Patrik Danielson

University of British Columbia - Vancouver, Vancouver, British Columbia, Canada

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Publications (34)98.1 Total impact

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    ABSTRACT: It has been hypothesised that an upregulation of the neuropeptide substance P (SP) and its preferred receptor, the neurokinin-1 receptor (NK-1 R), is a causative factor in inducing tenocyte hypercellularity, a characteristic of tendinosis, through both proliferative and antiapoptotic stimuli. We have demonstrated earlier that SP stimulates proliferation of human tenocytes in culture. The aim of this study was to investigate whether SP can mediate an antiapoptotic effect in tumour necrosis factor-α (TNF-α)-induced apoptosis of human tenocytes in vitro. A majority (approximately 75%) of tenocytes in culture were immunopositive for TNF Receptor-1 and TNF Receptor-2. Exposure of the cells to TNF-α significantly decreased cell viability, as shown with crystal violet staining. TNF-α furthermore significantly increased the amount of caspase-10 and caspase-3 mRNA, as well as both BID and cleaved-poly ADP ribosome polymerase (c-PARP) protein. Incubation of SP together with TNF-α resulted in a decreased amount of BID and c-PARP, and in a reduced lactate dehydrogenase release, as compared to incubation with TNF-α alone. The SP effect was blocked with a NK-1 R inhibitor. This study shows that SP, through stimulation of the NK-1 R, has the ability to reduce TNF-α-induced apoptosis of human tenocytes. Considering that SP has previously been shown to stimulate tenocyte proliferation, the study confirms SP as a potent regulator of cell-turnover in tendon tissue, capable of stimulating hypercellularity through different mechanisms. This gives further support for the theory that the upregulated amount of SP seen in tendinosis could contribute to hypercellularity.
    British journal of sports medicine 08/2013; · 3.67 Impact Factor
  • P Danielson
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    ABSTRACT: The biochemical micromilieu of human tendons has gained increasing interest during the last decade. Partly prompted by microdialysis studies of both Achilles and patellar tendons, demonstrating an unexpectedly augmented level of the neurotransmitter glutamate in tendinopathy,1 2 Khan et al first suggested a new paradigm concerning tendinopathy pathogenesis,3 in part contradicting already established theories. They suggested that the underlying mechanism of tendinopathy might be biochemical rather than structural. Since then, much contemporary research has been directed towards trying to answer the question of the possible role of biochemical agents in the development of tendon pain and degenerative-like tissue changes, that is, tendinosis. At the cellular level, tendon cells in tendinosis tissue have indeed been shown to produce an array of signal substances that were once thought to be restricted to neurones. Although the functional importance of such biochemical agents in tendinopathy remains to be determined, evidence of a dramatic change in local cell signalling within chronically painful tendons exists. Studies have demonstrated that there is a local, non-neuronal production in the tenocytes of traditionally neuronal mediators, like neuropeptides. These findings include acetylcholine,4(-)6 catecholamines,7(-)9 glutamate,10 and the neuropeptide substance P (SP).11 Furthermore, the receptors for several of these signal substances have been found on nerve fascicles and in blood vessel walls (as well as on the tenocytes themselves) of the tendon tissue. These results suggest that locally produced neuromodulators may influence pain signalling, angiogenesis and vascular regulation, as well as cellular and tissue changes, like cell proliferation and/or apoptosis and matrix remodelling, in tendinopathy.12 Results of novel experimental studies on both in vivo13 and in vitro14 models of tendinopathy have revealed the neuropeptide SP as a key player in cellular regulation of tendinosis. Endogenous production of SP by tendon tissue/cells is significantly increased after mechanical load14 15 and SP furthermore contributes to development of tendinosis tissue characteristics; promoting hypercellularity and angiogenesis.14 16 Very recent unpublished data, presented at this conference, further underline the role of SP, but also acetylcholine, as important mediators in tendinosis. Not least interesting in this respect is the fact that SP inhibits tenocyte apoptosis and consequently prevents self-regulatory mechanisms that should limit the amount of collagen producing cells and prohibit excessive collagen accumulation in tendinosis. All these studies strengthen the biochemical hypothesis,3 suggesting that the underlying pathology of tendinopathy is primarily of biochemical origin rather than mechanical (albeit perhaps indirectly through mechanotransduction). We believe that such a biochemical paradigm of tendinopathy can complement, rather than replace, existing theories. We furthermore believe that this hypothesis fits a theoretical model, put forth by Cook and Purdam, in which tendon pathology is proposed to exist on a continuum that at various points involves several tendon tissue abnormalities.17 This key note lecture aims at giving a brief orientation of the evidence to date in favour of the 'biochemical model of tendinopathy'.
