Reconstitution of full-thickness skin by microcolumn grafting

Characterization of heterogeneous skin constructs for full thickness skin regeneration in murine wound models

An autologous heterogeneous skin construct (AHSC) has been developed and used clinically as an alternative to traditional skin grafting techniques for treatment of cutaneous defects. AHSC is manufactured from a small piece of healthy skin in a manner that preserves endogenous regenerative cellular populations. To date however, specific cellular and non-cellular contributions of AHSC to the epidermal and dermal layers of closed wounds have not been well characterized given limited clinical opportunity for graft biopsy following wound closure. To address this limitation, a three-part mouse full-thickness excisional wound model was developed for histologic and macroscopic graft tracing. First, fluorescent mouse-derived AHSC (mHSC) was allografted onto non-fluorescent recipient mice to enable macroscopic and histologic time course evaluation of wound closure. Next, mHSC-derived from haired pigmented mice was allografted onto gender- and major histocompatibility complex (MHC)-mismatched athymic nude mouse recipients. Resulting grafts were distinguished from recipient murine skin via immunohistochemistry. Finally, human-derived AHSC (hHSC) was xenografted onto athymic nude mice to evaluate engraftment and hHSC contribution to wound closure. Experiments demonstrated that mHSC and hHSC facilitated wound closure through production of viable, proliferative cellular material and promoted full-thickness skin regeneration, including hair follicles and glands in dermal compartments. This combined macroscopic and histologic approach to tracing AHSC-treated wounds from engraftment to closure enabled robust profiling of regenerated architecture and further understanding of processes underlying AHSC mechanism of action. These models may be applied to a variety of wound care investigations, including those requiring longitudinal assessments of healing and targeted identification of donor and recipient tissue contributions.

Full-thickness skin columns: A method to reduce healing time and donor site morbidity in deep partial-thickness burns

The current standard of care for the coverage of large wounds often involves split thickness skin grafts (STSGs) which have numerous limitations. One promising technique that has gained traction is fractional autologous skin grafting using full-thickness skin columns (FTSC). Harvesting occurs orthogonally by taking numerous individual skin columns containing the epidermis down through the dermis and transferring them to the wound bed. The purpose of this porcine study was to investigate the efficacy of implanting FTSCs directly into deep partial-thickness burn wounds, as well as examining donor site healing at the maximal harvest density. It was hypothesised that by utilising FTSCs, the rate of healing in deep partial thickness burns can be improved without incurring the donor morbidity seen in other methods of skin grafting. Deep partial-thickness burns were created on the dorsum of female red duroc swine, debrided 3 days later and FTSCs were implanted at varying expansion ratios directly into the burn wounds. At day 14, 1:50 expansion ratio showed significantly faster re-epithelialisation compared to the debrided burn control and 1:200. Donor sites (at 7%-10% harvest density) were 100% re-epithelialised by day 7. Additionally, the maximal harvest density was determined to be 28% in an ex vivo model, which then five donor sites were harvested at 28% density on a red duroc swine and compared to five STSG donor sites. At maximal harvest density, FTSC donor sites were significantly less hypopigmented compared to STSGs, but no significant differences were observed in re-epithelialisation, contraction, blood flow or dermal thickness. In conclusion, implantation directly into deep partial-thickness burns is a viable option for the application of FTSCs, favouring lower expansion ratios like 1:50 or lower. Little difference in donor site morbidity was observed between FTSC at a maximal harvest density of 28% and STSGs, exceeding the optimal harvest density.

