In this era of modern medicine, impaired wound healing is still a major medical problem with limited treatment options, especially for the elderly and for diabetic patients. One of the molecules that are recognized to be critical in wound healing is transforming growth factor (TGF-beta). Exogenous direct application of TGF-beta to the wound promotes healing in animal models. Since this property of TGF-beta is cell context-dependent, the present study investigated the role of ischemia/reperfusion using a pig-skin flap model (in vivo). In addition, we studied the effects of: (i) hypoxia/reperfusion, (ii) steroids, and (iii) the combined effect of both hypoxia and steroids on the TGF-beta signaling pathway (TGF-beta, its receptors and its downstream mediators, Smad2 and Smad3) in vitro; all of these were studied using human primary skin fibroblasts and a human keratinocyte cell line (HaCat cells). / Our in vivo results showed that the TGF-beta receptors (RI, RII, and RIII) and TGF-beta1 are markedly increased under acute ischemic conditions in dermal blood vessels and fibroblasts. Our in vitro experiments showed that short-term (2 hours) and long-term (24 hours) exposure to hypoxia differentially regulates TGF-beta components, namely, active TGF-beta, RII mRNA, phosphorylated (P) and total Smad2 and Smad3. Our studies have also shown that steroids are able to strongly modulate TGF-beta signaling and that these effects are critically dependent on the type of steroid used and on treatment duration. Analysis of the combined effect of hypoxia and steroids revealed that steroid effects on the TGF-beta signaling machinery is potentially modulated by oxygen tension, with hypoxia acting synergistically or antagonistically in a steroid-specific manner. In summary, we have identified oxygen tension and steroids as regulators of the action of TGF-beta in skin cells. We demonstrated that their effects are critically dependent on the duration of treatment and that they may act synergistically or antagonistically on the components of the TGF-beta pathway, emphasizing the complexity of TGF-beta signaling. Identification of these agents as modulators of TGF-beta signaling provides a basis for the development of strategies for the manipulation of TGF-beta action in the skin. This may contribute towards the development of agents that promote wound healing.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.85629 |
| Date | January 2004 |
| Creators | Mortazavi, Roya |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Division of Surgical Research.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002198812, proquestno: AAINR12914, Theses scanned by UMI/ProQuest. |
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