Challenging the Conventional Therapy: Emerging Skin Graft Techniques for Wound Healing

Benefits of Aerosolized, Point-of-care, Autologous Skin Cell Suspension (ASCS) for the Closure of Full-thickness Wounds From Thermal and Nonthermal Causes: Learning Curves From the First 50 Consecutive Cases at an Urban, Level 1 Trauma Center

OBJECTIVE

To determine the utility of Autologous Skin Cell Suspension (ASCS) in closing full-thickness (FT) defects from injury and infection.

BACKGROUND

Although ASCS has documented success in closing partial-thickness burns, far less is known about the efficacy of ASCS in FT defects.

METHODS

Fifty consecutive patients with FT defects (burn 17, necrotizing infection 13, crush 7, degloving 5, and other 8) underwent closure with the bilayer technique of 3:1 widely meshed, thin, split-thickness skin graft and 80:1 expanded ASCS. End points were limb salvage rate, donor site reduction, operative and hospital throughput, incidence of complications, and re-epithelialization by 4, 8, and 12 weeks.

RESULTS

Definitive wound closure was achieved in 76%, 94%, and 98% of patients, at 4, 8, and 12 weeks, respectively. Limb salvage occurred in 42/43 patients (10 upper and 33 lower extremities). The mean area grafted was 435 cm 2 ; donor site size was 212 cm 2 , representing a potential reduction of 50%. The mean surgical time was 71 minutes; the total operating room time was 124 minutes. The mean length of stay was 26.4 days; the time from grafting to discharge was 11.2 days. Four out of 50 patients (8%) required 6 reoperations for bleeding (1), breakdown (4), and amputation (1). Four out of 50 patients (8%) developed hypertrophic scarring, which responded to silicone sheeting (2) and laser resurfacing (2). The mean follow-up was 92.7 days.

CONCLUSIONS

When used for the closure of FT wounds, point-of-care ASCS is effective and safe. Benefits include rapid re-epithelialization, high rate of limb salvage, reduction of donor site size and morbidity, and low incidence of hypertrophic scarring.

Wound healing induced by new synthetic peptide, A7-1, in C57BL/6 mouse model

The effects of the novel synthetic peptide, A7-1, on wound healing and skin grafts were evaluated in a C57BL/6 mouse model. Two 15-mm wide circular skin excisions were made on the backs of mice and to each excision, 100 µM A7-1 or normal saline was applied daily. The treatments were applied and sutured for skin graft analysis. Digital photos were acquired on days 4, 7, 11, and 14 and fluorescein angiography was conducted. Wound sizes were verified using stereoscopic microscopy. Histological analysis was performed via hematoxylin and eosin staining and Masson's trichrome staining. Western blotting was performed using vascular endothelial growth factor. Using a stereoscopic microscope, significantly faster wound healing (17.3%) and skin graft healing (16.5%) were observed in the A7-1 treatment group in comparison to that of the control. The angiogenesis was significantly faster in fluorescein angiography examination in wound healing (11%) and skin grafts (15%). However, the average completion of epithelization (overall time for wound healing), did not show any significant differences. In comparison to the control, the new protein, A7-1, led to significantly faster wound healing in the initial angiogenesis.

Advances in skin gene therapy: utilizing innovative dressing scaffolds for wound healing, a comprehensive review

The skin, serving as the body's outermost layer, boasts a vast area and intricate structure, functioning as the primary barrier against external threats. Disruptions in the composition and functionality of the skin can lead to a diverse array of skin conditions, such as wounds, burns, and diabetic ulcers, along with inflammatory disorders, infections, and various types of skin cancer. These disorders not only exacerbate concerns regarding skin health and beauty but also have a significant impact on mental well-being. Due to the complexity of these disorders, conventional treatments often prove insufficient, necessitating the exploration of new therapeutic approaches. Researchers develop new therapies by deciphering these intricacies and gaining a thorough understanding of the protein networks and molecular processes in skin. A new window of opportunity has opened up for improving wound healing processes because of recent advancements in skin gene therapy. To enhance skin regeneration and healing, this extensive review investigates the use of novel dressing scaffolds in conjunction with gene therapy approaches. Scaffolds that do double duty as wound protectors and vectors for therapeutic gene delivery are being developed using innovative biomaterials. To improve cellular responses and speed healing, these state-of-the-art scaffolds allow for the targeted delivery and sustained release of genetic material. The most recent developments in gene therapy techniques include RNA interference, CRISPR-based gene editing, and the utilization of viral and non-viral vectors in conjunction with scaffolds, which were reviewed here to overcome skin disorders and wound complications. In the future, there will be rare chances to develop custom methods for skin health care thanks to the combination of modern technology and collaboration among disciplines.

The efficacy and safety of autologous epidermal cell suspensions for re-epithelialization of skin lesions: A systematic review and meta-analysis of randomized trials

BACKGROUND

Successful usage of autologous skin cell suspension (ASCS) has been demonstrated in some clinical trials. However, its efficacy and safety have not been verified. This latest systematic review and meta-analysis aim to examine the effects of autologous epidermal cell suspensions in re-epithelialization of skin lesions.

METHODS

Relevant articles were retrieved from PubMed, Embase, Cochrane Database, Web of Science, International Clinical Trials Registry Platform, China National Knowledge Infrastructureris, VIP Database for Chinese Technical Periodicals and Wanfang database. The primary output measure was the healing time, and the secondary outputs were effective rate, size of donor site for treatment, size of study treatment area, operation time, pain scores, repigmentation, complications, scar scale scores and satisfaction scores. Data were pooled and expressed as relative risk (RR), mean difference (MD) and standardized mean difference (SMD) with a 95% confidence interval (CI).

RESULTS

Thirty-one studies were included in this systematic review and meta-analysis, with 914 patients who received autologous epidermal cell suspensions (treatment group) and 883 patients who received standard care or placebo (control group). The pooled data from all included studies demonstrated that the treatment group has significantly reduced healing time (SMD = -0.86; 95% CI: -1.59-0.14; p = 0.02, I2 = 95%), size of donar site for treatment (MD = -115.41; 95% CI: -128.74-102.09; p<0.001, I2 = 89%), operation time (MD = 25.35; 95% CI: 23.42-27.29; p<0.001, I2 = 100%), pain scores (SMD = -1.88; 95% CI: -2.86-0.90; p = 0.0002, I2 = 89%) and complications (RR = 0.59; 95% CI: 0.36-0.96; p = 0.03, I2 = 66%), as well as significantly increased effective rate (RR = 1.20; 95% CI: 1.01-1.42; p = 0.04, I2 = 77%). There were no significant differences in the size of study treatment area, repigmentation, scar scale scores and satisfaction scores between the two groups.

CONCLUSION

Our meta-analysis showed that autologous epidermal cell suspensions is beneficial for re-epithelialization of skin lesions as they significantly reduce the healing time, size of donar site for treatment, operation time, pain scores and complications, as well as increased effective rate. However, this intervention has minimal impact on size of treatment area, repigmentation, scar scale scores and satisfaction scores.

