Autologous human keratinocytes cultured on membranes composed of benzyl ester of hyaluronic acid for grafting in nonhealing diabetic foot lesions: a pilot study

Recent advances in the adjunctive management of diabetic foot ulcer: Focus on noninvasive technologies

Diabetic foot ulcer (DFU) is one of the most costly and serious complications of diabetes. Treatment of DFU is usually challenging and new approaches are required to improve the therapeutic efficiencies. This review aims to update new and upcoming adjunctive therapies with noninvasive characterization for DFU, focusing on bioactive dressings, bioengineered tissues, mesenchymal stem cell (MSC) based therapy, platelet and cytokine-based therapy, topical oxygen therapy, and some repurposed drugs such as hypoglycemic agents, blood pressure medications, phenytoin, vitamins, and magnesium. Although the mentioned therapies may contribute to the improvement of DFU to a certain extent, most of the evidence come from clinical trials with small sample size and inconsistent selections of DFU patients. Further studies with high design quality and adequate sample sizes are necessitated. In addition, no single approach would completely correct the complex pathogenesis of DFU. Reasonable selection and combination of these techniques should be considered.

Specific Features of the Functional Activity of Human Adipose Stromal Cells in the Structure of a Partial Skin-Equivalent

Mesenchymal adipose stromal cells (ASCs) are considered the most promising and accessible material for translational medicine. ASCs can be used independently or within the structure of scaffold-based constructs, as these not only ensure mechanical support, but can also optimize conditions for cell activity, as specific features of the scaffold structure have an impact on the vital activity of the cells. This manuscript presents a study of the secretion and accumulation that occur in a conditioned medium during the cultivation of human ASCs within the structure of such a partial skin-equivalent that is in contact with it. It is demonstrated that the ASCs retain their functional activity during cultivation both within this partial skin-equivalent structure and, separately, on plastic substrates: they proliferate and secrete various proteins that can then accumulate in the conditioned media. Our comparative study of changes in the conditioned media during cultivation of ASCs on plastic and within the partial skin-equivalent structure reveals the different dynamics of the release and accumulation of such secretory factors in the media under a variety of conditions of cell functioning. It is also demonstrated that the optimal markers for assessment of the ASCs' secretory functions in the studied partial skin-equivalent structure are the trophic factors VEGF-A, HGF, MCP, SDF-1α, IL-6 and IL-8. The results will help with the development of an algorithm for preclinical studies of this skin-equivalent in vitro and may be useful in studying various other complex constructs that include ASCs.

Therapeutic Efficacy of Polymeric Biomaterials in Treating Diabetic Wounds-An Upcoming Wound Healing Technology

Diabetic wounds are one of the serious, non-healing, chronic health issues faced by individuals suffering from diabetic mellitus. The distinct phases of wound healing are either prolonged or obstructed, resulting in the improper healing of diabetic wounds. These injuries require persistent wound care and appropriate treatment to prevent deleterious effects such as lower limb amputation. Although there are several treatment strategies, diabetic wounds continue to be a major threat for healthcare professionals and patients. The different types of diabetic wound dressings that are currently used differ in their properties of absorbing wound exudates and may also cause maceration to surrounding tissues. Current research is focused on developing novel wound dressings incorporated with biological agents that aid in a faster rate of wound closure. An ideal wound dressing material must absorb wound exudates, aid in the appropriate exchange of gas, and protect from microbial infections. It must support the synthesis of biochemical mediators such as cytokines, and growth factors that are crucial for faster healing of wounds. This review highlights the recent advances in polymeric biomaterial-based wound dressings, novel therapeutic regimes, and their efficacy in treating diabetic wounds. The role of polymeric wound dressings loaded with bioactive compounds, and their in vitro and in vivo performance in diabetic wound treatment are also reviewed.

