ENHANCED COLLAGEN ACCUMULATION FOLLOWING DIRECT TRANSFECTION OF THE INDUCIBLE NITRIC-OXIDE SYNTHASE GENE IN CUTANEOUS WOUNDS

Inducible nitric oxide synthase (iNOS) is expressed during cutaneous w ound repair. Mounting evidence suggests that wound nitric oxide (NO) a ugments collagen accumulation. We hypothesized that in vivo transfecti on of around cells with the iNOS gene would increase physiological wou nd NO levels and thus augment collagen accumulation. Polyvinyl alcohol sponges were instilled with a mammalian expression plasmid (pMP6) con taining either the chloramphenicol acetyl transferase (CAT) reporter o r murine iNOS gene driven by a CMV immediate-early promoter. Plasmid D NA was injected alone or in complex with cationic liposomes, and the s ponges were placed subcutaneously in male Sprague-Dawley rats which ha d received a longitudinal dorsal midline incision. Animals were sacrif iced at different time points post-wounding and the sponges assayed fo r CAT activity, transfected iNOS mRNA, total nitrate and nitrite conce ntration (NOx) (as an index of wound NO synthesis), and hydroxyproline content (as an index of sponge collagen accumulation). The results de monstrate that wound cells were more efficiently transfected by naked DNA than by liposome mediated transfection and that maximal expression of both iNOS and CAT occurred at 48 hrs with a rapid decline after th is time point. After 7 days, iNOS transfected sponges had accumulated significantly more collagen than those transfected with CAT. We conclu de that cutaneous wounds can be successfully transfected by direct inj ection of naked DNA and that increased iNOS expression precedes an inc rease in collagen synthesis. (C) 1998 Academic Press.