Every year millions of individuals suffer from traumatic brain injury (TBI) leading to permanent disabilities and even death. Mild TBI (mTBI) is the most common form of TBI comprising about 80-90% of all occurrences. Following a CNS insult like an mTBI, astrocytes can undergo activation resulting in the transformation into reactive astrocytes (RAs). RAs also play an important role in brain remodeling following an mTBI. Research on the mechanical complexity of the brain has important implications for understanding brain function and dysfunction, as well as for the development of new diagnostic and therapeutic tools for neurological disorders. This study aimed to develop and utilize an emph{in vitro} mTBI platform to investigate the intricate mechanical interplay between the extracellular matrix (ECM) and astrocytes following a simulated mTBI. Cellular mechanisms underlying mTBI and the contribution of mechanical forces that result in prolonged brain damage are yet to be comprehensively understood. Successfully devised mechanical characterization techniques for tissue-engineered models were developed utilizing atomic force microscopy and rheology. Astrocyte exposure to high-rate overpressure revealed altered mechanical properties of the surrounding matrix and decreased expression of laminin and collagen IV, which are critical for brain function and may contribute to pathologies associated with mTBI. The developed platform and methods provide new insights into the mechanistic complexity underlying ECM-astrocyte interactions following an mTBI. / Master of Science / Every year, millions of people suffer from traumatic brain injury (TBI), which can lead to permanent disabilities or even death. The most common form of TBI is mild TBI (mTBI), which accounts for 80-90% of all cases. After a mTBI, astrocytes, the most common cell type in the brain, can become activated and turn into reactive astrocytes (RAs). RAs play an important role in the brain's recovery following a mTBI. Understanding the mechanical complexity of the brain is crucial for developing new diagnostic and therapeutic tools for neurological disorders. This study aimed to investigate the mechanical interplay between the modeled tissue and astrocytes following a simulated mTBI using an emph{in vitro} platform. Development of mechanical characterization techniques allowed for any alterations caused by the astrocytes to their environment to be detectable. The astrocyte exposure to the simulated mTBI revealed altered mechanical properties of the surrounding environment and decreased expression of proteins laminin and collagen IV, which are critical to brain function and may contribute to pathologies associated with mTBI. This study provides new insights into the mechanistic complexity underlying the interaction between astrocytes and their environment, which could lead to the development of new treatments.

The cardiovascular system of Drosophila melanogaster consists of a cardiac tube composed of myogenic cardiomyocytes and associating non-contractile pericardial cells, pumping hemolymph into the open circulatory system. The cardiac tube, known as the dorsal vessel, is embedded in a highly regulated extracellular matrix environment, required to maintain cellular integrity and cardiac function. After embryogenesis, the dorsal vessel undergoes extensive physiological changes, relying on the extracellular matrix to adapt and remodel accordingly. Three extracellular matrix proteins are investigated throughout this thesis: Type IV Collagen, Laminin and Pericardin. Due to their localization, morphology, and role in early development, the pericardial cells are candidate cells responsible for dorsal vessel extracellular matrix deposition and regulation throughout post-embryonic growth. Using immunofluorescence techniques in combination with confocal microscopy, I characterize the association between pericardial cells and extracellular matrix proteins, and quantify extracellular matrix protein deposition at the dorsal vessel throughout post-embryonic development. Gene knock-down experiments assess pericardial cell contribution to extracellular matrix synthesis and deposition at the dorsal vessel in third instar larva. Moreover, I quantify extracellular matrix protein deposition at the dorsal vessel in the absence of pericardial cells. These data suggests that pericardial cells regulate extracellular matrix protein deposition, localization and contribute to proper cardiac morphology in post-embryonic development. / Thesis / Master of Science (MSc)

