On the Reliability of Suction Measurements for Skin Characterization.

in vivo skin characterization methods were shown to be useful in the detection of microstructural alterations of the dermis due to skin diseases. Specifically, the diagnostic potential of skin suction has been widely explored, yet measurement uncertainties prevented so far its application in clinical assessment. In this work, we analyze specific factors influencing the reliability of suction measurements. We recently proposed a novel suction device, called Nimble, addressing the limitations of existing instruments, and applied it in clinical trials quantifying mechanical differences between healthy skin and scars. Measurements were performed with the commercial device Cutometer and with the new device. A set of new suction measurements was carried out on scar tissue and healthy skin, and FE-based inverse analysis was applied to determine corresponding parameters of a hyperelastic-viscoelastic material model. FE simulations were used to rationalize differences between suction protocols and to analyze specific factors influencing the measurement procedure. Tissue stiffness obtained from Cutometer measurements was significantly higher compared to the one from Nimble measurements, which was shown to be associated with the higher deformation levels in the Cutometer and the nonlinear mechanical response of skin. The effect of the contact force exerted on skin during suction measurements was quantified, along with an analysis of the effectiveness of a corresponding correction procedure. Parametric studies demonstrated the inherently higher sensitivity of displacement- over load-controlled suction measurements, thus rationalizing the superior ability of the Nimble to distinguish between tissues.

Preventive intervention for trauma reactions in young injured children: results of a multi-site randomised controlled trial.

BACKGROUND: Young children are at particular risk for injury. Ten per cent to twenty-five per cent develop posttraumatic stress disorder (PTSD). However, no empirically supported preventive interventions exist. Therefore, this study evaluated the efficacy of a standardised targeted preventive intervention for PTSD in young injured children. METHODS: Injured children (1-6 years) were enrolled in a multi-site parallel-group superiority prospective randomised controlled trial (RCT) in Australia and Switzerland. Screening for PTSD risk occurred 6-8 days postaccident. Parents of children who screened 'high-risk' were randomised to a 2-session CBT-based intervention or treatment-as-usual (TAU). Primary outcomes were PTSD symptom (PTSS) severity, and secondary outcomes were PTSD diagnosis, functional impairment and behavioural difficulties at 3 and 6 months postinjury using blinded assessments. Trials were registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000325606) and ClinicalTrials.gov (NCT02088814). Trial status is complete. RESULTS: One hundred and thirty-three children screened 'high-risk' were assigned to intervention (n = 62) or TAU (n = 71). Multilevel intention-to-treat analyses revealed a significant intervention effect on PTSS severity over time (b = 60.06, 95% CI: 21.30-98.56). At 3 months, intervention children (M = 11.02, SD = 10.42, range 0-47) showed an accelerated reduction in PTSS severity scores compared to control children (M = 17.30, SD = 13.94, range 0-52; mean difference -6.97, 95% CI: -14.02 to 0.08, p adj. = .055, d = 0.51). On secondary outcomes, multilevel analyses revealed significant treatment effects for PTSD diagnosis, functional impairment and behavioural difficulties. CONCLUSIONS: This multi-site RCT provides promising preliminary evidence for the efficacy of a targeted preventive intervention for accelerating recovery from PTSS in young injured children. This has important clinical implications for the psychological support provided to young children and parents during the acute period following a single-event trauma.

Negative pressure wound treatment in a neonate with epidermolysis bullosa simplex severe generalized: A case report.

Negative pressure wound treatment (NPWT) is very useful for the treatment of chronic or deep wounds and in the setting of skin grafting. Due to the need for adhesive dressings, this treatment is rarely attempted in patients with skin fragility secondary to hereditary epidermolysis bullosa (EB). We present a neonate with EB simplex, severe generalized in a critical clinical state where NPWT was successfully applied and describe the measures taken to avoid any further skin damage. This case is of clinical importance to physicians and health care staff treating patients with this rare disease where additional therapeutic measures for the treatment of chronic wounds are scarce.

Patient- and Physician-Reported Outcome of Combined Fractional CO2 and Pulse Dye Laser Treatment for Hypertrophic Scars in Children.