Limited debridement combined with ReCell® Techniques for deep second-degree burns

BACKGROUND

The purpose of this article is to introduce a method that combines limited debridement and ReCell® autologous cell regeneration techniques for the treatment of deep second-degree burn wounds.

METHOD

A total of 20 patients suffered with deep second-degree burns less than 10% of total body surface area (TBSA) who were admitted to our department, from June 2019 to June 2021, participated in this study. These patients first underwent limited debridement with an electric/pneumatic dermatome, followed by the ReCell® technique for secondary wounds. Routine treatment was applied to prevent scarring after the wound healed. Clinical outcomes were scored using the Vancouver Scar Scale (VSS).

RESULTS

All wounds of the patients healed completely. One patient developed an infection in the skin graft area and finally recovered by routine dressing changes. The average healing time was 12 days (range: 10-15 days). The new skin in the treated area was soft and matched the colour of the surrounding normal skin and the VSS score ranged from 3~5 for each patient. Of the 20 patients, 19 were very satisfied and 1 was satisfied.

CONCLUSIONS

This article reports a useful treatment method that combines electric dermatome-dependent limited debridement and the ReCell® technique for the treatment of deep second-degree burn wounds. It is a feasible and effective strategy that is easy to implement and minimally invasive, and it is associated with a short healing time, mild scar formation and little damage to the donor skin area.

Split-Thickness Skin and Dermal Pixel Grafts Can Be Expanded up to 500 Times to Re-Epithelialize a Full-Thickness Burn Wound

Objective: Autologous skin transplantation is limited by donor site availability for patients with extensive burns. The objective of this study was to demonstrate the feasibility and efficacy of split-thickness skin (STS) and dermal pixel grafts (PG) in the treatment of burns. Approach: The study was divided into three arms of validation, expansion, and combination that all followed the same study design. Sixteen deep partial-thickness burns were created on the dorsum of anesthetized pigs. Three days postinjury the burns were debrided and grafted with STS and dermal PGs. The PGs were prepared by harvesting two skin grafts (split-thickness skin graft [STSG] and dermal graft) from the same donor site going down in depth. The grafts were minced to 0.3 × 0.3 × 0.3 mm PGs and suspended in a small volume of hydrogel. Healing was monitored for 6, 10, 14, or 28 days. In the validation study the PGs at 1:2 expansion ratio were transplanted and compared with STSG and untreated controls. The expansion study investigated the maximum expansion potential of the PGs and the combination of the benefits of transplanting STS and dermal PGs together. Results: The validation study showed that when STS and dermal PGs were transplanted in a 1:2 ratio they fully re-epithelialized the wounds in 14 days. The expansion study demonstrated that using expansion ratios up to 1:500 the wounds were re-epithelialized by day 28. The combination study showed that there was no additional benefit to use STS and dermal PGs together. Innovation: Pixel grafting provides expansion ratios greater than conventional STSG. The possibility to harvest both STS and dermal PGs from the same donor area further reduces the need for healthy skin. Conclusion: STSG and dermal grafts can be minced to PGs with preserved viability and expanded up to 500 times to re-epithelialize a wound.

Challenges in the Management of Large Burns

Large burns provoke profound pathophysiological changes. Survival rates of patients with large burns have improved significantly with the advancement of critical care and adaptation of early excision protocols. Nevertheless, care of large burn wounds remains challenging secondary to limited donor sites, prolonged time to wound closure, and immunosuppression. The development of skin substitutes and new grafting techniques decreased time to wound closure. Individually, these methods have limited success, but a combination of them may yield more successful outcomes. Early identification of patients with likely poor prognosis should prompt goals of care discussion and involvement of a palliative care team when possible.

Autologous Skin Cell Suspension for Full-Thickness Skin Defect Reconstruction: Current Evidence and Health Economic Expectations

Despite differing etiologies, acute thermal burn injuries and full-thickness (FT) skin defects are associated with similar therapeutic challenges. When not amenable to primary or secondary closure, the conventional standard of care (SoC) treatment for these wound types is split-thickness skin grafting (STSG). This invasive procedure requires adequate availability of donor skin and is associated with donor site morbidity, high healthcare resource use (HCRU), and costs related to prolonged hospitalization. As such, treatment options that can facilitate effective healing and donor skin sparing have been highly anticipated. The RECELL® Autologous Cell Harvesting Device facilitates preparation of an autologous skin cell suspension (ASCS) for the treatment of acute thermal burns and FT skin defects. In initial clinical trials, the approach showed superior donor skin-sparing benefits and comparable wound healing to SoC STSG among patients with acute thermal burn injuries. These findings led to approval of RECELL for this indication by the US Food and Drug Administration (FDA) in 2018. Subsequent clinical evaluation in non-thermal FT skin wounds showed that RECELL, when used in combination with widely meshed STSG, provides donor skin-sparing advantages and comparable healing outcomes compared with SoC STSG. As a result, the device received FDA approval in June of 2023 for treatment of FT skin defects caused by traumatic avulsion or surgical excision or resection. Given that health economic advantages have been demonstrated for RECELL ± STSG versus STSG alone when used for burn therapy, it is prudent to examine similarities in the burn and FT skin defect treatment pathways to forecast the potential health economic advantages for RECELL when used in FT skin defects. This article discusses the parallels between the two indications, the clinical outcomes reported for RECELL, and the HCRU and cost benefits that may be anticipated with use of the device for non-thermal FT skin defects.

Multicellular bioprinted skin facilitates human-like skin architecture in vivo

Bioprinting is a promising alternative method to generate skin substitutes because it can replicate the structural organization of the skin into biomimetic layers in vitro. In this study, six primary human skin cell types were used to bioprint a trilayer skin construct consisting of epidermis, dermis, and hypodermis. Transplantation of the bioprinted skin with human cells onto full-thickness wounds of nu/nu mice promoted rapid vascularization and formation of epidermal rete ridges analogous to the native human epidermis, with a normal-looking extracellular matrix. Cell-specific staining confirmed the integration of the implanted cells into the regenerated skin. Using a similar approach, a 5 centimeter-by-5 centimeter bioprinted autologous porcine skin graft was transplanted onto full-thickness wounds in a porcine excisional wound model. The bioprinted skin graft improved epithelialization, reduced skin contraction, and supported normal collagen organization with reduced fibrosis. Differential gene expression demonstrated pro-remodeling protease activity in wounds transplanted with bioprinted autologous skin grafts. These results demonstrate that bioprinted skin can support skin regeneration to allow for nonfibrotic wound healing and suggest that the skin bioprinting technology may be applicable for human clinical use.

Comparison of Biatain Ag and Biatain Alginate Ag dressings on skin graft donor sites: a prospective clinical trial

OBJECTIVE

The aim of this study was to compare Biatain Ag and Biatain Alginate Ag (both Coloplast, Denmark) as skin graft donor site dressings.

