Effects of Stress Deprivation on Lubricin Synthesis and Gliding of Flexor Tendons in a Canine Model in Vivo

Abstract

Background: Lubricin facilitates boundary lubrication of cartilage. The synthesis of lubricin in cartilage is regulated by mechanical stimuli, especially shear force. Lubricin is also found in flexor tendons. However, little is known about the effect of mechanical loading on lubricin synthesis in tendons or about the function of lubricin in flexor tendons. The purpose of this study was to investigate the relationship of mechanical loading to lubricin expression and gliding resistance of flexor tendons.Methods: Flexor tendons were harvested from canine forepaws that had been suspended without weight-bearing for twenty-one days and from the contralateral forepaws that had been allowed free motion. Lubricin expression in each flexor tendon was investigated with real-time RT-PCR (reverse transcription polymerase chain reaction) and immunohistochemistry. Lubricin in the flexor tendon was extracted and quantified with ELISA (enzyme-linked immunosorbent assay). The friction between the flexor tendon and the proximal pulley was measured.Results: The non-weight-bearing flexor tendons had a 40% reduction of lubricin expression (p < 0.01) and content (p < 0.01) compared with the flexor tendons in the contralateral limb. However, the gliding resistance of the tendons in the nonweight-bearing limb was the same as that of the tendons on the contralateral, weight-bearing side.Conclusions: Mechanical loading affected lubricin expression in flexor tendons, resulting in a 40% reduction of lubricin content, but these changes did not affect the gliding resistance of the flexor tendons.

Lubricin in human achilles tendon: The evidence of intratendinous sliding motion and shear force in achilles tendon

“…It facilitates the movement of tendon gliding against the surround tissues, and is also present between tendon fascicles, suggesting a lubricating role with regard to motion between the fascicles within the tendon . Stress deprivation reduces lubricin synthesis in canine flexor tendon . The distribution of lubricin in tendon, at locations where intratendinous shear forces have been postulated to occur, indicates that shear force may play a role in stimulating lubricin expression.…”

What is the best candidate allograft for ACL reconstruction? An in vitro mechanical and histologic study in a canine model

“…Lubricin was expressed mainly on the surface of the FDP tendon and ACL, with less lubricin expression on the surface of ACH and PAT. The frictional force of tendon and ligament was coincided with the expression of lubricin (Sun et al, 2008; Sun et al, 2013). …”

“…Under physiological conditions, the frictional force of the FDP tendon did not increase with the increase of cycle (Ozasa et al, 2013). In the present study, a glass rod, which has a higher frictional coefficient than the tendon tissue (Sun et al, 2008; Sun et al, 2013), was used against tendon gliding, which caused the frictional force to increase with the increase of the cycle.…”

“…It has been reported to be able to reduce friction in joints and tendons. Sun et al (Sun et al, 2008; Sun et al, 2013) demonstrated that removal of lubricin using trypsin dramatically increased the frictional force of the FDP tendon. Taguchi et al (Taguchi et al, 2009) found that lubricin compound could reduce the gliding resistance of peroneus longus significantly.…”

“…These slides were used for hematoxylin-eosin staining. Lubricin immunohistochemical staining was performed in accordance with previous methods (Sun et al, 2008; Sun et al, 2013). Briefly, these sections were rinsed 3 times with phosphate buffered saline (PBS) and fixed with a 4% paraformaldehyde buffer for 5 minutes.…”