Correlation Between the Warrior/Worrier Gene on Post Burn Pruritus and Scarring: A Prospective Cohort Study.

INTRODUCTION: Associations between genetic variation and clinical conditions suggest that single nucleotide polymorphisms (SNPs) might correlate with postburn outcomes. COMT modulates catecholamine metabolism, and polymorphisms within the rs4680 allele result in variable enzyme activity. Catechol-amines are known to modulate the inflammatory process and may affect scar formation. The aim of this study was to determine whether variants in the rs4680 SNP of the COMT gene are associated with post-burn pruritus and scarring. METHODS: Adult burn patients, admitted between 2007 and 2017, with deep partial-thickness burns or delayed healing provided blood samples for genotyp-ing and self-reported itch scores within 1 year of injury. Scarring was measured using the Vancouver Scar Scale (VSS). Itch scores ≥ 4 and VSS scores >7 were considered severe. Genomic deoxyribonucleic acid was genotyped for the rs4680 SNP using realtime polymerase chain reaction (PCR). RESULTS: Median itch and VSS scores were highest for GG homozygotes and lowest for AA homozygotes. This difference was statistically significant for VSS score (P < 0.0001) and approached significance for itch (P = 0.052). After accounting for confounding variables, including race/ethnicity, age, sex, and burn size, the GG homozygotes demonstrated worse scarring (odds ratio 1.88, P = 0.005) compared to AG heterozygotes whereas the AA homozygotes trended towards a protective effect against scarring (odds ratio 0.71, P = 0.10). itch did not demonstrate a statistically significant difference between rs4680 genotype. CONCLUSIONS: Our analysis identifies a trend between COMT genotype with scarring, with rs4680 genetic variation constituting an independent risk factor for VSS score.

MC1R gene polymorphisms are associated with dysfunctional immune responses and wound infection after burn injury.

BACKGROUND: Systemic inflammatory response syndrome (SIRS) is associated with organ failure and infectious complications after major burn injury. Recent evidence has linked melanocortin signaling to anti-inflammatory and wound-repair functions, with mutations in the melanocortin 1 receptor (MC1R) gene leading to increased inflammatory responses. Our group has previously demonstrated that MC1R gene polymorphisms are associated with postburn hypertrophic scarring. Thus, we hypothesized that MC1R single nucleotide polymorphisms (SNPs) would be associated with increased burn-induced SIRS and increased infectious complications. METHODS: We performed a retrospective cohort study of adults (>18 y of age) admitted to our burn center with >20% total body surface area (TBSA) partial/full thickness burns between 2006 and 2013. We screened for five MC1R SNPs (V60L, V92M, R151C, R163Q, T314T) by polymerase chain reaction from genomic DNA isolated from blood samples. We performed a detailed review of each patient chart to identify age, sex, race, ethnicity, %TBSA burned, burn wound infections (BWIs), and 72-hr intravenous fluid volume, the latter a surrogate for a dysfunctional inflammatory response to injury. Association testing was based on multivariable regression. RESULTS: Of 106 subjects enrolled, 82 had complete data for analysis. Of these, 64 (78%) were male, with a median age of 39 and median burn size of 30% TBSA. A total of 36 (44%) subjects developed BWIs. The median total administered IV crystalloid in first 72h was 24.6 L. In multivariate analysis, the R151C variant allele was a significant independent risk factor for BWI (adjusted prevalence ratio 2.03; 95% CI: 1.21-3.39; P = 0.007), and the V60L variant allele was independently associated with increased resuscitation fluid volume (P = 0.021). CONCLUSIONS: This is the first study to demonstrate a significant association between genetic polymorphisms and a nonfatal burn-induced SIRS complication. Our findings suggest that MC1R polymorphisms contribute to dysfunctional responses to burn injury that may predict infectious and inflammatory complications.

Genome-wide Association Study of Postburn Scarring Identifies a Novel Protective Variant.