METHOD

A single-centre, prospective, randomised clinical study was conducted. In patients who had undergone a skin graft operation, adjacent split-thickness skin graft donor sites were dressed with Biatain Ag and Biatain Alginate Ag, respectively. The primary outcomes were time to re-epithelialisation and pain score after the operation. The secondary outcomes were scar scores of the donor site after the operation, haematoma rates, infection rates, and exudation rates before wound healing. Results were compared using the Wilcoxon test and the Chi-squared test.

RESULTS

A total of 16 paired wounds in 16 patients were studied. The donor sites dressed with Biatain Ag needed more time for >90% re-epithelialisation than those dressed with Biatain Alginate Ag. On day 3 postoperatively, the pain scores with Biatain Ag were significantly less severe than those with Biatain Alginate Ag. On days 6, 9 and 12, the pain scores of both dressings did not differ significantly. The scar scores of the donor site dressed with Biatain Ag were significantly worse than those dressed with Biatain Alginate Ag at 6 months. With respect to infection rates, no significant differences were detected between these two groups. However, the exudation rates of the donor site dressed with Biatain Ag were significantly lower than those dressed with Biatain Alginate Ag.

CONCLUSION

As skin graft donor site dressings, both Biatain Ag and Biatain Alginate Ag have advantages.

3D bioprinting-a model for skin aging

Human lifespan continues to extend as an unprecedented number of people reach their seventh and eighth decades of life, unveiling chronic conditions that affect the older adult. Age-related skin conditions include senile purpura, seborrheic keratoses, pemphigus vulgaris, bullous pemphigoid, diabetic foot wounds and skin cancer. Current methods of drug testing prior to clinical trials require the use of pre-clinical animal models, which are often unable to adequately replicate human skin response. Therefore, a reliable model for aged human skin is needed. The current challenges in developing an aged human skin model include the intrinsic variability in skin architecture from person to person. An ideal skin model would incorporate innate functionality such as sensation, vascularization and regeneration. The advent of 3D bioprinting allows us to create human skin equivalent for use as clinical-grade surgical graft, for drug testing and other needs. In this review, we describe the process of human skin aging and outline the steps to create an aged skin model with 3D bioprinting using skin cells (i.e. keratinocytes, fibroblasts and melanocytes). We also provide an overview of current bioprinted skin models, associated limitations and direction for future research.

Evaluation in a porcine wound model and long-term clinical assessment of an autologous heterogeneous skin construct used to close full-thickness wounds

Acute and chronic wounds involving deeper layers of the skin are often not adequately healed by dressings alone and require therapies such as skin grafting, skin substitutes, or growth factors. Here we report the development of an autologous heterogeneous skin construct (AHSC) that aids wound closure. AHSC is manufactured from a piece of healthy full-thickness skin. The manufacturing process creates multicellular segments, which contain endogenous skin cell populations present within hair follicles. These segments are physically optimized for engraftment within the wound bed. The ability of AHSC to facilitate closure of full thickness wounds of the skin was evaluated in a swine model and clinically in 4 patients with wounds of different etiologies. Transcriptional analysis demonstrated high concordance of gene expression between AHSC and native tissues for extracellular matrix and stem cell gene expression panels. Swine wounds demonstrated complete wound epithelialization and mature stable skin by 4 months, with hair follicle development in AHSC-treated wounds evident by 15 weeks. Biomechanical, histomorphological, and compositional analysis of the resultant swine and human skin wound biopsies demonstrated the presence of epidermal and dermal architecture with follicular and glandular structures that are similar to native skin. These data suggest that treatment with AHSC can facilitate wound closure.

Emerging Therapies for Full-Thickness Skin Regeneration

The classical treatment of extensive full-thickness skin loss due to trauma or burns has been the split-thickness skin graft. While split-thickness skin grafts close the wound, they leave patients with visible scars, dry skin, pruritis, pain, pigmentation alterations, and changes in sensation. The optimal replacement for full-thickness skin loss is replacement with intact full-thickness skin. New technologies combined with advances in the understanding of the mechanisms behind wound healing have led to the development of techniques and products that may eventually recapitulate the functions, appearance, and physical properties of normal skin. Autologous homologous skin constructs, minimal functional skin units, and composite bioengineered skin with dermal substitutes all represent potential avenues for full-thickness composite skin development and application in extensive wounds. This article summarizes the progress, state, and future of full-thickness skin regeneration in burn and massive wound patients.

Use of acellular intact fish skin grafts in treating acute paediatric wounds during the COVID-19 pandemic: a case series

Objective:

More specific strategies are needed to support children requiring skin grafting. Our goal was to identify procedures that reduce operating times, post-operative complications, pain and length of hospital stay. Patient safety, optimal wound bed support and quick micro-debridement with locoregional anaesthesia were prioritised. Ultimately, a novel acellular fish skin graft (FSG) derived from north Atlantic cod was selected for use.

Method:

We admitted consecutive paediatric patients with various lesions requiring skin grafting for definitive wound closure. All FSGs were applied and bolstered in the operating room following debridement.

Results:

In a cohort of 15 patients, the average age was 8 years and 9 months (4 years 1 month–13 years 5 months). Negative pressure wound therapy (NPWT) was given to 12 patients. Rapid wound healing was observed in all patients, with a wound area coverage of 100% and complete healing in 95% of wounds. Time until engraftment in patients receiving NPWT was reduced by about a half (to an average 12 days) from our standard experience of 21 days. Ten patients received locoregional anaesthesia and were discharged after day surgery. The operating time was <60 minutes, and no complications or allergic reactions were reported. Excellent pliability of the healed wound was achieved in all patients, without signs of itching and scratching in the postoperative period. This case series is the first and largest using FSG to treat paediatric patients with different wound aetiologies. We attribute the rapid transition to acute wound status and the good pliability of the new epidermal–dermal complex to the preserved molecular components of the FSG, including omega-3.

Conclusion:

FSG represents an innovative and sustainable solution for paediatric wound care that results in shorter surgery time and reduced hospital stays, with accelerated wound healing times.

Wound Healing After Fractional Skin Harvesting

BACKGROUND

Autologous fractional full-thickness skin grafting is a method of harvesting full-thickness skin with reduced donor site morbidity compared with conventional skin grafting.

OBJECTIVE

To demonstrate that full-thickness skin microbiopsies can be harvested with minimal scarring or complications.

MATERIALS AND METHODS

In a nonrandomized, self-controlled, pilot trial, subjects (n = 8) underwent tissue harvesting of full-thickness skin columns of 200, 400, 500, 600, 800 μm, 1, and 2 mm diameters. The extent of scarring was measured by using the Patient and Observer Scar Assessment Scale and blinded evaluation of photographs at 6 weeks postprocedure. Pain visual analog scale (VAS) and side effects were recorded.

