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Development and execution of clinical studies; tendinopathy
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Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - Nov 2020)
The mechanisms that regulate angiogenic activity in injured or mechanically loaded tendons are poorly understood. In this study we hypothesised that repetitive stretching of tendon cells alters the expression and release of angiogenic factors which may promote tendon vascularization. In order to examine the effects of repetitive stretching on the expression of angiogenic genes, primary human tendon cells were subjected to cyclic stretching. Cyclic stretching of two-dimensional primary tenocyte cell cultures increased the expression of VEGF, bFGF and Cox-2. But, by extending the time course, VEGF, bFGF and Cox-2 were progressively downregulated. Angiogenic profiling of tendon cells by qPCR array identified a number of other genes (ANGPTL4, FGF-1, TGFα, VEGF-C and SPHK1) that responded to tensile loading in a similar pattern. Further experiments revealed that cyclic stretching of human tendon fibroblasts stimulated the expression and release of ANGPTL4 protein via TGF-β and HIF-1α signalling. ANGPTL4 promoted the angiogenic activity of endothelial cells. Angiogenic activity was also increased following injury and following ANGPTL4 injection into mouse patellar tendons, whereas the patellar tendons of ANGPTL4 knock out mice displayed reduced angiogenesis following injury. In human rotator cuff tendons, there were both spatial and quantitative associations of ANGPTL4 with tendon endothelial cells. The experiments described in this thesis have shown that ANGPTL4 may assist in the regulation of vascularity in injured or mechanically loaded tendon. TGF-β and HIF-1α are two signalling pathways that modulate the expression of ANGPTL4 by tendon fibroblasts and which could, in future, be manipulated to influence tendon healing or adaptation.
Tendinopathy is a common problem in the population leaving people in pain, unable to work or be physically active. High levels of musculotendinous strain (resulting from heavy lifting or obesity) and repetitive movements are risk factors for tendinopathy. Because MMPs and TIMPs play a crucial role in the repair, remodeling, and degeneration of collagen fibers in tendon, the aim of this dissertation was to identify the potential roles of MMPs, TIMPs and collagens type I and III, using in-vitro and in-vivo models of overuse and repair. Having identified a potential role of MMP2 in these laboratory models, a clinical study was also conducted to evaluate the serum levels of MMPs and TIMPs in patients who had experienced Achilles tendon rupture. Cultured tendon cells, controlled by high frequency or high strain stimulation, simulating overuse, increased MMP2 mRNA expression. Collagen type I mRNA and protein levels were increased in cultured tendon cells by controlled mechanical stimulation with intermittent rest periods compared to continuous mechanical stimulation.In both the normal healthy rabbit and an overuse model of the rabbits’ Achilles tendon, regional differences in mRNA expression and histological structure were observed. After two weeks of repetitive tendon loading, collagen intensity, measured by second harmonic generation microscopy, was decreased in the flexor digitorum superficialis (FDS) tendon compared to the contralateral FDS tendon and healthy control FDS tendon, indicating damage or remodelling of the collagen in response to overuse. Structural changes were observed locally, combined with elevated tissue MMP2 protein levels suggesting a possible contribution of MMP2 to the development of early collagen degradation. MMP2 appears to play a role early in the response of tendon to repetitive loading. It is detectable in serum after 1 week of overuse, and high repetition number and high strain level are independent modulators of MMP2 expression in tenocytes. However, MMP2 levels in serum decline to baseline after 2 weeks in the animal model, and were downregulated compared to controls in patients with a more Achilles tendon rupture. Further research into the specific processes of tendon injury and repair played by MMP2 are warranted.
Master's Student Supervision (2010 - 2018)
There has been growing interest in studying the possible effects of statins on tendons due to case studies and retrospective chart reviews that reported a potential relationship between statin use and tendon pathology, as well as laboratory studies demonstrating that statins directly influence tenocyte metabolism. However, a recent epidemiological study found no association between statin use and the risk of tendon rupture. Since statins are widely used cholesterol-lowering medications, it is important to understand the potential relationship between statin use and tendon health. With the use of Ultrasound Tissue Characterization (UTC), the aims of this pilot cross-sectional study were to see if there were signs of reduced collagen organization or increased cross-sectional area (CSA) of the Achilles tendon in individuals who had been taking statins for at least a year (the Statin group), compared to those who had never taken a statin (the Control group). We hypothesized that individuals in the Statin group would demonstrate a greater cross-sectional area and reduced collagen organization (determined by the percent of echo-type I) of their Achilles tendons compared to individuals in the Control group. To test this hypothesis, we analyzed the UTC scans of 66 individuals who were either taking Statins (n=33) or who had never taken statins (n=33, control group) and compared their resulting Achilles tendon CSA and echo-type I values. There were no significant differences in Achilles tendon CSA or proportion of echo-type I patterns between the two groups, implying that statins do not negatively impact the health of the Achilles tendon. In the entire cohort (n=66), there were significant effects of age (r = -0.31, p = 0.012) and BMI (r = -0.31, p = 0.012) on echo-type I values. These findings support previous work which demonstrated a lack of association betweenstatin use and tendon pathology, but demonstrate the negative effects of aging and elevated BMI on tendon health.