Innovative Cell and Platelet Rich Plasma Therapies for Diabetic Foot Ulcer Treatment: The Allogeneic Approach

Cutaneous chronic wounds are a major global health burden in continuous growth, because of population aging and the higher incidence of chronic diseases, such as diabetes. Different treatments have been proposed: biological, surgical, and physical. However, most of these treatments are palliative and none of them can be considered fully satisfactory. During a spontaneous wound healing, endogenous regeneration mechanisms and resident cell activity are triggered by the released platelet content. Activated stem and progenitor cells are key factors for ulcer healing, and they can be either recruited to the wound site from the tissue itself (resident cells) or from elsewhere. Transplant of skin substitutes, and of stem cells derived from tissues such as bone marrow or adipose tissue, together with platelet-rich plasma (PRP) treatments have been proposed as therapeutic options, and they represent the today most promising tools to promote ulcer healing in diabetes. Although stem cells can directly participate to skin repair, they primarily contribute to the tissue remodeling by releasing biomolecules and microvesicles able to stimulate the endogenous regeneration mechanisms. Stem cells and PRP can be obtained from patients as autologous preparations. However, in the diabetic condition, poor cell number, reduced cell activity or impaired PRP efficacy may limit their use. Administration of allogeneic preparations from healthy and/or younger donors is regarded with increasing interest to overcome such limitation. This review summarizes the results obtained when these innovative treatments were adopted in preclinical animal models of diabetes and in diabetic patients, with a focus on allogeneic preparations.

Polymer-Based Wound Dressing Materials Loaded with Bioactive Agents: Potential Materials for the Treatment of Diabetic Wounds

Diabetic wounds are severe injuries that are common in patients that suffer from diabetes. Most of the presently employed wound dressing scaffolds are inappropriate for treating diabetic wounds. Improper treatment of diabetic wounds usually results in amputations. The shortcomings that are related to the currently used wound dressings include poor antimicrobial properties, inability to provide moisture, weak mechanical features, poor biodegradability, and biocompatibility, etc. To overcome the poor mechanical properties, polymer-based wound dressings have been designed from the combination of biopolymers (natural polymers) (e.g., chitosan, alginate, cellulose, chitin, gelatin, etc.) and synthetic polymers (e.g., poly (vinyl alcohol), poly (lactic-co-glycolic acid), polylactide, poly-glycolic acid, polyurethanes, etc.) to produce effective hybrid scaffolds for wound management. The loading of bioactive agents or drugs into polymer-based wound dressings can result in improved therapeutic outcomes such as good antibacterial or antioxidant activity when used in the treatment of diabetic wounds. Based on the outstanding performance of polymer-based wound dressings on diabetic wounds in the pre-clinical experiments, the in vivo and in vitro therapeutic results of the wound dressing materials on the diabetic wound are hereby reviewed.

Immunological challenges associated with artificial skin grafts: available solutions and stem cells in future design of synthetic skin

The repair or replacement of damaged skins is still an important, challenging public health problem. Immune acceptance and long-term survival of skin grafts represent the major problem to overcome in grafting given that in most situations autografts cannot be used. The emergence of artificial skin substitutes provides alternative treatment with the capacity to reduce the dependency on the increasing demand of cadaver skin grafts. Over the years, considerable research efforts have focused on strategies for skin repair or permanent skin graft transplantations. Available skin substitutes include pre- or post-transplantation treatments of donor cells, stem cell-based therapies, and skin equivalents composed of bio-engineered acellular or cellular skin substitutes. However, skin substitutes are still prone to immunological rejection, and as such, there is currently no skin substitute available to overcome this phenomenon. This review focuses on the mechanisms of skin rejection and tolerance induction and outlines in detail current available strategies and alternatives that may allow achieving full-thickness skin replacement and repair.

Current Concepts in Tissue Engineering: Skin and Wound

BACKGROUND

Pure regenerative healing with little to no donor morbidity remains an elusive goal for both surgeon and patient. The ability to engineer and promote the development of like tissue holds so much promise, and efforts in this direction are slowly but steadily advancing.

METHODS

Products selected and reviewed reflect historical precedence and importance and focus on current clinically available products in use. Emerging technologies we anticipate will further expand our therapeutic options are introduced. The topic of tissue engineering is incredibly broad in scope, and as such the authors have focused their review on that of constructs specifically designed for skin and wound healing. A review of pertinent and current clinically related literature is included.

RESULTS

Products such as biosynthetics, biologics, cellular promoting factors, and commercially available matrices can be routinely found in most modern health care centers. Although to date no complete regenerative or direct identical soft-tissue replacement exists, currently available commercial components have proven beneficial in augmenting and improving some types of wound healing scenarios. Cost, directed specificity, biocompatibility, and bioburden tolerance are just some of the impending challenges to adoption.