Tissue Engineering-Based Strategies for Diabetic Foot Ulcer Management

Significance: Diabetic foot ulcers (DFU) are a mounting problem with the increasingly frail population. Injuries that would otherwise heal are kept open by risk factors such as diabetes, obesity, and age-related conditions, which interferes with the natural wound healing processes. Recent Advances: This review summarizes recent advancements in the field of tissue engineering for the treatment of DFUs. FDA-approved approaches, including signaling-based therapies, stem cell therapies, and skin substitutes are summarized and cutting-edge experimental technologies that have the potential to manage chronic wounds, such as skin printing, skin organogenesis, skin self-assembly, and prevascularization, are discussed. Critical Issues: The standard of care for chronic wounds involves wound debridement, wound dressings, and resolving the underlying cause such as lowering the glycemic index and reducing wound pressure. Current DFU treatments are limited by low wound closure rates and poor regrown skin quality. New adjuvant therapies that facilitate wound closure in place of or in conjunction with standard care are critically needed. Future Directions: Tissue engineering strategies are limited by the plasticity of adult human cells. In addition to traditional techniques, genetic modification, although currently an emerging technology, has the potential to unlock human regeneration and can be incorporated in future therapeutics.

Autologous wound margin point columnar full‐thickness skin grafting combined with negative pressure wound therapy improves wound healing in refractory diabetic foot ulcers

Diabetic lower extremity ulcers (DLEUs) are a severe complication of diabetes mellitus (DM) and are difficult to heal. This study aimed to explore the efficacy of autologous point columnar full-thickness skin graft taken from the ulcer wound margin combined with negative pressure wound therapy (NPWT) in refractory DLEUs. This is a prospective cohort study. A total of 40 inpatients with refractory DLEUs were recruited in the Diabetes Foot Center of Guangxi Zhuang Autonomous Region People's Hospital from October 2019 to November 2021. According to the doctors' professional suggestions and the patients' personal wishes, these enrolled patients were divided into two groups based on different topical wound management: the graft group (n = 18) and the conventional wound therapeutic (CWT) group (n = 22). The efficacy evaluations included the time to complete re-epithelialization of the wound and healing speed within 14 days of graft treatment or after 14 days of graft treatment in the two groups. Before the treatment, the graft group had a significantly larger ulcer area than the CWT group [27.22 (15.28, 46.59) versus 10.92 (7.00, 24.93) cm² , P < .01]. However, the time to complete wound re-epithelialization in the graft group was shorter than in the CWT group [58.22 ± 30.60 versus 86.09 ± 49.54 d, P < .05]. Meanwhile, the healing speed in graft group was markedly faster than in CWT group, whether within 14 days [0.60 (0.40, 0.92) versus 0.16 (0.07, 0.34) cm² /d, P < .01] or after 14 days of graft treatment [0.57 (0.45, 0.91) versus 0.13 (0.08, 0.27) cm² /d, P < .01]. However, the total treatment cost in the graft group was lower than in the CWT group [419.59 ± 137.20 versus 663.97 ± 497.02 $, P < .05]. The novel treatment modality of autologous full-thickness skin graft taken from the ulcer wound margin combined with NPWT has hereby proposed for the first time, and is a safe, effective, and reliable method with a good performance-to-cost ratio to promote wound healing and shorten the healing time for DLEUs.

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.

Injectable multifunctional CMC/HA-DA hydrogel for repairing skin injury

Injectable Hydrogels with adhesive, antioxidant and hemostatic properties are highly desired for promoting skin injury repair. In this study, we prepared a multi-functional carboxymethyl chitosan/hyaluronic acid-dopamine (CMC/HA-DA) hydrogel, which can be crosslinked by horseradish peroxidase and hydrogen peroxide. The antioxidation, gelation time, degradability, rheology and antihemorrhagic properties of hydrogels can be finely tuned by varying composition ratio. The cytocompatibility test and hemolysis test confirmed that the designed hydrogel holds good biocompatibility. More importantly, the repair effect of the hydrogel on full-thickness skin injury model in mice was studied. The results of wound healing, collagen deposition, immunohistochemistry and immunofluorescence showed that CMC/HA-DA hydrogel could significantly promote angiogenesis and cell proliferation at the injured site. Notably, the inflammatory response can also be regulated to promote the repair of full-thickness skin defect in mice. Results indicate that this injectable CMC/HA-DA hydrogel holds high application prospect for promising wound healing.