    British journal of sports medicine 06/2013; 47(9):e2. · 3.67 Impact Factor
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    ABSTRACT: Treatment of midportion Achilles tendinopathy has been known to be difficult. Recent ultrasound(US) and Doppler(CD) findings (high blood flow outside ventral tendon), together with results of immunohistochemical analyses (marked presence of blood vessels accompanied by nerve fascicles in the ventral peritendinous tissue) have led to new treatment approaches like sclerosing polidocanol injections, where US and CD-guided injections in the region with high blood flow and nerves outside the tendon have shown good results. However, for satisfying pain relief multiple injection treatments were often needed. Therefore, based on the same principles as for the sclerosing injections, a more radical and one stage mini-surgical procedure has been invented. 107 patients (66 men, 41 women), mean age 43 years (range 24-77), with tendinosis in 125 Achilles tendons were, in local anaesthesia, treated with a US+CD-guided new surgical approach outside the ventral tendon. Pain during tendon loading activity (VAS) and satisfaction with treatment, were evaluated. Before surgery, the mean VAS was 77. After surgery (follow up mean 18 months, range 6-33) the mean VAS was 2 in 111 tendons (89%) from satisfied patients back in full Achilles tendon loading activity. US+CD-guided scraping/tenolysis in the region with rich vascularity and innervation outside the ventral tendon shows good short term clinical results in midportion Achilles tendinopathy.
    British journal of sports medicine 06/2013; 47(9):e2. · 3.67 Impact Factor
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    ABSTRACT: Studies on human patellar and Achilles tendons have shown that tendon cells not only have the capacity to produce acetylcholine (ACh) but also express muscarinic ACh receptors (mAChRs), of subtype M2 (M2R), and that both the production and receptor expression seem to be increased in tendinosis. Hypercellularity and angiogenesis are key histopathologic features in tendinosis tissue. In this study, we aimed at testing the hypothesis that ACh increases the proliferation rate of tenocytes through mAChR stimulation, as well as investigating whether this mechanism is mediated by the extracellular activation (phosphorylation) of the epidermal growth factor receptor (EGFR), which has been shown to elicit DNA synthesis and cell proliferation in other fibroblastic cells types, through an intracellular pathway including activation/phosphorylation of the mitogen activated protein kinases ERK1/2. Human Achilles tenocytes were seeded in cell culture plates and incubated in serum-starved conditions. The cells were pre-treated with the EGFR inhibitor AG1478, the matrix metalloproteinase (MMP) inhibitor GM6001 or the mAChR antagonist atropine. The cells were then stimulated with ACh (10(-6) M) or the vehicle. To determine the levels of phospho-ERK1/2 and phospho-EGFR, Western blot analysis was performed. 5-Bromo-2'-deoxy-uridine (BrdU) and crystal violet staining were used to assess cell proliferation and cell viability, respectively. The primary human tendon cells in culture expressed enzymes related to ACh synthesis (choline acetyltransferase and vesicular acetylcholine transporter), along with vimentin and tenomodulin, which confirm the tenocyte phenotype. The cells also expressed the M2R. By administering exogenous ACh, the tenocytes were stimulated to significantly proliferate and increase in viability. In addition, Western blot showed that ACh stimulation resulted in increased phosphorylation of both EGFR and ERK1/2. When the cells were exposed to atropine, or the EGFR-blocking substance, the proliferative effect of ACh decreased. Simultaneously, the increase in ERK1/2 phosphorylation induced by incubation with ACh was effectively blocked in the presence of the mAChR antagonist atropine. Inhibition of either EGFR or MMP with specific blockers reduced the phosphorylation of ERK1/2. Based on the results of the present study, as well as from previously established studies, we propose that human tenocytes, with their innate ability to produce ACh, increase ACh production during tendinosis development. Via an autocrine loop, the ACh produced by tenocytes stimulates mAChRs on the cell surface, thereby activating MMPs to cleave a cell surface-associated EGFR ligand. The ligand then binds to EGFR which in turn after activation increases ERK1/2 phosphorylation, leading to the increased cell proliferation and hypercellularity as seen in tendinosis (figure 1). In an early stage of tendinosis, hypercellularity might be a part of a healing or adaptive response, but in the chronic stage excessive tenocyte proliferation could be detrimental to tendon structure and function. The non-neuronal cholinergic system of tendon tissue is thus a possible target for future modulation of these processes in tendinosis. Figure 1.Schematic drawing of proposed cellular pathways involved in ACh-induced proliferation of human tendon cells. ACh stimulates membrane bound muscarinic ACh receptors (mAChRs) that in turn activate matrix metalloproteinases (MMPs) to cleave a cell surface-associated EGFR ligand. The ligand then binds to EGFR which in turn increases cell proliferation through phosphorylation of the mitogen-activated protein kinases ERK1/2.
