Browsing by Author "Hart, David A."
Now showing 1 - 20 of 33
Results Per Page
Sort Options
Item Open Access The Characterization of Proteoglycan 4 and Hyaluronan Composition in the Vitreous Humour and Their Potential Contributions to Steady Shear Viscosity(2020-01-27) Alarifi, Abdulaziz A.; Schmidt, Tannin A.; Hart, David A.; Krawetz, Roman J.; Stell, William K.; Moritz, Orson L.Background and aim: The vitreous humour is a connective tissue in the eye that contributes to several physiological and pathological processes. The full details of the complex vitreous humour composition and the extent of its functionality remain elusive. Proteoglycan 4 (PRG4), a mucin-like O-linked glycosylated protein, has recently been identified in human vitreous humour. PRG4 is known to act synergistically with hyaluronan (HA) in synovial fluids, where it functions as a boundary lubricant, contributes to viscosity, and more. Studying PRG4 in this newly discovered site might advance knowledge about its rheological properties (specifically within the eye) and whether or not PRG4 is involved. The aim of this thesis was to analyze the presence, source and potential function of PRG4 in vitreous humour. The objectives were: 1) to quantify the PRG4 and HA (including its molecular weight (MW) distribution) content, 2) to immunolocalize PRG4 in the eye globe, and examine its local synthesis, and 3) to characterize the viscosity of vitreous humour samples with varying PRG4 and HA concentrations. Methods: Human vitreous humour samples were collected from post-mortem human patients. Alpha amplified luminescent proximity homogeneous assay (AlphaLISA) and enzyme-linked immunosorbent assay (ELISA) tests were performed to measure the concentration of PRG4 and HA, respectively. The MW distribution of HA was determined by agarose gel electrophoresis. Vitreous humour cells were cultured from porcine to examine the synthesis of PRG4. PRG4 was immunolocalized in eye globes from wild type (WT) and PRG4-KO mice. Steady shear viscosity was characterized for human vitreous humour using a rheometer, before and after adding exogenous recombinant human PRG4 (rh PRG4). Results: The mean (± standard deviation) concentration of PRG4 in human vitreous humour (N=36) was 25 ± 32 µg/mL. For HA, the mean concentration in human vitreous humour was 344±317 µg/mL, and 71% of the overall HA in vitreous humour was below 459 kDa. Increasing age was positively correlated with concentration of PRG4. PRG4 was synthesized by cultured porcine vitreous humour cells. Using wild type and PRG4-KO (knockout) mice, PRG4 was immunolocalized in the ciliary body, cornea, sclera, vitreous cortex, and some parts of the retina. Viscosities for human vitreous humour samples showed minor variations, and were negatively correlated with HA MW. Conclusion: This is the first investigation of both the presence and potential function of PRG4 in vitreous humour. The findings serve to expand understanding of vitreous humour composition, and how that might be a factor in ocular pathology and potential therapies.Item Open Access A clinically relevant BTX-A injection protocol leads to persistent weakness, contractile material loss, and an altered mRNA expression phenotype in rabbit quadriceps muscles(Journal of Biomechanics, 2015-07-16) Fortuna, Rafael; Sawatsky, Andrew; Herzog, Walter; Vaz, Marco Aurélio; Hart, David A.Botulinum toxin type-A (BTX-A) injections have become a common treatment modality for patients suffering from muscle spasticity. Despite its benefits, BTX-A treatments have been associated with adverse effects on target muscles. Currently, application of BTX-A is largely based on clinical experience, and research quantifying muscle structure following BTX-A treatment has not been performed systematically. The purpose of this study was to evaluate strength, muscle mass, and contractile material six months following a single or repeated (2 and 3) BTX-A injections into the quadriceps femoris of New Zealand white rabbits. Twenty three skeletally mature rabbits were divided into four groups: experimental group rabbits received 1, 2, or 3 injections at intervals of 3 months (1-BTX-A, 2-BTX-A, 3-BTX-A, respectively) while control group rabbits received volume-matched saline injections. Knee extensor strength, quadriceps muscle mass, and quadriceps contractile material of the experimental group rabbits were expressed as a percentage change relative to the control group rabbits. One-way ANOVA was used to determine group differences in outcome measures (α=0.05). Muscle strength and contractile material were significantly reduced in experimental compared to control group rabbits but did not differ between experimental groups. Muscle mass was the same in experimental BTX-A and control group rabbits. We concluded from these results that muscle strength and contractile material do not fully recover within six months of BTX-A treatment.Item Open Access Clonal analysis of synovial fluid-derived mesenchymal stems cells in a porcine model(2012) Kutcher, Josh; Frank, Cyril B.; Hart, David A.Mesenchymal stem cells (MSCs) were isolated from porcine synovial fluid (SF), and clonal populations derived through limiting dilution. Eighteen clones from three pigs (6 per pig) were then analyzed for their proliferative and differentiation characteristics. All 18 clones were able to undergo at least 25 population doublings, suggesting a high self-renewal capability. Their differentiation properties were assessed using histological stains and RT-PCR. Less than 50% of clones were capable of osteogenic differentiation, while greater than 75% were bipotent chondro-adipo progenitors; a phenotype never reported in other tissue types. In addition, all but one clone differentiated into chondrocytes, indicating an enhanced potential for cartilage regeneration. Despite using clonal populations, a great deal of variation was present between clones showing distinct differentiation potentials. The presented study suggests that clonal analysis is an effective method of identifying subpopulations in porcine SF, and that SF-derived MSCs may be an ideal tissue source for regenerating cartilage.Item Open Access Curbing Inflammation in Multiple Sclerosis and Endometriosis: Should Mast Cells Be Targeted?(2015-10-15) Hart, David A.Inflammatory diseases and conditions can arise due to responses to a variety of external and internal stimuli. They can occur acutely in response to some stimuli and then become chronic leading to tissue damage and loss of function. While a number of cell types can be involved, mast cells are often present and can be involved in the acute and chronic processes. Recent studies in porcine and rabbit models have supported the concept of a central role for mast cells in a “nerve-mast cell-myofibroblast axis” in some inflammatory processes leading to fibrogenic outcomes. The current review is focused on the potential of extending aspects of this paradigm into treatments for multiple sclerosis and endometriosis, diseases not usually thought of as having common features, but both are reported to have activation of mast cells involved in their respective disease processes. Based on the discussion, it is proposed that targeting mast cells in these diseases, particularly the early phases, may be a fruitful avenue to control the recurring inflammatory exacerbations of the conditions.Item Open Access Diet-Induced Obesity and Musculoskeletal Health: Studies in a Rat Model(2017) Collins, Kelsey Helen-Marie Collins; Herzog, Walter; Hart, David A.; Reimer, Raylene A; Frank, Cyril BThe primary goal of this Thesis is to develop a model of diet-induced obesity (DIO), using a high-fat/high-sucrose (HFS) diet to evaluate the impact of DIO on the musculoskeletal health of rats. The overarching hypothesis is that DIO can induce deleterious musculoskeletal changes in this animal model. In the first study, the role of DIO in the onset of joint damage is assessed by superimposing the diet on a model of post-traumatic osteoarthritis (PTA) progression. This study recapitulated changes in systemic and local inflammation with DIO that had been described in the clinical literature, had not been demonstrated in a preclinical model of osteoarthritis (OA). The next study linked diet-induced knee damage, without trauma, to changes in gut microbiota for the first time. The third study explored time-course changes in systemic and local inflammatory mediators in conjunction with joint damage and response to DIO. Given the changes in the systemic inflammatory environment, the next study then evaluated other synovial joints in addition to the knee joint. This study suggested that the knee and shoulder are uniquely vulnerable to damage with DIO, while the hip joint is protected. Additionally, muscle is implicated in both OA progression and the pathophysiology of metabolic syndrome, and therefore the effects of HFS DIO on muscle were measured. The fifth study evaluated DIO-induced changes in the integrity of the Vastus Lateralis (VL) quadriceps muscle. Given the severity of