BACKGROUND: Hypertrophic scars are commonly seen in children and associated with pruritus, pain, functional impairment, and aesthetic disfigurement. Ablative fractional CO2 and pulse dye laser are emerging techniques to improve scar quality. Only limited data are available on children, nonburn scars, and patient-reported outcome. We aimed to investigate safety and outcome of repeated laser therapy for hypertrophic scars originating from burns and other conditions by means of patient- and physician-reported outcome measures. METHODS: This was a retrospective before-after analysis of laser treatments in children with hypertrophic scars. Outcome was measured using Patient and Observer Scar Assessment Scale, Vancouver Scar Scale and Itch Man Scale. With respect to safety, laser- and anesthesia-related complications were analyzed. RESULTS: Seventeen patients, aged 11.37 ± 4.82 years with 27 scars, underwent 102 distinct laser treatments, mainly combined CO2 and pulse dye laser (94%), with few CO2 only (6%). Vancouver Scar Scale total score before the first and after the first session decreased significantly from 7.65 ± 2.12 to 4.88 ± 1.73; Patient and Observer Scar Assessment Scale observer overall opinion also dropped from 5.88 ± 1.57 to 4.25 ± 1.70. Pruritus improved significantly. Patient age and timing of laser intervention did not have an impact on treatment response. Complications related to laser treatment were seen in 2% (wound infection, n = 2) and to anesthesia in 4% (insignificant n = 2, minor n = 1). CONCLUSIONS: Combined laser therapy significantly improves quality, pain, and pruritus of hypertrophic scars in children. When provided by experienced laser and anesthesia teams, it is safe with a low rate of complications.

Surgical treatment of children and youth with congenital melanocytic nevi: self- and proxy-reported opinions.

PURPOSE: The role of surgery in the management of congenital melanocytic nevi (CMN) is controversial. Data on surgical outcomes and predictors of satisfaction remain scarce. METHODS: An online survey was employed following worldwide recruitment of youth aged 14-25 years (n = 44) and parents of children ≤ 18 years (n = 249) with CMN to query patterns of treatment and satisfaction with and opinions about the benefits of surgery. RESULTS: In proxy-reports, 121 of 249 (49%) and in self-reports 30 of 44 (75%) participants underwent CMN excision. The most common reasons for surgery were psychosocial determinants, aesthetic improvement, and melanoma risk reduction. The overall satisfaction with surgical management was good, although no predictors for satisfaction could be identified. Higher current age of the child was found to predict decision regret in proxy-reports. Most participants indicated that having a scar is more socially acceptable than a CMN. Opinions differed on whether surgery should be deferred until the child is old enough to be involved in the decision-making process. CONCLUSIONS: Whether and when to perform surgery in children with CMN is a multifaceted question. Awareness of common concerns as well as risks and benefits of surgery are essential to ensure critical reflection and balanced decision-making.

Predictors of Health-related Quality of Life and Psychological Adjustment in Children and Adolescents With Congenital Melanocytic Nevi: Analysis of Parent Reports.

Objectives This cross-sectional study assessed health-related quality of life (HRQOL) and psychological adjustment in children and adolescents affected by congenital melanocytic nevi (CMN) and identified potential predictors of adjustment. Methods Participants were recruited worldwide with the help of patient organizations. Data were obtained from parents of 235 children affected by CMN, aged between 1 month and 18 years (M = 6.3 y; SD = 5.0 y), using a web-based survey. Measures included the Pediatric Quality of Life InventoryTM 4.0 and the Strengths and Difficulties Questionnaire. Sample scores were compared to normative data. Demographic characteristics as well as CMN-related variables were examined as possible predictors of outcome, using multivariate analyses. Results Parents of children and adolescents born with a CMN reported significantly lower HRQOL and somewhat higher emotional and behavioral problems compared to community norms. Impairments in HRQOL and psychological adjustment were predicted by lower socioeconomic status, neurological problems, skin-related discomfort (e.g., itch or pain), and perceived stigmatization. The size of the CMN and whether or not the CMN had been (partially) removed by surgery were no significant predictors. The relationship between visibility of the skin lesion and psychological adjustment and psychosocial health was found to be mediated by perceived stigmatization. Conclusions In children and adolescents affected by CMN, those experiencing neurological problems, skin-related discomfort or high levels of perceived stigmatization are particularly vulnerable for impaired HRQOL and psychological maladjustment and therefore might need special monitoring and support.