    British journal of sports medicine 06/2013; 47(9):e2. · 3.67 Impact Factor
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    L J Backman, G Andersson, P Danielson
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    ABSTRACT: Substance P (SP) and its preferred receptor, the neurokinin-1 receptor (NK-1 R), are expressed in human tenocytes and this is particularly seen in the tenocytes in cases of tendinosis. Hypercellularity, angiogenesis, and collagen disorganisation are common tissue features of this disease. Excessive apoptosis is also microscopically observed in tendinosis tissues. The role of SP and NK-1 R in the regulation of apoptosis and cell survival of tenocytes is poorly understood, but we have previously shown that SP increases tenocyte hypercellularity both in vitro and in vivo. It is possible that SP contributes to tenocyte hypercellularity by both stimulation of proliferation and inhibition of apoptosis. Akt, a protein kinase also called protein kinase B and known to be phosphorylated into its active form by SP, plays a critical role in controlling the balance of cell survival and apoptosis in other cell types. Activated/phosphorylated Akt (Phos-Akt) promotes cell survival and inhibits apoptosis by targeting the pro-apoptotic Bcl-2 family (which otherwise cause cytochrome C leakage from the mitochondria), and also by regulating expression of anti-apoptotic Bcl-2 family members and caspases. Furthermore, Akt activation is known to protect cells against apoptosis agents belonging to the TNF family of death ligands, such as Fas ligand (FasL) which acts through the Fas receptor (FasR). The focus of this study is to investigate (1) if FasR stimulation (Anti-Fas) is a good apoptosis model for human tenocytes, (2) if SP protects from Anti-Fas induced apoptosis, and (3) by which mechanisms SP mediates a possible anti-apoptotic response. Human Achilles tenocytes were grown as primary cultures and used for experiment at passage 3-5. All experiments were performed in serum-starved conditions. Cell viability (crystal violet), TUNEL-staining, and cytotoxicity assay (measuring lactate dehydrogenase (LDH)) were used to evaluate the endpoint effect of Anti-Fas alone or together with SP and/or a specific NK-1 R inhibitor. Immunocytochemistry, qPCR, and Western Blot were used to determine the pathways of Anti-Fas induced apoptosis and the specific inhibitory effect of SP. The majority of the tenocytes expressed FasR. The LDH assay demonstrated that Anti-Fas treatment results in a time- and dose-dependent release of LDH, and that SP dose-dependently reduces the Anti-Fas induced release of LDH. In parallel, the same trend was seen for the TUNEL assay, that is, SP reduced Anti-Fas induced apoptosis via a NK-1 R specific pathway. In addition it was shown that SP reduced the Anti-Fas induced decrease in cell viability. mRNA and/or protein analysis confirmed that the Anti-Fas induced activation of caspase-8, caspase-3, BID, BAX, and PARP were all down-regulated when SP was included, and that this SP effect was mediated through a NK-1 R specific pathway (for PARP and caspase-3, see figure 1). SP treatment resulted in activation of Akt, and by inhibiting Akt the anti-apoptotic effect of SP was confirmed to be, at least partly, induced through an Akt-dependent pathway. Figure 1.Cleavage of PARP and caspase-3 after Anti-Fas treatment alone or together with SP and/or the NK-1 R inhibitor illustrating the anti-apoptotic effect of SP. Pan-caspase inhibitor zVAD confirms a caspase dependent cleavage of PARP. We show that SP reduces Anti-Fas induced apoptosis in human tenocytes and that this anti-apoptotic effect of SP is mediated through the NK-1 R and an Akt pathway. Considering previous results that SP has a proliferative effect on tenocytes, the present study identifies SP as a potent regulator of cell-turnover in tendinosis tissue, capable of stimulating hypercellularity through different mechanisms. The fact that the FasR is abundantly expressed in tenocytes and that a possible source of the Fas ligand in tendinosis is the inflammatory infiltrated cells in the paratendon, makes it possible that the excessive apoptosis seen in tendinosis is partly explained by FasR stimulation. Most interestingly, as tenocytes are known to endogenously produce SP and express the NK-1 R, it is possible that SP in an autocrine loop rescues cells from Anti-Fas induced apoptosis, via Akt stimulation, thus contributing to tenocyte hypercellularity in tendinosis.