OBJECTIVE: To identify genetic variants associated with the severity of postburn hypertrophic scarring (HTS) using a genome-wide approach. BACKGROUND: Risk of severe postburn HTS is known to depend on race, but the genetic determinants of HTS are unknown. METHODS: We conducted a genome-wide association study (GWAS) in a prospective cohort of adults admitted with deep-partial-thickness burns from 2007 through 2014. Scar severity was assessed over time using the Vancouver Scar Scale (VSS), and DNA was genotyped with a >500,000-marker array. We performed association testing of single-nucleotide polymorphisms (SNPs) with minor allele frequency (MAF) >0.01 using linear regression of VSS height score on genotype adjusted for patient and injury characteristics as well as population genetic structure. Array-wide significance was based on Bonferroni correction for multiple testing. RESULTS: Of 538 patients (median age 40 years, median burn size 6.0% of body surface area), 71% were men and 76% were White. The mean VSS height score was 1.2 (range: 0-3). Of 289,639 SNPs tested, a variant in the CUB and Sushi multiple domains 1 (CSMD1) gene (rs11136645; MAF = 0.49), was significantly associated with decreased scar height (regression coefficient = -0.23, P = 7.9 × 10). CONCLUSIONS: In the first published GWAS of HTS, we report that a common intronic variant in the CSMD1 gene is associated with reduced severity of postburn HTS. If this association is confirmed in an independent cohort, investigating the potential role of CSMD1 in wound healing may elucidate HTS pathophysiology.

Targeted metabolic profiling of wounds in diabetic and nondiabetic mice.

While cellular metabolism is known to regulate a number of key biological processes such as cell growth and proliferation, its role in wound healing is unknown. We hypothesized that cutaneous injury would induce significant metabolic changes and that the impaired wound healing seen in diabetes would be associated with a dysfunctional metabolic response to injury. We used a targeted metabolomics approach to characterize the metabolic profile of uninjured skin and full-thickness wounds at day 7 postinjury in nondiabetic (db/-) and diabetic (db/db) mice. By liquid chromatography mass spectrometry, we identified 129 metabolites among all tissue samples. Principal component analysis demonstrated that uninjured skin and wounds have distinct metabolic profiles and that diabetes alters the metabolic profile of both uninjured skin and wounds. Examining individual metabolites, we identified 62 with a significantly altered response to injury in the diabetic mice, with many of these, including glycine, kynurenate, and OH-phenylpyruvate, implicated in wound healing for the first time. Thus, we report the first comprehensive analysis of wound metabolic profiles, and our results highlight the potential for metabolomics to identify novel biomarkers and therapeutic targets for improved wound healing outcomes.

Minimum information and guidelines for reporting a multiplexed assay of variant effect.

Multiplexed assays of variant effect (MAVEs) have emerged as a powerful approach for interrogating thousands of genetic variants in a single experiment. The flexibility and widespread adoption of these techniques across diverse disciplines have led to a heterogeneous mix of data formats and descriptions, which complicates the downstream use of the resulting datasets. To address these issues and promote reproducibility and reuse of MAVE data, we define a set of minimum information standards for MAVE data and metadata and outline a controlled vocabulary aligned with established biomedical ontologies for describing these experimental designs.

Guidelines for releasing a variant effect predictor.

Computational methods for assessing the likely impacts of mutations, known as variant effect predictors (VEPs), are widely used in the assessment and interpretation of human genetic variation, as well as in other applications like protein engineering. Many different VEPs have been released to date, and there is tremendous variability in their underlying algorithms and outputs, and in the ways in which the methodologies and predictions are shared. This leads to considerable challenges for end users in knowing which VEPs to use and how to use them. Here, to address these issues, we provide guidelines and recommendations for the release of novel VEPs. Emphasising open-source availability, transparent methodologies, clear variant effect score interpretations, standardised scales, accessible predictions, and rigorous training data disclosure, we aim to improve the usability and interpretability of VEPs, and promote their integration into analysis and evaluation pipelines. We also provide a large, categorised list of currently available VEPs, aiming to facilitate the discovery and encourage the usage of novel methods within the scientific community.