Multidisciplinary long-term care and modern surgical treatment of congenital melanocytic nevi - recommendations by the CMN surgery network.

In recent years, our knowledge of congenital melanocytic nevi (CMN) has greatly expanded. This has led to a paradigm shift. The present article represents a commentary by an interdisciplinary group of physicians from German-speaking countries with extensive experience in long-term care and surgical treatment of children and adults with CMN (CMN surgery network, "Netzwerk Nävuschirurgie", NNC). The authors address aspects such as the indication for treatment as well as treatment planning and implementation under these new premises. Adequate counseling of parents on conservative and/or surgical management requires an interdisciplinary exchange among physicians and individualized planning of the intervention, which frequently involves a multi-stage procedure. Today, the long-term aesthetic outcome is at the center of any therapeutic endeavor, whereas melanoma prevention plays only a minor role. The premise of "removal at any cost" no longer holds. Potential treatment-related adverse effects (hospitalization, wound healing disorders, and others) must be carefully weighed against the prospects of a beneficial outcome. In this context, the use of dermabrasion in particular must be critically evaluated. At a meeting of the NNC in September 2018, its members agreed on a consensus-based position on dermabrasion, stating that the procedure frequently leads to impaired wound healing and cosmetically unfavorable or hypertrophic scarring. Moreover, dermabrasion is considered to be commonly associated with considerable repigmentation that usually occurs a number of years after the procedure. In addition, the NNC members saw no benefit in terms of melanoma prevention. In the future, physicians should therefore thoroughly caution about the potential risks and often limited cosmetic benefits of dermabrasion.

Topical Timolol for Infantile Hemangiomas: Evidence for Efficacy and Degree of Systemic Absorption.

BACKGROUND: Topical use of timolol for infantile hemangiomas has recently emerged with promising results. It is unknown whether topical ß-blockers act locally or if their effect is partly due to systemic absorption. This study investigates whether topically applied timolol is absorbed and reports on the efficacy of this treatment. METHODS: We treated 40 infants with small proliferating hemangiomas with topical timolol gel 0.5% twice daily and assessed urinary excretion and serum levels in a proportion of patients. Clinical response was evaluated on a visual analog scale of standardized photographs after 1, 2, 3, and 5 months. RESULTS: Forty infants with a median age of 18 weeks (range 2-35 wks) were included; 23 (58%) had superficial and 17 (42%) mixed-type hemangiomas. The median size was 3 cm(2) (range 0.1-15 cm(2) ) and nine hemangiomas were ulcerated. The hemangiomas improved significantly during treatment, with a median increase in visual analog scale of 7 points after 5 months (p < 0.001). Urinalysis for timolol was performed in 24 patients and was positive in 20 patients (83%). In three infants, serum levels of timolol were also measured and were all positive (median 0.16 ng/mL [range 0.1-0.18 ng/mL]). No significant side effects were recorded. CONCLUSION: Topical therapy with timolol is effective for infantile hemangiomas, but systemic absorption occurs. Serum levels in our patients were low, suggesting that using timolol for small hemangiomas is safe, but caution is advised when treating ulcerated or large hemangiomas, very young infants, or concomitantly using systemic propranolol.

Characterization of pigmented dermo-epidermal skin substitutes in a long-term in vivo assay.

In our laboratory, we have been using human pigmented dermo-epidermal skin substitutes for short-term experiments since several years. Little is known, however, about the long-term biology of such constructs after transplantation. We constructed human, melanocyte-containing dermo-epidermal skin substitutes of different (light and dark) pigmentation types and studied them in a long-term animal experiment. Developmental and maturational stages of the epidermal and dermal compartment as well as signs of homoeostasis were analysed 15 weeks after transplantation. Keratinocytes, melanocytes and fibroblasts from human skin biopsies were isolated and assembled into dermo-epidermal skin substitutes. These were transplanted onto immuno-incompetent rats and investigated 15 weeks after transplantation. Chromameter evaluation showed a consistent skin colour between 3 and 4 months after transplantation. Melanocytes resided in the epidermal basal layer in physiological numbers and melanin accumulated in keratinocytes in a supranuclear position. Skin substitutes showed a mature epidermis in a homoeostatic state and the presence of dermal components such as Fibrillin and Tropoelastin suggested advanced maturation. Overall, pigmented dermo-epidermal skin substitutes show a promising development towards achieving near-normal skin characteristics and epidermal and dermal tissue homoeostasis. In particular, melanocytes function correctly over several months whilst remaining in a physiological, epidermal position and yield a pigmentation resembling original donor skin colour.

