds. Although the overall response of both groups of fibroblasts to hypoxia and to the contact with endothelial cells was similar, especially chronic wound fibroblasts seemed to benefit from the endothelial interaction during hypoxia and displayed better migration characteristics. The study shows (1) that the assay can identify specific features of fibroblasts derived from different human wounds and (2) that wound fibroblasts are varying in their response to the chosen parameters. Thus, current therapeutic approaches and individual healing prediction might benefit from this assay.     

The role of oxidised regenerated cellulose/collagen in chronic wound repair and its potential mechanism of action

Normal wound healing is a carefully controlled balance of destructive processes necessary to remove damaged tissue and repair processes which lead to new tissue formation. Proteases and growth factors play a pivotal role in regulating this balance, and if disrupted in favour of degradation then delayed healing ensues; a trait of chronic wounds. Whilst there are many types of chronic wounds, biochemically they are thought to be similar in that they are characterised by a prolonged inflammatory phase, which results in elevated levels of proteases and diminished growth factor activity. This increase in proteolytic activity and subsequent degradation of growth factors is thought to contribute to the net tissue loss associated with these chronic wounds.

In this study, we describe a new wound treatment, comprising oxidised regenerated cellulose and collagen (ORC/collagen), which can redress this imbalance and modify the chronic wound environment. We demonstrate that ORC/collagen can inactivate potentially harmful factors such as proteases, oxygen free radicals and excess metal ions present in chronic wound fluid, whilst simultaneously protecting positive factors such as growth factors and delivering them back to the wound.

These characteristics suggest a beneficial role for this material in helping to re-balance the chronic wound environment and therefore promote healing.     

微小RNA miR-21在皮肤创伤愈合中的研究进展

微小RNA是一类真核细胞中广泛存在的内源性转录后调控分子,其在细胞的增殖、分化、凋亡、迁移等过程中发挥了重要的调控作用。皮肤创伤修复涉及复杂的细胞与分子的相互作用网络。近年来研究表明micro RNAs在皮肤创伤修复中发挥调控作用,引人关注。miR-21作为重要的癌基因是目前研究的最多的miRNAs分子之一,其在皮肤创伤修复中的作用研究也越来越受到重视。研究表明miR-21参与了细胞增殖与迁移、炎症反应、血管生成和细胞外基质合成等重要修复相关事件的调控。因此,阐明miR-21分子在正常皮肤创伤愈合中的作用,厘清miR-21表达失调在修复不足和修复过度中的功能,将深化我们对于皮肤创伤愈合基本理论的认识,并为促进创面愈合与防治修复不足和过度提供潜在的治疗靶点。本文就miR-21分子在正常皮肤创伤修复、慢性难愈性创面和增生性瘢痕中作用的研究进展进行综述展望。     

Roles of lactoferrin on skin wound healing

Skin wound healing is a complex biological process that requires the regulation of different cell types, including immune cells, keratinocytes, fibroblasts, and endothelial cells. It consists of 5 stages: hemostasis, inflammation, granulation tissue formation, re-epithelialization, and wound remodeling. While inflammation is essential for successful wound healing, prolonged or excess inflammation can result in nonhealing chronic wounds. Lactoferrin, an iron-binding glycoprotein secreted from glandular epithelial cells into body fluids, promotes skin wound healing by enhancing the initial inflammatory phase. Lactoferrin also exhibits anti-inflammatory activity that neutralizes overabundant immune response. Accumulating evidence suggests that lactoferrin directly promotes both the formation of granulation tissue and re-epithelialization. Lactoferrin stimulates the proliferation and migration of fibroblasts and keratinocytes and enhances the synthesis of extracellular matrix components, such as collagen and hyaluronan. In an in vitro model of wound contraction, lactoferrin promoted fibroblast-mediated collagen gel contraction. These observations indicate that lactoferrin supports multiple biological processes involved in wound healing.     

Circulating fibrocyte mobilization in negative pressure wound therapy

Non‐healing diabetic wounds are difficult to treat. They also create heavy financial burdens for both patients and society. Negative pressure wound therapy (NPWT) has been adopted to treat intractable wounds and has proved to be effective. However, the mechanisms that underlie the effects of this treatment are not entirely understood. Circulating fibrocytes are unique haematopoietic‐derived stem cells that have been reported to play a pivotal role in wound healing. Here, we have investigated the effect of NPWT on fibrocyte mobilization and the role of fibrocyte mobilization in the healing of diabetic wounds during NPWT. We show that the NPWT group exhibited 2.6‐fold to 12.1‐fold greater numbers of tail vein‐injected PKH‐26‐labelled fibrocytes in the diabetic wound sites compared with the control group. We also demonstrate that the full‐thickness skin wounds treated with NPWT exhibit significantly reduced mRNA and protein expression, blood vessel density and proliferating cells when exogenous fibrocyte mobilization is inhibited. We speculate that systemic mobilization of fibrocytes during NPWT may be a mechanism for healing intractable wounds in a diabetic rat model experiment and that enhancement of cell mobilization may represent a potential treatment idea for intractable wound healing across all fields of surgery.     