Defining and Reducing Variant Classification Disparities.

Background: Multiplexed Assays of Variant Effects (MAVEs) can test all possible single variants in a gene of interest. The resulting saturation-style data may help resolve variant classification disparities between populations, especially for variants of uncertain significance (VUS). Methods: We analyzed clinical significance classifications in 213,663 individuals of European-like genetic ancestry versus 206,975 individuals of non-European-like genetic ancestry from All of Us and the Genome Aggregation Database. Then, we incorporated clinically calibrated MAVE data into the Clinical Genome Resource's Variant Curation Expert Panel rules to automate VUS reclassification for BRCA1, TP53, and PTEN . Results: Using two orthogonal statistical approaches, we show a higher prevalence ( p ≤5.95e-06) of VUS in individuals of non-European-like genetic ancestry across all medical specialties assessed in all three databases. Further, in the non-European-like genetic ancestry group, higher rates of Benign or Likely Benign and variants with no clinical designation ( p ≤2.5e-05) were found across many medical specialties, whereas Pathogenic or Likely Pathogenic assignments were higher in individuals of European-like genetic ancestry ( p ≤2.5e-05). Using MAVE data, we reclassified VUS in individuals of non-European-like genetic ancestry at a significantly higher rate in comparison to reclassified VUS from European-like genetic ancestry ( p =9.1e-03) effectively compensating for the VUS disparity. Further, essential code analysis showed equitable impact of MAVE evidence codes but inequitable impact of allele frequency ( p =7.47e-06) and computational predictor ( p =6.92e-05) evidence codes for individuals of non-European-like genetic ancestry. Conclusions: Generation of saturation-style MAVE data should be a priority to reduce VUS disparities and produce equitable training data for future computational predictors.

Differentiation state determines neural effects on microvascular endothelial cells.

Growing evidence indicates that nerves and capillaries interact paracrinely in uninjured skin and cutaneous wounds. Although mature neurons are the predominant neural cell in the skin, neural progenitor cells have also been detected in uninjured adult skin. The aim of this study was to characterize differential paracrine effects of neural progenitor cells and mature sensory neurons on dermal microvascular endothelial cells. Our results suggest that neural progenitor cells and mature sensory neurons have unique secretory profiles and distinct effects on dermal microvascular endothelial cell proliferation, migration, and nitric oxide production. Neural progenitor cells and dorsal root ganglion neurons secrete different proteins related to angiogenesis. Specific to neural progenitor cells were dipeptidyl peptidase-4, IGFBP-2, pentraxin-3, serpin f1, TIMP-1, TIMP-4 and VEGF. In contrast, endostatin, FGF-1, MCP-1 and thrombospondin-2 were specific to dorsal root ganglion neurons. Microvascular endothelial cell proliferation was inhibited by dorsal root ganglion neurons but unaffected by neural progenitor cells. In contrast, microvascular endothelial cell migration in a scratch wound assay was inhibited by neural progenitor cells and unaffected by dorsal root ganglion neurons. In addition, nitric oxide production by microvascular endothelial cells was increased by dorsal root ganglion neurons but unaffected by neural progenitor cells.

An Atlas of Variant Effects to understand the genome at nucleotide resolution.

