English

Wound healing phases comprise of highly synchronized process that begins due to a damage and restores the integrity of the injured tissues. Wound healing reduces the damage in tissue and supply sufficient oxygen and tissue perfusion, provide proper nourishment and humid wound healing atmosphere to re-establish the essential status of exaggerated parts. The untreated wound becomes susceptible for pus development, bacterial infection and complications like sepsis. Traditional and modern approaches are in practice to treat acute, open and chronic injuries, however, present wound care management has met with challenges and minimal positive effects. Stem cells have possible wound healing capability to overwhelm restrictions of the current wound care practices as it produces faster tissue regeneration in wound repair. Stem cells are unspecialized cells derived from adult body tissues and embryos that differentiate into any cell of an organism and capable of self-regeneration. The understanding on molecular mechanisms of stem cells has become the central and promising field in scientific study. This review focuses on the pre-existing traditional and modern treatments for wound healing, and types and roles of stem cells in wound care management. This review also focuses on the fundamental molecular characterization and factors influencing the molecular mechanisms of stem cells in wound healing.

Umbilical remnant allograft application in the treatment of erosive pustular dermatosis of the scalp

Management and treatment of chronic wounds remain a significant problem in clinical practice. Stem cell therapies are an important and promising approach for regenerative medicine because of their self-renewal and differentiation potential. Mesenchymal stem cells (MSCs), a major cellular source for regeneration, are present in almost all tissues. The use of embryonic stem cells is morally controversial because of the need to nurture and destroy embryonic cells. Therefore, adult umbilical cord tissues are of particular importance as an alternative source of perinatal tissues. Wharton Jelly is a gelatinous connective tissue in the umbilical cord containing MSCs that can differentiate into osteogenic, adipose, chondrogenic, and other lineages. These cells do not express the MHC-II molecule and show immunomodulatory properties that make them viable for allogeneic and xenogenic transplants in cell therapy. Therefore, the umbilical cord, especially the part named Wharton's jelly, is an important and promising source of mesenchymal stem cells.

There are many studies devoted to the role of hair follicle stem cells in wound healing as well as in follicle self-restoration. At the same time, the influence of the inflammatory cells on the hair follicle cycling in both injured and intact skin is well established. Immune cells of all wound healing stages, including macrophages, γδT cells, and Tregs, may activate epidermal stem cells to provide re-epithelization and wound-induced hair follicle neogenesis. In addition to the ability of epidermal cells to maintain epidermal morphogenesis through differentiation program, they can undergo de-differentiation and acquire stem features under the influence of inflammatory milieu. Simultaneously, a stem cell compartment may undergo re-programming to adopt another fate. The proportion of skin resident immune cells and wound-attracted inflammatory cells (e.g., neutrophils and macrophages) in wound-induced hair follicle anagen and plucking-induced anagen is still under discussion to date. Experimental data suggesting the role of reactive oxygen species and prostaglandins, which are uncharacteristic of the intact skin, in the hair follicle cycling indicates the role of neutrophils in injury-induced conditions. In this review, we discuss some of the hair follicles stem cell activities, such as wound-induced hair follicle neogenesis, hair follicle cycling, and re-epithelization, through the prism of inflammation. The plasticity of epidermal stem cells under the influence of inflammatory microenvironment is considered. The relationship between inflammation, scarring, and follicle neogenesis as an indicator of complete wound healing is also highlighted. Taking into consideration the available data, we also conclude that there may exist a presumptive interlink between the stem cell activation, inflammation and the components of programmed cell death pathways.

The development of new wound therapies, such as bioengineered skin equivalents, is an ongoing process. Multi-potent mesenchymal stem cells (MSCs) give rise to many tissue lineages and have been implicated in wound healing making them a potential candidate for cell-based bioengineered products for injured tissue. In this study, we investigated the mesenchymal/epithelial interactions of cultured MSCs in comparison to cultured fibroblasts on epidermal proliferation, differentiation, and extracellular matrix (ECM) protein expression using a de-epidermalized dermis (DED) skin model. We also studied whether MSCs can transdifferentiate to keratinocytes using the same model. Keratinocytes were cultured on unseeded DED or DED populated with fibroblasts or MSCs at an air-liquid interface to induce epidermal differentiation. Fibroblasts or MSCs were also seeded on the papillary surface of the DED alone or on the reticular surface. General histology and immunostaining was performed on the skin equivalents to examine the expression of pan keratin (K) (K1, K5, K6, and K18) and protein markers for epidermal differentiation (K10), hyperproliferation (K6), proliferation (PCNA), ECM component (collagen type IV), and mesenchymal marker (vimentin). Keratinocyte-fibroblast skin model and keratinocyte-MSC skin model both displayed an epidermal phenotype similar to epidermis in vivo. Positive expression of proliferation, differentiation and ECM protein markers was observed. MSCs failed to adopt an epithelial phenotype in the DED skin model. Our findings highlight the potential use of MSCs in bioengineered tissue for the treatment of wounds.