    British journal of sports medicine 06/2013; 47(9):e2. · 3.67 Impact Factor
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    ABSTRACT: In September 2010, the first International Scientific Tendinopathy Symposium (ISTS) was held in Umeå, Sweden, to establish a forum for original scientific and clinical insights in this growing field of clinical research and practice. The second ISTS was organised by the same group and held in Vancouver, Canada, in September 2012. This symposium was preceded by a round-table meeting in which the participants engaged in focused discussions, resulting in the following overview of tendinopathy clinical and research issues. This paper is a narrative review and summary developed during and after the second ISTS. The document is designed to highlight some key issues raised at ISTS 2012, and to integrate them into a shared conceptual framework. It should be considered an update and a signposting document rather than a comprehensive review. The document is developed for use by physiotherapists, physicians, athletic trainers, massage therapists and other health professionals as well as team coaches and strength/conditioning managers involved in care of sportspeople or workers with tendinopathy.
    British journal of sports medicine 04/2013; · 3.67 Impact Factor
  • Patrik Danielson, Alex Scott
    British journal of sports medicine 03/2013; · 3.67 Impact Factor
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    ABSTRACT: Studies of human patellar and Achilles tendons have shown that primary tendon fibroblasts (tenocytes) not only have the capacity to produce acetylcholine (ACh) but also express muscarinic ACh receptors (mAChRs) through which ACh can exert its effects. In patients with tendinopathy (chronic tendon pain) with tendinosis, the tendon tissue is characterised by hypercellularity and angiogenesis, both of which might be influenced by ACh. In this study, we have tested the hypothesis that ACh increases the proliferation rate of tenocytes through mAChR stimulation and have examined whether this mechanism operates via the extracellular activation of the epidermal growth factor receptor (EGFR), as shown in other fibroblastic cells. By use of primary human tendon cell cultures, we identified cells expressing vimentin, tenomodulin and scleraxis and found that these cells also contained enzymes related to ACh synthesis and release (choline acetyltransferase and vesicular acetylcholine transporter). The cells furthermore expressed mAChRs of several subtypes. Exogenously administered ACh stimulated proliferation and increased the viability of tenocytes in vitro. When the cells were exposed to atropine (an mAChR antagonist) or the EGFR inhibitor AG1478, the proliferative effect of ACh decreased. Western blot revealed increased phosphorylation, after ACh stimulation, for both EGFR and the extracellular-signal-regulated kinases 1 and 2. Given that tenocytes have been shown to produce ACh and express mAChRs, this study provides evidence of a possible autocrine loop that might contribute to the hypercellularity seen in tendinosis tendon tissue.