RESULTS

When present, scars were first observed after 2 to 4 weeks, much more often for wounds >400 μm (p < .001). Blinded dermatologists increasingly identified clinical scarring on photographs with larger harvested microcolumn diameters (p < .001). Median VAS pain score was 0 (range 0-4). All subjects rated the procedure safe and tolerable.

CONCLUSION

Harvesting full-thickness skin microcolumns is well-tolerated over a wide range of column diameters. At diameters of less than 500 μm, side effects including scarring are minimal.

Self-assembly of tessellated tissue sheets by expansion and collision

Tissues do not exist in isolation—they interact with other tissues within and across organs. While cell-cell interactions have been intensely investigated, less is known about tissue-tissue interactions. Here, we studied collisions between monolayer tissues with different geometries, cell densities, and cell types. First, we determine rules for tissue shape changes during binary collisions and describe complex cell migration at tri-tissue boundaries. Next, we propose that genetically identical tissues displace each other based on pressure gradients, which are directly linked to gradients in cell density. We present a physical model of tissue interactions that allows us to estimate the bulk modulus of the tissues from collision dynamics. Finally, we introduce TissEllate, a design tool for self-assembling complex tessellations from arrays of many tissues, and we use cell sheet engineering techniques to transfer these composite tissues like cellular films. Overall, our work provides insight into the mechanics of tissue collisions, harnessing them to engineer tissue composites as designable living materials.

Tissue boundaries in our body separate organs and enable healing, but boundary mechanics are not well known. Here, the authors define mechanical rules for colliding cell monolayers and use these rules to make complex, predictable tessellations.

The emerging therapeutic targets for scar management: genetic and epigenetic landscapes

Background

Wound healing is a complex process including hemostasis, inflammation, proliferation, and remodeling during which an orchestrated array of biological and molecular events occurs to promote skin regeneration. Abnormalities in each step of the wound healing process lead to reparative rather than regenerative responses, thereby driving the formation of cutaneous scar. Patients suffering from scars represent serious health problems such as contractures, functional and esthetic concerns as well as painful, thick, and itchy complications, which generally decrease the quality of life and impose high medical costs. Therefore, therapies reducing cutaneous scarring are necessary to improve patients' rehabilitation.

Summary

Current approaches to remove scars, including surgical and nonsurgical methods, are not efficient enough, which is in principle due to our limited knowledge about underlying mechanisms of pathological as well as the physiological wound healing process. Thus, therapeutic interventions focused on basic science including genetic and epigenetic knowledge are recently taken into consideration as promising approaches for scar management since they have the potential to provide targeted therapies and improve the conventional treatments as well as present opportunities for combination therapy. In this review, we highlight the recent advances in skin regenerative medicine through genetic and epigenetic approaches to achieve novel insights for the development of safe, efficient, and reproducible therapies and discuss promising approaches for scar management.

Key Message

Genetic and epigenetic regulatory switches are promising targets for scar management, provided the associated challenges are to be addressed.

Chronic wounds: Treatment consensus

The Wound Healing Foundation (WHF) recognised a need for an unbiased consensus on the best treatment of chronic wounds. A panel of 13 experts were invited to a virtual meeting which took place on 27 March 2021. The proceedings were organised in the sub-sections diagnosis, debridement, infection control, dressings, grafting, pain management, oxygen treatment, outcomes and future needs. Eighty percent or better concurrence among the panellists was considered a consensus. A large number of critical questions were discussed and agreed upon. Important takeaways included that wound care needs to be simplified to a point that it can be delivered by the patient or the patient's family. Another one was that telemonitoring, which has proved very useful during the COVID-19 pandemic, can help reduce the frequency of interventions by a visiting nurse or a wound care center. Defining patient expectations is critical to designing a successful treatment. Patient outcomes might include wound specific outcomes such as time to heal, wound size reduction, as well as improvement in quality of life. For those patients with expectations of healing, an aggressive approach to achieve that goal is recommended. When healing is not an expectation, such as in patients receiving palliative wound care, outcomes might include pain reduction, exudate management, odour management and/or other quality of life benefits to wound care.

Advances in spray products for skin regeneration

To date, skin wounds are still an issue for healthcare professionals. Although numerous approaches have been developed over the years for skin regeneration, recent advances in regenerative medicine offer very promising strategies for the fabrication of artificial skin substitutes, including 3D bioprinting, electrospinning or spraying, among others. In particular, skin sprays are an innovative technique still under clinical evaluation that show great potential for the delivery of cells and hydrogels to treat acute and chronic wounds. Skin sprays present significant advantages compared to conventional treatments for wound healing, such as the facility of application, the possibility to treat large wound areas, or the homogeneous distribution of the sprayed material. In this article, we review the latest advances in this technology, giving a detailed description of investigational and currently commercially available acellular and cellular skin spray products, used for a variety of diseases and applying different experimental materials. Moreover, as skin sprays products are subjected to different classifications, we also explain the regulatory pathways for their commercialization and include the main clinical trials for different skin diseases and their treatment conditions. Finally, we argue and suggest possible future trends for the biotechnology of skin sprays for a better use in clinical dermatology.

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Skin sprays represent a promising technique for wound healing applications.

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Skin sprays can deliver cells and hydrogels with great facility over large wounds.

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Many skin spray products have been studied, only a few have been commercialized.

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Numerous clinical trials study spray products for skin diseases like psoriasis.

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Improved spraying devices should be developed for different materials and cells.

An overview on the manufacturing of functional and mature cellular skin substitutes

There are different types of skin diseases due to chronic injuries that impede the natural healing process of the skin. Tissue engineering (TE) has focused on the development of bioengineered skin or skin substitutes that cover the wound, providing the necessary care to restore the functionality of injured skin. There are two types of substitutes: acellular skin substitutes (ASSs), which offer a low response of the body, and cellular skin substitutes (CSSs), which incorporate living cells and appear as a great alternative in the treatment of skin injuries due to them presenting a greater interaction and integration with the rest of the body. For the development of a CSS, it is necessary to select the most suitable biomaterials, cell components, and methodology of biofabrication for the wound to be treated. Moreover, these CSSs are immature substitutes that must undergo a maturing process in specific bioreactors, guaranteeing their functionality. The bioreactor simulates the natural state of maturation of the skin by controlling parameters such as temperature, pressure, or humidity, allowing a homogeneous maturation of the CSSs in an aseptic environment. The use of bioreactors not only contributes to the maturation of the CSSs, but also offers a new way of obtaining large sections of skin substitutes or natural skin from small portions acquired from the patient, donor, or substitute. Based on the innovation of this technology and the need to develop efficient CSSs, this work offers an update on bioreactor technology in the field of skin regeneration.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

A novel therapeutic phosphate-based glass improves full-thickness wound healing in a rat model

