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  • 1.
    Alfredson, Håkan
    et al.
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    Bjur, Dennis
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    Thorsen, Kim
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    Lorentzon, Ronny
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    Sandström, Patrick
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    High intratendinous lactate levels in painful chronic Achilles tendinosis. An investigation using microdialysis technique.2002In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 20, no 5, p. 934-938Article in journal (Refereed)
    Abstract [en]

    In this investigation the microdialysis technique was used to study the concentrations of lactate in Achilles tendons with painful chronic tendinosis and in normal pain-free tendons. In four patients (mean age 40.7 years) with a painful thickening localized at the 2-6 cm level in the Achilles tendon (chronic Achilles tendinosis) and in five controls (mean age 37.2 years) with normal Achilles tendons the local concentrations of lactate were registered under resting conditions. All tendons were examined using ultrasonography. In the tendons with tendinosis the painful thickening corresponded to a widened tendon and structural tendinosis changes. Normal tendons showed no widening and a normal structure. A standard microdialysis catheter was inserted into the Achilles tendon under local anesthesia. Samplings were done every 15 min during a 4 h period. The results showed significantly higher mean concentrations of lactate in tendons with tendinosis compared to normal tendons (2.15 mmol/l vs. 1.14 mmol/l). The lactate concentrations in the tendons with tendinosis were stable, and approximately twofold higher than in the normal tendons during the whole 4 h investigation period. In conclusion, the higher concentrations of lactate in Achilles tendons with painful tendinosis indicate that there are anaerobic conditions in the area with tendinosis. The importance of this finding for the pathogenesis and pain mechanisms in this chronic condition needs to be further investigated.

  • 2.
    Alfredson, Håkan
    et al.
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    Forsgren, Sture
    Umeå University, Faculty of Medicine, Integrative Medical Biology, Anatomy.
    Thorsen, Kim
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    Lorentzon, Ronny
    Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences, Sports Medicine.
    In vivo microdialysis and immunohistochemical analyses of tendon tissue demonstrated high amounts of free glutamate and glutamate NMDAR1 receptors, but no signs of inflammation, in Jumper's knee.2001In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 19, no 5, p. 881-886Article in journal (Refereed)
    Abstract [en]

    This investigation describes, to our knowledge, the first experiment where the microdialysis technique was used to study certain metabolic events in human patellar tendons in combination with immunohistochemical analyses of tendon biopsies. In five patients (four men and one woman) with a long duration (range 12-36 months) of pain symptoms from Jumper's knee (localized tenderness in the patellar tendon verified as tendon changes with ultrasonography or MRI), and in five controls (four men and one woman) with normal patellar tendons, a standard microdialysis catheter was inserted into the patellar tendon under local anestesia. The local concentrations of glutamate (excitatory neurotransmitter) and prostaglandin E2 (PGE2) were registered under resting conditions. Samplings were done every 15 min during a 2 h period. In all individuals (patients and controls) biopsies were taken for immunohistochemical analyses. The results showed that it was possible to detect and measure the concentrations of glutamate and PGE2 in the patellar tendon with the use of microdialysis technique. There were significantly higher concentrations of free glutamate, but not PGE2, in tendons with tendinosis compared to normal tendons. In the biopsies, there were no inflammatory cell infiltrates, but, for the first time, it was shown that there was immunoreaction for the glutamate receptor NMDAR1 in association with nerve structures in human patellar tendons. These findings altogether indicate that glutamate might be involved in painful Jumper's knee, and further emphasizes that there is no chemical inflammation (normal PGE2 levels) in this chronic condition.

