doi: 10.1242/10.1242/jcs.00303
Mechanical loading regulates the expression of tenascin-C in the myotendinous junction and tendon but does not induce de novo synthesis in the skeletal muscle
Tero A. H. Järvinen1,2,*,
Lászlo Józsa1,2,3,
Pekka Kannus1,2,4,
Teppo L. N. Järvinen1,2,
Timo Hurme5,
Martti Kvist5,
Markku Pelto-Huikko1,2,
Hannu Kalimo5 and
Markku Järvinen1,2
1 Institute of Medical Technology and Medical School, University of Tampere,
Tampere, Finland
2 Department of Surgery, Tampere University Hospital, Tampere, Finland
3 Department of Morphology, National Institute of Traumatology, Budapest,
Hungary
4 The Accident and Trauma Research Center, the UKK-Institute and the Tampere
Research Center of Sports Medicine, Tampere; Finland
5 Department of Pathology, University Hospital of Turku and Paavo Nurmi Center,
Turku, Finland
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Fig. 1. The experimental design of the study. C, control group at 3 weeks; IM,
immobilization group at 3 weeks; C, control group at 11 weeks; FR, free
remobilization group at 11 weeks; LR, low-intensity running group at 11 weeks;
HR, high-intensity running group at 11 weeks.
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Fig. 2. (A) The percentage area of intramuscular connective tissue, (B) capillary
density and (C) cross-sectional area of type I and (D) type II fibers of the
rat gastrocnemius muscle after inactivity and restitution of mechanical
loading (three different intensities). Values are means±s.d. Group
abbreviations are as defined in Fig.
1. Significant immobilized-to-non-immobilized hindlimb
differences, **P<0.05. For other comparisons, see
text.
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Fig. 3. (A) The expression of TN-C can be seen both at the MTJ and the microtendon
(arrows). (B) Strong expression of TN-C can also be detected in the myofascial
junction, whereas the endomysial and perimysial connective tissues are
negative for TN-C immunoreactivity. (C) Only TN-C immunoreactivity that can be
detected in the skeletal muscle is visible in the intramuscular
myofiber-myofiber junctions at the tips of muscle cells (arrows). (D) In the
tendon, immunohistochemical expression of TN-C is visible in the
tenocyte—collagen-fiber interface (arrows) as well as on the surface of
the collagen fiber bundles of the Achilles tendon. Magnification: A,C,D
x100, B x50.
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Fig. 4. mRNA in situ hybridization of TN-C. No signal for TN-C mRNA can be detected
in the skeletal muscle (cross-sectional section) either (A) after the
immobilization or (B) after the high-intensity treadmill running of eight
weeks, whereas in the tendon (longitudinal section) (C-E), mechanical loading
regulates the mRNA expression of TN-C. (C) A strong signal can be detected
from the normal Achilles tendon (longitudinal section), (D) the expression
almost disappears after the three-week immobilization, whereas (E) a strong
singal for TN-C mRNA is detectable after the high-intensity treadmill running
of eight weeks. Magnification x5.
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Fig. 5. (A) A marked reduction in the immunohistochemical expression of TN-C can be
seen in the MTJ after the three-week immobilization. (B) Only faint TN-C
immunopositive signal is visible in the immobilized Achilles tendon after
three weeks. Magnification: A,B x50.
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Fig. 6. Strong immunohistochemical expression of TN-C can be seen in the MTJs of
both the previously immobilized (A) and the healthy contralateral muscles (B)
after the high-intensity treadmill running of eight weeks. The mechanical
loading can not induce the de novo expression of TN-C in the previously
immobilized nor the healthy contralateral skeletal muscle. Magnification: A,B
x100.
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© The Company of Biologists Ltd 2003