Long-term expression pattern of melanocyte markers in light- and dark-pigmented dermo-epidermal cultured human skin substitutes.

PURPOSE: Transplantation of pigmented tissue-engineered human autologous skin substitutes represents a promising procedure to cover skin defects. We have already demonstrated that we can restore the patient's native light or dark skin color by adding melanocytes to our dermo-epidermal skin analogs. In this long-term study, we investigated if melanocytes in our skin substitutes continue to express markers as BCL2, SOX9, and MITF, known to be involved in survival, differentiation, and function of melanocytes. METHODS: Human epidermal melanocytes and keratinocytes, as well as dermal fibroblasts from light- and dark-pigmented skin biopsies were isolated and cultured. Bovine collagen hydrogels containing fibroblasts were prepared, and melanocytes and keratinocytes were seeded in a 1:5 ratio onto the gels. Pigmented dermo-epidermal skin substitutes were transplanted onto full-thickness wounds of immuno-incompetent rats and analyzed for the expression of melanocyte markers after 15 weeks. RESULTS: Employing immunofluorescence staining techniques, we observed that our light and dark dermo-epidermal skin substitutes expressed the same typical melanocyte markers including BCL2, SOX9, and MITF 15 weeks after transplantation as normal human light and dark skin. CONCLUSIONS: These data suggest that, even in the long run, our light and dark dermo-epidermal tissue-engineered skin substitutes contain melanocytes that display a characteristic expression pattern as seen in normal pigmented human skin. These findings have crucial clinical implications as such grafts transplanted onto patients should warrant physiological numbers, distribution, and function of melanocytes.

Tissue-engineered dermo-epidermal skin analogs exhibit de novo formation of a near natural neurovascular link 10 weeks after transplantation.

PURPOSE: Human autologous tissue-engineered skin grafts are a promising way to cover skin defects. Clearly, it is mandatory to study essential biological dynamics after transplantation, including reinnervation. Previously, we have already shown that human tissue-engineered skin analogs are reinnervated by host nerve fibers as early as 8 weeks after transplantation. In this study, we tested the hypothesis that there is a de novo formation of a "classical" neurovascular link in tissue-engineered and then transplanted skin substitutes. METHODS: Keratinocytes, melanocytes, and fibroblasts were isolated from human skin biopsies. After expansion in culture, keratinocytes and melanocytes were seeded on dermal fibroblast-containing collagen type I hydrogels. These human tissue-engineered dermo-epidermal skin analogs were transplanted onto full-thickness skin wounds on the back of immuno-incompetent rats. Grafts were analyzed after 3 and 10 weeks. Histological sections were examined with regard to the ingrowth pattern of myelinated and unmyelinated nerve fibers into the skin analogs using markers such as PGP9.5, NF-200, and NF-160. Blood vessels were identified with CD31, lymphatic vessels with Lyve1. In particular, we focused on alignment patterns between nerve fibers and either blood and/or lymphatic vessels with regard to neurovascular link formation. RESULTS: 3 weeks after transplantation, blood vessels, but no nerve fibers or lymphatic vessels could be observed. 10 weeks after transplantation, we could detect an ingrowth of myelinated and unmyelinated nerve fibers into the skin analogs. Nerve fibers were found in close proximity to CD31-positive blood vessels, but not alongside Lyve1-positive lymphatic vessels. CONCLUSION: These data suggest that host-derived innervation of tissue-engineered dermo-epidermal skin analogs is initiated by and guided alongside blood vessels present early post-transplantation. This observation is consistent with the concept of a cross talk between neurovascular structures, known as the neurovascular link.

Analysis of blood and lymph vascularization patterns in tissue-engineered human dermo-epidermal skin analogs of different pigmentation.