changes seen in the VL, short-term exposure to HFS was then explored in the VL muscle in study six, as were diet-induced changes in the gut microbiota and systemic inflammation. Because muscles have different phenotypes, related to their substrate utilization, force-producing capacity, and fatigability, we then explored another muscle, the soleus, which was previously suggested to be protected against diet-induced changes. Collectively, this Thesis demonstrates that DIO can result in structural damage across musculoskeletal tissues, while implicating several opportunities for therapeutic intervention to mitigate or prevent damage across musculoskeletal tissues. These relations and opportunities are summarized in Chapter 10, which is an integrative review on the influence of diet-induced systemic inflammation on musculoskeletal tissues.Item Open Access Do Mechanical and Structural Characteristics of Degenerated Intervertebral Discs Contribute to Development of Degenerative Scoliosis and Spondylolisthesis?(2023-08-28) Bader, Taylor J.; Swamy, Ganesh; Hart, David A.; Duncan, Neil; Salo, PaulIntervertebral disc (IVD) degeneration is the age-related breakdown of the cushioned discs that serve as the principal connection between the vertebral bodies. Although affecting 80% of individuals over the age of 50, the causes of the highly varied severity of this disease are not well understood. Additionally, in some cases, primarily in women, the degeneration of the IVD leads to spinal deformities. Degenerative scoliosis (dScoli), the lateral translation and rotation of the vertebrae, and degenerative spondylolisthesis (dSpondy), the forward slippage of the vertebrae with respect to its caudal neighbour, both potentially lead to immobility and pain. These conditions involve increased instability of motion segments of the spine, cascading into further degeneration. The aim of this study was to compare the shear mechanical behaviour of the annulus fibrosus (AF), the outer portion of the IVD, in normal, non-deformity degenerated (degen), dScoli, and dSpondy patients. Small sections of the AF were collected from healthy donors and surgical patients and sheared, mimicking the translation seen in spinal deformity. These same AF sections were scored for degeneration through histology and their lamellar structure was measured with optical coherence tomography (OCT). From these tests, the structure-function relationship of degenerated AF was analyzed to explore degenerative changes. A reduced shear stiffness in degen samples (radial 27 ± 24 kPa, circumferential 57 ± 43 kPa) when compared to normal tissue (radial 80 ± 38 kPa, circumferential 231 ± 73 kPa) was found (p < 0.05). dScoli tissue were further reduced in shear stiffness (radial 12 ± 6 kPa, circumferential 33 ± 21 kPa), although not significantly. There were significant trends linking an increase in structure degeneration, by histology (rS = -0.58, p < 0.01) and OCT (rS = -0.70, p < 0.01), to decreased circumferential shear modulus. Differences in structure and shear stiffness will serve as the backbone for further research into surgical tissue to better understand the progression of IVD degeneration and spinal deformities. Through understanding of the structure-function relationship of the AF, predictors of outcomes and potential treatments could help patients better manage these painful conditions.Item Open Access The Effect of Glucagon-Like Peptide-2 Receptor Agonists on Colonic Anastomotic Wound Healing(Hindawi Publishing Corporation, 2010-07-29) Redstone, Heather A.; Buie, William D.; Hart, David A.; Wallace, Laurie; Hornby, Pamela J.; Sague, Sarah; Hoist, Jen J.; Sigalet, David L.Item Open Access Expression of urokinase and plasminogen activator type-1 by the human hepatoma cell line HuH-7(1990) Arndt, Allan David; Hart, David A.Item Open Access Genomic variations in the mmp-1 promoter influence estrogen receptor beta mediated activity in mechanically activated environments(2010) Thaler, John David; Hart, David A.; Shrive, Nigel G.Item Open Access High-Fat High-Sucrose Diet Leads to Dynamic Structural and Inflammatory Alterations in the Rat Vastus Lateralis Muscle(Journal of Orthopaedic Research, 2016) Herzog, Walter; Collins, Kelsey; Hart, David A.; Reimer, Raylene A.; Seerattan, Ruth A.; Banker, Christine W.; Sibole, Scott C.The influence of obesity on muscle integrity is not well understood. The purpose of this study 37 was to quantify structural and molecular changes in the rat vastus lateralis (VL) muscle as a 38 function of a 