The Role of Decorin and Factors Influencing its Expression in Wound Healing and Hypertrophic Scarring

• Author / Creator

  Kwan, Peter O

• Hypertrophic scarring following deep burn injury is a significant problem for many burn patients, and can cause lifelong morbidity including impaired physical function, and reduced psychosocial function from poor cosmesis. While a significant body of research exists, there is still no gold standard effective clinical treatment—a reflection of the complexity of both wound healing and hypertrophic scar formation. Decorin, a small leucine-rich proteoglycan, has been demonstrated in various models of fibrosis to counteract the effects of transforming growth factor-β, the prototypic profibrotic cytokine. In addition, it also has numerous effects on various other cell surface receptors, and collagen type I (a main constituent of extracellular matrix). Given its multiple important roles in wound healing, the use and role of decorin in modulating wound healing serves as a springboard from which to explore hypertrophic scar formation in burn patients. The first paper presented in this thesis is a general review of wound healing, and explores the roles of various known factors from cells to cytokines. It serves as the background to the experimental work conducted in this thesis, and lays the foundation for appreciating the complexity of wound healing as a whole, and hypertrophic scar formation in particular. The second paper presented explores the role of decorin and other cytokines in predicting the formation of hypertrophic scar, and explores their role in creating both local and systemic profibrotic environments. Efforts to predict those patients at risk of hypertrophic scar formation have been previously limited to the use of clinically available factors such as age, sex, and burn size. However, given the previously established importance of decorin, interleukin-1β, and transforming growth factor-β1 in wound healing and hypertrophic scar, it was hypothesized their serum levels could aid in predicting the risk of hypertrophic scar formation. It was found that early serum levels of decorin and interleukin-1β, and late levels of transforming growth factor-β1 were predictive of hypertrophic scar formation. Furthermore, these temporal combinations were found to create both local and systemic profibrotic environments, and prime the homing of fibrocytes to burn wounds. The third paper presented explores the downregulation of decorin by transforming growth factor-β1, and methods of reversing this downregulation to reduce the profibrotic effects of transforming growth factor-β1. It was hypothesized that there could be a microRNA upregulated by transforming growth factor-β1, which in turn downregulated decorin. A number of potential miRNA were screened, and it was found that miR-181b was upregulated by transforming growth factor-β1, and that miR-181b downregulated decorin expression through three binding sites. This effect on decorin could be reversed using an antagomiR to miR-181b, and this both increased decorin expression and reduced myofibroblast conversion in the face of transforming growth factor-β1 stimulation in vitro. Thus suggesting that antagomiR-181b could be a potential therapy for hypertrophic scar. The fourth paper presented explores the upregulation of decorin using an adenoviral gene therapy vector to treat deep dermal fibroblasts used to populate collagen scaffolds. These collagen scaffolds serve as the base platform for the creation of cultured skin substitutes, which are a promising therapy for burn patients with large wounds and limited donor sites. It was hypothesized that the collagen scaffold remodeling behavior of deep dermal fibroblasts, which are profibrotic, could be altered to more closely match that of superficial dermal fibroblasts, which are regenerative. As there are significantly more deep dermal fibroblasts present in dermal biopsies used to grow cultured skin substitutes, this has the potential to significantly increase the number of regenerative fibroblasts available for tissue engineering. It was found that an adenoviral decorin vector significantly upregulated decorin production by deep dermal fibroblasts, and this altered their collagen scaffold remodeling to match that of superficial dermal fibroblasts, as measured by collagen fibril thickness and collagen orientation index. By using decorin as a basis for investigating hypertrophic scar, this thesis has explored opportunities for improving the prediction of hypertrophic scar formation, treating hypertrophic scar using microRNA modulation, and preventing hypertrophic scar formation by improving cultured skin substitutes using an adenoviral gene vector. It is hoped that these promising avenues of future research will ultimately improve the clinical outcomes of burn patients, and perhaps others suffering from fibrotic diseases as well.

• Subjects / Keywords

  • Hypertrophic scars
  • Burn
  • Decorin

• Graduation date

  Spring 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3ST7F86S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.