Elisa M. Konieczko

Immunohistological detection of relaxin binding to anterior cruciate ligaments.

Relaxin, a member of the insulin-like growth factor family, alters collagen metabolism in fibroblasts. It was hypothesized that relaxin interacts with the anterior cruciate ligament (ACL), contributing to its elasticity. Twelve ACL specimens were collected from reconstruction surgeries, sectioned, rinsed, and exposed to rh-relaxin overnight. Polyclonal antirelaxin antibodies, in conjunction with HRP-AEC, localized areas of tissue binding. Controls were used to infer binding specificity. Staining was present in the positive control and all 12 ACL specimens; little or no staining occurred in the negative controls. These data suggest that relaxin binding to the ACL is specific, indicative of a receptor-mediated event.

Relaxin's involvement in extracellular matrix homeostasis.

Burgeoning evidence suggests that the hormone relaxin modulates collagen in the extracellular matrix of diverse tissues. In separate lines of study, we provide further substantiation of this hypothesis. Immunofluorescence was used to probe isolated fibroblasts derived from volar oblique ligament explant culture for vimentin, actin, RXFP1, and estrogen receptor beta. Ligaments were obtained as surgical waste from thumb reconstruction patients. Four specimens have been examined to date. Cells derived from these patients expressed vimentin and actin, consistent with fibroblast morphology. Putative fibroblasts derived from two of three female patients expressed RXFP1 receptors; the solitary male was negative. Given the small sample, however, the data are considered preliminary. Immunohistochemistry was used on frozen sections from 26 skin biopsies obtained from children undergoing genitoplasty. A subset of samples was also probed for transforming growth factor (TGF‐β1) and TGF‐β3. Appropriate controls were used. Finally, a subset of patient blood was assayed for relaxin by using an enzyme‐linked immunosorbent assay‐based method. The results showed RXFP1 receptor expression in the cells that populate the basement membrane in 96% of patients, regardless of gender. Most tissue expressed TGF‐β. Finally, serology suggested that relaxin was detectable in these children. Our two lines of research provide additional evidence for the diverse tissue tropism of relaxin. In particular, connective tissues as diverse as ligaments and basal lamina keratinocytes express RXFP1. These data lend support to our contention that relaxin affects ligament integrity and wound healing.

Lipid Peroxidation and Polybrominated Diphenyl Ethers – A Toxicological Perspective

© 2012 Vagula and Konieczko, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Lipid Peroxidation and Polybrominated Diphenyl Ethers – A Toxicological Perspective

Immunohistochemical detection of relaxin binding to ligaments of the thumb and knee

Osteoarthritis of the thumb basal joint and rupture of the anterior cruciate ligament of the knee are particularly vexing issues for women. Prevalence rates for these pathologies range from two to more than ten times that of age- and activity-matched males [1,2]. The reason for this gender discrepancy is unclear, but hormonal-mediated changes in joint stability are a plausible explanation. Joint laxity has been proposed as a risk factor for joint morbidity [2–6]. Furthermore, estrogen release during menstruation has been linked to ACL injury [7]. Other studies have revealed in vivo and in vitro perturbations in ACL ligament physiology as a function of estrogen dosing [8,9]. Relaxin may be a less obvious but equally culpable hormonal agent of ligamentous changes. Previous studies have demonstrated its ability to alter collagen and collagenase production in cultured fibroblasts [10–13]. Gravidity studies have also linked relaxin to increased laxity in knee and finger joints [14–16]. Given its systemic distribution [17], we hypothesized that relaxin binds to the ACL and palmar oblique ligaments, prime stabilizers of the knee and thumb, respectively. Since neither receptor antibodies nor cDNA probes are available, detection was based on an indirect immunohistochemical method.