Efficacy and safety of the freeze-dried cultured human keratinocyte lysate, LyphoDermtm 0.9%, in the treatment of hard-to-heal venous leg ulcers

Autologous Skin Grafts, versus Tissue-engineered Skin Constructs: A Systematic Review and Meta-analysis

For over 100 years, autologous skin grafts have remained the gold standard for the reconstruction of wounds but are limited in availability. Acellular tissue-engineered skin constructs (acellular TCs) and cellular tissue-engineered skin constructs (cellular TCs) may address these limitations. This systematic review and meta-analysis compare outcomes between them.

Methods

A systematic review was conducted using PRISMA guidelines, querying MEDLINE, Embase, Web of Science, and Cochrane to assess graft incorporation, failure, and wound healing. Case reports/series, reviews, in vitro/in vivo work, non-English articles or articles without full text were excluded.

Results

Sixty-six articles encompassing 4076 patients were included. No significant differences were found between graft failure rates (P = 0.07) and mean difference of percent reepithelialization (p = 0.92) when split-thickness skin grafts were applied alone versus co-grafted with acellular TCs. Similar mean Vancouver Scar Scale was found for these two groups (p = 0.09). Twenty-one studies used at least one cellular TC. Weighted averages from pooled results did not reveal statistically significant differences in mean reepithelialization or failure rates for epidermal cellular TCs compared with split-thickness skin grafts (p = 0.55).

Conclusions

This systematic review is the first to illustrate comparable functional and wound healing outcomes between split-thickness skin grafts alone and those co-grafted with acellular TCs. The use of cellular TCs seems promising from preliminary findings. However, these results are limited in clinical applicability due to the heterogeneity of study data, and further level 1 evidence is required to determine the safety and efficacy of these constructs.

Functionalised-biomatrix for wound healing and cutaneous regeneration: future impactful medical products in clinical translation and precision medicine

Skin tissue engineering possesses great promise in providing successful wound injury and tissue loss treatments that current methods cannot treat or achieve a satisfactory clinical outcome. A major field direction is exploring bioscaffolds with multifunctional properties to enhance biological performance and expedite complex skin tissue regeneration. Multifunctional bioscaffolds are three-dimensional (3D) constructs manufactured from natural and synthetic biomaterials using cutting-edge tissue fabrication techniques incorporated with cells, growth factors, secretomes, antibacterial compounds, and bioactive molecules. It offers a physical, chemical, and biological environment with a biomimetic framework to direct cells toward higher-order tissue regeneration during wound healing. Multifunctional bioscaffolds are a promising possibility for skin regeneration because of the variety of structures they provide and the capacity to customise the chemistry of their surfaces, which allows for the regulated distribution of bioactive chemicals or cells. Meanwhile, the current gap is through advanced fabrication techniques such as computational designing, electrospinning, and 3D bioprinting to fabricate multifunctional scaffolds with long-term safety. This review stipulates the wound healing processes used by commercially available engineered skin replacements (ESS), highlighting the demand for a multifunctional, and next-generation ESS replacement as the goals and significance study in tissue engineering and regenerative medicine (TERM). This work also scrutinise the use of multifunctional bioscaffolds in wound healing applications, demonstrating successful biological performance in the in vitro and in vivo animal models. Further, we also provided a comprehensive review in requiring new viewpoints and technological innovations for the clinical application of multifunctional bioscaffolds for wound healing that have been found in the literature in the last 5 years.

Advances in Skin Tissue Engineering and Regenerative Medicine

There are an estimated 500,000 patients treated with full-thickness wounds in the United States every year. Fire-related burn injuries are among the most common and devastating types of wounds that require advanced clinical treatment. Autologous split-thickness skin grafting is the clinical gold standard for the treatment of large burn wounds. However, skin grafting has several limitations, particularly in large burn wounds, where there may be a limited area of non-wounded skin to use for grafting. Non-cellular dermal substitutes have been developed but have their own challenges; they are expensive to produce, may require immunosuppression depending on design and allogenic cell inclusion. There is a need for more advanced treatments for devastating burns and wounds. This manuscript provides a brief overview of some recent advances in wound care, including the use of advanced biomaterials, cell-based therapies for wound healing, biological skin substitutes, biological scaffolds, spray on skin and skin bioprinting. Finally, we provide insight into the future of wound care and technological areas that need to be addressed to support the development and incorporation of these technologies.