12-week obesity induction period and a subsequent adaptation period (additional 39 16-weeks). Male Sprague-Dawley rats consumed a high-fat, high-sucrose (DIO, n=40) diet or a 40 chow control-diet (n=14). At 12-weeks, DIO rats were grouped as prone (DIO-P, top 33% of 41 weight change) or resistant (DIO-R, bottom 33%). Animals were euthanized at 12-weeks or 28-42 weeks on the diet. At sacrifice, body composition was determined and VL muscles were 43 collected. Intramuscular fat, fibrosis, and CD68+ cells were quantified histologically and 44 relevant molecular markers were evaluated using RT-qPCR. At 12- and 28-weeks post obesity 45 induction, DIO-P rats had more mass and body fat than DIO-R and chow rats (p<0.05). DIO-P 46 and DIO-R rats had similar losses in muscle mass, which were greater than those in chow rats 47 (p<0.05). mRNA levels for MAFbx/atrogin1 were reduced in DIO-P and DIO-R rats at 12- and 48 28-weeks compared to chow rats (p<0.05), while expression of MURF was similar to chow 49 values. DIO-P rats demonstrated increased mRNA levels for pro-inflammatory mediators, 50 inflammatory cells, and fibrosis compared to DIO-R and chow animals, despite having similar 51 levels of intramuscular fat. The down-regulation of MAFbx/atrogin1 may suggest onset of 52 degenerative changes in VL muscle integrity of obese rats. DIO-R animals exhibited fewer 53 inflammatory changes compared to DIO-P animals, suggesting a protective effect of obesity 54 resistance on local inflammation.Item Open Access IGF-1 Gene Transfer to Human Synovial MSCs Promotes Their Chondrogenic Differentiation Potential without Induction of the Hypertrophic Phenotype(2017-06-27) Ikeda, Yasutoshi; Sakaue, Morito; Chijimatsu, Ryota; Hart, David A.; Otsubo, Hidenori; Shimomura, Kazunori; Madry, Henning; Suzuki, Tomoyuki; Yoshikawa, Hideki; Yamashita, Toshihiko; Nakamura, NorimasaMesenchymal stem cell- (MSC-) based therapy is a promising treatment for cartilage. However, repair tissue in general fails to regenerate an original hyaline-like tissue. In this study, we focused on increasing the expression levels for insulin-like growth factor-1 (IGF-1) to improve repair tissue quality. The IGF-1 gene was introduced into human synovial MSCs with a lentiviral vector and examined the levels of gene expression and morphological status of MSCs under chondrogenic differentiation condition using pellet cultures. The size of the pellets derived from IGF-1-MSCs were significantly larger than those of the control group. The abundance of glycosaminoglycan (GAG) was also significantly higher in the IGF-1-MSC group. The histology of the IGF-1-induced pellets demonstrated similarities to hyaline cartilage without exhibiting features of a hypertrophic chondrocyte phenotype. Expression levels for the Col2A1 gene and protein were significantly higher in the IGF-1 pellets than in the control pellets, but expression levels for Col10, MMP-13, ALP, and Osterix were not higher. Thus, IGF-1 gene transfer to human synovial MSCs led to an improved chondrogenic differentiation capacity without the detectable induction of a hypertrophic or osteogenic phenotype.Item Open Access In vitro mechanical loading of osteoblast-like mg-63 cells: insights into bone remodelling(2008) Parreno, Justin; Hart, David A.Item Open Access Item Open Access Isolation, characterization and regulation of expression of plasminogen activator inhibitors from tissue culture cells(1988) Rehemtulla, Alnawaz, 1959-; Hart, David A.Item Open Access Knee joint biomechanics in ovine models of post-traumatic osteoarthritis(2018-08-23) Shekarforoush, Seyed Mohammad Mehdi; Shrive, Nigel; Hart, David A.; Goldsmith, Peter B.Post-traumatic osteoarthritis (PTOA) is a sub-type of osteoarthritis, which can develop after injury to a joint and to date, many aspects of the etiology of the disease remain unclear. The main objective of this research was to quantify the subtle changes in the kinematic and the kinetic variables in the ovine stifle (knee) joint following different types of ligamentous and meniscal injury, and to investigate possible consequences of those biomechanical changes on gross morphological osteoarthritis-like damage in the joints. Overall, there was a high degree of inter-subject variability in the measured variables. We found different degrees of instabilities in the 6 degree-of-freedom kinematics and finite helical axis variables of the joints after ligamentous and meniscal injuries. Nevertheless, we did not detect correlations between the magnitudes of the