High speed intravital microscopy has emerged as an essential tool for studying cellular dynamics in live tissue. A limitation of this technique, however, is that the timescale that a sample can be continuously imaged is limited by practical considerations to several hours. Long term observation of live tissue is of great interest for a variety of research areas. We present methods for observing long term cellular dynamics in live tissue based on three-dimensional registration of time-lapse intravital microscopy images. For these experiments we utilized a custom multimodal microscope that allows simultaneous and co-registered acquisition of optical coherence (OCM) and multiphoton (MPM) microscopy images. OCM allows the structure of a sample to be visualized based on backscattered light while MPM excited fluorescence allows individual cells and cell function to be visualized. The OCM images of tissue structure are used to register data sets taken at different time points. The transformations of the OCM images are applied to MPM images to determine the migration of cell populations. This method of image registration is applied to in vivo tracking of bone-marrow derived GFP-labeled stem cells in mouse skin following bone marrow transplants from GFP donors into species-matched wildtype hosts. The use of three-dimensional image registration of time-lapse microscopy images enables tracking these cells after local cutaneous injury, and for investigating the role of skin stem cells in wound healing.

Engineering strategies to enhance the research progress of mesenchymal stem cells in wound healing

Healing skin wounds with anatomic and functional integrity, especially under chronic pathological conditions, remain an enormous challenge. Due to their outstanding regenerative potential, mesenchymal stem cells (MSCs) have been explored in many studies to determine the healing ability for difficult-to-treat diseases. In this article, we review current animal studies and clinical trials of MSC-based therapy for chronic wounds, and discuss major challenges that confront future clinical applications. We found that a wealth of animal studies have revealed the versatile roles and the benefits of MSCs for chronic wound healing. MSC treatment results in enhanced angiogenesis, facilitated reepithelialization, improved granulation, and accelerated wound closure. There are some evidences of the transdifferentiation of MSCs into skin cells. However, the healing effect of MSCs depends primarily on their paracrine actions, which alleviate the harsh microenvironment of chronic wounds and regulate local cellular responses. Consistent with the findings of preclinical studies, some clinical trials have shown improved wound healing after transplantation of MSCs in chronic wounds, mainly lower extremity ulcers, pressure sores, and radiation burns. However, there are some limitations in these clinical trials, especially a small number of patients and imperfect methodology. Therefore, to better define the safety and efficiency of MSC-based wound therapy, large-scale controlled multicenter trials are needed in the future. In addition, to build a robust pool of clinical evidence, standardized protocols, especially the cultivation and quality control of MSCs, are recommended. Altogether, based on current data, MSC-based therapy represents a promising treatment option for chronic wounds. Impact statement Chronic wounds persist as a significant health care problem, particularly with increasing number of patients and the lack of efficient treatments. The main goal of this article is to provide an overview of current status of mesenchymal stem cell (MSC)-based therapy for chronic wounds. The roles of MSCs in skin wound healing, as revealed in a large number of animal studies, are detailed. A critical view is made on the clinical application of MSCs for lower extremity ulcers, pressure sores, and radiation burns. Main challenges that confront future clinical applications are discussed, which hopefully contribute to innovations in MSC-based wound treatment.