Background: Fibulin-1, an extracellular matrix component and mediator in cardiac fibrosis, is expressed in cardiac valves, heart muscles and blood vessels and may contribute to different cardiovascular pathological conditions such as hypertension, aortic valve stenosis, atrial fibrillation and coronary artery disease. The most conspicuous functions of fibulin-1 include cell adhesion and cell migration within the extracellular matrix (ECM). This was found to reflect vascular dysfunction contributing to the development of fibrosis in the myocardium by means of changes in the ECM, possibly as a result of inflammation. Inflammatory mediators such as C-reactive protein (CRP) and albumin have been investigated over the years for the role they play in the inflammatory processes. However, one inflammatory mediator, soluble urokinase-type plasminogen activator receptor (suPAR), only emerged as a potential biomarker in the development of sclerotic disease. SuPAR is a soluble bioactive form of the urokinase-type plasminogen activator receptor (uPAR) secreted by inflammatory cells such as macrophages, endothelial cells and monocytes. The most profound functions of suPAR such as cell migration and cell adhesion contribute to the development of diseases such as infection, autoimmune diseases, cancer and atherosclerosis. Motivation and aim: This study was motivated by an awareness of the limited data on the potential link between fibulin-1 and suPAR, along with other markers of inflammation (CRP and albumin). We aimed to compare the levels of a marker of cardiac fibrosis (fibulin-1) and inflammatory mediators (suPAR, CRP and albumin) in African and Caucasian men and women. A second aim was to explore fibulin-1 and its potential association with these inflammatory markers independent of haemodynamic and metabolic risk factors in a bi-ethnic cohort from South Africa. Methodology: Data from the cross-sectional SAfrEIC study (South African study regarding the role of Sex, Age and Ethnicity on Insulin sensitivity and Cardiovascular function) were used, which initially included 756 participants. Our study population comprised 290 Africans (men: n=130; women: n=160) and 343 Caucasians (men: n=160; women: n=183). We excluded HIV-infected participants (n=115) as well as those with missing data (n=8). Traditional cardiovascular measurements together with the relevant biochemical analyses were done. T-tests and Chi-square tests were used to compare means and proportions between groups, respectively. Single and partial correlations were performed to determine the relationship of fibulin-1 with suPAR, CRP and albumin, with adjustments for age. SuPAR, CRP and albumin were divided into tertiles to explore the association with fibulin-1 levels, while adjusting for age, body mass index (BMI) and diastolic blood pressure (DBP) by using analysis of covariance (ANCOVA). Multiple regression analysis was performed to explore independent associations. Results: Participants were divided into African and Caucasian men and women due to significant interactions of the main effects of ethnicity and gender on the association of fibulin-1 with suPAR (ethnicity: F(633)=7.29; p<0.001 and gender: F(633)=7.99; p<0.001). Fibulin-1 levels were higher in African men (p=0.010), whereas CRP was higher in African women (p<0.001) compared to their Caucasian counterparts. In both gender groups suPAR levels were higher and albumin lower in Africans compared to Caucasians (p<0.006). In single regression analyses, a positive correlation existed between fibulin-1 and suPAR in African (r=0.19; p=0.028) and Caucasian men (r=0.37; p<0.001), also in African (r=0.193; p=0.028) and Caucasian women (r=0.14; p=0.036). After adjustments were applied for age, this correlation remained in African (r=0.23; p=0.010) and Caucasian men (r=0.22; p=0.005) only. An inverse correlation was found between fibulin-1 and albumin in African men (r=-0.28; p=0.002), but not in Caucasian men (r=-0.09; p=0.245). No significant correlation was found between fibulin-1 and CRP in any group. Forward stepwise regression analysis was performed in men and the previous associations between fibulin-1 and suPAR were confirmed in African and Caucasian men; along with the inverse relationship of fibulin-1 with albumin (Adj. R2=0.217; β=–0.210; p=0.013) in African men only. Conclusion: Fibulin-1 was positively associated with suPAR in African and Caucasian men, but not in women. We also found fibulin-1 to be negatively associated with albumin in African men only. These results are indicative of the presence of potential subclinical low-grade inflammation as depicted by suPAR within the extracellular matrix. This low-grade inflammation may contribute to the potential onset of cardiac fibrosis or vascular sclerosis among these South African men with lower albumin levels. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014