    Cell and Tissue Research 12/2012; · 3.68 Impact Factor
  • Johan Bagge, Patrik Danielson, Sture Forsgren
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    ABSTRACT: Brain derived neurotrophic factor (BDNF) is a multipotent neurotrophin known for its growth-influencing and apoptosis-modulating functions, as well as for its function to interact with neurotransmitters/neuromodulators. BDNF is reported to be mainly produced in the brain. BDNF can be absorbed into peripheral tissue from the blood stream. Expression of this neurotrophin at the protein level, as well as of the neurotrophin receptor p75, has been previously shown for the principal cells (tenocytes) of the Achilles tendon. However, there is no proof at the mRNA level that BDNF is produced by the tenocytes. As the Achilles tendon tenocytes show "neuronal-like" characteristics, in the form of expressions favouring synthesis of several neuromodulators/neurotransmitters, and as BDNF especially is produced in neurons, it is of interest to confirm this. In the present study, therefore, in situ hybridization for demonstration of BDNF mRNA was performed on biopsies from Achilles tendons of patients with tendinosis and pain-free non-tendinosis individuals. The results showed that the tenocytes of both groups exhibited BDNF mRNA reactions. These observations indeed favour the idea that BDNF is produced by tenocytes in the human Achilles tendon, why Achilles tendon tissue is a tissue in which BDNF can be locally produced. BDNF can have modulatory functions for the tenocytes, including apoptosis-modifying effects via actions on the p75 receptor and interactive effects with neurotransmitters/neuromodulators produced in these cells. This possibility should be further studied for Achilles tendon tissue.
    Histology and histopathology 09/2012; 27(9):1239-46. · 2.28 Impact Factor
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    ABSTRACT: The loss of collagen organization is considered a hallmark histopathologic feature of tendinosis. At the cellular level, tenocytes have been shown to produce signal substances that were once thought to be restricted to neurons. One of the main neuropeptides implicated in tendinosis, substance P (SP), is known to influence collagen organization, particularly after injury. The aim of this study was to examine the influence of SP on collagen remodeling by primary human tendon cells cultured in vitro in three-dimensional collagen lattices. We found that SP stimulation led to an increased rate of collagen remodeling mediated via the neurokinin-1 receptor (NK-1 R), the preferred cell receptor for SP. Gene expression analysis showed that SP stimulation resulted in significant increases in MMP3, COL3A1 and ACTA2 mRNA levels in the collagen lattices. Furthermore, cyclic tensile loading of tendon cell cultures along with the administration of exogenous SP had an additive effect on MMP3 expression. Immunoblotting confirmed that SP increased MMP3 protein levels via the NK-1 R. This study indicates that SP, mediated via NK-1 R, increases collagen remodeling and leads to increased MMP3 mRNA and protein expression that is further enhanced by cyclic mechanical loading. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
    Journal of Orthopaedic Research 07/2012; · 2.88 Impact Factor
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    ABSTRACT: The histopathology of tendons with painful tendinopathy is often tendinosis, a fibrosis-like condition of unclear pathogenesis characterized by tissue changes including hypercellularity. The primary tendon cells (tenocytes) have been shown to express adrenoreceptors (mainly alpha-2A) as well as markers of catecholamine production, particularly in tendinosis. It is known that adrenergic stimulation can induce proliferation in other cells. The present study investigated the effects of an exogenously administered alpha-2 adrenergic agonist in an established in vivo Achilles tendinosis model (rabbit) and also in an in vitro human tendon cell culture model. The catecholamine producing enzyme tyrosine hydroxylase and the alpha-2A-adrenoreceptor (α(2A) AR) were expressed by tenocytes, and alpha-2 adrenergic stimulation had a proliferative effect on these cells, in both models. The proliferation was inhibited by administration of an α(2A) AR antagonist, and the in vitro model further showed that the proliferative alpha-2A effect was mediated via a mitogenic cell signaling pathway involving phosphorylation of extracellular-signal-regulated kinases 1 and 2. The results indicate that catecholamines produced by tenocytes in tendinosis might contribute to the proliferative nature of the pathology through stimulation of the α(2A) AR, pointing to a novel target for future therapies. The study furthermore shows that animal models are not necessarily required for all aspects of this research.