Wound healing is a highly dynamic process and innovative therapeutic approaches are currently developed to address challenges of providing optimal wound care. In this study, phosphate-based glasses in the (CuO)_x ·(KPO₃ )_79.5-x ·(ZnO)₂₀ ·(Ag₂ O)_0.5 system (CuKPO₃ ZnAg), with different CuO/ KPO₃ ratios were prepared by melt-quenching technique. Constant Cu concentrations were released from the samples during immersion in Simulated Body Fluid (SBF), while Zn concentrations were slightly decreased over time. Glass surface phosphatation leading to formation of Zn crystalline salts was revealed through spectroscopic techniques. This finding was supported by SEM images that illustrated new compound formation. Subsequent cytotoxicity evaluation on HaCaT Keratinocytes using the indirect MTT cell viability assay revealed a CuO concentration-dependent cytotoxicity profile and excellent biocompatibility at low CuO concentrations, in all CuKPO₃ ZnAg glasses. Furthermore, the (CuO)₅ ·(KPO₃ )_74.5 ·(ZnO)₂₀ ·(Ag₂ O)_0.5 sample (5CuKPO₃ ZnAg)_, demonstrated superior antibacterial potency against S. aureus (ATCC 25923) strain compared to amoxicillin and ciprofloxacin. In vivo full-thickness wound healing evaluation showed a significantly higher regenerative effect of the 5CuKPO₃ ZnAg sample, in terms of angiogenesis, collagen synthesis and re-epithelialization compared to non-treated wounds. These findings advance our understanding of the therapeutic perspectives of phosphate-based glasses, showing promising potential for wound-healing applications.

Skin substitutes with noncultured autologous skin cell suspension heal porcine full-thickness wounds in a one-stage procedure

Clinical application of skin substitute is typically a two-stage procedure with application of skin substitute matrix to the wound followed by engraftment of a split-thickness skin graft (STSG). This two-stage procedure requires multiple interventions, increasing the time until the wound is epithelialised. In this study, the feasibility of a one-stage procedure by combining bioengineered collagen-chondroitin-6-sulfate (DS1) or decellularised fetal bovine skin substitute (DS2) with autologous skin cell suspension (ASCS) in a porcine full-thickness wound healing model was evaluated. Twelve full-thickness excisional wounds on the backs of pigs received one of six different treatments: empty; ASCS; DS1 with or without ASCS; DS2 with or without ASCS. The ASCS was prepared using a point-of-care device and was seeded onto the bottom side of DS1, DS2, and empty wounds at 80 000 cells/cm² . Wound measurements and photographs were taken on days 0, 9, 14, 21, 28, 35, and 42 post-wounding. Histological analysis was performed on samples obtained on days 9, 14, 28, and 42. Wounds in the empty group or with ASCS alone showed increased wound contraction, fibrosis, and myofibroblast density compared with other treatment groups. The addition of ASCS to DS1 or DS2 resulted in a marked increase in re-epithelialisation of wounds at 14 days, from 15 ± 11% to 71 ± 20% (DS1 vs DS1 + ASCS) or 28 ± 14% to 77 ± 26 (DS2 vs DS2 + ASCS) despite different mechanisms of tissue regeneration employed by the DS used. These results suggest that this approach may be a viable one-stage treatment in clinical practice.

Addressing Full-Thickness Skin Defects: A Review of Clinically Available Autologous Skin Replacements

Autologous keratinocyte culture, and combinations of scaffolds, different cell types, solutions of macromolecules, or growth factors have contributed to the resurfacing of full-thickness skin defects. Ideally, a treatment for full-thickness skin defects should not merely reestablish continuity of the surface of the skin but should restore its structure to allow skin to function as a dynamic biological factory that can participate in protein synthesis, metabolism, and cell signaling, and form an essential part of the body's immune, nervous, and endocrine systems. This paper provides a review of clinically available autologous skin replacements, highlighting the importance of regenerating an organ that will function physiologically.

Nanoceutical Adjuvants as Wound Healing Material: Precepts and Prospects

Dermal wound healing describes the progressive repair and recalcitrant mechanism of 12 damaged skin, and eventually, reformatting and reshaping the skin. Many probiotics, nutritional supplements, metal nanoparticles, composites, skin constructs, polymers, and so forth have been associated with the improved healing process of wounds. The exact mechanism of material-cellular interaction is a point of immense importance, particularly in pathological conditions such as diabetes. Bioengineered alternative agents will likely continue to dominate the outpatient and perioperative management of chronic, recalcitrant wounds as new products continue to cut costs and improve the wound healing process. This review article provides an update on the various remedies with confirmed wound healing activities of metal-based nanoceutical adjuvanted agents and also other nano-based counterparts from previous experiments conducted by various researchers.

Hair Follicle Transplantation for Wound Repair

Significance: Hair follicles are complex miniorgans that reside in the dermal layer of the skin. When the skin is wounded, epidermal stem cells in the hair follicle activate and start migrating into the wound site, differentiating into epidermal cells. and contributing to the reepithelialization of the wound. The hair follicles represent the deepest epidermal elements in the skin, which are extremely beneficial in partial-thickness burns and abrasions where the skin can regenerate from the hair follicles. Recent Advances: Advanced animal models have demonstrated that the contribution of epidermal stem cells in the hair follicle bulge and isthmus regions is important for wound healing. In addition, several clinical studies have shown successful harvesting and transplantation of hair follicles as a treatment modality to accelerate wound healing. Critical Issues: Deep and large wounds require hospitalization and, without exception, surgical treatment. Harvesting and direct transplantation of hair follicles could provide a great source of autologous epidermal stem cells for wound healing. The procedure can be done in an outpatient setting, quickly and without creating a large donor site wound. Future Directions: Transplantation of hair follicles in a combination with novel biomaterials could provide advantageous treatment possibilities for both chronic wounds and burns. There is a substantial amount of molecular signaling data available on the role of hair follicles during wound repair, but almost all the data are derived from rodent models, and thus, more information from large animals and most importantly from humans would be beneficial and help to advance this promising treatment further.

Concepts in Early Reconstruction of the Burned Hand

BACKGROUND

Early reconstruction of burn sequelae of the hand can be challenging owing to high goals for functional and aesthetic outcome. A variety of reconstructive procedures with ascending levels of complexity exists and warrants careful indication.

METHODS

In this case series, the main reconstructive techniques for reconstruction of burn defects of the hand are described, illustrated, and discussed: split thickness skin grafting (STSG) with fibrin glue, dermal matrices with STSG, distant random pattern (abdominal bridge) flap, distant pedicled flap (superficial circumflex iliac artery flap), and free microvascular tissue transfer (anterolateral thigh flap). An algorithm for decision making in the reconstructive process is proposed.

RESULTS

Split thickness skin grafting provides sufficient coverage for partial thickness defects without exposure of functional structures; fixation with fibrin glue avoids unnecessary stapling. Dermal matrices under STSG provide vascularized granulation tissue on full thickness defects and can be used as salvage procedure on functional structures. Distant random pattern or pedicled flaps provide sufficient coverage of large full thickness defects with exposed functional structures but pose some challenges regarding patient compliance and immobilization. Free tissue transfer allows tailored reconstruction of large full thickness defects with exposed functional structures and can be safely and feasibly performed. Secondary and tertiary procedures are needed with more complex techniques; if applied correctly and consequently, all methods can yield favorable functional and aesthetic outcomes.