Longitudinal Evaluation of Biomarkers in Wound Fluids from Venous Leg Ulcers and Split-thickness Skin Graft Donor Site Wounds Treated with a Protease-modulating Wound Dressing

Venous leg ulcers represent a clinical challenge and impair the quality of life of patients. This study examines impaired wound healing in venous leg ulcers at the molecular level. Protein expression patterns for biomarkers were analysed in venous leg ulcer wound fluids from 57 patients treated with a protease-modulating polyacrylate wound dressing for 12 weeks, and compared with exudates from 10 acute split-thickness wounds. Wound healing improved in the venous leg ulcer wounds: 61.4% of the 57 patients with venous leg ulcer achieved a relative wound area reduction of ≥ 40%, and 50.9% of the total 57 patients achieved a relative wound area reduction of ≥ 60%. Within the first 14 days, abundances of S100A8, S100A9, neutrophil elastase, matrix metalloproteinase-2, and fibronectin in venous leg ulcer exudates decreased significantly and remained stable, yet higher than in acute wounds. Interleukin-1β, tumour necrosis factor alpha, and matrix metalloproteinase-9 abundance ranges were similar in venous leg ulcers and acute wound fluids. Collagen (I) α1 abundance was higher in venous leg ulcer wound fluids and was not significantly regulated. Overall, significant biomarker changes occurred in the first 14 days before a clinically robust healing response in the venous leg ulcer cohort.

Selection of Appropriate Wound Dressing for Various Wounds

There are many factors involved in wound healing, and the healing process is not static. The therapeutic effect of modern wound dressings in the clinical management of wounds is documented. However, there are few reports regarding the reasonable selection of dressings for certain types of wounds in the clinic. In this article, we retrospect the history of wound dressing development and the classification of modern wound dressings. In addition, the pros and cons of mainstream modern wound dressings for the healing of different wounds, such as diabetic foot ulcers, pressure ulcers, burns and scalds, and chronic leg ulcers, as well as the physiological mechanisms involved in wound healing are summarized. This article provides a clinical guideline for selecting suitable wound dressings according to the types of wounds.

Skin tissue regeneration for burn injury

The skin is the largest organ of the body, which meets the environment most directly. Thus, the skin is vulnerable to various damages, particularly burn injury. Skin wound healing is a serious interaction between cell types, cytokines, mediators, the neurovascular system, and matrix remodeling. Tissue regeneration technology remarkably enhances skin repair via re-epidermalization, epidermal-stromal cell interactions, angiogenesis, and inhabitation of hypertrophic scars and keloids. The success rates of skin healing for burn injuries have significantly increased with the use of various skin substitutes. In this review, we discuss skin replacement with cells, growth factors, scaffolds, or cell-seeded scaffolds for skin tissue reconstruction and also compare the high efficacy and cost-effectiveness of each therapy. We describe the essentials, achievements, and challenges of cell-based therapy in reducing scar formation and improving burn injury treatment.

Dressings and topical agents for treating venous leg ulcers

BACKGROUND

Venous leg ulcers are open skin wounds on the lower leg which can be slow to heal, and are both painful and costly. The point prevalence of open venous leg ulcers in the UK is about 3 cases per 10,000 people, and many people experience recurrent episodes of prolonged ulceration. First-line treatment for venous leg ulcers is compression therapy, but a wide range of dressings and topical treatments are also used. This diversity of treatments makes evidence-based decision-making challenging, and a clear and current overview of all the evidence is required. This review is a network meta-analysis (NMA) which assesses the probability of complete ulcer healing associated with alternative dressings and topical agents.

OBJECTIVES

To assess the effects of (1) dressings and (2) topical agents for healing venous leg ulcers in any care setting and to rank treatments in order of effectiveness, with assessment of uncertainty and evidence quality.

SEARCH METHODS

In March 2017 we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also scanned reference lists of relevant included studies as well as reviews, meta-analyses, guidelines and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting. We updated this search in March 2018; as a result several studies are awaiting classification.

SELECTION CRITERIA

We included published or unpublished randomised controlled trials (RCTs) that enrolled adults with venous leg ulcers and compared the effects of at least one of the following interventions with any other intervention in the treatment of venous leg ulcers: any dressing, or any topical agent applied directly to an open venous leg ulcer and left in situ. We excluded from this review dressings attached to external devices such as negative pressure wound therapies, skin grafts, growth factors and other biological agents, larval therapy and treatments such as laser, heat or ultrasound. Studies were required to report complete wound healing to be eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction. We conducted this NMA using frequentist meta-regression methods for the efficacy outcome; the probability of complete healing. We assumed that treatment effects were similar within dressings classes (e.g. hydrocolloid, foam). We present estimates of effect with their 95% confidence intervals (CIs) for individual treatments focusing on comparisons with widely used dressing classes, and we report ranking probabilities for each intervention (probability of being the best, second best, etc treatment). We assessed the certainty (quality) of the body of evidence using GRADE for each network comparison and for the network as whole.