PURPOSE: Bioengineered dermo-epidermal skin analogs containing melanocytes represent a promising approach to cover large skin defects including restoration of the patient's own skin color. So far, little is known about the development of blood and lymphatic vessels in pigmented skin analogs after transplantation. In this experimental study, we analyzed the advancement and differences of host blood and lymphatic vessel ingrowth into light- and dark-pigmented human tissue-engineered skin analogs in a rat model. METHODS: Keratinocytes, melanocytes, and fibroblasts from light- and dark-pigmented skin biopsies were isolated, cultured, and expanded. For each donor, melanocytes and keratinocytes were seeded in ratios of 1:1, 1:5, and 1:10 onto fibroblast-containing collagen gels. The skin analogs were subsequently transplanted onto full-thickness wounds of immuno-incompetent rats and quantitatively analyzed for vascular and lymphatic vessel density after 8 and 15 weeks. RESULTS: The skin analogs revealed a significant difference in vascularization patterns between light- and dark-pigmented constructs after 8 weeks, with a higher amount of blood vessels in light compared to dark skin. In contrast, no obvious difference could be detected within the light- and dark-pigmented group when varying melanocyte/keratinocyte ratios were used. However, after 15 weeks, the aforementioned difference in blood vessel density between light and dark constructs could no longer be detected. Regarding lymphatic vessels, light and dark analogs showed similar vessel density after 8 and 15 weeks, while there were generally less lymphatic than blood vessels. CONCLUSION: These data suggest that, at least during early skin maturation, keratinocytes, melanocytes, and fibroblasts from different skin color types used to construct pigmented dermo-epidermal skin analogs have distinct influences on the host tissue after transplantation. We speculate that different VEGF expression patterns might be involved in this disparate revascularization pattern observed.

Tissue engineering of skin: human tonsil-derived mesenchymal cells can function as dermal fibroblasts.

PURPOSE: It is unclear whether dermal fibroblasts are indispensable key players for tissue engineering of dermo-epidermal skin analogs. In this experimental study, we wanted to test the hypothesis that tonsil-derived mesenchymal cells can assume the role of dermal fibroblasts when culturing pigmented skin analogs for transplantation. METHODS: Mesenchymal cells from excised tonsils and keratinocytes, melanocytes, and fibroblasts from skin biopsies were isolated, cultured, and expanded. Melanocytes and keratinocytes were seeded in a ratio of 1:5 onto collagen gels previously populated either with tonsil-derived mesenchymal cells or with autologous dermal fibroblasts. These laboratory engineered skin analogs were then transplanted onto full-thickness wounds of immuno-incompetent rats and analyzed after 3 weeks with regard to macroscopic and microscopic epidermal characteristics. RESULTS: The skin analogs containing tonsil-derived mesenchymal cells showed the same macroscopic appearance as the ones containing dermal fibroblasts. Histologically, features of epidermal stratification, pigmentation, and cornification were identical to those of the controls assembled with autologous dermal fibroblasts. Transmission electron microscopy confirmed these findings. CONCLUSION: These data suggest that human tonsil-derived mesenchymal cells can assume dermal fibroblast functions, indicating that possibly various types of mesenchymal cells can successfully be employed for "skingineering" purposes. This aspect may have clinical implications when sources for dermal fibroblasts are scarce.

As time goes by - Overlooking 40 years of inpatient burn treatment at a national pediatric burn center in Switzerland.

BACKGROUND: Despite extensive prevention programs, burns remain a frequent cause of injury in Switzerland with a known age peak in children. Pediatric burns may cause substantial morbidity, a psyochological burden and therapy related high economic costs. To improve preventive measures, precise knowledge of etiology and treatment of pediatric burns in Switzerland as well as their temporal evolution is indispensable. METHODS: The present retrospective analysis included pediatric burn patients admitted for acute treatment to the Pediatric Burn Center of the University Children`s Hospital Zurich over the last four decades. Sociodemographic, injury related, and treatment related data were extracted from medical records. Linear regression analysis was applied to determine temporal changes during the past four decades and chi-square and t-tests were applied wherever applicable. RESULTS: A total of 3425 acute burn patients were included in the study between 1977 and 2020, corresponding to a mean of 89 patients/year. Mean age was 3.60 ± 4.12 years, three quarters of all patients were preschool children (0-5 years) and mean total body surface area (TBSA) burned was 8.01% ± 9.57%, however only around one fifth had severe burns (>10% TBSA). Scald burns (65.31%) and flame burns (32.99%) were most commonly seen. Linear regression analysis showed the total number of thermal injuries treated at our center to have increased significantly as of 2004 (p < 0.001). Separate analysis showed the same for small and medium (<10% TBSA) burns (p < 0.001), whereas the number of severe burns did not increase significantly. Length of stay (LOS) was highly associated with %TBSA burned. The percentage of female patients amongst all patients increased over time (p = 0.012). LOS per TBSA burned decreased significantly (p < 0.001). CONCLUSION: The present data show pediatric burns to remain a major health burden in Switzerland, especially small and medium burns in preschool children. Prevention programs should focus on this age population as well as on scald and flame burns as most common etiologies. The observed decrease in length of stay suggests a major improvement in overall quality of care in pediatric burns and supports centralization of care.