CONCLUSIONS

Reconstruction of the burned hand may require a broad armamentarium of surgical techniques with different levels of complexity, versatility, and applicability. Excellent results can be achieved with the right procedure for the right patient.

Multi-faceted enhancement of full-thickness skin wound healing by treatment with autologous micro skin tissue columns

Impaired wound healing is an immense medical challenge, and while autologous skin grafting remains the "gold-standard" therapeutic option for repairing wounds that cannot be closed by primary or secondary intention, it is limited by substantial donor site morbidity. We previously developed the alternative approach of harvesting full-thickness skin tissue in the form of "micro skin tissue columns" (MSTCs), without causing scarring or any other long-term morbidity. In this study we investigated how MSTC treatment affects the different cellular processes involved in wound healing. We found that MSTC-derived cells were able to remodel and repopulate the wound volume, and positively impact multiple aspects of the wound healing process, including accelerating re-epithelialization by providing multiple cell sources throughout the wound area, increasing collagen deposition, enhancing dermal remodeling, and attenuating the inflammatory response. These effects combined to enhance both epidermal and dermal wound healing. This MSTC treatment approach was designed for practical clinical use, could convey many benefits of autologous skin grafting, and avoids the major drawback of donor site morbidity.

Open-label Venous Leg Ulcer Pilot Study Using a Novel Autolologous Homologous Skin Construct

Venous leg ulcers (VLUs) are often refractory to compression therapy, and their prevalence is increasing. An autologous homologous skin construct (AHSC) that uses the endogenous regenerative capacity of healthy skin has been developed to treat cutaneous defects, with a single application. The ability of AHSC to close VLUs with a single treatment was evaluated in an open-label, single-arm feasibility study to test the hypothesis that AHSC treatment will result in wound closure by providing healthy autologous tissue to the wound bed.

METHODS

Ten VLUs were treated with a single application of AHSC. A 1.5 cm2 full-thickness skin harvest from the proximal calf was collected and sent to a Food and Drug Administration-registered facility, where it was processed into AHSC and returned to the provider within 48 hours. AHSC was spread evenly across the wound and dressed with silicone. The primary endpoint was wound closure rate at 12 weeks. Wound closure was followed with 3-dimensional planimetry, and closure was confirmed by a panel of plastic surgeons. Additional endpoints followed for 12 weeks included graft take, harvest site closure, adverse event rate, complications, and patient-reported pain.

RESULTS

All 10 VLUs demonstrated successful graft take as evidenced by graft persisting in wound and harvest site closure. Eight VLUs exhibited complete closure within 12 weeks. One VLU that failed to heal with a prior split thickness skin graft closed within 13.5 weeks with AHSC. The mean time of closure was 34 days (95% confidence interval, 14-53). Pain improved by closure confirmation visit. There was 1 serious adverse event unrelated to the product or procedure.

CONCLUSION

This pilot study demonstrated that AHSC may be a viable single-application topical intervention for VLUs and warrants further investigation in larger, controlled studies.

Auto Micro Atomization Delivery of Human Epidermal Organoids Improves Therapeutic Effects for Skin Wound Healing

Severe skin wounds are often associated with large areas of damaged tissue, resulting in substantial loss of fluids containing electrolytes and proteins. The net result is a vulnerability clinically to skin infections. Therapies aiming to close these large openings are effective in reducing the complications of severe skin wounds. Recently, cell transplantation therapy showed the potential for rapid re-epithelialization of severe skin wounds. Here, we show the improved effects of cell transplantation therapy using a robust protocol of efficient expansion and delivery of epidermal cells for treatment of severe skin wounds. Human skin tissues were used to generate human epidermal organoids maintained under newly established culture conditions. The human epidermal organoids showed an improved capacity of passaging for at least 10 rounds, enabling organoids to expand to cell numbers required for clinical applications. A newly designed auto micro-atomization device (AMAD) was developed for delivery of human epidermal organoids onto the sites of severe skin wounds enhancing uniform and concentrated delivery of organoids, facilitating their engraftment and differentiation for skin reconstitution. With the optimal design and using pneumatic AMAD, both survival and functions of organoids were effectively protected during the spraying process. Cells in the sprayed human epidermal organoids participated in the regeneration of the epidermis at wound sites in a mouse model and accelerated wound healing significantly. The novel AMAD and out new protocol with enhanced effects with respect to both organoid expansion and efficient transplantation will be used for clincal treatments of complex, uneven, or large-area severe skin wounds.

Cell-free fat extract promotes tissue regeneration in a tissue expansion model

Background

Tissue expansion techniques play an important role in plastic surgery. How to improve the quality of the expanded skin and shorten the expansion period are still worth investigating. Our previous studies found that a cell-free fat extract (CEFFE) possessed pro-angiogenic and pro-proliferative activities. However, the role of CEFFE on tissue expansion has remained unclear. The purpose of this study was to evaluate the effect of CEFFE on tissue expansion.

Methods

A rat tissue expansion model was used. Animals were treated with CEFFE by subcutaneous injection. After 4 weeks of tissue expansion, the skin necrosis and retraction rates were evaluated, the thicknesses of the epidermis and dermis were determined by histological analyses, blood vessel density was measured by anti-CD31 staining, cell proliferation was assessed by proliferating cell nuclear antigen staining, and the expression of specific proteins was evaluated by western blot analyses. In addition, the effects of CEFFE on the proliferation and cell cycle of cultured HaCaT cells were evaluated in vitro.

Results

CEFFE treatment significantly decreased the necrosis rate and retraction of the expanded skin. The thickness of the epidermal and dermal layers was higher in CEFFE-treated compared to untreated skin. The density of blood vessels and cell proliferation in the epidermis of the expanded skin was improved by CEFFE treatment. In addition, CEFFE treatment significantly increased the expression of the vascular endothelial growth factor receptor, epidermal growth factor receptor, collagen type 1, and collagen type 3. CEFFE also increased the proliferation of HaCaT cells in culture.

Conclusions

CEFFE improves the quality of the expanded skin by promoting angiogenesis and cell proliferation. It could be potentially used clinically for augmenting tissue expansion.