Multipotent adult progenitor cells: their role in wound healing and the treatment of dermal wounds

The use of cellular therapy in the treatment of dermal wounds is currently an active area of investigation. Multipotent adult progenitor cells (MAPC) are an attractive choice for cytotherapy because they have a large proliferative potential, the ability to differentiate into different cell types and produce a variety of cytokines and growth factors important to wound healing. Whole bone marrow (BM) was one of the initial attempts to treat impaired wounds. While it has shown some promise, the low frequency of progenitor cell populations in BM and the large number of inflammatory cells make it less attractive. Multipotent mesenchymal stromal cells (MSC) and endothelial progenitor cells are populations of BM-derived progenitor cells that have been isolated and used to treat chronic wounds with some success. Skin-derived MAPC are another heterogeneous population of progenitor cells present in the skin with the potential to differentiate into skin elements and participate in wound healing. All of these progenitor cell populations are potential sources for cytotherapy of wounds. This review focused on the contribution of adult progenitor cell populations to dermal wound healing and their potential for use in cytotherapy.     

A Three Species Model to Simulate Application of Hyperbaric Oxygen Therapy to Chronic Wounds

Chronic wounds are a significant socioeconomic problem for governments worldwide. Approximately 15% of people who suffer from diabetes will experience a lower-limb ulcer at some stage of their lives, and 24% of these wounds will ultimately result in amputation of the lower limb. Hyperbaric Oxygen Therapy (HBOT) has been shown to aid the healing of chronic wounds; however, the causal reasons for the improved healing remain unclear and hence current HBOT protocols remain empirical. Here we develop a three-species mathematical model of wound healing that is used to simulate the application of hyperbaric oxygen therapy in the treatment of wounds. Based on our modelling, we predict that intermittent HBOT will assist chronic wound healing while normobaric oxygen is ineffective in treating such wounds. Furthermore, treatment should continue until healing is complete, and HBOT will not stimulate healing under all circumstances, leading us to conclude that finding the right protocol for an individual patient is crucial if HBOT is to be effective. We provide constraints that depend on the model parameters for the range of HBOT protocols that will stimulate healing. More specifically, we predict that patients with a poor arterial supply of oxygen, high consumption of oxygen by the wound tissue, chronically hypoxic wounds, and/or a dysfunctional endothelial cell response to oxygen are at risk of nonresponsiveness to HBOT. The work of this paper can, in some way, highlight which patients are most likely to respond well to HBOT (for example, those with a good arterial supply), and thus has the potential to assist in improving both the success rate and hence the cost-effectiveness of this therapy.     

Mitochondrial DNA damage induces apoptosis in senescent cells

Senescence is a cellular response to damage and stress. The senescence response prevents cancer by suppressing the proliferation of cells with a compromised genome and contributes to optimal wound healing in normal tissues. Persistent senescent cells are also thought to drive aging and age-associated pathologies through their secretion of inflammatory factors that modify the tissue microenvironment and alter the function of nearby normal or transformed cells. Understanding how senescent cells alter the microenvironment would be aided by the ability to induce or eliminate senescent cells at will in vivo. Here, we combine the use of the synthetic nucleoside analog ganciclovir (GCV) with herpes simplex virus thymidine kinase (HSVtk) activity to create or eliminate senescent human cells. We show that low concentrations of GCV induce senescence through the accumulation of nuclear DNA damage while higher concentrations of GCV, similar to those used in vivo, kill non-dividing senescent cells via mitochondrial DNA (mtDNA) damage and caspase-dependent apoptosis. Using this system, we effectively eliminated xenografted normal human senescent fibroblasts or induced senescence in human breast cancer cells in vivo. Thus, cellular senescence and mtDNA damage are outcomes of synthetic nucleoside analog treatment, indicating that the GCV–HSVtk combination can be used effectively to promote the targeted formation or eradication of senescent cells.     

生长激素在创面愈合中的应用

软组织损伤创面在合并糖尿病、放射治疗等情况下,常常延迟愈合、不愈、或反复发作,转变为慢性难愈性创面,成为长期困扰,临床治疗的一大难题。通常采用的皮肤移植疗法,无论自体还是异体皮都受到供体来源少的限制,异体皮和人工合成皮还存在免疫排斥等问题。生长激素在慢性创面愈合中的作用受到广泛关注,为慢性难愈创面的治疗提供了新的途径,有望带来突破性的治疗效果。     

Anti‐aging pharmacology in cutaneous wound healing: effects of metformin,resveratrol, and rapamycin by local application

