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Granulation And Genomic Evaluation Of Easy To Use Novel Negative Pressure Wound Therapy Dressings
Kathleen Derrick, M.S.1, Diwi Allen, M.S.1, Marisa Schmidt, B.S.1, Tim Robinson, Ph.D.2, Chris Locke, B.S.2, Ronald Silverman, M.D.1, Kris Kieswetter, Ph.D.1.
1KCI, San Antonio, TX, USA, 2KCI, Ferndown, United Kingdom.

Introduction
NPWT with reticulated open cell foam (ROCF) has impacted the practice of healing wounds. New approaches have been contemplated for longer wear dressings. Two novel dressings were evaluated for cellular genomic responses, granulation tissue thickness formation, and average peel force to remove the dressing in a porcine wound healing study.
Methods
Eleven domestic swine were used to obtain samples from full-thickness surgical wounds treated with either NPWT ROCF+, NPWT novel dressing 1#, or NPWT novel dressing 2*. Biopsy samples were taken at study termination on either Day 7 or Day 13. Porcine polymerase chain reaction (PCR) wound healing arrays (Qiagen, Valencia, CA) were performed to determine differences in gene expression (>2 fold difference; p<0.05). Histopathology evaluations and morphometry measurements assessed granulation tissue quality and thickness, respectively. The peel force required to remove the dressings was obtained using a custom test device.
Results
Granulation: In the day 13 group, there was a significant difference (p<0.0441) in granulation tissue thickness between ROCF + interfacial layer (ROCF + IFL) (5.33 mm ± 0.14) as compared to CPUF (7.43 mm ± 0.33). No significant difference were seen between ROCF + IFL (5.33 mm ± 0.14) and GM (5.80 mm ± 0.22). Moreover, each treatment group (ROCF + IFL, CPUF, and GM) demonstrated a significant increase in granulation tissue deposition over time (p<0.04).
Genomics: The novel GM dressing at Day 13, relative to Day 7, demonstrated greater upregulation in cell binding and catalytic activity which included Matrix metallopeptidase 1 (6.58), Matrix metallopeptidase 3 (8.83) and Decorin (2.15). These are important epithelial markers and known for collagen binding. Novel CPUF dressing at Day 13, as compared at Day 7, demonstrated similar results. There was in increase in MMP1 (10.30) and MMP3 (13.46), both of which are important in keratinocyte migration and endothelial cell activity. There was an increase in Catenin (2.29), which may be responsible for the inhibition signal that causes cells to stop dividing once the epithelial sheet is complete. In addition, cell adhesion genes (Integrins: ITGA2, ITGB3 and ITGB6) were all up regulated (2.01, 2.62, 6.90 respectively).
Peel Force: Regardless of group or timepoint, ROCF required significantly greater average force for removal. A dressing change at day 4 did not statistically affect the amount of peel force required to remove ROCF for the groups with a day 7 end of in-life/termination. The use of the interfacial layer with GF brought the force required for removal as low as the other novel dressings.
Conclusions
This preclinical study illustrates that the tested novel dressings induced more granulation tissue formation with less peel force, and interesting genomic responses than the controls. Following 13 days of treatment
in a porcine model, the novel NPWT dressings have been shown to increase genes involved in epithelization while increasing granulation tissue and decreasing dressing removal force, which might lead to better wound healing outcomes.
KCI Licensing, San Antonio, TX
+V.A.C.® Therapy with GRANUFOAM™
#GM dressing (NPWT novel dressing 1)
*CPUF dressing (NPWT novel dressing 2)


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