CONCLUSIONS

Quality of life and in fact the ability to sustain life is dependent on our most complex and remarkable organ, skin. Although pure regenerative healing and engineered soft-tissue constructs elude us, surgeons and health care providers are slowly gaining comfort and experience with concepts and strategies to improve the healing of wounds.

Diabetic ulcer regeneration: stem cells, biomaterials, growth factors

The impairment of ulcer wound healing in diabetic patients is a vital clinical problem affecting millions of patients. Several clinical and basic science studies have demonstrated that stem cell therapy, to be effective in healing diabetic ulcer. Furthermore, these ulcer wounds may be healed from molecular maneuvering of growth factors to improve microcirculation within the ulcer wound. In addition, ulcer wound dressings may be employed as medicated systems, through the delivery of drugs, growth factors, peptides and stem cells. These dressing materials can include natural, modified and synthetic polymers, as well as their mixtures or combinations. This review paper will give a summary of some of the recent advances on the application of stem cells, biomaterials and growth factors in the treatment of diabetic ulcer wound.

Recent advances in biomaterials for the treatment of diabetic foot ulcers

Diabetes mellitus is one of the most challenging epidemics facing the world today, with over 300 million patients affected worldwide.

Current wound healing procedures and potential care

In this review, we describe current and future potential wound healing treatments for acute and chronic wounds. The current wound healing approaches are based on autografts, allografts, and cultured epithelial autografts, and wound dressings based on biocompatible and biodegradable polymers. The Food and Drug Administration approved wound healing dressings based on several polymers including collagen, silicon, chitosan, and hyaluronic acid. The new potential therapeutic intervention for wound healing includes sustained delivery of growth factors, and siRNA delivery, targeting microRNA, and stem cell therapy. In addition, environment sensors can also potentially utilize to monitor and manage microenvironment at wound site. Sensors use optical, odor, pH, and hydration sensors to detect such characteristics as uric acid level, pH, protease level, and infection - all in the hopes of early detection of complications.

Wound Healing: Biologics, Skin Substitutes, Biomembranes and Scaffolds

This review will explore the latest advancements spanning several facets of wound healing, including biologics, skin substitutes, biomembranes and scaffolds.

Biological skin substitutes for wound cover and closure

In the past 30 years, the development and use of artificial skin in the treatment of acute and chronic wounds has advanced from an experimental concept to a working reality. However, while there have been an increasing number of artificial skin substitutes licensed for clinical use, they have yet to supplant the current gold standard of an autologous tissue graft for most applications. This article reviews the advantages and disadvantages of the currently available, biologically based substitutes, with special emphasis on their relative efficacy and suitability for treatment of particular wound types. Economic considerations, desirable improvements of currently available materials and the potential impact of future advances in the field will also be discussed.

Recent advances on the development of wound dressings for diabetic foot ulcer treatment--a review

Diabetic foot ulcers (DFUs) are a chronic, non-healing complication of diabetes that lead to high hospital costs and, in extreme cases, to amputation. Diabetic neuropathy, peripheral vascular disease, abnormal cellular and cytokine/chemokine activity are among the main factors that hinder diabetic wound repair. DFUs represent a current and important challenge in the development of novel and efficient wound dressings. In general, an ideal wound dressing should provide a moist wound environment, offer protection from secondary infections, remove wound exudate and promote tissue regeneration. However, no existing dressing fulfills all the requirements associated with DFU treatment and the choice of the correct dressing depends on the wound type and stage, injury extension, patient condition and the tissues involved. Currently, there are different types of commercially available wound dressings that can be used for DFU treatment which differ on their application modes, materials, shape and on the methods employed for production. Dressing materials can include natural, modified and synthetic polymers, as well as their mixtures or combinations, processed in the form of films, foams, hydrocolloids and hydrogels. Moreover, wound dressings may be employed as medicated systems, through the delivery of healing enhancers and therapeutic substances (drugs, growth factors, peptides, stem cells and/or other bioactive substances). This work reviews the state of the art and the most recent advances in the development of wound dressings for DFU treatment. Special emphasis is given to systems employing new polymeric biomaterials, and to the latest and innovative therapeutic strategies and delivery approaches.