  • 3.
    Alfredson, Håkan
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
    Lorentzon, Mattias
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
    Bäckman, Stina
    Umeå University, Faculty of Medicine, Department of Odontology, Oral Cell Biology.
    Bäckman, Assar
    Umeå University, Faculty of Medicine, Department of Odontology, Oral Cell Biology.
    Lerner, Ulf H
    Umeå University, Faculty of Medicine, Department of Odontology, Oral Cell Biology.
    cDNA-arrays and real-time quantitative PCR techniques in the investigation of chronic Achilles tendinosis.2003In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 21, no 6, p. 970-975Article in journal (Refereed)
    Abstract [en]

    The aetiology and pathogenesis of chronic painful Achilles tendinosis are unknown. This investigation aimed to use cDNA arrays and real-time quantitative polymerase chain reaction (real-time PCR) technique to study tendinosis and control tissue samples. Five patients (females mean age 57.1+/-4.3 (years+/-SD)) with chronic painful Achilles tendinosis were included. From all patients, one biopsy was taken from the area with tendinosis and one from a clinically normal area (control) of the tendon. The tissue samples were immediately immersed in RNAlater and frozen at -80 degrees C until RNA extraction. Portions of pooled RNA from control and tendinosis sites, respectively, were transcribed to cDNA, radioactively labelled (32P), hybridized to cDNA expression arrays, and exposed to phosphoimager screens over night. Expressions of specific genes, shown to be regulated in the cDNA array analysis, were analyzed in the individual samples using real-time PCR. cDNA arrays showed that gene expressions for matrix-metalloproteinase-2 (MMP-2), fibronectin subunit B (FNRB), vascular endothelial growth factor (VEGF), and mitogen-activated protein kinase p38 (MAPKp38) were up-regulated, while matrix-metalloproteinase-3 (MMP-3) and decorin were down-regulated, in tendinosis tissue compared with control tissue. Using real-time PCR, 4/5 and 3/5 patients showed up-regulation of MMP-2 and FNRB mRNA, respectively. For decorin, VEGF, and MAPKp38, real-time PCR revealed a great variability among patients. Interestingly, the mRNAs for several cytokines and cytokine receptors were not regulated, indicating the absence of an inflammatory process in chronic painful Achilles tendinosis. In conclusion, cDNA-arrays and real-time PCR can be used to study differences in gene expression levels between tendinosis and control tendon tissue.

  • 4.
    Fong, Gloria
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Backman, Ludvig J.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Hart, David A.
    Vancouver Coastal Hlth & Res Inst, Ctr Hip Hlth & Mobil, Vancouver, BC, Canada.
    Danielson, Patrik
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    McCormack, Bob
    Vancouver Coastal Hlth & Res Inst, Ctr Hip Hlth & Mobil, Vancouver, BC, Canada.
    Scott, Alex
    Univ British Columbia, Dept Phys Therapy, Vancouver, BC V5Z 1M9, Canada.
    Substance P enhances collagen remodeling and MMP-3 expression by human tenocytes2013In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 31, no 1, p. 91-98Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Parkkinen, Jyrki
    et al.
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Chondrogenic and Osteogenic Differentiation Group.
    Helminen, Heikki
    Chondrogenic and Osteogenic Differentiation Group.
    Tammi, Markku
    Chondrogenic and Osteogenic Differentiation Group.
    Local stimulation of proteoglycan synthesis in articular cartilage explants by dynamic compression in vitro.1992In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 10, no 5, p. 610-620, article id 1500975Article in journal (Refereed)
    Abstract [en]

    Cultured bovine articular cartilage was subjected to 50 ms, 0.5-1.0 MPa compressions repeated at intervals of 2-60 s for 1.5 h and simultaneously labeled with 35SO4. The compression was delivered with a 4-mm-diameter nonporous loading head on an 8-mm-diameter cartilage explant. This method created directly compressed (central) and uncompressed (border) areas within the tissue. Analysis of the whole explant under a 0.5 MPa load showed significantly increased 35SO4 incorporation by compression repeated at 2- and 4-s but not at 20- and 60-s intervals. When the incorporation was studied separately in the border and central areas, a statistically significant stimulation was noticed in the central area with a 4-s cycle, while the border area was stimulated with a 2-s cycle. Autoradiography of the central area showed that the stimulation with 0.5 MPa and a 4-s cycle occurred through the whole depth of the cartilage, while raising the pressure to 1 MPa or the frequency to 2 s reduced the stimulation, particularly in the superficial cartilage. In the border area the stimulation with 0.5 MPa and a 2-s cycle was noted in the superficial zone only. The stimulation of proteoglycan synthesis is thus limited to certain loading frequencies and pressures and occurs in specific areas under and around the loaded site. Its rapid appearance suggests enhanced glycosylation or sulfation of core proteins or enhanced speed of posttranslational processing.