Background: Fibulin-1, an extracellular matrix component and mediator in cardiac fibrosis, is expressed in cardiac valves, heart muscles and blood vessels and may contribute to different cardiovascular pathological conditions such as hypertension, aortic valve stenosis, atrial fibrillation and coronary artery disease. The most conspicuous functions of fibulin-1 include cell adhesion and cell migration within the extracellular matrix (ECM). This was found to reflect vascular dysfunction contributing to the development of fibrosis in the myocardium by means of changes in the ECM, possibly as a result of inflammation. Inflammatory mediators such as C-reactive protein (CRP) and albumin have been investigated over the years for the role they play in the inflammatory processes. However, one inflammatory mediator, soluble urokinase-type plasminogen activator receptor (suPAR), only emerged as a potential biomarker in the development of sclerotic disease. SuPAR is a soluble bioactive form of the urokinase-type plasminogen activator receptor (uPAR) secreted by inflammatory cells such as macrophages, endothelial cells and monocytes. The most profound functions of suPAR such as cell migration and cell adhesion contribute to the development of diseases such as infection, autoimmune diseases, cancer and atherosclerosis. Motivation and aim: This study was motivated by an awareness of the limited data on the potential link between fibulin-1 and suPAR, along with other markers of inflammation (CRP and albumin). We aimed to compare the levels of a marker of cardiac fibrosis (fibulin-1) and inflammatory mediators (suPAR, CRP and albumin) in African and Caucasian men and women. A second aim was to explore fibulin-1 and its potential association with these inflammatory markers independent of haemodynamic and metabolic risk factors in a bi-ethnic cohort from South Africa. Methodology: Data from the cross-sectional SAfrEIC study (South African study regarding the role of Sex, Age and Ethnicity on Insulin sensitivity and Cardiovascular function) were used, which initially included 756 participants. Our study population comprised 290 Africans (men: n=130; women: n=160) and 343 Caucasians (men: n=160; women: n=183). We excluded HIV-infected participants (n=115) as well as those with missing data (n=8). Traditional cardiovascular measurements together with the relevant biochemical analyses were done. T-tests and Chi-square tests were used to compare means and proportions between groups, respectively. Single and partial correlations were performed to determine the relationship of fibulin-1 with suPAR, CRP and albumin, with adjustments for age. SuPAR, CRP and albumin were divided into tertiles to explore the association with fibulin-1 levels, while adjusting for age, body mass index (BMI) and diastolic blood pressure (DBP) by using analysis of covariance (ANCOVA). Multiple regression analysis was performed to explore independent associations. Results: Participants were divided into African and Caucasian men and women due to significant interactions of the main effects of ethnicity and gender on the association of fibulin-1 with suPAR (ethnicity: F(633)=7.29; p<0.001 and gender: F(633)=7.99; p<0.001). Fibulin-1 levels were higher in African men (p=0.010), whereas CRP was higher in African women (p<0.001) compared to their Caucasian counterparts. In both gender groups suPAR levels were higher and albumin lower in Africans compared to Caucasians (p<0.006). In single regression analyses, a positive correlation existed between fibulin-1 and suPAR in African (r=0.19; p=0.028) and Caucasian men (r=0.37; p<0.001), also in African (r=0.193; p=0.028) and Caucasian women (r=0.14; p=0.036). After adjustments were applied for age, this correlation remained in African (r=0.23; p=0.010) and Caucasian men (r=0.22; p=0.005) only. An inverse correlation was found between fibulin-1 and albumin in African men (r=-0.28; p=0.002), but not in Caucasian men (r=-0.09; p=0.245). No significant correlation was found between fibulin-1 and CRP in any group. Forward stepwise regression analysis was performed in men and the previous associations between fibulin-1 and suPAR were confirmed in African and Caucasian men; along with the inverse relationship of fibulin-1 with albumin (Adj. R2=0.217; β=–0.210; p=0.013) in African men only. Conclusion: Fibulin-1 was positively associated with suPAR in African and Caucasian men, but not in women. We also found fibulin-1 to be negatively associated with albumin in African men only. These results are indicative of the presence of potential subclinical low-grade inflammation as depicted by suPAR within the extracellular matrix. This low-grade inflammation may contribute to the potential onset of cardiac fibrosis or vascular sclerosis among these South African men with lower albumin levels. / MSc (Physiology), North-West University, Potchefstroom Campus, 2014

