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

Abstract

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.

Fig 1

A 50-year-old patient presented with a non-healing chronic wound and osteomyelitis of the tibia in the left pretibial region. The wound was more than 12 months old and 2 × 1 × 1 cm in size (A). The patient was planned to undergo a staged procedure. After debridement, biopsies were taken and TNP was applied. After 5 days of TNP the dressing was removed and the wound bed looked well vascularized (B). Again biopsies of the wound bed and edge were taken and defect coverage was achieved using a distally pedicled Arteria tibialis anterior perforator flap with a size of 9 × 3.5 cm and split skin graft on the donor side. Three months post-operatively stable defect closure was obtained and the patient was mobilized (C).

Fig 2

A 70-year-old patient presented with a necrotic soft tissue area of the right ventral lower leg with a size of 5 × 8 cm due to a post-operative compartment syndrome after implantation of a total knee endoprothesis (A). The patient was planned to undergo a staged procedure. After initial debridement, biopsies were taken and TNP was applied. Four weeks after the initial operation, TNP was removed and again biopsies were taken. The wound bed appeared well vascularized (B). Defect coverage was obtained using a free rectus abdominis flap with a skin island. Three months post-operatively stable defect closure was obtained (C).

Fig 3

Venn diagram of raw probe data from Partek®. There were a total of 606 probes [541 plus 65] differentially expressed on day 0 and 851 probes [786 plus 65] differentially expressed for day 7 following TNP with ROCF. Of these, 65 probes were commonly expressed between time-points (P < 0.001).

Fig 4

Venn diagram of unique gene data sets from Ingenuity Biomarker analysis tool showing; 2551 unique genes were expressed for day 7 (after TNP/ROCF), whereas only 213 unique genes were expressed for day 0 (before treatment). A total of 211 genes were commonly expressed between days 0 and 7.

Fig 5

Venn diagram of unique gene data sets from Ingenuity Biomarker analysis tool – biofiltered for human epidermis gene expression only showing; 1277 unique genes were expressed on day 7 (after TNP/ROCF treatment), whereas 102 unique genes were expressed on day 0 (before treatment). A total of 113 epidermis related genes were expressed in common between the two time-points.