Effects of Relaxin on the Mechanical Properties of Collagen Rich Tissues

A collagenous scar capsule forms around biomaterial implants and for deformable implants such as a breast prosthesis, this phenomenon of capsular scar contracture may lead to deformation and hardening of the implant. Relaxin, a peptide hormone of pregnancy which is known to affect collagen rich tissues, was given to mice in an attempt to eliminate or lessen this contracture. A short (8 day) study was performed to observe the effects of relaxin and estrogen on the mechanical properties of Skin and the interpubic ligament. A longer (27 day) study observed the effects of relaxin in estrogen primed mice containing implants. Changes in skin, interpubic ligament, scar capsule and contracture phenomenon were noted. Stress-strain characterization, dynamic mechanical spectroscopy and light microscopy were used to characterize the effects of relaxin and estradiol on the contracture phenomenon. Qualitatively, relaxin given to estrogen primed mice was shown to lessen implant contracture and deformability. Administration of relaxin produced the documented changes in the interpubic ligament, but differences were noted between the 8 and 27 day studies. Differences in the failure stress and strain and modulus for the long implant and short non-implant study were noted for the relaxin treated mice.