Histochemical and ultrastructural study of human muscles after spontaneous rupture of the tendon

Costamere protein expression and tissue composition of rotator cuff muscle after tendon release in sheep

Previous studies suggested that degradation of contractile tissue requires cleavage of the costamere, a structural protein complex that holds sarcomeres in place. This study examined if costamere turnover is affected by a rotator cuff tear in a previously established ovine model. We found the activity of focal adhesion kinase (FAK), a main regulator of costamere turnover, was unchanged at 2 weeks but decreased by 27% 16 weeks after surgical release of the infraspinatus tendon. This was accompanied by cleavage of the costamere protein talin into a 190 kDa fragment while full length talin remained unchanged. At 2 weeks after tendon release, muscle volume decreased by 17 cm³ from an initial 185 cm³ , the fatty tissue volume was halved, and the contractile tissue volume remained unchanged. After 16 weeks, the muscle volume decreased by 36 cm³ , contractile tissue was quantitatively lost, and the fat content increased by 184%. Nandrolone administration mitigated the loss of contractile tissue by 26% and prevented fat accumulation, alterations in FAK activity, and talin cleavage. Taken together, these findings imply that muscle remodeling after tendon release occurs in two stages. The early decrease of muscle volume is associated with reduction of fat; while, the second stage is characterized by substantial loss of contractile tissue accompanied by massive fat accumulation. Regulation of costamere turnover is associated with the loss of contractile tissue and seems to be impacted by nandrolone treatment. Clinically, the costamere may represent a potential intervention target to mitigate muscle loss after a rotator cuff tear. © 2017 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 36:272-281, 2018.

Skeletal muscle response to tenotomy

Tenotomy is a commonly encountered clinical entity, whether traumatic or iatrogenic. This article reviews the response of skeletal muscle to tenotomy. The changes are subdivided into molecular, architectural, and functional categories. Architectural disruption of the muscle includes myofiber disorganization, central core necrosis, Z-line streaming, fibrosis of fibers and Golgi tendon organs, changes in sarcomere number, and alterations in the number of membrane particles. Molecular changes include transient changes in myosin heavy chain composition and expression of neural cell adhesion molecule (NCAM). Functionally, tenotomized muscle produces decreased maximum tetanic and twitch tension. Alterations in normal skeletal muscle structure and function are clinically applicable to the understanding of pathological states that follow tendon rupture and iatrogenic tenotomy.

The effect of tenotomy and immobilization on muscle spindles and tendon organs of the rat calf muscles. A histochemical and morphometrical study

The morphological and histochemical alterations in the muscle spindles and Golgi tendon organs of tenotomized or immobilized calf muscles of rats (m. soleus, m. gastrocnemius) were studied in 54 animals. The intact contralateral feet served as controls. There was no change in the number of mechanoreceptors in either the tenotomized or the immobilized muscles. The diameter of the intrafusal fibers was increased somewhat after 1 week, but decreased by 14% to 40% in 3 weeks. The periaxial space of muscle spindle had diminished or disappeared by 2 weeks from the beginning of the procedures. The thickness of the outer capsule of the spindles had markedly increased, especially in the polar region. In the Golgi tendon organs the capsule had also thickened significantly and the internal space diminished. The alterations were similar following tenotomy or immobilization, but more marked after tenotomy than after immobilization.

The effect of tourniquet ischaemia on intact, tenotomized and motor nerve injured human hand muscles

Ultrastructural examination of the intrinsic hand muscles was performed on young healthy patients undergoing reconstructive operation following tendon or nerve lesions. The muscle specimens were taken at the start and then every fifteen to twenty minutes until the end of the tourniquet ischaemia. The authors have not found any morphological alterations following the use of a tourniquet up to two hours in either the intact or previously injured muscles.

Capillary density of tenotomized skeletal muscles. II. Observations on human muscles after spontaneous rupture of tendon

Alterations in the capillary density of the M. biceps brachii was studied in 20 cases during 2 months after spontaneous rupture of the tendon. The fiber typing was done using succinic dehydrogenase and myofibrillar ATP-ase at pH 9.4 for the staining, the capillaries were visualized with alkaline phosphatase and PAS reactions, and in each case 1,000 muscle fibers with their capillaries were estimated. In the intact muscles the capillary count ranged from 1,500 to 1,910 (mean 1,740) per 1,000 fibers. During the 1st month following the rupture the decrease in the capillary count of the muscle occurred rapidly, being after 4-7, 8-10, and 18-29 days 36%, 52%, and 66%, respectively, as compared to the contralateral muscles. After 2 months a decrease of approx. 70% was found in the amount of capillaries compared with the contralateral muscles. The obliteration of the capillaries was particularly pronounced in the amount of anastomoses. These results indicate that the capillary supply of the human M. biceps brachii decreases enormously during the 1st month after a tenotomy.

Capillary density of tenotomized skeletal muscles. I. Experimental study in the rat

Our purpose was to study the capillary density of rat gastrocnemius muscle by microangiography 7-21 days after achillotenotomy or immobilization in a plaster cast. Sixteen animals were tenotomized, 12 immobilized in a plaster cast, and 4 served as controls. The number of capillaries was counted per 1,000 muscle fibres from each sample. No site differences were found in control muscles, where on an average 1,250 capillaries per 1,000 muscle fibers were found. After tenotomy the number of capillaries was decreased 35%, 31%, and 32% on days 7, 14, and 21, respectively. In immobilized muscles the decrease in capillary density occurred slowly, the corresponding decrease being 23%, 33%, and 28% on days 7, 14, and 21, respectively. These results indicate that the capillary density of muscular tissue is greatly decreased following the disuse produced by tenotomy or immobilization.