Summary

Background Several surgical techniques are available for the treatment of stable leucoderma. The use of noncultured epidermal cellular grafting was introduced in 1992. Data on long-term follow-up regarding stability of the repigmented area, time to achieve the final repigmentation, colour matching, reaction to sun exposure and patient satisfaction with treatment have been reported only a few times previously.



Objectives  To evaluate the long-term results of the noncultured epidermal cellular grafting technique in patients with different types of leucoderma, including segmental vitiligo (n = 33), generalized vitiligo (n = 33), mixed vitiligo (n = 6), halo naevi (n = 11), piebaldism (n = 3) and naevus depigmentosus (n = 1).



Methods  Patients were evaluated by examination and questionnaire in a retrospective setting after transplantation by autologous noncultured cellular grafting. Percentage of repigmentation was evaluated in 82 patients using a digital imaging analysis system (mean follow-up 15 months). Long-term results were evaluated by 54 patients using a questionnaire up to 7·7 years after treatment (mean 4 years).



Results  More than 75% repigmentation was achieved in 71% of patients. Best results were obtained in segmental vitiligo, halo naevi and piebaldism, whereas results in generalized or mixed vitiligo were inferior. According to the patients, final repigmentation was achieved after a mean of 10 months post-treatment. In 80% some colour mismatch (hyperpigmentation and hypopigmentation) was reported between the treated area and the surrounding skin, although this was not disturbing for the majority. This colour mismatch was reported significantly less after sun exposure (P = 0·012). During follow-up 7% of patients, all with generalized vitiligo, observed some loss of the achieved repigmentation.



Conclusions  Autologous epidermal cellular grafting achieved a high percentage of repigmentation, which was maintained during follow-up in the majority of patients. Although it improved quality of life, a perfect colour match was seldom obtained.

Long-term results of noncultured epidermal cellular grafting in vitiligo, halo naevi, piebaldism and naevus depigmentosus

Wound healing is an important function of skin; however, after significant skin injury (burns) or in certain dermatological pathologies (chronic wounds), this important process can be deregulated or lost, resulting in severe complications. To avoid these, studies have focused on developing tissue-engineered skin substitutes (TESSs), which attempt to replace and regenerate the damaged skin. Autologous cultured epithelial substitutes (CESs) constituted of keratinocytes, allogeneic cultured dermal substitutes (CDSs) composed of biomaterials and fibroblasts and autologous composite skin substitutes (CSSs) comprised of biomaterials, keratinocytes and fibroblasts, have been the most studied clinical TESSs, reporting positive results for different pathological conditions. However, researchers' purpose is to develop TESSs that resemble in a better way the human skin and its wound healing process. For this reason, they have also evaluated at preclinical level the incorporation of other human cell types such as melanocytes, Merkel and Langerhans cells, skin stem cells (SSCs), induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs). Among these, MSCs have been also reported in clinical studies with hopeful results. Future perspectives in the field of human-TESSs are focused on improving in vivo animal models, incorporating immune cells, designing specific niches inside the biomaterials to increase stem cell potential and developing three-dimensional bioprinting strategies, with the final purpose of increasing patient's health care. In this review we summarize the use of different human cell populations for preclinical and clinical TESSs under research, remarking their strengths and limitations and discuss the future perspectives, which could be useful for wound healing purposes.

/pdf/cellular-human-tissue-engineered-skin-substitutes-r1x878s850.pdf

Cellular human tissue-engineered skin substitutes investigated for deep and difficult to heal injuries.

