IDENTIFICATION OF SEX-HORMONE RECEPTORS IN HUMAN AND RABBIT LIGAMENTSOF THE KNEE BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION - EVIDENCE THAT RECEPTORS ARE PRESENT IN TISSUE FROM BOTH MALE AND FEMALE SUBJECTS

Gender-related factors have been attributed to observed differences in the rate of injury to ligaments (e.g., anterior cruciate ligament) be tween male and female subjects. These differences may be a result of u nique regulatory mechanisms within the tissue in response to the sex h ormones estrogen and progesterone. These hormones, when bound to speci fic intracellular receptors (estrogen receptor and progesterone recept or, respectively), modulate gene expression within hormone-responsive tissue. The purpose of this study was to evaluate the expression of th e estrogen and progesterone receptors in ligament tissue from male and female rabbits and humans by the sensitive molecular technique of rev erse transcription-polymerase chain reaction. Total RNA was extracted from human anterior cruciate ligament tissue and from medial cruciate ligament, anterior cruciate ligament, patellar tendon, and synovium ti ssue of the New Zealand White rabbit by the newly developed TRIspin me thod. The total RNA was reverse transcribed and analyzed by polymerase chain reaction to assess the expression of estrogen and progesterone receptors. Our results demonstrate that estrogen and progesterone rece ptor transcripts are expressed in ligament tissue of male and female r abbits and humans and that alterations in receptor expression occur in ligaments during pregnancy. In the human samples, only a small percen tage of the estrogen receptor appeared to be a nonfunctional mRNA spli ce variant, and the predominant form contained the estrogen-binding do main.