Relaxin Receptor RXFP1 and RXFP2 Expression in Ligament, Tendon, and Shoulder Joint Capsule of Rats

Numerous musculoskeletal disorders are caused by thickened ligament, tendon stiffness, or fibrosis of joint capsule. Relaxin, a peptide hormone, can exert collagenolytic effect on ligamentous and fibrotic tissues. We hypothesized that local injection of relaxin could be used to treat entrapment neuropathy and adhesive capsulitis. Because hormonal effect depends on the receptor of the hormone on the target cell, it is important to confirm the presence of such hormonal receptor at the target tissue before the hormone therapy is initiated. The aim of this study was to determine whether there were relaxin receptors in the ligament, tendon, and joint capsular tissues of rats and to identify the distribution of relaxin receptors in these tissues. Transverse carpal ligaments (TCLs), inguinal ligaments, anterior cruciate ligaments (ACLs), Achilles tendons, and shoulder joint capsules were obtained from male Wistar rats. Western blot analysis was used to identify relaxin receptor isoforms RXFP1 and RXFP2. The distribution of relaxin receptors was determined by immunohistochemical staining. The RXFP1 isoform was found in all tissues examined. The RXFP2 isoform was present in all tissues but the TCLs. Its expression in ACLs tissues was relatively weak compared to that in other tissues. Our results revealed that RXFP1 and RXFP2 were distributed in distinctly different patterns according to the type of tissue (vascular endothelial cells, fibroblast-like cells) they were identified.

Changes of Posterior Bulging of the Lumbar Intervertebral Discs with Flexion and Extension in Central Disc Bulges and Disc Degeneration

OBJECTIVE: To determine the changes of posterior bulging of the lumbar intervertebral discs with flexion and extension movement of the spine in patients with central disc bulges or disc degeneration. METHOD: Twenty patients with low back pain were studied. Nine patients had central type disc bulging and eleven patients had disc degeneration only. The spines were scanned in neutral, flexion, and extension positions in a vertically open 0.5T MR scanner. Degree of posterior bulging of the lumbar intervertebral disc of the pathological level was measured. RESULTS: In the patients with disc bulge, posterior bulging of the disc decreased in all of the patients by 0.8 0.6 mm with flexion of the spine and increased in 77.8% of the patients by 1.0 0.8 mm with extension of the spine. In the patients with disc degeneration, posterior bulging decreased with flexion in 36.7% of the patients. With extension, posterior bulging increased in 55.6% of the patients. CONCLUSION: This study found that patients with low back pain and central disc bulges have consistent and marked discrepancies in posterior bulging with flexion-extension in comparison with our previous study with asymptomatic patients with normal MRIs.