Stigmatization predicts psychological adjustment and quality of life in children and adolescents with a facial difference.

OBJECTIVES: This cross-sectional study assessed psychological adjustment and health-related quality of life (HRQOL) in children and adolescents with congenital or acquired facial differences and identified potential predictors of adjustment. METHODS: Data were obtained from 88 children, ages 9 months to 16 years, by means of parent questionnaires (n = 86) and standardized interviews with children ≥7 years old (n = 31). Evaluation measures included the Child Behavior Checklist (CBCL), KIDSCREEN-27, TNO-AZL Preschool Quality of Life Questionnaire (TAPQOL), and Perceived Stigmatization Questionnaire. RESULTS: Psychological adjustment, as measured by the CBCL, was within norms. Parent-reported HRQOL was good in preschool children. Parent- and self-reported HRQOL of participants 7-16 years old was impaired in several dimensions, including psychological well-being. Psychological adjustment (especially internalizing behavior problems) and HRQOL were predicted primarily by perceived stigmatization. CONCLUSIONS: Identification of stigma experiences and appropriate support may be crucial to enhancing psychological adjustment and quality of life in children with facial disfigurement.

Dermatofibrosarcoma protuberans in childhood treated with slow Mohs micrographic surgery.

Dermatofibrosarcoma protuberans (DFSP) in childhood is a rare tumor with high recurrence rates. Wide local excision can result in disfiguring mutilation, whereas Mohs micrographic surgery (MMS) reduces surgical margins. MMS in children is not performed routinely, as the required infrastructures such as a histopathology lab in close proximity to the operating room is often lacking. We retrospectively reviewed children diagnosed with DFSP treated at our hospital over 2 years. We recorded surgical treatment details, including margins, duration of inpatient stay, outcome, follow-up, and molecular genetic tumor tissue analysis. Four children with a median age of 6.8 years (range 6.0-8.8 years) were identified who had a diagnostic delay of a median of 2.5 years (range 0.5-4.0 years); all underwent complete tumor excision using the slow MMS technique using vacuum-assisted closure systems between repeated excisions and before wound closure. The median maximal safety margins were 1.5 cm (range 1.0-3.0 cm). By using vacuum-assisted closure systems, no dressing changes were needed, pain was limited, and full mobility was maintained in all children. The median total time in the hospital was 11 days (range 10-14 days). No relapses occurred during a median follow-up of 25.8 months (range 11.3-32.6 months). Collagen 1A1/platelet-derived growth factor B (COL1A1/PDGFB) translocation on chromosomes 17 and 22 was detected in all three analyzable specimens. Lesions suspected of being DFSP warrant prompt histologic evaluation; interdisciplinary management is mandatory in particular for children. Micrographic surgery allows smaller surgical margins than wide excision and should be considered as the treatment of choice in children with DFSP. The interim usage of vacuum-assisted closure systems increases patient comfort. Translocations in the COL1A1/PDGFB gene imply susceptibility to targeted treatment modalities for therapy-resistant cases.

"Trooping the color": restoring the original donor skin color by addition of melanocytes to bioengineered skin analogs.

