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Notizen: JCR:LA-cp/cp obese rats and their lean controls were evaluated as a type 2 diabetic wound healing model and the healing quality was characterized. This model of insulin resistance has been used extensively to study atherosclerosis but has not previously been used to study wound healing. Six circular excisional wounds were made on the dorsum of each rat and followed to day 21.Tracings of the wounds were made and used to assess the rate of wound closure. Planimetry showed a significantly diminished contraction of wounds in obese rats, but no significant difference in reepithelialization was observed. Collagen content was determined from the hydroxyproline content in wounded and unwounded skin. There were significantly lower levels of hydroxyproline in the wounds of obese compared to lean animals at day 21. Histology showed adipose tissue in place of dermal tissue in the JCR:LA-cp/cp rat in both unwounded tissue and in the wound at day 21. Active transforming growth factor-β1 (TGF-β1) was measured in the serum using the plasminogen activator inhibitor-1/luciferase assay and serum total TGF-β was measured using an enzyme-linked immunosorbent assay. Active TGF-β was significantly higher in the serum of obese animals compared with lean animals, while total TGF-β1 was not significantly different between the groups. Both active and total TGF-β was measured in tissue sections using the plasminogen activator inhibitor-1/luciferase assay. There was no significant difference in active TGF-β between genotypes, while obese rats had significantly higher levels of total TGF-β at day 21. These results indicate a deficiency in wound healing in obese animals characterized by decreased wound contraction, decreased collagen production, and changes in histology. The JCR:LA-cp rat develops insulin resistance, atherosclerosis and early type 2 diabetes and may be a good model for impairment of wound healing in humans with metabolic syndrome.

Notizen: Transforming growth factor-β1 is a fibrogenic cytokine that is important in the development of fibroproliferative disorders of the skin after injury. To investigate the role of transforming growth factor-β1 produced by keratinocytes during wound healing, a plasmid with the human transforming growth factor-β1 gene coupled with the keratin 14 promoter (pG3Z: K14-TGF-β1) was constructed. The construct was tested successfully in vitro before being used to generate transgenic animals, which were subsequently bred into homozygous and heterozygous lines. Genotype screening of founders and progeny was performed by Southern blotting and targeting of the transgene to the epidermis by the keratin 14 promoter was shown by reverse transcription polymerase chain reaction. The major phenotypic change observed in the transgenic animals was “scruffiness” of the fur attributed to transgene expression in the skin, seen primarily in the homozygous line. A significant reduction in the rate of reepithelialization of full-thickness excisional wounds of dorsal skin was seen in homozygous animals compared with normal litter-mate controls at day 7 (p 〈 0.05, Fisher's Exact test) and day 9 (p 〈 0.01) postwounding. Wounds in heterozygous animals also healed more slowly at day 9 (p 〈 0.01). Northern analysis of mRNA extracted from the wounds showed increased human transforming growth factor-β1 message levels in homozygous and heterozygous animals, maximal at day 5. Significant increases in transforming growth factor-β1 activity in healing wounds measured using the plasminogen activator inhibitor-1/luciferase assay were found in the transgenic strains at day 9 postinjury as compared with the normal litter-mate control mice (p 〈 0.001, ANOVA). Type I procollagen mRNA expression was higher in the homozygous and heterozygous animals, with the highest levels reached at day 9. By day 5 postwounding, biopsies of both homozygous and heterozygous tissues were significantly higher in collagen as compared with wounds in control animals (p 〈 0.05, ANOVA). Based on these data, the K14-TGF-β1 transgenic mouse shows that excessive latent transforming growth factor-β1 produced in the epidermal layer of the skin delays reepithelialization in excisional wounds but subsequently the cells of the epidermis stimulate dermal fibroblasts leading to fibrosis through a paracrine mechanism. (WOUND REP REG 2002;10:)