Chitosan/Gelatin Composite Nonwoven Fabric Scaffold Seeding Minimal Function Unit of Skin for Functional Skin Regeneration

The construction of intact functional skin is a challenging field in tissue engineering. Traditional skin tissue engineering, using "seed cells" as a bioactive source for scaffolding materials maybe not efficient enough. Here a new strategy is shown for constructing functional tissue-engineered skin with Minimal Functional Unit of Skin (MFUS) as the source of bioactivity. Chitosan/gelatin non-woven fabric is used as the scaffold. MFUS is derived from autologous skin with full-thickness skin microstructure and complete functional skin unit harvesting. A mathematical model is used to calculate the MFUS Minimal Harvest Diameter and Angle (MHDA). Chitosan/gelatin non-woven fabric (CS+GEL) is porous and absorbable, with an elastic modulus meeting the requirement of skin engineering. It supports layered and 3D growth of MFUS. The degradation rate of chitosan, including filament diameter and density is evaluated in vivo. MFUS-engineered skin could reduce the density of local nerve fibers in the early stage, potentially reducing pain during wound healing, as well as could limit excessive fibroblast cell migration in the later stage, potentially reducing scar formation. This study proposes a new strategy for the clinical treatment of large full-thickness skin defects by constructing intact functional at minimal cost.

The Antibiofilm Nanosystems for Improved Infection Inhibition of Microbes in Skin

Biofilm formation is an important virulence factor for the opportunistic microorganisms that elicit skin infections. The recalcitrant feature of biofilms and their antibiotic tolerance impose a great challenge on the use of conventional therapies. Most antibacterial agents have difficulty penetrating the matrix produced by a biofilm. One novel approach to address these concerns is to prevent or inhibit the formation of biofilms using nanoparticles. The advantages of using nanosystems for antibiofilm applications include high drug loading efficiency, sustained or prolonged drug release, increased drug stability, improved bioavailability, close contact with bacteria, and enhanced accumulation or targeting to biomasses. Topically applied nanoparticles can act as a strategy for enhancing antibiotic delivery into the skin. Various types of nanoparticles, including metal oxide nanoparticles, polymeric nanoparticles, liposomes, and lipid-based nanoparticles, have been employed for topical delivery to treat biofilm infections on the skin. Moreover, nanoparticles can be designed to combine with external stimuli to produce magnetic, photothermal, or photodynamic effects to ablate the biofilm matrix. This study focuses on advanced antibiofilm approaches based on nanomedicine for treating skin infections. We provide in-depth descriptions on how the nanoparticles could effectively eliminate biofilms and any pathogens inside them. We then describe cases of using nanoparticles for antibiofilm treatment of the skin. Most of the studies included in this review were supported by in vivo animal infection models. This article offers an overview of the benefits of nanosystems for treating biofilms grown on the skin.

MagneTEskin-Reconstructing skin by magnetically induced assembly of autologous microtissue cores

Skin wounds are immense medical and socioeconomic burdens, and autologous skin grafting remains the gold standard for wound repair. We recently found that full-thickness micro skin tissue columns (MSTCs) can be harvested with minimal donor site morbidity, and that MSTCs applied to wounds “randomly” (without maintaining their natural epidermal-dermal orientation) can accelerate re-epithelialization. However, despite MSTCs containing all the cellular and extracellular contents of full-thickness skin, normal dermal architecture was not restored by random MSTCs. In this study, we developed a magnetically induced assembly method to produce constructs of densely packed, oriented MSTCs that closely resemble the overall architecture of full-thickness skin to test the hypothesis that maintaining MSTCs’ orientation could further hasten healing and restore a normal dermis. Our method led to faster and more orderly re-epithelialization but unexpectedly did not improve the retention of dermal architecture, which reveals a hitherto unappreciated role for tissue morphology in determining dermal remodeling outcomes.