    Scandinavian Journal of Medicine and Science in Sports 01/2012; · 3.21 Impact Factor
  • Ludvig J Backman, Patrik Danielson
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    ABSTRACT: Patellar tendinopathy (PT) is one of the most common reasons for sport-induced pain of the knee. Low ankle dorsiflexion range might predispose for PT because of load-bearing compensation in the patellar tendon. The purpose of this 1-year prospective study was to analyze if a low ankle dorsiflexion range increases the risk of developing PT for basketball players. Cohort study (prognosis); Level of evidence, 2. Ninety junior elite basketball players were examined for different characteristics and potential risk factors for PT, including ankle dorsiflexion range in the dominant and nondominant leg. Data were collected over a 1-year period and follow-up, including reexamination, was made at the end of the year. Seventy-five players met the inclusion criteria. At the follow-up, 12 players (16.0%) had developed unilateral PT. These players were found to have had a significantly lower mean ankle dorsiflexion range at baseline than the healthy players, with a mean difference of -4.7° (P = .038) for the dominant limb and -5.1° (P = .024) for the nondominant limb. Complementary statistical analysis showed that players with dorsiflexion range less than 36.5° had a risk of 18.5% to 29.4% of developing PT within a year, as compared with 1.8% to 2.1% for players with dorsiflexion range greater than 36.5°. Limbs with a history of 2 or more ankle sprains had a slightly less mean ankle dorsiflexion range compared to those with 0 or 1 sprain (mean difference, -1.5° to -2.5°), although this was only statistically significant for nondominant legs. This study clearly shows that low ankle dorsiflexion range is a risk factor for developing PT in basketball players. In the studied material, an ankle dorsiflexion range of 36.5° was found to be the most appropriate cutoff point for prognostic screening. This might be useful information in identifying at-risk individuals in basketball teams and enabling preventive actions. A history of ankle sprains might contribute to reduced ankle dorsiflexion range.
    The American journal of sports medicine 09/2011; 39(12):2626-33. · 3.61 Impact Factor
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    ABSTRACT: Physical activity affects the pain symptoms for Achilles tendinosis patients. Brain-derived neurotrophic factor (BDNF), tumor necrosis factor-alpha (TNF-α) and their receptors have been detected in human Achilles tendon. This pilot study aimed to compare serum BDNF and soluble tumor necrosis factor receptor I (sTNFRI) levels in Achilles tendinosis patients and healthy controls and to examine the influence of physical activity, and BMI and gender, on these levels. Physical activity was measured with a validated questionnaire, total physical activity being the parameter analyzed. Physical activity was strongly correlated with BDNF among tendinosis women [Spearman's rho (ρ)=0.90, P<0.01] but not among control women (ρ=-0.08, P=0.83), or among tendinosis and control men. Physical activity was significantly correlated with sTNFRI in the entire tendinosis group and among tendinosis men (ρ=0.65, P=0.01), but not in the entire control group or among control men (ρ=0.04, P=0.91). Thus, the physical activity pattern is related to the TNF and BDNF systems for tendinosis patients but not controls, the relationship being gender dependent. This is new information concerning the relationship between physical activity and Achilles tendinosis, which may be related to pain for the patients. This aspect should be further evaluated using larger patient materials.
    Scandinavian Journal of Medicine and Science in Sports 08/2011; 21(6):e430-8. · 3.21 Impact Factor
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    ABSTRACT: Following tendon injury, cartilage, bone and fat metaplasia are often observed, making the optimization of tenocyte differentiation an important clinical goal. In this study we examined the effect of static and cyclic mechanical loading on the expression of genes which play a role in tenocyte differentiation and function, namely scleraxis (Scx) and Type I collagen (Col1a1), and determined the effect of varying mechanical parameters including (1) static vs dynamic load, (2) increasing strain magnitude, (3) inclusion of 10 s rest periods, and (4) increasing cycle number. Cyclic loading resulted in a greater increase of tenocyte gene expression than static loading over 3 weeks in culture. Increasing strain levels potentiated the induction of tenocyte genes. The insertion of a 10 s rest periods further enhanced tenocyte gene expression, as did increasing repetition numbers. These results suggest that mechanical signaling exerts an important influence on the expression of genes which play a role in determining the tendon phenotype. Further work is required to confirm and extend these findings in primary cells such as resident tendon progenitor/stem cells, in order to provide an improved understanding of biology from which optimized rehabilitation programs can be developed.