MAIN RESULTS

We included 78 RCTs (7014 participants) in this review. Of these, 59 studies (5156 participants, 25 different interventions) were included in the NMA; resulting in 40 direct contrasts which informed 300 mixed-treatment contrasts.The evidence for the network as a whole was of low certainty. This judgement was based on the sparsity of the network leading to imprecision and the general high risk of bias in the included studies. Sensitivity analyses also demonstrated instability in key aspects of the network and results are reported for the extended sensitivity analysis. Evidence for individual contrasts was mainly judged to be low or very low certainty.The uncertainty was perpetuated when the results were considered by ranking the treatments in terms of the probability that they were the most effective for ulcer healing, with many treatments having similar, low, probabilities of being the best treatment. The two most highly-ranked treatments both had more than 50% probability of being the best (sucralfate and silver dressings). However, the data for sucralfate was from one small study, which means that this finding should be interpreted with caution. When exploring the data for silver and sucralfate compared with widely-used dressing classes, there was some evidence that silver dressings may increase the probability of venous leg ulcer healing, compared with nonadherent dressings: RR 2.43, 95% CI 1.58 to 3.74 (moderate-certainty evidence in the context of a low-certainty network). For all other combinations of these five interventions it was unclear whether the intervention increased the probability of healing; in each case this was low- or very low-certainty evidence as a consequence of one or more of imprecision, risk of bias and inconsistency.

AUTHORS' CONCLUSIONS

More research is needed to determine whether particular dressings or topical agents improve the probability of healing of venous leg ulcers. However, the NMA is uninformative regarding which interventions might best be included in a large trial, largely because of the low certainty of the whole network and of individual comparisons.The results of this NMA focus exclusively on complete healing; whilst this is of key importance to people living with venous leg ulcers, clinicians may wish to take into account other patient-important outcomes and factors such as patient preference and cost.

Advances in Skin Regeneration Using Tissue Engineering

Tissue engineered skin substitutes for wound healing have evolved tremendously over the last couple of years. New advances have been made toward developing skin substitutes made up of artificial and natural materials. Engineered skin substitutes are developed from acellular materials or can be synthesized from autologous, allograft, xenogenic, or synthetic sources. Each of these engineered skin substitutes has their advantages and disadvantages. However, to this date, a complete functional skin substitute is not available, and research is continuing to develop a competent full thickness skin substitute product that can vascularize rapidly. There is also a need to redesign the currently available substitutes to make them user friendly, commercially affordable, and viable with longer shelf life. The present review focuses on providing an overview of advances in the field of tissue engineered skin substitute development, the availability of various types, and their application.

Keratinocyte regulation of TGF-beta and connective tissue growth factor expression: a role in suppression of scar tissue formation

Allogeneic keratinocytes applied to large full-thickness wounds promote healing while suppressing scar tissue formation. This effect may be mediated in part by their effect on the levels of transforming growth factor-betas (TGF-betas) and connective tissue growth factor (CTGF) in the wound and subsequent modulation of fibroblast activity. We have examined the levels of TGF-beta and CTGF produced by keratinocytes and fibroblasts, and the effect of keratinocyte-conditioned medium using monolayer and living skin-equivalent cultures. Keratinocyte monolayers did not release any detectable TGF-beta1, but released moderate levels of TGF-beta2 into culture medium, and stained strongly for TGF-beta1, but only weakly for TGF-beta2. Fibroblasts released large amounts of TGF-beta1, no TGF-beta2, and stained strongly for TGF-beta1. Neither cell type released TGF-beta3, but both stained strongly for TGF-beta3. Keratinocyte-conditioned medium suppressed the levels of TGF-betas and CTGF associated with the fibroblasts compared with fibroblasts incubated in Dulbecco's minimal essential medium and fibroblast-conditioned medium. In living skin equivalents, keratinocytes stained very strongly for TGF-beta1 and CTGF, moderately strongly for TGF-beta3, and only weakly for TGF-beta2. Fibroblasts stained strongly for TGF-beta1 and 3 and CTGF. These observations suggest that keratinocytes may affect the TGF-beta profile in such a way as to suppress the formation of scar tissue.