changes in the kinematic variables with significant change and osteoarthritis-like damage in the joints. The kinematic analyses also suggest that the absolute change of the tibiofemoral translation vector could be an important risk factor for osteoarthritis development after ligament injuries. The magnitude of the joint angular velocities was decreased in extension during swing after different types of injury and the reduction was correlated with the morphological damage for two multiple ligament injury groups. We also found a weak correlation between the increase in some components of the tibiofemoral sliding velocity during stance after partial- anterior cruciate ligament (ACL) and medial collateral ligament (MCL) transection (p-ACL/MCL Tx) and the joint morphological damage in both the lateral and medial compartments of the joint. Kinetic analyses demonstrated a reduction in LCL load, slight increase in the PCL load and a consistent increase in the healed MCL load, especially during the stance stage of gait, after p-ACL/MCL Tx. Overall, the medial meniscus carried a higher magnitude of load than the lateral meniscus and the magnitude of the medial meniscus load was increased consistently in the animals through some parts of the gait cycle, 20 weeks after p-ACL/MCL Tx. No correlation was detected between variation in the meniscal loads and morphological damage in the joints, suggesting that the increase in the meniscal load after p-ACL/MCL Tx might not result in visible post-traumatic osteoarthritis damage in the short term after injury in an ovine model. Finally, we did not detect any consistent correlation between the changes in the ligament or meniscal loads and changes in analyzed kinematic variables, suggesting that ligamentous and meniscal loading regimes are not linear functions of different kinematic variables. The results improve our insight on how joint mechanical abnormalities can result in the development of post-traumatic osteoarthritis.Item Open Access Lithium enhances survival in murine models of autoimmune disease: evidence for target organ effects(1995) Lenz, Steven Paul; Hart, David A.Item Open Access The mechanical and biochemical properties of tail tendon in a rat model of obesity: effect of moderate exercise and prebiotic fibre supplementation(2019-05-09) Rios, Jaqueline Lourdes; Ko, Loretta; Joumaa, Venus; Liu, Shuyue; Diefenthaeler, Fernando; Sawatsky, Andrew; Hart, David A.; Reimer, Raylene A.; Herzog, WalterThe worldwide trajectory of increasing obesity rates is a major health problem precipitating a rise in the prevalence of a variety of co-morbidities and chronic diseases. Tendinopathy, in weight and non-weight bearing tendons, in individuals with overweight or obesity has been linked to metabolic dysfunction resulting from obesity. Exercise and dietary fibre supplementation (DFS) are common countermeasures to combat obesity and therefore it seems reasonable to assume that they might protect tendons from structural and mechanical damage in a diet-induced obesity (DIO) model. The purpose of this study was to determine the effects of a DIO, DIO combined with moderate exercise, DIO combined with DFS (prebiotic oligofructose), and DIO combined with moderate exercise and DFS on the mechanical and biochemical properties of the rat tail tendon. Twenty-four male Sprague-Dawley rats, fed a high-fat/high-sucrose diet were randomized into a sedentary, a moderate exercise, a DFS, or a moderate exercise combined with DFS group for 12 weeks. Additionally, six lean age-matched animals were included as a sedentary control group. DIO in combination with exercise alone and with exercise and DFS reduced the Young's Modulus but not the collagen content of the rat tail tendons compared to lean control animals. However, no differences in the mechanical and biochemical properties of the rat tail tendon were detected between the DIO and the lean control group, suggesting that DIO by itself did not impact the tail tendon. It seems that longer DIO exposure periods may be needed to develop overt differences in our DIO model.Item Open Access Molecular and cell biology of pig skin: a model for wound healing(2003) Wang, Jian Fei; Hart, David A.Item Open Access Molecular and cell biology of rabbit menisci and articular cartilage of the knee: a model of osteoarthritis(2000) Hellio Le Graverand-Gastineau, Marie-Pierre; Hart, David A.Item Open Access Molecular biology of anabolic and catabolic activities in rabbit knee joint connective tissues(2000) Sciore, Paul; Hart, David A.