Porous, resorbable biomaterials can serve as temporary scaffolds that support cell infiltration, tissue formation, and remodeling of nonhealing skin wounds. Synthetic biomaterials are less expensive to manufacture than biologic dressings and can achieve a broader range of physiochemical properties, but opportunities remain to tailor these materials for ideal host immune and regenerative responses. Polyesters are a well-established class of synthetic biomaterials; however, acidic degradation products released by their hydrolysis can cause poorly controlled autocatalytic degradation. Here, we systemically explored reactive oxygen species (ROS)–degradable polythioketal (PTK) urethane (UR) foams with varied hydrophilicity for skin wound healing. The most hydrophilic PTK-UR variant, with seven ethylene glycol (EG7) repeats flanking each side of a thioketal bond, exhibited the highest ROS reactivity and promoted optimal tissue infiltration, extracellular matrix (ECM) deposition, and reepithelialization in porcine skin wounds. EG7 induced lower foreign body response, greater recruitment of regenerative immune cell populations, and resolution of type 1 inflammation compared to more hydrophobic PTK-UR scaffolds. Porcine wounds treated with EG7 PTK-UR foams had greater ECM production, vascularization, and resolution of proinflammatory immune cells compared to polyester UR foam–based NovoSorb Biodegradable Temporizing Matrix (BTM)–treated wounds and greater early vascular perfusion and similar wound resurfacing relative to clinical gold standard Integra Bilayer Wound Matrix (BWM). In a porcine ischemic flap excisional wound model, EG7 PTK-UR treatment led to higher wound healing scores driven by lower inflammation and higher reepithelialization compared to NovoSorb BTM. PTK-UR foams warrant further investigation as synthetic biomaterials for wound healing applications. Description Hydrophilic polythioketal urethane foam scaffolds promote skin wound healing in pigs. Designing degradable dressings Synthetic scaffolds are an attractive option for dressings to treat skin wounds because they are shelf stable, have tunable and defined chemical compositions, and are more affordable than naturally derived scaffolds or cell-based dermal substitutes. Here, Patil and colleagues investigated the role of scaffold hydrophilicity in polythioketal-based polyurethane (PTK-UR) foam scaffold resorption and promotion of tissue regeneration in wound healing. They found that hydrophilic scaffolds with seven ethylene glycol units between the thioketal bonds in the polymer backbone exhibited optimal reactive oxygen species–dependent degradation and porcine skin wound healing, including ischemic flap excisional wounds. Results support further investigation of PTK-UR formulations as alternatives to commercially available wound matrices.

Reactive oxygen species–degradable polythioketal urethane foam dressings to promote porcine skin wound repair

http://www.westlaboratory.org/wp-content/uploads/2011/05/Gerlach-2011-Autologous-skin-cell-spray-transplantation-for-a-deep-dermal-burn-patient....pdf

Autologous skin cell spray-transplantation for a deep dermal burn patient in an ambulant treatment room setting.

The skin graft was born in 1869 and since then, surgeons have been using split skin grafts for wound repair. Nevertheless, this asset fails the big burn patient, who deserves an elastic, mobile and robust outcome but who receives the poorest possible outcome based on donor site paucity. Negating the need for the skin graft requires an autologous composite cultured skin and a material capable of temporising the burn wound for four weeks until the composite is produced. A novel, biodegradable polyurethane chemistry has been used to create two such products. This paper describes the design, production, optimisation and evaluation of several iterations of these products. The evaluation has occurred in a variety of models, both in vitro and in vivo, employing Hunterian scientific principles, and embracing Hunter's love and appreciation of comparative anatomy. The process has culminated in significant human experience in complex wounds and extensive burn injury. Used serially, the products offer robust and elastic healing in deep burns of any size within 6 weeks of injury.

https://publishing.rcseng.ac.uk/doi/pdf/10.1308/rcsann.2017.0110

The evolution of acute burn care – retiring the split skin graft

The aims were to (1) describe the in vivo studies leading to an optimized model of the biodegradable temporizing matrix (BTM), (2) describe our efforts in effecting closure over this optimized matrix after integration with a cultured composite skin (CCS), and (3) reexamine the ability of the CCS to definitively close fresh wounds (without BTM). Foam scaffolds of biodegradable polyurethane were created to allow in vivo tissue ingrowth or in vitro co-culture. Using the porcine surgical model, multiple BTM optimization studies took place before the BTM-CCS main study was conducted. For the CCS study, optimized sealed 2 mm matrices were implanted into 6-mm deep, 8 × 8 cm wounds (three per pig) and allowed to integrate for 21 days, whereas collected blood and harvested skin tissue were used to prepare autologous composite skins in similar (unsealed) 1 mm matrices. These were then applied at day 21 either over the integrated BTMs or into a freshly created fourth wound. All of the optimized matrices integrated fully, without loss, and were found to resist wound contraction effectively until the composites were ready for application at day 21. The composites demonstrated the ability to generate a bilayer repair with robust epidermis anchored by a basement membrane visible from day 7 after application. The final optimized sealed BTM delaminates easily to produce a clean, temporized wound bed and will be used in the upcoming burn clinical trial. Although the CCS is a magnitude away from human trials, it is still capable of generating a bilayer repair in both BTM-integrated and fresh wounds (onto fat), and with further refinement and optimization of foam structure, seeding densities, and timing, consistent success should be possible.