Randomized, controlled, single-blind study on use of autologous keratinocytes on a transfer dressing to treat nonhealing diabetic ulcers

AIM

To compare the rate of healing of diabetic neuropathic ulcers using cultured autologous keratinocytes delivered on chemically defined transfer discs (Myskin) (active treatment) versus healing obtained with cell-free discs (placebo).

MATERIALS AND METHODS

After a 4-week lead-in period patients (randomly assigned) received active or placebo treatments weekly for 6 weeks. All patients then received active treatments for a maximum of 12 treatments where required. Altogether, 16 patients with a total of 21 ulcers resistant to conventional therapy were recruited from four specialist diabetic centers in three cities.

RESULTS

All 21 ulcers were treated and of these ten healed and eight improved, with two failing to respond (one ulcer was lost due to autoamputation). For analysis according to the study criteria, however, only the 12 patients with 12 index ulcers who completed treatment protocols were eligible - five in the placebo group and seven in the active group. Of these, five ulcers healed completely and seven were reduced by more than 50%. Complete healing took a median of ten active applications.

CONCLUSIONS

Repeated regular applications of the patient's keratinocytes, delivered on the carrier dressing, initiated wound healing in ulcers resistant to conventional therapy, with 18 out of 21 ulcers responding. The healing observed did not appear attributable to patient recruitment or the cell-free carrier dressing but to the delivery of the cultured cells.

Treatment of recalcitrant venous leg ulcers with autologous keratinocytes in fibrin sealant: a multinational randomized controlled clinical trial

In a multicenter trial, the effect of a commercially available combination of autologous keratinocytes (3-6 x 10(6)/mL) with fibrin sealant (Tissucol Duo S Immuno, Baxter Hyland Immuno) on the healing of recalcitrant venous leg ulcers (duration >3 months) was compared with standard care. The primary endpoint was time to healing, and the secondary endpoint was number of healed ulcers in both groups. Both groups received compression therapy with short-stretch bandages. Forty-four (38.3%) of the 116 patients who had BioSeed-S treatment achieved complete healing of the target ulcer compared with 24 (22.4%) of 109 patients who received standard treatment. The advantage for treatment with BioSeed-S over standard treatment was statistically significant (chi-square test: p=0.0106). Time to complete healing of ulcers: the log-rank test for equality over strata revealed a superiority of treatment with BioSeed-S+compression (median: 176 days) over compression+standard care (median >201 days) (p<0.0001). This study, to date the largest multicenter study with autologous keratinocytes, provides evidence for its efficacy in the treatment of patients with therapy-resistant chronic venous leg ulcers.

A systematic review of randomized controlled trials of wound dressings for chronic venous ulcer

OBJECTIVE

To determine whether more "modern" complex wound dressings further improve the healing of venous ulcers over that with simple wound dressings, we conducted a systematic review of randomized controlled trials (RCTs) of wound dressing trials that were published from October 1, 1997, through September 1, 2005.

METHODS

We searched MEDLINE, CINAHL, and the Cochrane Controlled Trials Registry Database to identify RCTs. Criteria for ultimate selection included treatment with compression and an objective outcome describing the proportion of wounds healed. Twenty RCTs were identified that satisfied these criteria and were classified into three wound dressing classes: semiocclusive/occlusive group (n = 8), growth factor group (n = 7), and human skin equivalent group (n = 5).

RESULTS

Assessment of study design quality for the 20 RCTs showed a low percentage (<49%) of RCTs that incorporated at least 3 of 7 indicators of trial quality, but it seemed better in the 5 RCTs that showed significance for ulcer healing; 4 of the studies used at least 6 of the 7 characteristics of adequate study design. Five (25%) of the 20 RCTs had a statistically significantly improved proportion of ulcers healed in the experimental dressing group over control values: zinc oxide paste bandage (79% vs 56%) and Tegasorb (59% vs 15%) in the semiocclusive/occlusive group and perilesional injection of granulocyte-macrophage colony-stimulating factor (57% vs 19%) and porcine collagen derived from small-intestine submucosa (Oasis; 55% vs 34%) in the growth factor group. In the sole significant RCT from the human skin equivalent group, Apligraf (63%) was superior to Tegapore (48%). Four of these five studies also showed an improved time to complete healing by Kaplan-Meier estimate.

CONCLUSIONS

Certain wound dressings can improve both the proportion of ulcers healed and the time to healing over that achieved with adequate compression and a simple wound dressing. The selection of a specific dressing, however, will depend on the dressing characteristics for ease of application, patient comfort, wound drainage absorption, and expense.