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.

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.

Full-thickness Skin Micro-columns within a Dermal Matrix: A Novel Method for "Donor-free" Skin Replacement

Split-thickness skin graft has been the standard in the coverage of large full-thickness skin defects. However, donor sites can be associated with significant pain and scarring. Further, the recipient sites frequently lack some basic skin functions, such as temperature regulation, uniform texture, appropriate color, normal pliability, elasticity, and lubrication. Full-thickness skin grafts, while able to more adequately recapitulate skin function, have even greater donor site requirements. Implantation of full-thickness skin micro-columns is a relatively novel concept in which the skin is harvested orthogonally rather than tangentially. These micro-columns contain elements of full-thickness skin grafts, including reticular dermal fibroblasts, hair follicles, skin adnexa, and adipose tissue-all elements that contribute to skin function. Notably, it has been shown that the diameter of the skin micro-columns determine donor site morbidity; however, in most cases, full-thickness skin micro-column harvest results in a trivial donor site far less invasive or morbid than a traditional full-thickness skin graft or split-thickness skin graft harvest. Here, we present 2 cases in which full-thickness skin micro-columns were harvested and implanted into a bilayer dermal regeneration matrix (Integra) to achieve durable single-stage skin replacement with practically no donor site morbidity.

Novel application of autologous micrografts in a collagen-glycosaminoglycan scaffold for diabetic wound healing

BACKGROUND

Therapeutic strategies that successfully combine two techniques-autologous micrografting and biodegradable scaffolds-offer great potential for improved wound repair and decreased scarring. In this study we evaluate the efficacy of a novel modification of a collagen-glycosaminoglycan scaffold with autologous micrografts using a murine dorsal wound model.

METHODS

db/db mice underwent dorsal wound excision and were treated with a collagen-glycosaminoglycan scaffold (CGS), a modified collagen-glycosaminoglycan scaffold (CGS+MG) or simple occlusive dressing (Blank). The modified scaffold was created by harvesting full thickness micrografts and transplanting these into the collagen-glycosaminoglycan membrane. Parameters of wound healing, including cellular proliferation, collagen deposition, keratinocyte migration, and angiogenesis were assessed.

RESULTS

The group treated with the micrograft-modified scaffold healed at a faster rate, showed greater cellular proliferation, collagen deposition, and keratinocyte migration with higher density and greater maturity of microvessels. The grafts remained viable within the scaffold with no evidence of rejection. Keratinocytes were shown to migrate from the wound border and from the micrograft edges towards the center of the wound, while cellular proliferation was present both at the wound border and wound bed.

CONCLUSION

We report successful treatment of diabetic wounds with a novel collagen-glycosaminoglycan scaffold modified with full-thickness automicrografts. Differences in cellular migration and proliferation offer maiden evidence on the mechanisms of wound healing. Clinically, the successful scaffold engraftment, micrograft viability and improved wound healing offer promising results for the development of a new therapeutic modality for wound repair.

Skin Microcolumns as a Source of Paracrine Signaling Factors

Objective: We recently developed the approach of using “microcolumns” of autologous full-thickness skin tissue for wound repair. The small size of these micro skin tissue columns (MSTCs, ∼0.5 mm in diameter) allows donor sites to heal quickly without scarring. Treatment with MSTCs significantly accelerate wound healing, and suppled various skin cell types and skin structures to replenish the wound volume. This technology is now starting clinical use. In this study, we investigate whether MSTCs may also influence wound healing by releasing soluble signaling factors.

Approach: Freshly harvested MSTCs were incubated in culture medium for 24 h. The conditioned medium was collected and tested for its effects on migration and proliferation of human dermal fibroblasts, and its ability to induce tube formation by human umbilical vein endothelial cells (HUVECs). Proteins released into the conditioned medium were characterized by multiplex enzyme-linked immunosorbent assay (ELISA), and compared with medium conditioned by an equivalent mass of intact full-thickness skin.

