Impaired wound healing post trauma or surgical procedure is a serious health problem. Transforming growth factor-beta 1 (TGFbeta1) has both positive and negative effects on wound healing, which greatly affect the wound healing outcome. Altering TGFbeta signaling either positively or negatively has been considered as therapeutic strategies for impaired wound healing. To design an optimal therapeutic approach that manipulates TGFbeta signaling at the right time and in an appropriate manner, it is crucial to define the stage-specific roles of TGFbeta1 and its antagonistic factor(s) in wound healing. In this application, we will utilize our newly developed gene-switch-TGFbeta1 and gene-switch-Smad7 transgenic mouse models, which represent upregulation and downregulation of TGFbeta signaling, respectively. Using these two models we will temporally induce expression of TGFbeta or Smad7 in keratinocytes at different levels and during one or more following stages of wound healing: inflammation, reepithelialization, granulation tissue formation, wound contraction and tissue remodeling (Aims 1 and 2). In addition, our preliminary data show that Smad7 overexpression in keratinocytes accelerates wound healing with phenotypes and molecular changes opposite to those induced by TGFbeta1 overexpression. Thus, we will test whether induction of Smad7 expression in keratinocytes selectively blocks the negative effects of TGFbeta1 on wound healing, such as inhibition of reepithelialization and excessive inflammation (Aim 3). Furthermore, since direct target genes of Smad7 during wound healing are largely unknown, we will perform gene expression profiling in wound samples with acute and sustained induction of Smad7 transgene expression (Aim 4). These target genes may be difficult to distinguish from the secondary events by using conventional transgenic/knockout approaches. We will also examine expression of specific TGFI3-responsive genes in wound samples being generated in the first three aims to evaluate whether Smad7 overcomes the negative effects of TGFbeta1 by blocking its transcriptional activities (Aim 4). The proposed studies will provide important insights into future design of therapeutic approaches for impaired wound healing through up- or down-regulation of TGFbeta signaling and through manipulating TGFbeta1 and/or Smad7 target genes.
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