Dear Sir Malaria with estimated annual global mortality from 700,000 to 2.7 million, caused by Plasmodium falciparum, the most deadly Plasmodium species prevails mainly in Africa (1,2). The pleomorphic clinical outcomes display a remarkable range of disease from acute primary stages to complicated clinical presentations, depending on the transmission intensity, age, immunity and genetic background of the affected individuals (3). Cerebral malaria (CM) is one of the manifestations of sever malaria with enormous morbidity and mortality worldwide. It affects approximately more than 500 million people annually, primarily in sub-Saharan Africa (WHO 2011). CM with the high case fatality rate remains one of the major causes of acquired disability throughout much of the tropical and subtropical world plagued by malaria (4,5). It imposes a substantial economic and palliative care and cost burden to households, which impedes economic development in countries with low national gross products. CM is characterised by a generalised systemic process with high overall level of cytokines related to predominant Th1 response. The shift of immune balance towards Th1 arm is simultaneous with under presentation of the Th2/T (reg) immune regulatory (5). Overproduction of Th1-related proinflammatory cytokines, mainly as interferon-γ, tumour necrosis factor-α (TNF-α), interleukin-1b (IL-1b) and IL-6 combined with underproduction of Th2-related anti-inflammatory cytokines, mainly as IL-10, IL-4 and transforming growth factor-β (TGF-β) is seen in CM (6,7). Raised levels of proinflammatory cytokines have been consistently observed in the cases affected with CM followed by schizont rupture (8). Th1-related proinflammatory cytokines modulate production of eicosanoides (prostaglandines and leukotrienes), thromboxane B2, 5-LOX, phospholipase A2, COX1 and COX2 in peripheral circulation (9). The balance between induced immune suppressive versus immune stimulating state by prostaglandins and leukotrines, respectively, is critical for development of CM (9). Finally, these excreted inflammatory mediators lead to the upregulation of intercellular adhesion molecule-1 (ICAM-1), nitric oxide (NO) production and immune proliferation within spleen (10,11). The pathological scenario evolved from these molecular events is enhanced vessel leakage following pronounced cytoadherence of parasitised erythrocytes and activated mononuclear cells to vascular endothelial cells (6). Preliminary animal and human investigations showed that prior infection with parasites such as Schistosoma hematonium, Ascaris lumbricoides and hookworms has been associated with reduced malaria severity in an age and dose-dependent manner (6,12). Pre-existing helmintic infection has been shown to exert 64% protection against murine CM (6). The suppression of both cellular and humoral immune responses essential for establishment and maintenance of coinfected parasites has been speculated as the main mechanism (13). This competitive parasitic milieu is owned by the influential effects of excessive production of IL-4 and IL-10 by stimulated Th2 lymphocytes and decreased Th1 responses (6). Decreased TNF-α production and IL-6 secretion could simply reflect amplified Th2 responses through non specific B lymphocyte presentation (13). This pattern of cytokine expression is also observed consistently in non CM (6). The induced CD23/NO pathway, increased immunoglobulin E concentrations, decreased ICAM-1 expression and cytoadherence of parasitised red blood cells exert additive effects in this context (12). Therefore, it is translated clinically that factors which alter the polarisation of naÏve T helper cells towards the Th2 phenotype can potentially improve disease profile. Several factors rather than pathogens can influence the host immune network particularly those causing chronic inflammation. Chronic non healing wounds, associated with arose chronic inflammatory state, alter the sum of Th1 versus Th2/T (reg) cytokines with promoted differentiation of precursor Th cells into the Th1 subset (14). Mutually, wounds might get chronic non healing state by standing in deteriorating Th1-dominant immune milieu. Complex inflammatory cascade in chronic non healing wounds is extensively characterised by suppression of IL-10, a prowound healing cytokine (14). Thus coexistence of persistent wounds might play a role in changing the clinical course of CM through elicited pathogenic Th1-type immune response. Lack of IL-10 predominance in chronic non healing wounds is such event seen in episodes of CM (6). The observed microcirculatory dysfunction and angiogenic failure in chronic non healing wounds is a favoured milieu for induction of CM's pathogenesis (15,16). Hence, non healing wounds would synergistically enhance load on immune system in CM. The possible influence of chronic wounds on the acquisition of immunity against CM would likely result in a higher rate of CM. This combination might confer lethality and exacerbation of symptoms. It needs to be determined at the population level whether patients with underlying chronic non healing wounds require a higher sequestered parasite biomass to develop CM or not. Each stage of wound carriage might play an important role in shaping the immunity against malaria and CM and this shared exposure should not be neglected simply. Both of these multifactorial diseases are largely seen in association with poor nutrition and socioeconomic status. The possible influence of chronic wounds on the immune response to malaria, parasite development and cytoadherence phenomena needs to be determined. Chronic non healing wounds continue to be a pandemic health problem (17). Animal studies would be of paramount value in this regard. Chronic wounds are major public-health problem in developing countries prone to CM: coendemic. The possibility that chronic non healing wounds could markedly affect the CM disease burden in malaria endemic area and their relevance to clinical disease deserves further investigations. Comparison between rate of CM resistance or tolerance between population widely devastated by chronic wounds and wound-free areas will illuminate the possible wound–CM interaction. Comparison of wound distribution among sites with peak occurrence of CM and variable malaria transmission intensities also seems helpful. This implies that treating one burden (wounds) could potentially relieve the other (CM), but it is not yet clinically proved. This would offer affordable means to roll back CM and its consequent complications and costs. If deleterious effects of concomitant non healing wounds on CM are confirmed, vigorous therapeutic measures for chronic wounds might become a priority in malaria endemic area before the progress towards CM. Perhaps, little paid attentions to the pre-existing non healing wounds merely before the onset of rainy seasons with the peak malaria transmissions would be of paramount impact on CM elimination. This seasonal attention to wounds or even every factor able to aggravate much of the hyperimmune responsiveness associated with CM expected to be economically more cost effective. The data regarding favoured season could be derived from district statistics and informed to resident clinicians. Considering the high prevalence of chronic non healing wounds in malaria endemic area as sub-Saharan Africa and the fatality rate of CM in this area, the fundamental practical implication of dewounding on the outcome of CM will be perceived easier. It is also convincible to address this hypothesis that wounds will get non healing fate in the cases experienced fatal CM. Mohaddeseh Behjati 1 The author declares no conflicts of interest.