Sequencing has revealed hundreds of millions of human genetic variants, and continued efforts will only add to this variant avalanche. Insufficient information exists to interpret the effects of most variants, limiting opportunities for precision medicine and comprehension of genome function. A solution lies in experimental assessment of the functional effect of variants, which can reveal their biological and clinical impact. However, variant effect assays have generally been undertaken reactively for individual variants only after and, in most cases long after, their first observation. Now, multiplexed assays of variant effect can characterise massive numbers of variants simultaneously, yielding variant effect maps that reveal the function of every possible single nucleotide change in a gene or regulatory element. Generating maps for every protein encoding gene and regulatory element in the human genome would create an 'Atlas' of variant effect maps and transform our understanding of genetics and usher in a new era of nucleotide-resolution functional knowledge of the genome. An Atlas would reveal the fundamental biology of the human genome, inform human evolution, empower the development and use of therapeutics and maximize the utility of genomics for diagnosing and treating disease. The Atlas of Variant Effects Alliance is an international collaborative group comprising hundreds of researchers, technologists and clinicians dedicated to realising an Atlas of Variant Effects to help deliver on the promise of genomics.

Minimum information and guidelines for reporting a Multiplexed Assay of Variant Effect.

Multiplexed Assays of Variant Effect (MAVEs) have emerged as a powerful approach for interrogating thousands of genetic variants in a single experiment. The flexibility and widespread adoption of these techniques across diverse disciplines has led to a heterogeneous mix of data formats and descriptions, which complicates the downstream use of the resulting datasets. To address these issues and promote reproducibility and reuse of MAVE data, we define a set of minimum information standards for MAVE data and metadata and outline a controlled vocabulary aligned with established biomedical ontologies for describing these experimental designs.

Unsaturated fatty acids induce mesenchymal stem cells to increase secretion of angiogenic mediators.

Mesenchymal stem cells (MSC) represent emerging cell-based therapies for diabetes and associated complications. Ongoing clinical trials are using exogenous MSC to treat type 1 and 2 diabetes, cardiovascular disease and non-healing wounds due to diabetes. The majority of these trials are aimed at exploiting the ability of these multipotent mesenchymal stromal cells to release soluble mediators that reduce inflammation and promote both angiogenesis and cell survival at sites of tissue damage. Growing evidence suggests that MSC secretion of soluble factors is dependent on tissue microenvironment. Despite the contribution of fatty acids to the metabolic environment of type 2 diabetes, almost nothing is known about their effects on MSC secretion of growth factors and cytokines. In this study, human bone marrow-derived MSC were exposed to linoleic acid, an omega-6 polyunsaturated fatty acid, or oleic acid, a monounsaturated fatty acid, for seven days in the presence of 5.38 mM glucose. Outcomes measured included MSC proliferation, gene expression, protein secretion and chemotaxis. Linoleic and oleic acids inhibited MSC proliferation and altered MSC expression and secretion of known mediators of angiogenesis. Both unsaturated fatty acids induced MSC to increase secretion of interleukin-6, VEGF and nitric oxide. In addition, linoleic acid but not oleic acid induced MSC to increase production of interleukin-8. Collectively these data suggest that exposure to fatty acids may have functional consequences for MSC therapy. Fatty acids may affect MSC engraftment to injured tissue and MSC secretion of cytokines and growth factors that regulate local cellular responses to injury.

Mesenchymal stem cells induce dermal fibroblast responses to injury.

Although bone marrow-derived mesenchymal stem cells have been shown to promote repair when applied to cutaneous wounds, the mechanism for this response remains to be determined. The aim of this study was to determine the effects of paracrine signaling from mesenchymal stem cells on dermal fibroblast responses to injury including proliferation, migration and expression of genes important in wound repair. Dermal fibroblasts were co-cultured with bone marrow-derived mesenchymal stem cells grown in inserts, which allowed for paracrine interactions without direct cell contact. In this co-culture model, bone marrow-derived mesenchymal stem cells regulate dermal fibroblast proliferation, migration and gene expression. When co-cultured with mesenchymal stem cells, dermal fibroblasts show increased proliferation and accelerated migration in a scratch assay. A chemotaxis assay also demonstrated that dermal fibroblasts migrate towards bone marrow-derived mesenchymal stem cells. A PCR array was used to analyze the effect of mesenchymal stem cells on dermal fibroblast gene expression. In response to mesenchymal stem cells, dermal fibroblasts up-regulate integrin alpha 7 expression and down-regulate expression of ICAM1, VCAM1 and MMP11. These observations suggest that mesenchymal stem cells may provide an important early signal for dermal fibroblast responses to cutaneous injury.