Optimization of a polyurethane dermal matrix and experience with a polymer-based cultured composite skin.

Randomized controlled trials in the literature investigating the efficacy of noncultured keratinocyte/melanocyte suspensions are scarce; however, the advocates of such techniques press the value of their application based largely on case studies and anecdote. Caucasian patients with burn hypopigmentation seldom request cosmetic revision making worthwhile clinical trials difficult so that informal case treatments with new therapies generate anecdotal results. A randomized, placebo-controlled trial was carried out to evaluate whether cosuspensions of noncultured skin cells are capable of (1) decreasing the time to reepithelialization and (2) reestablishing pigmentation in vitiligo leukoderma following epidermal/superficial dermal ablation (in the knowledge that a positive result would make the technique likely to be successful in burn hypopigmentation). Vitiligo is common and is socially more debilitating such that suitable trial subjects for new therapies from this pool are more forthcoming. This study demonstrated that suspensions of noncultured keratinocytes and melanocytes do not decrease the time to epithelialization of superficial partial thickness wounds compared with controls. It also suggested that the achievement, quality, and duration of any pigmentation were unpredictable and largely disappointing. Some pigmentation was recorded in placebo-treated areas indicating an effect of the method of epidermal ablation in these patients. These findings have mandated a complete review of the use of these techniques in burn care at the Royal Adelaide Hospital; they have been omitted from surgical protocols where the aim of use was to speed reepithelialization. Their infrequent use in burns hypopigmentation will continue contingent on the successful repigmentation of a test patch.

Noncultured Keratinocyte/Melanocyte Cosuspension: Effect on Reepithelialization and Repigmentation—A Randomized, Placebo-Controlled Study

This study aimed to investigate the ability of an autologous cultured composite skin (CCS) to close similar biodegradable temporizing matrix (BTM)-integrated wounds, and its effectiveness in healing fresh full-thickness wounds after the failure of cultured epithelial autograft in its two forms (sheets and suspensions) to epithelialize over an integrated polymer BTM. Using a porcine model, autologous split-skin grafts were harvested three of four dorsal 8 × 8 cm treatment sites. These three sites were subsequently converted to full-thickness wounds and BTMs were implanted. The grafts were used to produce autologous CCSs for each pig. These consisted of a 1 mm thick biodegradable polymer foam scaffold into which fibroblasts and keratinocytes harvested from the grafts were cocultured. At Day 28, on each animal, the autologous CCSs were applied to two of the integrated BTMs, an autologous split-skin graft was applied to the third integrated BTM, and one CCS was applied immediately into a fresh, "naked" (no BTM applied) wound. The CCSs were capable of generating a bilayer repair over the naked wound's fat base and BTM-integrated wounds, which consisted of dermal elements and a keratinized stratified squamous epidermis anchored with a basement membrane by day 7. The CCSs behaved in different ways: either as a delivery vehicle allowing similar development of a bilayer repair while the polymer foam was shed from the wound, or generating a bilayer repair with the foam scaffold being retained (composite "take"). These results conclude our porcine program and provide proof of concept that the integrated BTM can be closed with an autologous CCS. Once fully optimized, this may provide robust repair without resorting to the split-skin graft, important in those cases where unburned donor site is unavailable.

"Take" of a polymer-based autologous cultured composite "skin" on an integrated temporizing dermal matrix: proof of concept.

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Optimization of a polyurethane dermal matrix and experience with a polymer-based cultured composite skin.

Noncultured Keratinocyte/Melanocyte Cosuspension: Effect on Reepithelialization and Repigmentation—A Randomized, Placebo-Controlled Study

"Take" of a polymer-based autologous cultured composite "skin" on an integrated temporizing dermal matrix: proof of concept.