No abstract available.
Achilles tendon (AT) is the strongest tendon in the body. One of the major causes of AT pathology, chronic tendinopathy, is frequently due to excessive loading. Despite the risk of overuse injury, exercise training with appropriate mechanical loading parameters has been found to trigger an adaptation response in the AT. However, the influence of some loading parameters, such as the duration of rest periods between exercise repetitions, remains unknown. Therefore, the aim of this study was to examine the effect of 10s rest insertion during isometric resistance training (Long rest training; LRT) on the morphological properties of human AT, compared with same training intensity and volume but with 3s rest insertion (short rest training; SRT). I hypothesized that ATs exposed to LRT would demonstrate increased tendon collagen organization and tendon cross-sectional area (CSA) compared with baseline, but that SRT would not demonstrate any change in either variable.To test my hypothesis, we recruited healthy adults, and randomly allocated one leg to LRT and the other to SRT. The exercise protocol consisted of 5 sets of 10 isometric calf presses at 90% of maximum voluntary contraction, three times a week over a 12-weeks training period. Tendon collagen organization (proportion of type I echoes) and CSA were measured by ultrasound tissue characterization before and after the 12-weeks period. The primary outcome was the proportion of type I echoes.In contrast to our hypothesis, neither LRT nor SRT induced an improvement in collagen organization or tendon CSA. However, tendons exposed to SRT demonstrated a reduction in the proportion of type I echoes following exercise from 0.66 (95% CI= 0.60 to 0.70) to 0.55 (95% CI=0.49 to 0.60), (p
Background: Resistance exercise is effective in relieving pain and improving grip strength in patients with lateral epicondylalgia (LE). However, patients’ activity-related pain can hinder their active participation in an exercise program. Acupuncture, particularly electro-acupuncture (EA), may be an effective complementary modality for pain control in order to promote patients’ participation in an exercise program and further to enhance therapeutic effects. Objectives: 1) assess the feasibility of a study designed to compare the effect size of analgesia induced by EA vs. standard acupuncture (SA); 2) estimate the time course of the analgesic effect of EA and SA for patients with LE; and 3) investigate if the analgesic effect of either intervention is associated with a change in pain-free grip strength. Methods: A double-blind, parallel-group randomized controlled feasibility trial was conducted at a research centre located in Vancouver, Canada. Twenty-one participants with unilateral LE lasting more than 6 weeks duration were enrolled in the study. The participants were randomly allocated to receive a single treatment of either EA (10-30 Hz) or SA. The primary outcome measure was pain-free grip strength, and the secondary outcome measures included the severity of lateral elbow pain (numeric rating scale), and patients’ global rating of change. Outcomes were measured over a 72-hour period. Results: No significant differences in outcome measures were found between the two treatment groups at any time point. A pattern of gradual improvement of pain-free grip strength (approximately 12N /day) over the 72-hour monitoring period in both treatment groups was observed, and this improvement was statistically significant compared to baseline at the 72-hour time point (38 ± 13N). In contrast, there was a statistically significant reduction in patients’ perceived pain level immediately after either treatment, and this improvement was maintained throughout the 72-hour follow-up period (-0.99~-1.59 ± 0.35). After 24 hours, 5% of patients reported themselves as feeling ‘much better’, 55% ‘slightly better’, 15% ‘unchanged’, 10% ‘slightly worse’, 10% ‘moderately worse’ and 5% ‘much worse’. Conclusion: Acupuncture may complement the therapeutic effect of rehabilitation exercise program as it provides immediate pain relief for patients with chronic LE.Trial registration: ISRCTN14667535Funding: none
Background: Exercise-based rehabilitation for chronic Achilles tendinopathy (CAT) has proven to be effective, but it can be a painful process. The purpose of this research is to see if a topically applied non-steroidal anti-inflammatory drug, diclofenac, will be able to relieve the pain associated with chronic tendinopathy. The effects of diclofenac on subjects’ pain and mechanical hyperalgesia will be evaluated at rest and during simple calf exercises. It is expected that diclofenac will reduce pain among subjects with Achilles tendinopathy. Methods:19 subjects (22 Achilles) with CAT were randomly assigned to a crossover treatment order (active gel containing 10% diclofenac, or placebo). The primary outcome measure was pain level during tendon loading (hopping) and at rest. The secondary outcome measures evaluated tendon loading characteristics, and mechanical hyperalgesia over the lesion, and over the bilateral trapezius muscles.Results:Pain was significantly reduced from baseline with the use of diclofenac during tendon loading (p=0.0003) and rest (p=0.0313). At baseline the average resting pain was 3.05 (+/-1.43), with the use of diclofenac the pain was 2.32 (+/- 1.52), and with the use of placebo the pain was 2.68 (+/- 2.03). At baseline the average hopping pain was 4.82 (+/-2.1), with the use of diclofenac the average hopping pain was 3.05 (+/-1.81), and with the use of placebo the average pain was 3.77 (+/-2.76). During the hopping test, subjects were able to generate significantly more force when experiencing less pain (p