Results: MSTC-conditioned medium increased fibroblast migration and proliferation, as well as HUVEC tube formation. MSTCs released many soluble factors known to play prominent roles in wound healing. A subset of proteins showed significantly different release profiles compared with intact full-thickness skin.

Innovation: The technology for harvesting and using MSTCs to augment wound healing was recently developed as an alternative to conventional autologous skin grafting. This study shows that MSTCs could also function as “cytokine factories.”

Conclusion: In addition to supplying autologous cells to repopulate the wound volume, MSTCs can also function as a source of growth factors and cytokines to further enhance wound healing.

Nanomaterials for Angiogenesis in Skin Tissue Engineering

Damage to skin tissue, which causes the disorder of the patient's body homeostasis, threatens the patient's life and increases the personal and social treatment burden. Angiogenesis, a key step in the wound healing process, provides sufficient oxygen and nutrients to the wound area. However, traditional clinical interventions are not enough to stabilize the formation of the vascular system to support wound healing. Due to the unique properties and multiple functions of nanomaterials, it has made a major breakthrough in the application of medicine. Nanomaterials provide a more effective treatment to hasten the angiogenesis and wound healing, by stimulating fundamental factors in the vascular regeneration phase. In the present review article, the basic stages and molecular mechanisms of angiogenesis are analyzed, and the types, applications, and prospects of nanomaterials used in angiogenesis are detailed. Impact statement Wound healing (especially chronic wounds) is currently a clinically important issue. The long-term nonhealing of chronic wounds often plagues patients, medical systems, and causes huge losses to the social economy. There is currently no effective method of treating chronic wounds in the clinic. Angiogenesis is an important step in wound healing. Nanomaterials had properties that are not found in conventional materials, and they have been extensively studied in angiogenesis. This review article provides readers with the molecular mechanisms of angiogenesis and the types and applications of angiogenic nanomaterials, hoping to bring inspiration to overcome chronic wounds.

Multifunctional Nano and Collagen-Based Therapeutic Materials for Skin Repair

A novel strategy is needed for treating nonhealing wounds, which is able to simultaneously eradicate pathogenic bacteria and promote tissue regeneration. This would improve patient outcome and reduce the number of lower limb amputations. In this work, we present a multifunctional therapeutic approach able to control bacterial infections, provide a protective barrier to a full-thickness wound, and improve wound healing in a clinically relevant animal model. Our approach uses a nanoengineered antimicrobial nanoparticle for creating a sprayable layer onto the wound bed that prevents bacterial proliferation and also eradicates preformed biofilms. As a protective barrier for the wound, we developed a thermoresponsive collagen-based matrix that has prohealing properties and is able to fill wounds independent of their geometries. Our results indicate that using a combination of the matrix with full-thickness microscopic skin tissue columns synergistically contributed to faster and superior skin regeneration in a nonhealing wound model in diabetic mice.

When Wounds Are Good for You: The Regenerative Capacity of Fractional Resurfacing and Potential Utility in Chronic Wound Prevention

Significance: Fractional resurfacing involves producing arrays of microinjuries on the skin, by thermal or mechanical means, to trigger tissue regeneration. Originally developed for cosmetic enhancement, fractional resurfacing induces a broad array of improvements in the structural and functional qualities of the treated skin and is especially effective at returning defective skin to a more normal state. In addition to fascinating questions about the nature of this remarkable regenerative capacity, there may be potential utility in ulcer prevention by halting or even reversing the progressive decline in overall skin quality that usually precedes chronic wound development. Recent Advances: Photoaging and scarring are the two skin defects most commonly treated by fractional resurfacing, and the treatment produces profound and long-lasting improvements in skin quality, both clinically and at the cellular/histologic level. Chronic wounds usually occur in skin that is compromised by various pathologic factors, and many of the defects found in this ulcer-prone skin are similar to those that have seen improvements after fractional resurfacing. Critical Issues: The mechanisms responsible for the regenerative capacity of fractional resurfacing are mostly unknown, as is how ulcer-prone skin, which is usually afflicted by stressors external to the skin tissue itself, would respond to fractional resurfacing. Future Directions: Better understanding of the cellular and molecular mechanisms underlying the unique healing response to fractional resurfacing could reveal fundamental information about adult tissue regeneration, lead to improvements in current applications, as well as new therapies in other pathologic conditions.