Substance P enhances wound closure in nitric oxide synthase knockout mice.

INTRODUCTION: The neuropeptide, substance P (SP), up-regulates nitric oxide production (NO). The purpose of this study was to determine whether SP enhances response to cutaneous injury in nitric oxide synthase knockout (NOS null) mice. METHODS: We studied mice with targeted deletions of the 3 NOS genes, neuronal NOS, inducible NOS, or endothelial NOS. Full thickness dorsal wounds were treated daily (d 0-6) with topical SP or normal saline (NaCl). Wounds were analyzed by flow cytometry for macrophage, leukocyte, endothelial, and dendritic cells. Healing time and wound epithelialization were compared using analysis of variance. RESULTS: Wound closure in the 3 NOS null mice was slower than the control mice (P < 0.05). SP treatment enhanced wound closure in NOS null mice (P < 0.02). NOS null wounds exhibited reduced inflammation. SP increased macrophage, leukocyte, and dendritic cell densities at d 3 and d 7 (P < 0.05) in all NOS null mice. SP increased endothelial cell number in neuronal NOS and inducible NOS null mice, but not in endothelial NOS null mice (P > 0.05). CONCLUSIONS: SP ameliorated the impaired wound healing response observed in NOS null mice by enhancing wound closure kinetics and epithelialization. SP increased inflammatory cell density in the wounds supporting the essential role of inflammatory cells, especially macrophages, in wound repair.

The Effects of Early Neuropathic Pain Control With Gabapentin on Long-Term Chronic Pain and Itch in Burn Patients.

Gabapentin has analgesic efficacy for neuropathic pain and is increasingly used in burn care. This study investigated the effect of a neuropathic pain control protocol, as well as early gabapentin initiation (<72 hours from injury) on total inpatient opioid use, chronic pain, and itch. This is a single-institution retrospective cohort study of patients over age 14 admitted between 2006 and 2016 with burns. They compared patients who did not receive gabapentin with those who had early gabapentin initiation vs late initiation. They also compared patients who used gabapentin before initiation of a neuropathic pain protocol (February 2015) to those after. Primary outcomes were total inpatient gabapentin, morphine equivalent dose (MED), longitudinal pain and itch, as well as SF-12v2® Health Survey mental and physical component summary (MCS/PCS) at discharge, 6, 12, and 24 months postinjury. Ordinal logistic regression analysis was used to examine pain and itch scores. Linear regression models examined MCS and PCS between groups. Models were adjusted for age, sex, TBSA burned, area grafted, MED, and ICU stay. There was no significant difference in MED with early initiation, yet inpatient gabapentin use increased from 43.9 to 59.5 g (P < .001) with late initiation. The neuropathic pain protocol did not significantly change total gabapentin use (P = .184) in patients receiving gabapentin but decreased opioid use from 58.1 to 17.4 g MED (P = .008). Their results suggest that neither early gabapentin nor its use in a standardized neuropathic pain protocol improves long-term pain, itch, PCS, or MCS.

Use of Best Practice Strategies to Improve Longitudinal Study Participation: Analysis of Telephone Contact Data From the Northwest Regional Burn Model System.