  • 6.
    Parkkinen, Jyrki
    et al.
    Deparment of Pathology and Fornesic Medicine, University of Kuopio, Kuopio, Finlandd.
    Lammi, Mikko
    Deparment of Anatomy, University of Kuopio, Kuopio, Finlandd.
    Inkinen, Ritva
    Deparment of Anatomy, University of Kuopio, Kuopio, Finlandd.
    Jortikka, Matti
    Deparment of Anatomy, University of Kuopio, Kuopio, Finlandd.
    Tammi, Markku
    Deparment of Anatomy, University of Kuopio, Kuopio, Finlandd.
    Virtanen, Ismo
    Department of Anatomy, University of Helsinki, Helsinki, Finland.
    Helminen, Heikki
    Deparment of Anatomy, University of Kuopio, Kuopio, Finlandd.
    Influence of short-term hydrostatic pressure on organization of stress fibers in cultured chondrocytes.1995In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 13, no 4, p. 495-502, article id 7545746Article in journal (Refereed)
    Abstract [en]

    The present study describes changes in the organization of stress fibers that occur in articular cartilage chondrocytes subjected to hydrostatic pressure. Primary cultures of chondrocytes from bovine articular cartilage, grown on coverslips, were subjected to 5, 15, or 30 MPa hydrostatic pressure at 37 degrees C. The pressure was applied continuously or cyclically at two frequencies: 0.125 Hz (4 seconds of pressure and 4 seconds of no pressure) or 0.05 Hz (1 second of pressure and 19 seconds of no pressure) for a period of 2 hours. Control chondrocytes showed a polygonal form with prominent stress fibers extending across the cells. The exposure of cells to 30 MPa pressure caused a nearly total disappearance of stress fibers and retraction of the cells from each other. With pressure at 15 MPa or cyclic pressure, the number of cells with stress fibers was decreased. In cells subjected to 5 MPa pressure, the stress fibers resembled those in control chondrocytes. The pressure effects were reversible after 2 hours. Pressure had no effect on the staining pattern of vinculin, which suggests that microfilaments are more vulnerable to pressure than vinculin. The results indicate that cytoskeletal changes may be an integral part of the response of chondrocytes to hydrostatic pressure.

  • 7.
    Puustjärvi, Kaija
    et al.
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Kiviranta, Ilkka
    Department of Surgery, Kuopio University Hospital, Kuopio, Finland.
    Helminen, Heikki
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Tammi, Markku
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Proteoglycan synthesis in canine intervertebral discs after long-distance running training.1993In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 11, no 5, p. 738-746, article id 8410474Article in journal (Refereed)
    Abstract [en]

    The alterations and distribution of proteoglycan (PG) synthesis in the intervertebral discs of young dogs exercised with long-distance running (40 km/day) were studied with a method based on image analysis of tissue sections. Ten dogs were run on a treadmill daily for 55 weeks, and 10 dogs from the same litters served as controls. The daily running distance gradually was increased to 40 km and was maintained at that level for the final 15 weeks. Midsagittal disc segments C7-T1, T8-9, and L1-2 were labeled with 35SO4, and histological sections of the segments were apposed against autoradiographic film to determine the synthesis of PGs. Next, the same sections were stained with safranin O to estimate possible alterations in PG concentration. The radiographs and stained sections were digitized with a flatbed scanner and measured by image analysis. The lumbar discs of runners displayed a significantly lower rate of 35SO4 incorporation, while a tendency toward enhanced incorporation was seen in the cervical and thoracic discs. Safranin O staining showed a pattern just opposite to 35SO4 incorporation: decreased staining in the cervical and thoracic discs and increased staining in the lumbar discs of the runners. The results demonstrate qualitatively different influences of long-term running training on PG metabolism at the cervical, thoracic, and lumbar levels in young dogs.