Cutaneous wounds are among the most common soft tissue injuries and are particularly hard to heal in aging. Caloric restriction (CR) is well documented to extend longevity; pharmacologically, profound rejuvenative effects of CR mimetics have been uncovered, especially metformin (MET), resveratrol (RSV), and rapamycin (RAPA). However, locally applied impacts and functional differences of these agents on wound healing remain to be established. Here, we discovered that chronic topical administration of MET and RSV, but not RAPA, accelerated wound healing with improved epidermis, hair follicles, and collagen deposition in young rodents, and MET exerted more profound effects. Furthermore, locally applied MET and RSV improved vascularization of the wound beds, which were attributed to stimulation of adenosine monophosphate‐activated protein kinase (AMPK) pathway, the key mediator of wound healing. Notably, in aged skin, AMPK pathway was inhibited, correlated with impaired vasculature and reduced healing ability. As therapeutic approaches, local treatments of MET and RSV prevented age‐related AMPK suppression and angiogenic inhibition in wound beds. Moreover, in aged rats, rejuvenative effects of topically applied MET and RSV on cell viability of wound beds were confirmed, of which MET showed more prominent anti‐aging effects. We further verified that only MET promoted wound healing and cutaneous integrity in aged skin. These findings clarified differential effects of CR‐based anti‐aging pharmacology in wound healing, identified critical angiogenic and rejuvenative mechanisms through AMPK pathway in both young and aged skin, and unraveled chronic local application of MET as the optimal and promising regenerative agent in treating cutaneous wound defects.     

Plasma treatments of dressings for wound healing: a review

This review covers the use of plasma technology relevant to the preparation of dressings for wound healing. The current state of knowledge of plasma treatments that have potential to provide enhanced functional surfaces for rapid and effective healing is summarized. Dressings that are specialized to the needs of individual cases of chronic wounds such as diabetic ulcers are a special focus. A summary of the biology of wound healing and a discussion of the various types of plasmas that are suitable for the customizing of wound dressings are given. Plasma treatment allows the surface energy and air permeability of the dressing to be controlled, to ensure optimum interaction with the wound. Plasmas also provide control over the surface chemistry and in cases where the plasma creates energetic ion bombardment, activation with long-lived radicals that can bind therapeutic molecules covalently to the surface of the dressing. Therapeutic innovations enabled by plasma treatment include the attachment of microRNA or antimicrobial peptides. Bioactive molecules that promote subsequent cell adhesion and proliferation can also be bound, leading to the recruitment of cells to the dressing that may be stem cells or patient-derived cells. The presence of a communicating cell population expressing factors promotes healing.     

Effects of CD100 promote wound healing in diabetic mice

Diabetes is a condition that causes delayed wound healing and results in chronic wounds. CD100 has been reported to promote and induce potent and obvious angiogenesis both in vivo and in vitro studies, the absence of which are a main cause of the diabetic chronic wound. In the present study, we investigated the effects of application of soluble CD100 on wound healing in diabetic mice. Four 5-mm full-thickness dermal wounds were made on each male db/db mouse. 12 mice from CD100 group were subcutaneously injected with 250 ng of CD100 (50 µl) per wound, in addition, 12 mice were injected with the same volume phosphate-balanced solution as the control. The animals were treated every other day until the wounds healed completely. Images were obtained to calculate the area ratio of the original area. HE and Masson’s trichrome staining were used for histological examination. Collagen remodeling, angiogenesis and wound bed inflammation were evaluated by immunohistochemical staining and western blot. We demonstrated that CD100 had distinct functions during the wound healing process. Histological and western blotting analysis showed a more organized epithelium and dermis, more collagen fibers, higher angiogenesis and lower inflammation in the CD100 group than in the PBS group. These findings suggest that CD100 may accelerate wound healing in diabetic mice by promoting angiogenesis in the wound and by reducing the inflammatory response.     

Senescent cells at the crossroads of aging,disease, and tissue homeostasis

Originally identified as an outcome of continuous culture of primary cells, cellular senescence has moved beyond the culture dish and is now a bona fide driver of aging and disease in animal models, and growing links to human disease. This cellular stress response consists of a stable proliferative arrest coupled to multiple phenotypic changes. Perhaps the most important of these is the senescence-associated secretory phenotype, or senescence-associated secretory phenotype —a complex and variable collection of secreted molecules release by senescent cells with a number of potent biological activities. Senescent cells appear in multiple age-associated conditions in humans and mice, and interventions that eliminate these cells can prevent or even reverse multiple diseases in mouse models. Here, we review salient aspects of senescent cells in the context of human disease and homeostasis. Senescent cells increase in abundance during several diseases that associated with premature aging. Conversely, senescent cells have a key role in beneficial processes such as development and wound healing, and thus can help maintain tissue homeostasis. Finally, we speculate on mechanisms by which deleterious aspects of senescent cells might be targeted while retaining homeostatic aspects in order to improve age-related outcomes.