The presence or absence of inflammatory cells in chronic Achilles tendinopathy has been a controversial subject in previous studies. Macrophages, T lymphocytes, and neutrophils have previously been detected in injured human Achilles tendons, whereas other authors have reported that there is no evidence for their occurrence. This controversy may stem from the fact that human Achilles tendon overuse injuries usually develop gradually over time, and the time course of inflammation in response to overuse has been difficult to establish in clinical populations. The aim of my study was to examine the presence of inflammatory cells in the Achilles tendon of rabbits that were subjected to repetitive mechanical loading of defined durations. Twenty-Four New Zealand male rabbits were subjected to repetitive mechanical loading of the Achilles tendon and grouped into four groups in this study, according to the exercise time period for each group: 0, 1, 3, and 6 weeks. Achilles tendons were harvested at the end of each time period. Achilles tendons sections were stained with Hematoxylin and Eosin to examine the histological changes. Both Neutrophils and T-lymphocytes were detected by Immunohistochemistry. Macrophages were detected using the Prussian blue staining. A very small number of inflammatory cells were detected in some tissue sections in the control group. Tissue sections from exercised groups 1, 3, and 6 weeks respectively, showed some qualitative changes in tendon morphology. Collagen bundles were disorganized, and hyalinized patches and spaces between collagen fibers were observed. Tenocyte nuclei were rounder and basophilic, and there was an increase in their numbers with loss of parallel alignment. Macrophages, T-lymphocytes, and neutrophils were detected in tendon sections, specifically in the paratenon. Statistically both lymphocytes and macrophages were significantly higher than control at 6 weeks. While the number of macrophages in the control was lower than the 6 weeks group, there was no significant difference between 1 week and 3 weeks. However, no lymphocytes were found at week 3. Neutrophils in all groups showed no significant difference. The evidence of inflammation was not evenly distributed, as some tissue sections from the same groups showed no evidence of inflammatory cells.
Tendinopathy is a major cause of morbidity in athletic populations and in the work force, traditionally thought to occur as a consequence of an imbalance between damage (resulting from mechanical loading) and repair. However, one third of the cases for midportion Achilles tendinopathy occur in sedentary individuals, and recent data suggests an association between hypercholesterolemia and the occurrence of tendon rupture or tendinopathy. The aim of this study was to examine the link between elevated lipids and tendon pathology. We used an apolipoprotein E-knockout model (ApoE-KO), in which apolipoprotein E deficiency leads to development of atherosclerosis. We hypothesized that tendons from ApoE-KO mice fed a high fat diet, in comparison to those fed a regular chow diet and the wild type (non-atherosclerotic mice), will demonstrate increased lipid deposition, increased cross-sectional area, and increased expression levels of collagen genes (Col1a1 and Col3a1), a growth factor gene (TGF-β), and an indicator of mast cell presence (Cpa3). To test these hypotheses, ApoE-KO and control mice were fed a regular or high fat diet and sacrificed at different time points: 0, 15, and 30 weeks. The morphological properties were examined on H&E stained Achilles tendon sections while the lipid content was analyzed with Oil Red O staining. Tendon thickening was measured by ultrasonography of patellar tendon cross-sectional area. qPCR analysis was carried out on tail tendons at 30 week time point to analyze gene expression of Cpa3, TGF-β, Col1a1, and Col3a1. ApoE-KO mice developed xanthomatous lesions, and showed less weight gain than control mice. ApoE-KO mice showed no appreciable changes in tendon histomorphology. Compared to control mice, ApoE-KO mice had lower tendon lipid content but demonstrated an increase in tendon cross-sectional area. Col1a1 gene expression levels were decreased in ApoE-KO mice. Cpa3, TGF-β, and Col3a1 showed no differences between strains; however, Cpa3 expression was decreased in mice that were fed the high fat diet. ApoE-KO mice demonstrated significant tendon alterations, demonstrating thicker tendons with decreased collagen expression. Future work is required to determine the mechanism involved and the potential impact on tendon function.