Skin substitutes: An Indian perspective

There have been numerous alternatives developed to replace skin. These can either be permanent substitutes or temporary substitutes, which need to be replaced later by autologous grafts. These have been tried in recent times as an attempt to reduce the need or in the case of permanent substitutes ,altogether replace autologous skin grafts. However till date no ideal skin substitute has been developed. Various factors have to be considered while choosing one of these substitutes. In a developing country like India awareness and availability of these skin substitutes is not adequate considering the volume of cases that require this modality of treatment. Also there are skin substitutes developed in our country that need to be highlighted. This article is an attempt to review the vast array of skin substitutes that have been developed and consider their utility and feasibility for developing countries.

Autologous skin fibroblast and keratinocyte grafts in the treatment of chronic foot ulcers in aging type 2 diabetic patients

BACKGROUND

we assessed the tolerability and efficacy of autologous skin cell grafts in older type 2 diabetic patients with chronic foot ulcers.

METHODS

treatment with Hyalograft 3D and Laserskin Autograft was proposed to a consecutive series of type 2 diabetic patients older than 65 years affected by long-standing (>6 months) foot ulcers with an area greater than 15 cm(2). Ulcer healing rates and measurements of ulcer area were determined monthly for 12 months.

RESULTS

seven patients with 12 ulcers, nine of which received the described treatment, were enrolled. During 12-month follow-up, all of the ulcers healed except one. In the remaining eight ulcers, the median healing time was 21 weeks (interquartile range, 4-29 weeks).

CONCLUSIONS

autologous skin cell grafts are feasible, well tolerated, and apparently effective in the treatment of diabetic ulcers of the lower limbs in advanced age. Age did not seem to moderate healing times.

Active wound coverings: bioengineered skin and dermal substitutes

Extensive skin loss and chronic wounds present a significant challenge to the clinician. With increased understanding of wound healing, cell biology, and cell culture techniques, various synthetic dressings and bioengineered skin substitutes have been developed. These materials can protect the wound, increase healing, provide overall wound coverage, and improve patient care. The ideal skin substitute may soon become a reality.

Effect of pravastatin on experimental diabetic wound healing

BACKGROUND

Impaired wound healing in diabetes has been associated with abnormalities in wound nitric oxide (NO) and nitric oxide synthase (NOS) availability. Efforts to alter the profile of NO expression in the wound microenvironment have proven to be successful in partially restoring wound healing deficits. We investigated the effects of pravastatin, a HMG Co A reductase inhibitor on endothelial nitric oxide synthase (eNOS) expression, NO production, and wound healing in a diabetic acute wound healing model.

MATERIALS AND METHODS

Of 70 male Sprague Dawley rats injected with streptozocin, 62 were confirmed diabetic after 1 wk. Animals were randomized into two groups: (1) diabetic control and (2) diabetic treated with pravastatin. Pravastatin sodium was gavaged at 0.4 mg/kg/d for 5 d, after which all animals underwent dorsal incision with insertion of subcutaneous sponges. Breaking strengths and hydroxyproline were measured on days 1, 3, and 10 post-wounding. Wound fluid was analyzed for nitrate/nitrite production. Tissue samples were analyzed for eNOS expression.

RESULTS

We demonstrated enhanced wound breaking strengths, hydroxyproline accumulation, an up-regulation in eNOS expression, and elevated NO levels in the pravastatin treated group.

CONCLUSION

We have shown that pravastatin, in an experimental model of diabetes may through up-regulation of eNOS and NO expression improve wound healing.

Bioengineered alternative tissues and hyperbaric oxygen in lower extremity wound healing

With the advent and clinical application of recombinant chemical and cellular mediators of wound healing and a better understanding of the importance of serial debridement, most foot wounds can be healed with little morbidity. Despite these advances, there remains the recalcitrant wound for which more heroic efforts seem warranted. For these patients, advanced wound healing technologies, orthobiologics, and bioengineered alternative tissues may tilt the scales in the direction of definitive wound closure.

