Epidermal micrografts produced via an automated and minimally invasive tool form at the dermal/epidermal junction and contain proliferative cells that secrete wound healing growth factors.

OBJECTIVE: The aim of this scientific study was to assess epidermal micrografts for formation at the dermal-epidermal (DE) junction, cellular outgrowth, and growth factor secretion. Epidermal harvesting is an autologous option that removes only the superficial epidermal layer of the skin, considerably limiting donor site damage and scarring. Use of epidermal grafting in wound healing has been limited because of tedious, time-consuming, and inconsistent methodologies. Recently, a simplified, automated epidermal harvesting tool (CelluTome Epidermal Harvesting System; Kinetic Concepts Inc, San Antonio, Texas) that applies heat and suction concurrently to produce epidermal micrografts has become commercially available. The new technique of epidermal harvesting was shown to create viable micrografts with minimal patient discomfort and no donor-site scarring. DESIGN: This study was a prospective institutional review board-approved healthy human study. SETTING: This study was conducted at the multispecialty research facility, Clinical Trials of Texas, Inc, in San Antonio, Texas. PATIENTS: The participants were 15 healthy human volunteers. RESULTS: Epidermal micrografts formed at the DE junction, and migratory basal layer keratinocytes and melanocytes were proliferative in culture. Basement membrane-specific collagen type IV was also found to be present in the grafts, suggesting that the combination of heat and vacuum might cause partial delamination of the basement membrane. Viable basal cells actively secreted key growth factors important for modulating wound healing responses, including vascular endothelial growth factor, hepatocyte growth factor, granulocyte colony-stimulating factor, platelet-derived growth factor, and transforming growth factor α. CONCLUSIONS: Harvested epidermal micrografts retained their original keratinocyte structure, which is critical for potential re-epithelialization and repigmentation of a wound environment.

Genomic and proteomic evaluation of tissue quality of porcine wounds treated with negative pressure wound therapy in continuous, noncontinuous, and instillation modes.

OBJECTIVE: Negative pressure wound therapy with instillation (NPWTi-d) combines NPWT with automated delivery and removal of topical wound treatment solutions. This porcine study compared genomic and proteomic responses of wounds treated with NPWTi-d with saline to wounds treated with NPWT in continuous and noncontinuous modes. METHODS: Full-thickness porcine dorsal excisional wounds were treated with continuous NPWT, intermittent NPWT, dynamic NPWT, or NPWTi-d with saline (n = 10 wounds per group). On day 7, animals were euthanized and tissues collected. Real-time quantitative polymerase chain reaction arrays profiled expression of 84 genes including extracellular matrix remodeling factors, inflammatory cytokines and chemokines, and growth factors and major signaling molecules. Concentrations of proteins associated with angiogenesis, extracellular matrix components, and cellular energetics were analyzed via enzyme-linked immunosorbent assays. RESULTS: Gene expression profiles for NPWTi-d with saline and continuous NPWT were similar. There were 5 upregulated and 18 downregulated genes overexpressed in NPWTi-d compared to NPWT wounds. Protein content was comparable in all treatment groups and similar to unwounded tissue. CONCLUSIONS: Previous preclinical studies have reported an increased rate of granulation tissue formation with NPWTi-d with saline compared to NPWT in continuous and noncontinuous modes. This evaluation of gene and protein expression suggests that the granulation tissue in these wounds has a similar quality. This first look at the differences in gene expression, particularly in genes related to remodeling, cell adhesion, inflammation, and growth factors, could help to clarify the observed differences in granulation rates.

Healed porcine incisions previously treated with a surgical incision management system: mechanical, histomorphometric, and gene expression properties.

BACKGROUND: Computer and bench models have shown previously that surgical incision management with negative pressure (SIM) immediately decreases lateral tissue tension and increases incisional apposition. Better apposition is known to improve healing. Thus, SIM was hypothesized to improve the quality of incisional healing. This study evaluated the impact that 5 days of SIM had on mechanical properties and associated changes in the histology/histomorphometry and gene expression of healed porcine incisions. METHODS: One incision in each of the 4 pairs of contralateral, sutured, full-thickness incisions in each of 6 Yucatan swine were treated with either SIM (Prevena™ Incision Management System; n = 24 incisions/treatment group) or standard of care (SOC; sterile absorbent abdominal pads; n = 24/group) for 5 days, after which both groups received SOC for an additional 5 days. Biopsies for gene-expression analyses were collected on days 5 (n = 6 pairs/group), 20 (n = 6 pairs/group), and 40 (n = 12 pairs/group). On day 40, the animals were killed, after which healed incisions were harvested for mechanical testing (n = 12/group) and histologic/histomorphometric evaluation (n = 12/group). RESULTS: Compared with SOC-treated incisions, SIM-treated incisions had significantly improved (p < 0.05) mechanical properties (strain energy density, peak strain) and a narrower scar/healed area in the deep dermis on day 40. Differences in gene expression between SOC- and SIM-treated specimens were observed primarily on day 5. The SIM-treated specimens had significantly fewer genes, which were differentially expressed and showed reduced upregulation of genes associated with inflammation, hypoxia, retardation of reepithelialization, impaired wound healing, and scarring. CONCLUSION: Early application of SIM improved the quality of healed porcine incisions in terms of mechanical, histomorphometric, and gene-expression properties. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Changes of anabolic processes at the cellular and molecular level in chronic wounds under topical negative pressure can be revealed by transcriptome analysis.

Chronic wounds--as defined by the World Union of Wound Healing Societies (WUWHS)--are a considerable worldwide health care expense and impair quality of life. In order for chronic wounds to heal, these wounds must be transformed to a more acute state to begin the healing process. Topical negative pressure (TNP) with reticulated open cell foam (ROCF) is known to promote healing in certain types of chronic wounds. However, little is known about changes at the cellular or molecular level in wounds under various treatments, especially under the physical forces induced to tissue by TNP. In the current study, chronic wound samples were obtained during routine wound debridements prior to treatment and 7-12 days after initiating TNP with a continuous setting at -125 mmHg. Whole genome transcriptome microarray analyses were performed on samples to better understand how TNP with ROCF affects these types of wounds. It was found that more genes were expressed following TNP with ROCF as compared to before therapy and to normal, non-wounded tissue. In this study, we show that TNP with ROCF transforms the chronic wound from its inflammation (non-healing) state into more of a progressive, healing phenotype from a molecular point of view with expression of genes that are commonly associated with these terms.

Comparative analysis of global gene expression profiles between diabetic rat wounds treated with vacuum-assisted closure therapy, moist wound healing or gauze under suction.

How differential gene expression affects wound healing is not well understood. In this study, Zucker diabetic fatty (fa/fa) male inbred rats were used to investigate gene expression during wound healing in an impaired wound-healing model. Whole genome microarray surveys were used to gain insight into the biological pathways and healing processes in acute excisional wounds treated with vacuum-assisted closure (V.A.C.). Therapy, moist wound healing (MWH) or gauze under suction (GUS). Global gene expression analyses after 2 days of healing indicated major differences with respect to both number of genes showing fold changes and pathway regulation between the three different wound treatments. Statistical analysis of expression profiles indicated that 5072 genes showed a >1.6-fold change with V.A.C. Therapy compared with 3601 genes with MWH and 3952 genes with GUS. Pathways and related genes associated with the early phases of wound healing diverged between treatment groups. For example, pathways involving angiogenesis, cytoskeletal regulation and inflammation were associated with elevated gene expression following V.A.C. Therapy. This study is the first to assess wound healing by whole genome interrogation in a diabetic rat model treated with different healing modalities.