    Journal of musculoskeletal & neuronal interactions 06/2011; 11(2):124-32. · 2.45 Impact Factor
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    ABSTRACT: To quantify the intratendinous levels of substance P (SP) at different stages of overload in an established model for Achilles tendinopathy (rabbit). Also, to study the distribution of the SP-receptor, the NK-1R, and the source of SP, in the tendon. Animals were subjected to the overuse protocol for 1, 3 or 6 weeks. One additional group served as unexercised controls. Immunoassay (EIA), immunohistochemistry (IHC), and in situ hybridisation (ISH) were performed. EIA revealed increased SP-levels in the Achilles tendon of the exercised limb in all the experimental groups as compared to in the controls (statistically significant; p=0.01). A similar trend in the unexercised Achilles tendon was observed but was not statistically significant (p=0.14). IHC and in ISH illustrated reactions of both SP and NK-1R mainly in blood vessel walls, but the receptor was also found on tenocytes. Achilles tendon SP-levels are elevated already after 1 week of loading. This shows that increased SP-production precedes tendinosis, as tendinosis-like changes occur only after a minimum of 3 weeks of exercise, as shown in a recent study using this model. We propose that central neuronal mechanism may be involved as similar trends were observed in the contralateral Achilles tendon.
    Journal of musculoskeletal & neuronal interactions 06/2011; 11(2):133-40. · 2.45 Impact Factor
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    ABSTRACT: Tenocytes produce substance P (SP), and its receptor (neurokinin-1 receptor (NK-1R)) is expressed throughout the tendon tissue, especially in patients with tendinopathy and tissue changes (tendinosis) including hypercellularity and vascular proliferation. Considering the known effects of SP, one might ask whether SP contributes to these changes. To test whether development of tendinosis-like changes (hypercellularity and angiogenesis) is accelerated during a 1-week course of exercise with local administration of SP in an established Achilles tendinopathy model. Rabbits were subjected to a protocol of Achilles tendon overuse for 1 week, in conjunction with SP injections in the paratenon. Exercised control animals received NaCl injections or no injections, and unexercised, uninjected controls were also used. Tenocyte number and vascular density, as well as paratendinous inflammation, were evaluated. Immunohistochemistry and in situ hybridisation to detect NK-1R were conducted. Results There was a significant increase in tenocyte number in the SP-injected and NaCl-injected groups compared with both unexercised and exercised, uninjected controls. Tendon blood vessels increased in number in the SP-injected group compared with unexercised controls, a finding not seen in NaCl-injected controls or in uninjected, exercised animals. Paratendinous inflammation was more pronounced in the SP-injected group than in the NaCl controls. NK-1R was detected in blood vessel walls, nerves, inflammatory cells and tenocytes. SP accelerated the development of tendinosis-like changes in the rabbit Achilles tendon, which supports theories of a potential role of SP in tendinosis development; a fact of clinical interest since SP effects can be effectively blocked. The angiogenic response to SP injections seems related to paratendinitis.
    British journal of sports medicine 05/2011; 45(13):1017-22. · 3.67 Impact Factor
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    ABSTRACT: To determine whether there are objective findings of tendinosis in a rabbit tendinopathy model on exercised and contralateral (non-exercised) Achilles tendons. Four groups of six New Zealand white rabbits per group were used. The animals of one (control) group were not subjected to exercise/stimulation. Animals were subjected to a protocol of electrical stimulation and passive flexion-extension of the right triceps surae muscle every second day for 1, 3 or 6 weeks. Tenocyte number and vascular density were calculated. Morphological evaluations were also performed as well as in-situ hybridisation for vascular endothelial growth factor (VEGF) messenger RNA. There was a significant increase in the tenocyte number after 3 and 6 weeks of exercise, but not after 1 week, in comparison with the control group. This was seen in the Achilles tendons of both legs in experimental animals, including the unexercised limb. The pattern of vascularity showed an increase in the number of tendon blood vessels in rabbits that had exercised for 3 weeks or more, compared with those who had exercised for 1 week or not at all. VEGF-mRNA was detected in the investigated tissue, with the reactions being more clearly detected in the tendon tissue with tendinosis-like changes (6-week rabbits) than in the normal tendon tissue (control rabbits). There were bilateral tendinosis-like changes in the Achilles tendons of rabbits in the current model after 3 weeks of training, suggesting that central neuronal mechanisms may be involved and that the contralateral side is not appropriate as a control.