Bioprinted Skin Recapitulates Normal Collagen Remodeling in Full-Thickness Wounds

Over 1 million burn injuries are treated annually in the United States, and current tissue engineered skin fails to meet the need for full-thickness replacement. Bioprinting technology has allowed fabrication of full-thickness skin and has demonstrated the ability to close full-thickness wounds. However, analysis of collagen remodeling in wounds treated with bioprinted skin has not been reported. The purpose of this study is to demonstrate the utility of bioprinted skin for epidermal barrier formation and normal collagen remodeling in full-thickness wounds. Human keratinocytes, melanocytes, fibroblasts, dermal microvascular endothelial cells, follicle dermal papilla cells, and adipocytes were suspended in fibrinogen bioink and bioprinted to form a tri-layer skin structure. Bioprinted skin was implanted onto 2.5 × 2.5 cm full-thickness excisional wounds on athymic mice, compared with wounds treated with hydrogel only or untreated wounds. Total wound closure, epithelialization, and contraction were quantified, and skin samples were harvested at 21 days for histology. Picrosirius red staining was used to quantify collagen fiber orientation, length, and width. Immunohistochemical (IHC) staining was performed to confirm epidermal barrier formation, dermal maturation, vascularity, and human cell integration. All bioprinted skin treated wounds closed by day 21, compared with open control wounds. Wound closure in bioprinted skin treated wounds was primarily due to epithelialization. In contrast, control hydrogel and untreated groups had sparse wound coverage and incomplete closure driven primarily by contraction. Picrosirius red staining confirmed a normal basket weave collagen organization in bioprinted skin-treated wounds compared with parallel collagen fibers in hydrogel only and untreated wounds. IHC staining at day 21 demonstrated the presence of human cells in the regenerated dermis, the formation of a stratified epidermis, dermal maturation, and blood vessel formation in bioprinted skin, none of which was present in control hydrogel treated wounds. Bioprinted skin accelerated full-thickness wound closure by promoting epidermal barrier formation, without increasing contraction. This healing process is associated with human cells from the bioprinted skin laying down a healthy, basket-weave collagen network. The remodeled skin is phenotypically similar to human skin and composed of a composite of graft and infiltrating host cells. Impact statement We have demonstrated the ability of bioprinted skin to enhance closure of full-thickness wounds through epithelialization and normal collagen remodeling. To our knowledge, this article is the first to quantify collagen remodeling by bioprinted skin in full-thickness wounds. Our methods and results can be used to guide further investigation of collagen remodeling by tissue engineered skin products to improve ongoing and future bioprinting skin studies. Ultimately, our skin bioprinting technology could translate into a new treatment for full-thickness wounds in human patients with the ability to recapitulate normal collagen remodeling in full-thickness wounds.

Regeneration of Functional, Full-Thickness Skin With Minimal Donor Site Contribution Using Autologous Homologous Skin Construct

Autologous skin grafts (autografts) remain the gold standard in the treatment of skin loss. For extensive wounds or burns, however, identifying adequate donor sites can be the limiting factor. Additionally, donor sites are associated with pain, risk of infection, and poor cosmetic outcomes. Many skin substitutes have been engineered as alternatives to traditional autografts. These substitutes, however, all leave something to be desired either functionally or cosmetically. This report describes the use of a new technology, autologous homologous skin constructs, to regenerate full-thickness skin grafts that maintain functional polarity, allowing important components of skin such as glands and hair follicles to regenerate. These grafts only require small samples of full-thickness skin from the patient, decreasing issues of donor site availability.

A Multicentre Study: The Use of Micrografts in the Reconstruction of Full-Thickness Posttraumatic Skin Defects of the Limbs-A Whole Innovative Concept in Regenerative Surgery

The skin graft is a surgical technique commonly used in the reconstructive surgery of the limbs, in order to repair skin loss, as well as to repair the donor area of the flaps and cover the dermal substitutes after engraftment. The unavoidable side effect of this technique consists of unaesthetic scars. In order to achieve the healing of posttraumatic ulcers by means of tissue regeneration and to avoid excessive scarring, a new innovative technology based on the application of autologous micrografts, obtained by Rigenera technology, was reported. This technology was able to induce tissue repair by highly viable skin micrografts of 80 micron size achieved by a mechanical disaggregation method. The specific cell population of these micrografts includes progenitor cells, which in association with the fragment of the Extracellular Matrix (ECM) and growth factors derived by patients' own tissue initiate biological processes of regeneration enhancing the wound healing process. We have used this technique in 70 cases of traumatic wounds of the lower and upper limbs, characterized by extensive loss of skin substance and soft tissue. In all cases, we have applied the Rigenera protocol using skin micrografts, achieving in 69 cases the complete healing of wounds in a period between 35 and 84 days. For each patient, the reconstructive outcome was evaluated weekly to assess the efficacy of this technique and any arising complication. A visual analogue scale (VAS) was administered to assess the amount of pain felt after the micrografts' application, whereas we evaluated the scars according to the Vancouver scale and the wound prognosis according to Wound Bed Score. We have thus been able to demonstrate that Rigenera procedure is very effective in stimulating skin regeneration, while reducing the outcome scar.

Regeneration and expansion of autologous full-thickness skin through a self-propagating autologous skin graft technology

New autologous skin regeneration technology yielded full-thickness skin as evidenced by clinical observation and skin biopsy 5 months after surgery, providing relief for debilitating split-thickness skin graft contracture in a pediatric burn case.

Outcome of the Modified Meek Technique in the Management of Major Pediatric Burns

INTRODUCTION

The modified Meek micrografting technique has been used in the treatment of severely burned patients and a number of articles have examined the use of the modified Meek technique in adults and in mixed-age groups. However, there is a paucity of research pertaining to the outcome in the pediatric age group. The aim of this study is to present our favorable outcome in pediatric major burns using the modified Meek technique.

METHODS

A retrospective review of burn cases in Hospital Universiti Sains Malaysia from 2010 to 2015 was conducted. Cases of major burns among pediatric patients grafted using the Meek technique were examined.

RESULTS

Twelve patients were grafted using the Meek technique. Ten (91.7%) patients were male, whereas 2 (8.3%) were female. The average age of patients was 6 years (range, 2-11 years). The average total body surface area was 35.4% (range, 15%-75%). Most burn mechanisms were due to flame injury (66.7%) as compared with scalds injury (16.7%) and chemical injury (16.7%). There was no mortality. All patients were completely grafted with a good donor site scar. The average graft take rate was 82.3%, although 8 cases had positive tissue cultures from the Meek-grafted areas. The average follow-up duration was 3.6 years (range, 1.1-6.7 years). Only 1 case developed contracture over minor joint.

CONCLUSIONS

The Meek technique is useful when there is a paucity of donor site in the pediatric group. The graft take is good, contracture formation is low, and this technique is cost-effective.

Development of de novo epithelialization method for treatment of cutaneous ulcers

Cutaneous ulcers are a common cause of morbidity. We have developed a de novo epithelialization method for treating cutaneous ulcers by means of reprogramming wound-resident mesenchymal cells in vivo into cells able to form a stratified epithelium: induced stratified epithelial progenitors (iSEPs). Administration of 4 transcription factors (DNP63A, GRHL2, TFAP2A, and cMYC) expressed via adeno-associated viral vectors enabled generation of epithelial cells and tissues, thereby acheiving de novo epithelialization from the surfaces of cutaneous ulcers in a mouse model. Generated epithelia, having barrier functions equivalent to the original epidermis, were maintained for more than 6 months. Our findings constitute a proof of concept for future development towards innovative therapies for cutaneous ulcers via de novo epithelialization.

