Browsing by Author "Kruger, Maria Jacoba"
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- ItemAntioxidant (Oxiprovin TM) supplementation and muscle recovery from contusion injury - an in vivo study(Stellenbosch : Stellenbosch University, 2007-12) Kruger, Maria Jacoba; Smith, Carine; Smith, R. M.; Myburgh, Kathryn H.; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Human studies on the response of muscle to contusion injury are limited, probably due to the large variability in injury severity and the non-specificity of clinical symptoms reported. To circumvent this problem, several experimental animal models have been designed to study muscle damage and regeneration after contusion injuries. However, the majority of techniques currently used to induce contusion injury are very invasive and therefore not optimal. Furthermore, published studies regarding clinical treatment of such injuries are limited. The main aims of this study were therefore: a) to establish and characterise an in vivo model of non-invasive contusion injury, and b) to assess the effect of pre-injury chronic administration of the antioxidant supplement Oxiprovin™ - a natural grape seed extract (GSE) - on skeletal muscle recovery after experimentallyinduced injury. Two groups of male Wistar rats were subjected to 14 days of oral administration of isovolaemic placebo (sterile isotonic saline) or GSE (20 mg/kg/day) prior to induced contusion. Contusion injury was induced with the mass-drop technique, and recovery parameters assessed for up to 14 days post-injury. Placebotreated rats on average exhibited a 56 % higher creatine kinase (CK) activity when compared to the GSE-treated rats when area under the curve (AUC) was calculated for 14 days post-injury (p < 0.001). In the placebo group, plasma oxygen radical absorbance capacity (ORAC) was unchanged over time, but muscle ORAC was significantly increased by day 7 post-injury (p < 0.001). In the GSE group, a significant decrease in both plasma (p < 0.01) and muscle ORAC (p < 0.001) was evident 4 hr after injury, followed by a significant increase by day 3 (p < 0.05 and p < 0.001 respectively). CD34+ satellite cell (SC) numbers (quiescent and activated) peaked earlier in GSE-treated rats when compared to placebo-treated rats (4 hours vs. day 7 post-injury). Total satellite cell number (CD56+) also peaked earlier in GSE-treated rats than in placebo-treated rats (4 hours vs. 3 days post-injury), while M-cadherin+ SC numbers (quiescent, activated or proliferating) in both treatment groups were significantly increased 4 hours post-injury (p < 0.001), but more so in the placebo group. In GSE-treated rats when compared to placebo-treated rats, newly generated muscle fibres (displaying central nuclei and MHCf +) both appeared (day 3 vs. day 7 post-injury) and peaked in number (day 3 vs. day 7 post-injury; increase from baseline p < 0.001 for both) earlier. The results of this study demonstrate that we have successfully established an in vivo model for non-invasive contusion injury in rats. Furthermore, we have shown that Oxiprovin™: a) increased the ability to scavenge reactive species generated after injury and b) resulted in the activation of satellite cells and formation of newly generated muscle fibres at an earlier time point, thus accelerating the recovery of skeletal muscle after a standardised contusion injury.
- ItemImmune and satellite cells : important role players in muscle recovery after injury(Stellenbosch : University of Stellenbosch, 2011-03) Kruger, Maria Jacoba; Smith, Carine; Myburgh, Kathryn H.; University of Stellenbosch. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Muscle injuries are associated with changes in skeletal muscle as well as the immune system. All studies investigating possible treatment modalities have found both positive and negative effects on muscle recovery. Since no universally accepted treatment modality exists, this thesis aims to determine whether a plant-derived antioxidant, proanthocyanidolic oligomer (PCO), might prove beneficial as treatment for sports injuries in order for athletes to return to the sports field quicker. The difference in recovery of muscle following both chronic (supplementation started 14 days prior to injury and continued thereafter) and acute supplementation (supplementation started two hours after injury) were also investigated. Both chronic and acute PCO supplementation in a rat hindlimb contusion injury model resulted in earlier muscle recovery, verified by an earlier satellite cell response compared to the placebo group. This effect was most prominent already at the four hour time point following injury, compared to day seven and three after chronic and acute placebo treatment respectively. PCO supplementation also resulted in quicker foetal myosin heavy chain (MHCf) expression compared to placebo treatment. Chronic supplementation specifically resulted in a blunted circulatory pro-inflammatory cytokine response, whilst allowing for a significant increase in IL-10, an anti-inflammatory cytokine, on day three (in the PCO group only). At tissue level, the response of the muscle pro-inflammatory cytokines, TNF- and IL- 6, coincided with the satellite cell response. Macrophage infiltration into the injured muscle also followed a similar pattern to that seen for the pro-inflammatory cytokines. Macrophages invaded the injured area quicker when supplemented with PCO chronically, however, macrophage infiltration could not explain the cytokine response seen with acute supplementation. Both chronic and acute supplementation with PCO was responsible for a severely blunted neutrophil response, a novel finding of this particular antioxidant. The main findings of the in vivo rodent study were that PCO was able to blunt the neutrophil response, whilst allowing for earlier macrophage infiltration. To establish possible mechanisms by which PCO might exert these beneficial effects, further analysis included determining macrophage phenotypes and neutrophil numbers in circulation. An in vitro neutrophil migration assay was also employed to further elucidate PCO’s ability to blunt neutrophil infiltration into the injured area. For this study, conditioned plasma were harvested from experimental animals and added together with neutrophils from control rats and granulocyte colony stimulating factor (G-CSF) to the insert of the migration chamber. A chemotactic factor, N-formyl methionine-leucine-phenylalanine (fMLP), was added to the bottom well and neutrophils were allowed to migrate for two hours. Results from this study indicated that neutrophil migration was attenuated in vitro in the presence of conditioned plasma from PCO supplemented rats only. The studies in this thesis on the effect of PCO on parameters of muscle and the immune system led to the following main conclusions: a) PCO supplementation resulted in earlier muscle recovery as a result of earlier satellite cell activation and MHCf synthesis; b) PCO favours an anti-inflammatory cytokine reaction, whilst blunting the pro-inflammatory cytokine response; and c) PCO blunted the neutrophil response whilst facilitating earlier macrophage infiltration into the injured area. The specific mechanism of action of PCO to blunt the neutrophil response specifically, possibly includes the ability to suppress adhesion molecule expression on the neutrophils themselves. However, this warrants further investigation.