PURPOSE: Autologous skin substitutes to cover large skin defects are used since several years. Melanocytes, although essential for solar protection and pigmentation of skin, are not yet systematically added to such substitutes. In this experimental study, we reconstructed melanocyte-containing dermo-epidermal skin substitutes from donor skins of different skin pigmentation types and studied them in an animal model. Features pertinent to skin color were analyzed and compared in both skin substitutes and original donor skin. METHODS: Keratinocytes, melanocytes, and fibroblast were isolated, cultured, and expanded from skin biopsies of light- and dark-pigmented patients. For each donor, melanocytes and keratinocytes were seeded in different ratios (1:1, 1:5, 1:10) onto collagen gels previously populated with autologous fibroblasts. Skin substitutes were then transplanted onto full-thickness wounds of immuno-incompetent rats. After 8 weeks, macroscopic and microscopic analyses were conducted with regard to skin color and architecture. RESULTS: Chromameter evaluation revealed that skin color of reconstructed light- and dark-pigmented skin was very similar to donor skin, independent of which melanocyte/keratinocyte ratio was added. Histological analyses of the skin analogs confirmed these findings. CONCLUSION: These data suggest that adding autologous melanocytes to bioengineered dermo-epidermal skin analogs can sustainably restore the patients' native skin color.

Rebuild, restore, reinnervate: do human tissue engineered dermo-epidermal skin analogs attract host nerve fibers for innervation?

PURPOSE: Tissue engineered skin substitutes are a promising tool to cover large skin defects, but little is known about reinnervation of transplants. In this experimental study, we analyzed the ingrowth of host peripheral nerve fibers into human tissue engineered dermo-epidermal skin substitutes in a rat model. Using varying cell types in the epidermal compartment, we wanted to assess the influence of epidermal cell types on reinnervation of the substitute. METHODS: We isolated keratinocytes, melanocytes, fibroblasts, and eccrine sweat gland cells from human skin biopsies. After expansion, epidermal cells were seeded on human dermal fibroblast-containing collagen type I hydrogels as follows: (1) keratinocytes only, (2) keratinocytes with melanocytes, (3) sweat gland cells. These substitutes were transplanted into full-thickness skin wounds on the back of immuno-incompetent rats and were analyzed after 3 and 8 weeks. Histological sections were examined with regard to myelinated and unmyelinated nerve fiber ingrowth using markers such as PGP9.5, NF-200, and NF-145. RESULTS: After 3 weeks, the skin substitutes of all three epidermal cell variants showed no neuronal ingrowth from the host into the transplant. After 8 weeks, we could detect an innervation of all three types of skin substitutes. However, the nerve fibers were restricted to the dermal compartment and we could not find any unmyelinated fibers in the epidermis. Furthermore, there was no distinct difference between the constructs resulting from the different cell types used to generate an epidermis. CONCLUSION: Our human tissue engineered dermo-epidermal skin substitutes demonstrate a host-derived innervation of the dermal compartment as early as 8 weeks after transplantation. Thus, our substitutes apparently have the capacity to attract nerve fibers from adjacent host tissues, which also grow into grafts and thereby potentially restore skin sensitivity.

Matriderm® 1 mm versus Integra® Single Layer 1.3 mm for one-step closure of full thickness skin defects: a comparative experimental study in rats.

PURPOSE: Dermal templates, such as Matriderm® and Integra®, are widely used in plastic and reconstructive surgery, often as two-step procedures. A recent development is the application of thin dermal templates covered with split thickness skin grafts in one-step procedures. In this experimental study, we compare the two thin matrices Matriderm® 1 mm and Integra® Single Layer in a one-step procedure with particular focus on neodermis formation. METHODS: Matriderm® 1 mm and Integra® Dermal Regeneration Template-Single Layer (1.3 mm) were compared in a rat model. In three groups of five animals each, a full thickness wound was covered with (a) Matriderm® 1 mm and neonatal rat epidermis, (b) Integra® Single Layer and neonatal rat epidermis, or, (c) neonatal rat epidermis only (control). Histological sections 2 weeks post transplantation were analyzed with regard to take of template and epidermis, neodermal thickness, collagen deposition, vascularization, and inflammatory response. RESULTS: Take of both templates was complete in all animals. The Matriderm®-based neodermis was thinner but showed a higher cell density than the Integra®-based neodermis. The other parameters were similar in both matrices. CONCLUSION: The two templates demonstrate a comparable biological behavior early after transplantation. The only difference was found regarding neodermal thickness, probably resulting from faster degradation of Matriderm®. These preliminary data suggest that both dermal templates appear similarly suitable for transplantation in a one-step procedure.