A review of microsampling techniques and their social impact

Conventional skin and blood sampling techniques for disease diagnosis, though effective, are often highly invasive and some even suffer from variations in analysis. With the improvements in molecular detection, the amount of starting sample quantity needed has significantly reduced in some diagnostic procedures, and this has led to an increased interest in microsampling techniques for disease biomarker detection. The miniaturization of sampling platforms driven by microsampling has the potential to shift disease diagnosis and monitoring closer to the point of care. The faster turnaround time for actionable results has improved patient care. The variations in sample quantification and analysis remain a challenge in the microsampling field. The future of microsampling looks promising. Emerging techniques are being clinically tested and monitored by regulatory bodies. This process is leading to safer and more reliable diagnostic platforms. This review discusses the advantages and disadvantages of current skin and blood microsampling techniques.

Keratinocyte sheets prepared with temperature-responsive dishes show enhanced survival after in vivo grafting on acellular dermal matrices in a rat model of staged bi-layered skin reconstruction

Introduction

Bi-layered skin reconstruction can be achieved by staged grafting of acellular dermal matrices (ADMs) and cultured epithelial keratinocyte sheets (KSs). Both KSs and ADMs have been used for long; yet, their combined use has shown poor effectiveness. This outcome has been related to the enzymatic treatment used in the preparation of KSs, which impairs their adhesion potential to ADMs and the formation of a basement membrane (BM). Temperature-responsive (TR) culture dishes allow for enzyme-free preparation of KSs with preservation of BMs and intercellular adhesion proteins; yet, their use has not been previously applied to staged bi-layered skin reconstruction. Using an in vivo rat model, we tested the hypothesis that TR cultures enhance KSs survival and BM preservation after sequential grafting on ADMs.

Methods

In nude rats (n = 9/group), a 9-cm [2] full-thickness dorsal skin defect was repaired with a commercial ADM. At 2 weeks after surgery, we grafted the ADM with KSs (circular, 25 mm diameter), prepared from human cells either by enzymatic Dispase treatment (DT control group) or a TR culture dish (TR experimental group). KSs survival and BMs preservation was assessed one week later by digital imaging, histology (hematoxylin & eosin), immunohistochemistry (collagen IV, pancytokeratins) and immunofluorescence (cytokeratin 1-5-6, laminin).

Results

The TR group showed a significantly higher KSs survival (120 ± 49 vs. 63 ± 42 mm²; p < 0.05) and epidermal thickness (165 ± 79 vs. 65 ± 54 μm; p < 0.01) compared with the control DT group, as well as higher epidermal maturation (cytokeratin) and a denser laminin and Collagen IV expression in the BMs in vitro and in vivo.

Conclusion

These findings suggest that KSs prepared with TR culture dishes have significantly enhanced survival when grafted on ADMs; these outcomes could help improve current clinical strategies in wound care by skin reconstruction.

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 Donor Site Pain After Fractional Autologous Full-Thickness Skin Grafting

Background: Despite the development of numerous wound treatment alternatives, 25% to 50% of leg ulcers and >30% of foot ulcers are not fully healed after 6 months of treatment. Autologous skin grafting is a time-tested therapy for these wounds; however, the creation of a new wound in the donor area yields a considerable limitation to this procedure.