Hyaluronic acid: the scientific and clinical evidence

Hyaluronic acid is a naturally occurring biopolymer whose molecular structure is highly conserved between mammalian species. First described in 1934, it has since been used across a wide variety of medical fields as diverse as neurosurgery and cutaneous wound healing. Presently it has reached prominence in cosmetic practice where it is now the injectable dermal filler of choice for most surgeons. We used our experience of this technology with searches in the English language literature for the purpose of a systematic review. We present an overview, including the scientific evidence for its use in wound healing and, briefly, in other fields. We summarise the evidence for and against hyaluronic acid and provide a resumé of the current technologies available in fields such as skin regeneration and wound healing, in addition to cosmetic surgery. This overview is not intended to teach the reader about the various formulations currently on the market or how to use these materials clinically - rather to provide a solid scientific background enabling the reader to understand the attributes (and otherwise) of the material. We hope to allow clinicians to assess the evidence for a material now in common use in order that they may be fully aware of its properties.

Autologous full-thickness skin substitute for healing chronic wounds

BACKGROUND

Chronic wounds represent a major problem to our society. Therefore, advanced wound-healing strategies for the treatment of these wounds are expanding into the field of tissue engineering.

OBJECTIVES

To develop a novel tissue-engineered, autologous, full-thickness skin substitute of entirely human origin and to determine its ability to heal chronic wounds.

METHODS

Skin substitutes (fully differentiated epidermis on fibroblast-populated human dermis) were constructed from 3-mm punch biopsies isolated from patients to be treated. Acellular allodermis was used as a dermal matrix. After a prior 5-day vacuum-assisted closure therapy to prepare the wound bed, skin substitutes were applied in a simple one-step surgical procedure to 19 long-standing recalcitrant leg ulcers (14 patients; ulcer duration 0.5-50 years).

RESULTS

The success rate in culturing biopsies was 97%. The skin substitute visibly resembled an autograft. Eleven of the 19 ulcers (size 1-10 cm2) healed within 8 weeks after a single application of the skin substitute. The other eight larger (60-150 cm2) and/or complicated ulcers healed completely (n = 5) or continued to decrease substantially in size (n = 3) after the 8-week follow-up period. Wound healing occurred by direct take of the skin substitute (n = 12) and/or stimulation of granulation tissue/epithelialization (n = 7). Skin substitutes were very well tolerated and pain relief was immediate after application.

CONCLUSIONS

Application of this novel skin substitute provides a promising new therapy for healing chronic wounds resistant to conventional therapies.

The effect of hyaluronan combined with KI3 complex (Hyiodine wound dressing) on keratinocytes and immune cells

Hyiodine (high molecular weight hyaluronan combined with KI3 complex) is a new non-adhesive wound dressing which significantly improves the healing process. The aim of the study was to investigate the effects of Hyoidine on functional properties of isolated human keratinocytes and leukocytes, and on those of U937 and HL60 cell lines. While KI3 complex inhibited the viability and proliferation of the cells tested, Hyiodine did not have any significant effect. The expression of CD11b, CD62L and CD69 on PMNL, monocytes and lymphocytes, as well as the oxidative burst of blood neutrophils, were not changed. On the contrary, Hyiodine inhibited the PMA-activated oxidative burst and significantly increased the production of IL-6 and TNF-alpha by lymphocytes. It was concluded that hyaluronan content of Hyiodine reduces the toxic effect of KI3 complex on cells and speeds up the wound healing process by increasing the production of inflammatory cytokines.

The molecular biology of chronic wounds and delayed healing in diabetes

Wound healing is a complicated and integrated process. Although there is some tolerance in terms of redundancy and interrelated control mechanisms, pushing beyond such limits may contribute to delayed wound healing, and in extreme cases lead to chronic wounds/ulcers and thus potentially to lower extremity amputation. Diabetes is associated with such disruption in wound healing. Research in humans and in animal models has identified a large number of changes associated with diabetes at the molecular level in delayed wound healing and to a lesser extent in chronic diabetic ulcers. Better overall understanding of these changes and how they are interrelated would allow for specifically targeted treatment, thus ensuring improved quality of life for patients and providing savings to the high costs that are associated with all aspects of chronic diabetic ulcers. This review examines the work done at the molecular level on chronic diabetic ulcers, as well as considering changes seen in diabetes in general, both in humans and animal models, that may in turn contribute to ulcer formation.

