Based on preliminary but variable results with direct DNA transfer into wounds, we evaluated in vivo gene transfer by particle-mediated DNA delivery to rat skin to determine whether overexpression of TGF-␤ 1 at the site of skin incisions would result in a significant improvement in repair. Optimization of the method with viral promoter-luciferase reporter constructs indicated that expression of luciferase activity persisted up to 5 d and was promoter, pressure, and site dependent (ventral Ͼ dorsal). Using cytomegalovirus (CMV)-driven human ␣ 1-antitrypsin, transgene expression was immunolocalized within keratinocytes of the stratum granulosum at 24 h. We measured tensile strength of skin incisions at 11-21 d in both normal and diabetic rats transfected with TGF-␤ 1 expression vectors at surgery. Native murine TGF-␤ 1 under an SV40 promoter produced positive effects, while wound strengthening was more pronounced in diabetic animals using a CMV-driven construct. Transfection of rat skin with constitutively active, mutant porcine TGF-␤ 1 under the control of the CMV and Moloney murine leukemia virus promoters significantly increased tensile strength up to 80% for 14-21 d after surgery. Transfection 24 h before surgery was more effective. Particle-mediated gene delivery can be used to deliver viral promoter-cytokine expression constructs into rat skin in a safe, efficient, and reproducible fashion. The extent of wound repair, as evidenced by enhanced tensile strength, can be markedly improved in tissues transfected with TGF-␤ 1 expression constructs. ( J. Clin. Invest . 1996. 98:2894-2902.)

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