Significance: Chronic skin wounds are a significant health problem around the world, often leading to amputation and even death. Although persistent inflammation is a hallmark of these poorly healing wounds, few available therapies have been designed to target inflammation. In this review, we summarize available evidence of the role of the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome in impaired wound healing and describe strategies to inhibit the inflammasome to improve wound healing. Recent Advances: The NLRP3 inflammasome plays an important physiological role in skin wound healing, during which transient inflammasome activity contributes to both epidermal and dermal healing. In contrast, sustained activity of the NLRP3 inflammasome leads to impaired epidermal and dermal healing associated with diabetes. Of importance, preclinical studies have demonstrated that inhibiting the NLRP3 inflammasome-induced resolution of inflammation, increased granulation tissue formation and collagen deposition, and accelerated reepithelialization and wound closure. Critical Issues: NLRP3 inflammasome inhibitors have appealing potential for translation into therapies for chronic wounds. Although preclinical studies have shown promising results, there is a need for human/clinical studies to evaluate dosing formulations, potential therapeutic effects, dose-response relationships, and possible side effects. Future Directions: Among strategies to inhibit the NLRP3 inflammasome, glyburide, metformin, peroxisome proliferator-activated receptor agonists, and the dipeptidyl peptidase 4 inhibitor saxagliptin appear to be closest to clinical translation, as these drugs are already Food and Drug Administration approved for other indications. Future clinical studies are needed to develop topical formulations of these drugs, and to assess the safety and efficacy of these inhibitors, to improve healing of chronic wounds.

To evaluate the effects of hyperbaric oxygen (HBO) therapy in the management of chronic wound and observe the correlation between wound healing and CD34+ endothelial progenitor cells (EPCs). A total of 119 patients with chronic wound in lower extremities lasting > 3 months were recruited for this randomized, single-center, placebo-controlled clinical trial. The changes of CD34+ average count before and after HBO therapy were detected by flow cytometry (FACS). There were 97 patients on long-term HBO therapy and in 22 patients on hyperbaric air therapy as control group. The CD34/Scal-1+ and CD34/CXCR4 dual-positive populations of gated cell were determined respectively by FACs. The outcomes of two groups were compared. Treatment was administered within a single-place hyperbaric chamber for 90-min daily (session duration 120 min) for 5 days a week for 4 weeks (20 treatment sessions). The wound size decreased at the 4-week end point (62.7% ± 22.3% in the HBO group vs 34.4% ± 20.6% in the control group, P < 0.05). After 10 episodes of HBO therapies for chronic non-healing wound, the peripheral CD34+ EPCs average count rose from 0.24% ± 0.03% at pre-treatment to 1.32% ± 0.05% while the number was 1.75% ± 0.17% after 20 episodes of HBO (P < 0.05). Both were significantly different from that of the patients at pre-treatment. However the overall circulating white cell count was not significantly elevated. The CD34/Scal-1+ and CD34/CXCR4 dual-positive populations of gated cell in HBO group were 5.8 and 5.2 folds than those at pre-treatment respectively. The number of EPCs was positively correlated with wound healing in lower extremities (correlation coefficient 0.84; P < 0.01). Adjunctive treatment of HBO facilitates the healing of chronic non-healing wound in selected patients through the mobilization of EPCs.

