Masters Degrees (Physiological Sciences)

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Browsing Masters Degrees (Physiological Sciences) by Author "Boodhoo, Kiara"

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    A comparison of the wound healing dynamics in an acute and newly developed chronic wound model using Neutral endopeptidase, an inhibitor of Substance P.
    (Stellenbosch : Stellenbosch University, 2020-03) Boodhoo, Kiara; Van de Vyver, Mari; Myburgh, Kathryn H.; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.
    ENGLISH ABSTRACT: Chronic wounds affect millions of people with diabetes world-wide. Various diabetic wound healing animal models exist, none of which currently replicate chronic wounds in diabetic patients. Animal models that do not closely resemble human conditions delay application of promising therapeutic strategies in clinical settings. Substance P is a neuropeptide that promotes wound healing by binding to neurokinin-1 receptor initiating the inflammatory process. Neutral endopeptidase (NEP) is a zinc metalloprotease that degrades substance P, thereby hindering the healing process. Increased NEP enzymatic activity is evident in chronic wounds of diabetic patients unlike in current animal models. This study aimed to determine the optimum dose of NEP for injection into wound edges in obese pre-diabetic mice (B6.Cg- Lepob/J, ob/ob) in order to create a chronic non-healing wound. Thereafter, the study investigated wound healing dynamics of this chronic non-healing wound compared to an acute wound treated with saline. In addition to a saline control, three concentrations of NEP [low NEP (0.33 mg/μL), medium NEP (0.68 mg/μL) or high NEP (1.02 mg/μL)] were used to obtain a dose-response curve. NEP activities did not differ between treatment groups however, substance P was lower in the wound areas for high NEP compared to low NEP groups. Therefore, less substance P was present to initiate wound healing with high NEP. MMP-9 was higher with high NEP treatment on day 2 compared to saline, low and medium NEP groups. Similarly, the cytokine profile within pooled samples of day 2 wound fluid was lowest with high NEP treatment. Therefore, high NEP application did mimic some characteristics of a chronic wound during the early stages post wounding, including delayed onset of inflammation. When comparing the healing dynamics of this chronic non-healing wound, induced by high NEP, to an acute wound [wild-type (C57BL/6J) saline-treated mice] that follows the normal progression of healing, the chronic wound displayed delayed wound closure (day 7), significantly greater MMP-9 expression (day 0, 2 and 7) with no formation of granulation tissue, re-epithelization and angiogenesis (day 7). Proteomic analysis of the acute saline-treated and chronic high NEP wounds at day 2 indicated significant differences in expression of proteins such as Stefin-1, Stefin-3, Microtubule-associated protein 1B, Band 4.1-like protein 2, Caveolae-associated protein 1 and Gamma-synuclein. These proteins have not been previously described as involved in wound healing and may be directly involved or have downstream interactions in the wound healing processes. This study identified two proteins previously described as playing a role in wound healing, via their involvement in inflammation (Alpha-1- acid glycoprotein 1) and proliferation and remodelling (Nidogen-1). In conclusion, high NEP administration in the wound boarders of obese pre-diabetic mice resulted in a chronic wound model that better mimics human diabetic chronic wounds, which could be used to test various treatment strategies. High NEP administration resulted in less wound closure that could be explained by higher MMP-9, lower cytokine content in wound fluid and differences in several proteins identified by proteomic analysis.