Successful acquisition of survey data in any longitudinal study is key to reducing bias and determining reliable, generalizable findings. As part of a multicenter longitudinal study of patient-reported outcomes, a minimum benchmark for follow-up was set at 80%. In review of our center's participation, we found this benchmark was not consistently met. Thus, we identified a set of actions for study personnel concerning data acquisition for subject surveys. These actions, termed Best Practices, were implemented in January 2015. The purpose of this review is to determine whether the Best Practices were associated with improved follow-up. A comparison of success rates for the 6-months prior to and following program implementation was made. In addition, cell phone records for the 6-month period following implementation were reviewed for call characteristics (e.g. minutes used, date, and time of call), demographic representation (call area code), call timing (day and time of week), and call success. A "successful call" was defined as a call time longer than 5 minutes with acquisition of survey data. For the cell phone review, we attempted to reach a total of 98 subjects. Table 1 outlines information gleaned from the review of records following implementation of the Best Practices. Table 2 outlines the success rates for the two time periods compared (significance set at < 0.05; two-tailed z-test). Use of the Best Practices by research personnel resulted in improved follow-up rates for 2 of 3 study time points. Of interest is the effort required to reach study participants by telephone with a success rate of only 12% of all calls made. These data provide information that can be used by investigators as they plan future research and require evidence to substantiate personnel effort and/or Full-Time-Equivalent (FTE) requirements.

Topical application of laminin-332 to diabetic mouse wounds.

BACKGROUND: Keratinocyte migration is essential for wound healing and diabetic wound keratinocytes migrate poorly. Keratinocyte migration and anchorage appears to be mediated by laminin-332 (LM-332). Impaired diabetic wound healing may be due to defective LM-332 mediated keratinocyte migration. OBJECTIVE: To evaluate LM-332 expression in diabetic (db/db) and control (db/-) mice and to test LM-332 wound healing effects when applied to mouse wounds. METHODS: LM-332 expression in mouse wounds was evaluated using immunohistochemistry. LM-332 wound healing effects were evaluated by directly applying soluble LM-332, a LM-332 biomaterial, or a control to mouse wounds. Percent wound closure and histology score, based on healing extent, were measured. RESULTS: Precursor LM-332 expression was markedly reduced in db/db when compared to db/- mice. In vitro, soluble LM-332 and LM-332 biomaterial demonstrated significant keratinocyte adhesion. In vivo, soluble LM-332 treated wounds had the highest histology score, but significant differences were not found between wound treatments (p>0.05). No differences in percentage wound closure between treatment and control wounds were found (p>0.05). CONCLUSION: The db/db wounds express less precursor LM-332 when compared to db/-. However, LM-332 application did not improve db/db wound healing. LM-332 purified from keratinocytes was primarily physiologically cleaved LM-332 and may not regulate keratinocyte migration. Application of precursor LM-332 rather than cleaved LM-332 may be necessary to improve wound healing, but this isoform is not currently available in quantities sufficient for testing.

Melanocortin-1 Receptor Polymorphisms and the Risk of Complicated Sepsis After Trauma: A Candidate Gene Association Study.

OBJECTIVE: The aim of the study was to determine if melanocortin-1 receptor (MC1R) single nucleotide polymorphisms (SNPs) are associated with complicated sepsis after trauma. BACKGROUND: Nosocomial infections are an important cause of morbidity and mortality after trauma. Several SNPs in inflammation-related genes have been associated with sepsis. MC1R is an anti-inflammatory mediator that may be involved in the immune response after trauma. PATIENTS AND METHODS: We genotyped eight common MC1R SNPs in genomic DNA from subjects enrolled in a previously reported prospective cohort study. Subjects were adult trauma patients admitted to the intensive care unit at a Level 1 trauma center (2003-2005). RESULTS: A total of 1,246 subjects were included in the analysis. The majority were male (70%), severely injured (81%), and injured by a blunt mechanism (89%). Forty percent developed sepsis, and 23% developed complicated sepsis, which was defined as sepsis with organ dysfunction. In logistic regression analysis, with adjustments for age, sex, body mass index, injury severity score, red blood cell transfusion requirement, and mechanism of injury, the MC1RR163Q variant (rs885479) was associated with a lower risk of developing complicated sepsis (adjusted odds ratio [ORadj] = 0.48, 95% confidence interval [CI]: 0.28-0.81, P = 0.006). In a subgroup of 511 subjects with genome-wide SNP data, the association between the MC1RR163Q variant and complicated sepsis remained significant after adjusting for genetic substructure (by principal components) and the above clinical factors (ORadj = 0.30, 95% CI: 0.13-0.70, P = 0.005). CONCLUSIONS: MC1RR163Q is associated with a lower risk of complicated sepsis after trauma. Therapeutic targeting of MC1R may be beneficial for trauma patients at risk for complicated sepsis.