L’obésité maternelle, dont la prévalence ne cesse d’augmenter, est associée à de nombreux troubles de l’accouchement, tels que des dépassements de terme à l’origine d’une augmentation du taux de césariennes. Ces troubles pourraient, en partie, s’expliquer par une concentration plasmatique de leptine plus élevée chez les femmes enceintes obèses ainsi que par les effets inhibiteurs, démontrés in vitro, de cette adipokine sur la contractilité myométriale. Au moment de l’accouchement, la transition phénotypique du myomètre d’un état de quiescence utérine à un état contractile est une étape clé indispensable à la mise en route du travail. Elle est associée à une activation de l’apoptose des cellules myométriales ainsi qu’à un remodelage de la matrice extracellulaire utérine. Le but de notre travail était d’étudier la capacité de la leptine à moduler l’apoptose et le remodelage myométriaux induits par le lipopolysaccharide (LPS).Les échantillons de myomètre ont été prélevés lors de césariennes réalisées avant la mise en route du travail, à la maternité du CHU de Dijon. Les effets de la leptine ont été évalués après incubation des explants myométriaux pendant 48 heures avec du LPS (10 µg/ml) avec ou sans leptine (de 10-10 à 10-8 M).Nos résultats ont démontré la capacité de la leptine à inhiber, de façon concentration-dépendante, l’apoptose induite par le LPS en diminuant l’expression des protéines pro-apoptotiques (caspase-3 clivée, BAX) et en augmentant celle du médiateur anti-apoptotique BCL2. Cet effet anti-apoptotique de la leptine dans le myomètre gestant était associé à l’activation de la voie de signalisation ERK1/2. De plus, nos résultats ont montré que la leptine était également capable de s’opposer, de façon concentration-dépendante, à la dégradation du collagène de la matrice extracellulaire myométriale induite par le LPS. Cet effet était associé à l’inhibition de l’activation et de la surexpression des métalloprotéinases MMP2 et MMP9 induites par le LPS.Ce travail a permis d’approfondir les connaissances sur le rôle de la leptine dans la régulation de l'activité du myomètre. Nos résultats suggèrent que les troubles de l’accouchement observés chez les femmes obèses résulteraient de l’inhibition de l’apoptose et du remodelage myométriaux par la leptine, en plus de l’inhibition de la contractilité utérine déjà décrite. / Maternal obesity is associated with a wide spectrum of delivery disorders, such as delayed or post-term delivery, that might be explained partly by the increase in plasma leptin levels in obese women, as leptin inhibits in vitro myometrial contractility. Delivery involves uterine apoptosis and remodelling of the extracellular matrix, via the activation of matrix metalloproteinases (MMP). This study was aimed to assess the role of leptin on human myometrium, by studying the interaction of leptin with lipopolysaccharide (LPS)-induced apoptosis and degradation of myometrial collagen.Myometrial biopsies were obtained from women undergoing caesarean delivery before labour onset. The effects of leptin on myometrial apoptosis and remodelling were assessed by incubating the strips for 48h with LPS (10 µg/ml) alone or with leptin (from 10-10 to 10-8 M).Leptin prevented LPS-induced apoptosis, in a concentration-dependent manner, by down-regulating cleaved caspase-3, BAX and up-regulating BCL2 expression. This effect was specifically mediated through leptin receptors stimulation followed by ERK1/2 signalling pathway activation. Leptin prevented, in a concentration-dependent manner, an LPS-induced decrease in myometrial collagen content, and this effect was associated with a decrease in MMP2 and MMP9 activity and overexpression. These effects of leptin were abolished by pre-treatment with a selective leptin receptor antagonist. These results suggest new potential pathways involved in delivery disorders of obese women and propose a role for leptin-induced inhibition of myometrial apoptosis and extracellular matrix remodelling in the development of such disorders.