The role of hyaluronic acid in wound healing: assessment of clinical evidence

Hyaluronic acid (hyaluronan), a naturally occurring polymer within the skin, has been extensively studied since its discovery in 1934. It has been used in a wide range of medical fields as diverse as orthopedics and cosmetic surgery, but it is in tissue engineering that it has been primarily advanced for treatment. The breakdown products of this large macromolecule have a range of properties that lend it specifically to this setting and also to the field of wound healing. It is non-antigenic and may be manufactured in a number of forms, ranging from gels to sheets of solid material through to lightly woven meshes. Epidermal engraftment is superior to most of the available biotechnologies and, as such, the material shows great promise in both animal and clinical studies of tissue engineering. Ongoing work centers around the ability of the molecule to enhance angiogenesis and the conversion of chronic wounds into acute wounds.

The cell based dressing with living allogenic keratinocytes in the treatment of foot ulcers: a case study

In this study, we aimed to investigate the efficacy of cell based dressing with living allogenic keratinocytes in diabetic foot patients. To address this issue, the cultured keratinocytes were attached to the microcarriers produced from polyethylene and silica. The microcarriers were then applied to the wounds at 3-day intervals. Forty patients with grade II and III diabetic foot ulcers were included into the study. The patients were randomised into two groups (n=20). The treatment and control groups received cell based dressing and microcarriers kept in culture medium overnight, respectively. The wound size was recorded at 3 days intervals. The wounds were also categorised by a specific scoring system considering the wound contraction, granulation tissue formation, epithelisation and discharge from the wounds. The high score indicates better condition. The mean reduction of the wound area was 92% in the treatment group and 32% in the control group at the end of the 30 days treatment (p<0.001). When considered the complete healing, the mean number of dressings was 9.2+/-3.2 in the treatment group whereas it was 16.5+/-2.3 in the control group (p<0.001). The initial mean score of the treatment and control groups were 2.5 and 2.35, respectively. At the end of the 30th day, the mean score of the treatment group was 17.15+/-2.7 and of control group was 9.05+/-3. Allogenic keratinocyte treatment delivered with microcarriers can make significant contributions to wound healing in diabetic foot patients.

In vitro reconstruction of an endothelialized skin substitute provided with a microcapillary network using biopolymer scaffolds

Successful in vitro reconstruction of skin requires the inclusion of several cell types that give rise in coculture to the specific elements present in native skin, and the appropriate scaffolding structure to house and support these cells. In addition to the two main structural components, epidermis and dermis, one critical apparatus of the skin is a capillary network that guarantees adequate perfusion of nutrients and oxygen. The aim of the present study was to develop an in vitro coculture system that assumed the human dermal-epidermal architecture and included a microcapillary network in a three-dimensional biomaterial that guaranteed ease of handling in a clinical setting. Endothelialized skin (ES) was prepared by coculturing three human cell types: keratinocytes, fibroblasts, and endothelial cells, obtained from human full-thickness skin samples, in scaffolds produced from modified hyaluronic acid. Results were evaluated by histological and immunohistochemical analyses at different time points. In vitro, engineered skin obtained with this composite culture developed into a well-differentiated upper layer of stratified keratinocytes lining a dermal-like structure, in which fibroblasts, extracellular matrix and a microvascular network were present. Furthermore, the biodegradable fabric produced from hyaluronic acid and used as the scaffolding support for this in vitro constructed skin graft greatly facilitated handling in the perioperative period.

Hyaluronic acid in the treatment and prevention of skin diseases: molecular biological, pharmaceutical and clinical aspects

The glycosaminoglycan hyaluronic acid (HA), or hyaluronan, is a major component of the extracellular matrix of skin, joints, eye and many other tissues and organs. In spite of its simple structure, HA demonstrates remarkable rheological, viscoelastic and hygroscopic properties which are relevant for dermal tissue function. Biological activities in skin, however, are also due to its interaction with various binding proteins (hyaladherins). Due to an influence on signaling pathways, HA is involved in the wound-healing process and scarless fetal healing. Increased HA concentrations have been associated with inflammatory skin diseases. In clinical trials, topical application of HA improved wound healing; in particular, acute radioepithelitis, venous leg ulcers or diabetic foot lesions responded to HA treatment. Moreover, as a topical drug delivery system for diclofenac, an HA gel has recently been approved for the treatment of actinic keratoses. Finally, chemical modifications led to new HA derivates and biomaterials, which may be introduced into therapy in the future. Therefore, ongoing research offers new horizons for the therapeutic use of this glycosaminoglycan which has been regarded as an inert structural component until recently.