Complex alterations in gene expression occur in the knee ligaments of the skeletally mature multiparous rabbit during pregnancy

Pregnancy is known to influence the function of ligaments of the knee in both humans and rabbits. During pregnancy, ligament laxity increases. The mechanism by which these changes in ligament function occur is unknown. The present study was undertaken to assess changes in the pattern of gene expression for a number of molecules which could be involved in the alterations in tissue function. Using RNA isolated from pregnant and age-matched nonpregnant rabbits, levels of mRNA for matrix molecules, proteinases and inhibitors, cytokines and growth factors and inducible nitric oxide synthase were assessed by semi-quantitative RT-PCR. The results indicate that the pregnancy-induced changes in the pattern of gene expression is very complex and differences in the changes observed for the medial collateral ligament and the anterior cruciate ligament may also indicate that ligament-specific effects of pregnancy occur, mRNA levels of some molecules were significantly elevated or suppressed, while others were unchanged, indicating that the changes observed were specific rather than general. While the extent of the molecules assessed was designed to be representative rather than exhaustive, the results indicate that there is likely no simple cause and effect relationship between the observed mechanical alterations during pregnancy and alterations in gene expression in the affected ligaments. (C) 1998 Elsevier Science B.V.