Therapeutic strategies for skin regeneration based on biomedical substitutes

Regenerative medicine and tissue engineering (TE) have experienced significant advances in the development of in vitro engineered skin substitutes, either for replacement of lost tissue in skin injuries or for the generation of in vitro human skin models to research. However, currently available skin substitutes present different limitations such as expensive costs, abnormal skin microstructure and engraftment failure. Given these limitations, new technologies, based on advanced therapies and regenerative medicine, have been applied to develop skin substitutes with several pharmaceutical applications that include injectable cell suspensions, cell-spray devices, sheets or 3Dscaffolds for skin tissue regeneration and others. Clinical practice for skin injuries has evolved to incorporate these innovative applications to facilitate wound healing, improve the barrier function of the skin, prevent infections, manage pain and even to ameliorate long-term aesthetic results. In this article, we review current commercially available skin substitutes for clinical use, as well as the latest advances in biomedical and pharmaceutical applications used to design advanced therapies and medical products for wound healing and skin regeneration. We highlight the current progress in clinical trials for wound healing as well as the new technologies that are being developed and hold the potential to generate skin substitutes such as 3D bioprinting-based strategies.

Comparative study on the donor site aesthetic outcome between epidermal graft and split-thickness skin graft

Donor site aesthetic outcomes of epidermal graft (EG) vs split-thickness skin graft (SSG) have yet to be objectively compared. Here, we evaluate donor site healing using a validated scar assessment tool and digital colorimetric technique, which compares colour in a consistent and objective manner. Ten patients (SSG (n = 5) and EG (n = 5)) were included. Donor site scarring was evaluated using the Vancouver Scar Scale (VSS) at Week 6 and Month 3. Colorimetric measurement was performed at Weeks 3 and 6 and Month 3. The mean donor site healing time for EG was significantly shorter (EG: 4.6 days (95% c.i. 3.8-5.3), SSG: 16.8 days (95% c.i. 13.3-20.1) (P = 0.003)). The VSS scores of the EG donor site were lower at Week 6 and Month 3(P < 0.001). The colour match between the donor site and surrounding skin for EG was better compared with SSG at all time points and was almost identical to their surrounding healthy skin at Month 3. This study is the first to objectively measure the clinical appearance of the EG donor site against SSG. EG donor site has faster healing with excellent scarring and good colour match with its surrounding normal skin at all time points compared with SSG.

Apparatus for Harvesting Tissue Microcolumns

This manuscript describes the production process for a laboratory apparatus, made from off-the-shelf components, that can be used to collect microcolumns of full-thickness skin tissue. The small size of the microcolumns allows donor sites to heal quickly without causing donor site scarring, while harvesting full-thickness tissue enables the incorporation of all cellular and extracellular components of skin tissue, including those associated with deeper dermal regions and the adnexal skin structures, which have yet to be successfully reproduced using conventional tissue engineering techniques. The microcolumns can be applied directly into skin wounds to augment healing, or they can be used as the autologous cell/tissue source for other tissue engineering approaches. The harvesting needles are made by modifying standard hypodermic needles, and they can be used alone for harvesting small amounts of tissue or coupled with a simple suction-based collection system (also made from commonly available laboratory supplies) for high-volume harvesting to facilitate studies in large animal models.

Evaluation of the efficacy of cell and micrograft transplantation for full-thickness wound healing

BACKGROUND

Skin grafting is the current standard of care in the treatment of full-thickness burns and other wounds. It is sometimes associated with substantial problems, such as poor quality of the healed skin, scarring, and lack of donor-site skin in large burns. To overcome these problems, alternative techniques that could provide larger expansion of a skin graft have been introduced over the years. Particularly, different cell therapies and methods to further expand skin grafts to minimize the need for donor skin have been attempted. The purpose of this study was to objectively evaluate the efficacy of cell and micrograft transplantation in the healing of full-thickness wounds.

MATERIALS AND METHODS

Allogeneic cultured keratinocytes and fibroblasts, separately and together, as well as autologous and allogeneic skin micrografts were transplanted to full-thickness rat wounds, and healing was studied over time. In addition, wound fluid was collected, and the level of various cytokines and growth factors in the wound after transplantation was measured.

RESULTS

Our results showed that both autologous and allogeneic micrografts were efficient treatment modalities for full-thickness wound healing. Allogeneic skin cell transplantation did not result in wound closure, and no viable cells were found in the wound 10 d after transplantation.

CONCLUSIONS

Our study demonstrated that allogeneic micrografting is a possible treatment modality for full-thickness wound healing. The allografts stayed viable in the wound and contributed to both re-epithelialization and formation of dermis, whereas allogeneic skin cell transplantation did not result in wound closure.

Advances in keratinocyte delivery in burn wound care

This review gives an updated overview on keratinocyte transplantation in burn wounds concentrating on application methods and future therapeutic cell delivery options with a special interest in hydrogels and spray devices for cell delivery. To achieve faster re-epithelialisation of burn wounds, the original autologous keratinocyte culture and transplantation technique was introduced over 3 decades ago. Application types of keratinocytes transplantation have improved from cell sheets to single-cell solutions delivered with a spray system. However, further enhancement of cell culture, cell viability and function in vivo, cell carrier and cell delivery systems remain themes of interest. Hydrogels such as chitosan, alginate, fibrin and collagen are frequently used in burn wound care and have advantageous characteristics as cell carriers. Future approaches of keratinocyte transplantation involve spray devices, but optimisation of application technique and carrier type is necessary.

Randomized clinical trial of autologous skin cell suspension for accelerating re-epithelialization of split-thickness donor sites

BACKGROUND

Split-thickness skin graft (STSG) is used frequently, but may result in complications at the donor site. Rapid healing of donor-site wounds is critical to relieving morbidity. This study investigated whether autologous skin cell suspension could improve healing of STSG donor-site wounds.

METHODS

Between September 2014 and February 2016, patients requiring STSGs were randomized to receive autologous skin cell suspension plus hydrocolloid dressings (experimental group) or hydrocolloid dressings alone (control group) for the donor site. The primary outcome was time to complete re-epithelialization. Secondary outcomes included pain and itching scores measured on a visual analogue scale, and adverse events. Patients were followed for 12 weeks to evaluate quality of healing. Analysis was by intention to treat.

RESULTS

Some 106 patients were included, 53 in each group. Median time to complete re-epithelialization was 9·0 (95 per cent c.i. 8·3 to 9·7) days in the experimental group, compared with 13·0 (12·4 to 13·6) days in the control group (P < 0·001). Overall postoperative pain and itching scores were similar in both groups. No between-group differences in treatment-related complications were observed. Both patients and observers were more satisfied with healing quality after autologous skin cell suspension had been used.

CONCLUSION

The use of autologous skin cell suspension with hydrocolloid dressings accelerated epithelialization and improved healing quality of the donor site compared with hydrocolloid dressings alone. Registration number: UMIN000015000 ( http://www.umin.ac.jp/ctr).