Poor angiogenesis and impaired proliferation of cells responsible for the repair of chronic ischemic wounds result in impaired wound healing. The continuous and efficient expression of therapeutic factors by means of gene transfection is an ideal adjuvant treatment method to promote cell proliferation and angiogenesis. A chimeric recombinant adenoviral vector, Ad5F35ET1-bFGF, was constructed that carried the basic fibroblast growth factor (bFGF) gene and used the endothelin-1 promoter to control the targeted expression of bFGF in endothelial cells and fibroblasts. Thus, the authors established a targeted gene therapy for chronic ischemic wounds. The chimeric adenovirus Ad5F35ET1-bFGF efficiently infected the endothelin-1-positive endothelial cells and fibroblasts, specifically expressed bFGF, and promoted cell proliferation. In the rabbit wound healing model, the chimeric recombinant adenovirus expressed a high level of bFGF in wound tissues, which continuously promoted angiogenesis and cell proliferation and thus accelerated wound healing. Targeted gene therapy that uses bFGF as a therapeutic gene provides an effective candidate strategy for the treatment of chronic ischemic wounds.

BACKGROUNDThe impairment of cutaneous wound healing results in chronic, non-healing wounds that are caused by altered wound environment oxygenation, tissue injury, and permissive microbial growth. Current modalities for the treatment of these wounds inadequately address the complex changes involved in chronic wound pathogenesis. Consequently, stem cell therapies have emerged as a potential therapeutic modality to promote cutaneous regeneration through trophic and paracrine activity.AIMTo investigate current literature regarding use of stem cell therapies for the clinical treatment of chronic, non-healing wounds.METHODSPubMed, EMBASE, Cochrane Library, Web of Science, and Scopus were queried with combinations of the search terms “mesenchymal stem cells,” “adult stem cells,” “embryonic stem cells,” “erythroid precursor cells,” “stem cell therapies,” and “chronic wounds” in order to find relevant articles published between the years of 2000 and 2019 to review a 20-year experience. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (reviews, case reports/series, retrospective/prospective studies, and clinical trials) were evaluated by the authors for their depiction of clinical stem cell therapy use. Data were extracted from the articles using a standardized collection tool.RESULTSA total of 43 articles describing the use of stem cell therapies for the treatment of chronic wounds were included in this review. While stem cell therapies have been explored in in vitro and in vivo applications in the past, recent efforts are geared towards assessing their clinical role. A review of the literature revealed that adipose-derived stem cells, bone marrow-derived stem cells, bone marrow-derived mononuclear cells, epidermally-derived mesenchymal stem cells, fibroblast stem cells, keratinocyte stem cells, placental mesenchymal stem cells, and umbilical cord mesenchymal stem cells have all been employed in the treatment of chronic wounds of various etiologies. Most recently, embryonic stem cells have emerged as a novel stem cell therapy with the capacity for multifaceted germ cell layer differentiation. With the capacity for self-renewal and differentiation, stem cells can enrich existing cell populations in chronic wounds in order to overcome barriers impeding the progression of wound healing. Further, stem cell therapies can be utilized to augment cell engraftment, signaling and activity, and resultant patient outcomes.CONCLUSIONAssessing observed clinical outcomes, potential for stem cell use, and relevant therapeutic challenges allows wound care stakeholders to make informed decisions regarding optimal treatment approaches for their patients’ chronic wounds.

The continuous improvements in the field of both regenerative medicine and tissue engineering have allowed the design of new and more efficacious strategies for the treatment of chronic or hard-to-heal skin wounds, which represent heavy burden, from a medical and economic point of view. These novel approaches are based on the usage of three key methodologies: stem cells, growth factors, and biomimetic scaffolds. These days, the adipose tissue can be considered the main source of multipotent mesenchymal stem cells, especially adipose-derived stem cells (ASCs). ASCs are easily accessible from various fat depots and show an intrinsic plasticity in giving rise to cell types involved in wound healing and angiogenesis. ASCs can be found in fat grafts, historically used in the treatment of chronic wounds, and have been evaluated as such in both animal models and human trials, to exploit their capability of accelerating wound closure and inducing a correct remodeling of the newly formed fibrovascular tissue. Since survival and fitness of ASCs need to be improved, they are now employed in conjunction with advanced wound dressings, together with dermal regenerative templates and platelet-rich plasma (as a source of growth and healing factors). In this work, we provide an overview of the current knowledge on the topic, based on existing studies and on our own experience.

Probing the Dose-Dependent Effect of Migration Stimulating Factor-Like Drug on Fibroblast Migration using Optical Tweezers