Characterization of pigment epithelium-derived factor expression in mechanically expanding skin

Abstract

Objective To characterize the pigment epithelium-derived factor (PEDF) expression in the mechanically expanding skin tissues. Methods The rat PEDF expression was identified by immunofluorescence staining on skin tissue sections and by quantitative characterization using Western blotting on tissue lysates originated from the mechanically expanding skin samples. To further elucidate the effects of expansion-relevant tissue microenvironment stimuli on the cellular PEDF expression, the PEDF gene transcription levels were determined respectively on epidermal cells that were incubated in vitro under either hypoxia or mechanical stretching conditions. Results For normal oxygen group, epidermal cell line HaCaT cells were cultured and collected at 1, 3, 6 and 9 h, and the PEDF mRNA espression levels were 0.392±0.174, 0.385±0.207, 0.491±0.134, 0.122±0.040 respectively at 1, 3, 6 and 9 h. For hypoxia group, PEDF mRNA expression levels were markedly upregulated correspondingly [2.271±0.781 (P<0.05), 3.419±0.774 (P<0.05), 2.886±0.019 (P<0.05), and 2.673±0.219 (P<0.05) respectively at 1, 3, 6 and 9 h]. For stretch group, HaCaT cells were applied to mechanical stretch for the same period under the normal oxygen. It was found that the PEDF mRNA expression levels were also upregulated correspondingly [1.535±0.199, 1.078±0.167, 1.295±0.012 and 1.500±0.104 respectively at 1, 3, 6 and 9 h]. However, the difference in the mRNA expression levels between stretch group and normal oxygen group was just significant at 1 h after the onset of mechanical stretching. Conclusion The microenvironmental hypoxia and mechanical strain significantly upregulate epidermal cellular PEDF expression respectively. Key words: Pigment epithelium-derived factor; Soft tissue expansion; HaCaT cells