Innovation: Fractional autologous full-thickness skin grafting (FFTSG) is a technique wherein multiple small full-thickness skin grafts (FTSGs) are harvested with possibly minor donor-site comorbidities. The first device used to harvest FFTSG (ART™ system, Medline, Northfield, IL) is a device capable of harvesting >300 small FTSGs and transferring them to a target wound.

Objective: To better evaluate patients' clinical experience, we sought to evaluate pain at the donor site associated with this procedure.

Approach: Pain was assessed with numeric visual analog pain scales at days 1, 2, 4, and 7. Nine subjects underwent this procedure with only six of them reporting any level of pain on day 1, and none disclosing pain after day 2.

Conclusion: In this study, we evidenced that this device manages to harvest FTSGs with minimal associated pain. Future research will need to evaluate other aspects of the procedure as well as long-term outcomes at the donor and recipient areas.

Facial Erosive Pustular Dermatosis After Cosmetic Resurfacing

Importance

Erosive pustular dermatosis (EPD) is a rare condition that typically affects actinically damaged skin of the scalp. Characterized by sterile pustules, erosions, and crusts, EPD is difficult to treat and heals slowly. The exact cause of EPD is unknown, although trauma is an inciting factor.

Objective

To describe 3 women who presented with prolonged facial erosions after cosmetic resurfacing procedures, specifically fully ablative carbon dioxide laser or medium-depth chemical peel.

Design, Setting, and Participants

This case series describes the clinical features, histopathological findings, laboratory results, and treatment of 3 patients with an ultimate diagnosis most consistent with facial EPD. Patients were evaluated between September 10, 2010, and May 6, 2016, in a dermatology clinic in an academic medical center. The patients were 3 women seeking diagnostic evaluation and therapeutic options for nonhealing facial erosions occurring after ablative procedures (carbon dioxide laser resurfacing or Jessner solution/trichloroacetic acid chemical peel).

Main Outcomes and Measures

Histologic examination and wound culture from initial presentation as well as clinical follow-up documenting improvement with therapeutic interventions.

Results

All 3 patients were women in their 50s or 60s for whom EPD was deemed to be the best diagnosis, after infection, immunobullous disorders, and other pustular dermatoses were considered. Histologic features were nonspecific. Treatment included a combination of topical and systemic therapies, such as corticosteroids, dapsone, isotretinoin, and/or antibiotics. Watchful waiting (tincture of time) appeared to be central to the healing process.

Conclusions and Relevance

After cosmetic resurfacing, patients may develop EPD isolated to the face. As a diagnosis of exclusion that should be considered in patients who have nonhealing wounds following ablative procedures, EPD is challenging to treat and may require the use of anti-inflammatory agents. Recognizing this condition is important, especially as cosmetic procedures become more widespread.

Reconstitution of full-thickness skin by microcolumn grafting

In addition to providing a physical barrier, skin also serves a diverse range of physiological functions through different specialized resident cell types/structures, including melanocytes (pigmentation and protection against ultraviolet radiation), Langerhans cells (adaptive immunity), fibroblasts (maintaining extracellular matrix, paracrine regulation of keratinocytes), sweat glands (thermoregulation) and hair follicles (hair growth, sensation and a stem cell reservoir). Restoration of these functional elements has been a long-standing challenge in efforts to engineer skin tissue, while autologous skin grafting is limited by the scarcity of donor site skin and morbidity caused by skin harvesting. We demonstrate an alternative approach of harvesting and then implanting μm-scale, full-thickness columns of human skin tissue, which can be removed from a donor site with minimal morbidity and no scarring. Fresh human skin microcolumns were used to reconstitute skin in wounds on immunodeficient mice. The restored skin recapitulated many key features of normal human skin tissue, including epidermal architecture, diverse skin cell populations, adnexal structures and sweat production in response to cholinergic stimulation. These promising preclinical results suggest that harvesting and grafting of microcolumns may be useful for reconstituting fully functional skin in human wounds, without donor site morbidity. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.