    British journal of sports medicine 04/2011; 45(5):399-406. · 3.67 Impact Factor
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    ABSTRACT: It has been hypothesised that substance P (SP) may be produced by primary fibroblastic tendon cells (tenocytes), and that this production, together with the widespread distribution of the neurokinin-1 receptor (NK-1 R) in tendon tissue, could play an important role in the development of tendinopathy, a condition of chronic tendon pain and thickening. The aim of this study was to examine the possibility of endogenous SP production and the expression of NK-1 R by human tenocytes. Because tendinopathy is related to overload, and because the predominant tissue pathology (tendinosis) underlying early tendinopathy is characterized by tenocyte hypercellularity, the production of SP in response to loading/strain and the effects of exogenously administered SP on tenocyte proliferation were also studied. A cell culture model of primary human tendon cells was used. The vast majority of tendon cells were immunopositive for the tenocyte/fibroblast markers tenomodulin and vimentin, and immunocytochemical counterstaining revealed that positive immunoreactions for SP and NK-1 R were seen in a majority of these cells. Gene expression analyses showed that mechanical loading (strain) of tendon cell cultures using the FlexCell© technique significantly increased the mRNA levels of SP, whereas the expression of NK-1 R mRNA decreased in loaded as compared to unloaded tendon cells. Reduced NK-1 R protein was also observed, using Western blot, after exogenously administered SP at a concentration of 10⁻⁷ M. SP exposure furthermore resulted in increased cell metabolism, increased cell viability, and increased cell proliferation, all of which were found to be specifically mediated via the NK-1 R; this in turn involving a common mitogenic cell signalling pathway, namely phosphorylation of ERK1/2. This study indicates that SP, produced by tenocytes in response to mechanical loading, may regulate proliferation through an autocrine loop involving the NK-1 R.
    PLoS ONE 01/2011; 6(11):e27209. · 3.53 Impact Factor
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    ABSTRACT: It is not known whether a glutamate signaling system is involved in muscle inflammation (myositis). In the present study, we examined this question in the soleus muscle in a laboratory model of myositis resulting from repetitive overuse induced by electrical stimulation and injection of pro-inflammatory substances. Sections of rabbit soleus muscle with an induced myositis, i.e., exhibiting infiltration of inflammatory cells, were examined immunohistochemically using antibodies against vesicular glutamate transporter VGluT2 and the glutamate receptor NMDAR1. In situ hybridization for demonstration of VGluT2 mRNA was also performed. Specific reactions for both VGluT2 and NMDAR1 could be observed immunohistochemically in the same cells. In situ hybridization demonstrated the occurrence of VGluT2 mRNA in the cells. Double staining showed that the VGluT2 reactions were detectable in cells marked with T cell/neutrophil marker and in cells expressing eosinophil peroxidase. These data suggest the occurrence of previously unknown glutamate-mediated autocrine/paracrine effects within the inflammatory infiltrates during the development of muscle inflammation.
    Inflammation 12/2010; 35(1):39-48. · 2.46 Impact Factor
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    ABSTRACT: Anti-cholinergic agents are used in the treatment of several pathological conditions. Therapy regimens aimed at up-regulating cholinergic functions, such as treatment with acetylcholinesterase inhibitors, are also currently prescribed. It is now known that not only is there a neuronal cholinergic system but also a non-neuronal cholinergic system in various parts of the body. Therefore, interference with the effects of acetylcholine (ACh) brought about by the local production and release of ACh should also be considered. Locally produced ACh may have proliferative, angiogenic, wound-healing, and immunomodulatory functions. Interestingly, cholinergic stimulation may lead to anti-inflammatory effects. Within this review, new findings for the locomotor system of a more widespread non-neuronal cholinergic system than previously expected will be discussed in relation to possible new treatment strategies. The conditions discussed are painful and degenerative tendon disease (tendinopathy/tendinosis), rheumatoid arthritis, and osteoarthritis.
    Orthopedic Reviews 06/2009; 1(1):e11.

Publication Stats

436 Citations
98.10 Total Impact Points

Institutions

  • 2013
    • University of British Columbia - Vancouver
      • Department of Physical Therapy
      Vancouver, British Columbia, Canada
  • 2006–2013
    • Umeå University
      • • Department of Integrative Medical Biology (IMB)
      • • Department of Surgical and Perioperative Sciences
      Umeå, Vaesterbotten, Sweden