The pig as a model for excisional skin wound healing: Characterization of the molecular and cellular biology, and bacteriology of the healing process

A pig model of wound healing was developed by excision of 2-cm-diameter ful l thickness skin in young Yorkshire pigs. The results indicated that wound re-epithelialization in this animal model took an average of 20 days. Analy sis of cellular change was assessed by use of DNA quantification and determ ination of apoptotic cells in tissue sections. The results indicate that RN A and DNA contents paralleled each other throughout the healing process, an d observed changes in the pattern of RNA and DNA content of the scar tissue s were consistent with cell loss due to apoptosis in this model. Expression of mRNA for relevant genes was assessed by use of semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis, using porcine s pecific primer sets and RNA isolated from normal skin and specimens obtaine d at various times after wounding. The mRNA values for tumor necrosis facto r-alpha (TNF-alpha), connective tissue growth factor (CTGF), insulin-like g rowth factor II (IGF-II), and decorin were significantly high at specific t imes after wounding, but mRNA values for the transcription factors (c-fos a nd c-jun) were significantly decreased. Quantitative bacteriologic results indicated that the total bacterial count in this animal model reached 10(9) colony-forming units (CFU)/g, with the highest value at post-wounding day 7, and Pseudomonas aeruginosa and Staphylocococci aureus were the most comm on bacteria detected in this model. Further definition of this model should identify unique points in the healing process, and such information could lead to development of therapeutic interventions to improve skin wound heal ing.