  • 8.
    Scott, Alexander
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Alfredson, Håkan
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences.
    Forsgren, Sture
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    VGluT2 expression in painful Achilles and patellar tendinosis: Evidence of local glutamate release by tenocytes2008In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 26, no 5, p. 685-692Article in journal (Other academic)
    Abstract [en]

    The pathogenesis of chronic tendinopathy is unclear. We have previously measured high intratendinous levels of glutamate in patients with tendinosis, suggesting potential roles of glutamate in the modulation of pain, vascular function, and degenerative changes including apoptosis of tenocytes. However, the origin of free glutamate found in tendon tissue is completely unknown. Surgical biopsies of pain-free normal tendons and tendinosis tendons (Achilles and patellar) were examined immunohistochemically using antibodies against vesicular glutamate transporters (VGluT1 and VGluT2), as indirect markers of glutamate release. In situ hybridization for VGluT2 mRNA was also conducted. Specific immunoreactions for VGluT2, but not VGluT1, could be consistently detected in tenocytes. However, there were interindividual variations in the levels of immunoreactivity. The level of immunoreaction for VGluT2 was higher in tendinosis tendons compared to normal tendons (p < 0.05). In situ hybridization of VGluT2 demonstrated that mRNA was localized in a similar pattern as the protein, with marked expression by certain tenocytes, particularly those showing abnormal appearances. Reactivity for VGluT1 and -2 was absent from nerves and vessel structures in both normal and painful tendons. The current data demonstrate that tenocytes may be involved in the regulation of extracellular glutamate levels in tendons. Specifically, the observations suggest that free glutamate may be locally produced and released by tenocytes, rather than by peripheral neurons. Excessive free glutamate is expected to impact a variety of autocrine and paracrine functions important in the development of tendinosis, including tenocyte proliferation and apoptosis, extracellular matrix metabolism, nociception, and blood flow. (c) 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

  • 9.
    Stensdotter, Ann-Katrin
    et al.
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.
    Holmgren, Christer
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
    Dalén, Tore
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Häger-Ross, Charlotte
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.
    The role of M. popliteus in unpredictable and in self-initiated balance provocations.2006In: Journal of Orthopaedic Research, ISSN 0736-0266, E-ISSN 1554-527X, Vol. 24, no 3, p. 524-530Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to determine whether m. popliteus (POP) activity would contribute to the control of knee joint position in unpredictable and in self-initiated provocations of standing balance. Ten healthy women (age 25.2 +/- 4.5 years, means and SD) without known knee pathology were tested for postural reactions (1) to unpredictable support surface translations in anterior and posterior directions, and (2) in self-initiated balance provocations in a reaction time (RT) forward reach-and-grip task. Electromyographic activity was recorded from POP and other leg muscles plus the deltoid muscle. Three-dimensional kinematics were captured for the knee joint and the body centre of mass was calculated. POP was active first of all the muscles recorded, regardless of translation direction, and knee joint movements elicited were either knee extension or external rotation of the tibia. In the RT task, the POP was active after initiation of reaching movement, and there was little consistency in the kinematic response. POP activity was not direction specific in response to support surface translation, but appeared triggered from reactive knee joint movement. The response to the support-surface translation suggests that POP served to control knee joint position rather than posture. In the RT task, we could not deduce whether POP activity was attributed to knee joint control or to postural control. Copyright 2006 Orthopaedic Research Society.

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