Dermal Fibroblasts from the Red Duroc Pig Have an Inherently Fibrogenic Phenotype: An In Vitro Model of Fibroproliferative Scarring.

BACKGROUND: The pathophysiology of hypertrophic scarring is unknown in part because of the lack of a robust animal model. Although the red Duroc pig has emerged as a promising in vivo model, the cellular mechanisms underlying Duroc scarring are unknown, and the size and cost of Duroc pigs are obstacles to their use. Given the central role of the dermal fibroblast in scarring, the authors hypothesized that dermal fibroblasts from the Duroc pig exhibit intrinsic differences in key aspects of the fibroblast response to injury compared with those from the Yorkshire pig, a same-species control that heals normally. METHODS: Duroc and Yorkshire dermal fibroblasts were isolated from uninjured dorsal skin. Actin stress fibers and focal adhesions were visualized by immunocytochemistry and transmission electron microscopy. Cell migration was measured using a scratch wound-closure assay. Contractile function was assessed by collagen gel contraction. Expression of scarring-related genes was determined by quantitative real-time reverse-transcriptase polymerase chain reaction, and transforming growth factor (TGF)-ß1 protein expression was determined by Western blotting. RESULTS: Duroc dermal fibroblasts display increased adhesion-complex formation, impaired migration, enhanced collagen contraction, and profibrotic gene and protein expression profiles compared with Yorkshire fibroblasts at baseline. In addition, Duroc fibroblasts overexpressed TGF-ß1 and were less responsive to exogenous TGF-ß1. CONCLUSIONS: Duroc dermal fibroblasts have inherent myofibroblastic differentiation that may account for the pathologic scarring in these animals. The authors' data further validate the Duroc model and support Duroc fibroblast cell culture as a simple, inexpensive, reproducible, and biologically tractable in vitro model for the study of fibroproliferative scarring.

Race Does Not Predict Melanocyte Heterogeneous Responses to Dermal Fibroblast-Derived Mediators.

INTRODUCTION: Abnormal pigmentation following cutaneous injury causes significant patient distress and represents a barrier to recovery. Wound depth and patient characteristics influence scar pigmentation. However, we know little about the pathophysiology leading to hyperpigmentation in healed shallow wounds and hypopigmentation in deep dermal wound scars. We sought to determine whether dermal fibroblast signaling influences melanocyte responses. METHODS AND MATERIALS: Epidermal melanocytes from three Caucasians and three African-Americans were genotyped for single nucleotide polymorphisms (SNPs) across the entire genome. Melanocyte genetic profiles were determined using principal component analysis. We assessed melanocyte phenotype and gene expression in response to dermal fibroblast-conditioned medium and determined potential mesenchymal mediators by proteome profiling the fibroblast-conditioned medium. RESULTS: Six melanocyte samples demonstrated significant variability in phenotype and gene expression at baseline and in response to fibroblast-conditioned medium. Genetic profiling for SNPs in receptors for 13 identified soluble fibroblast-secreted mediators demonstrated considerable heterogeneity, potentially explaining the variable melanocyte responses to fibroblast-conditioned medium. DISCUSSION: Our data suggest that melanocytes respond to dermal fibroblast-derived mediators independent of keratinocytes and raise the possibility that mesenchymal-epidermal interactions influence skin pigmentation during cutaneous scarring.