Gene expression in rabbit menisci during pregnancy

Abstract

Recent studies have indicated that pregnancy can affect cellular activity in connective tissues such as cartilage, ligaments, and tendons. However, the impact of pregnancy on cellular activity in the menisci, a critical component in joint function, has not been reported. Therefore,the purpose of this study was to evaluate mRNA levels for several relevant molecules in both medial and lateral menisci from the knees of first-time pregnant immature rabbits (primigravida), third-time pregnant mature rabbits (multiparous), and nonpregnant rabbits (age-matched immature and mature controls) by the sensitive molecular technique of semiquantitative reverse transcription--polymerase chain reaction. Total RNA yields from the medial meniscus of multiparous rabbits were reduced to 66% of age-matched control values; however, yields from medial and lateral menisci from primigravida animals or the lateral meniscus of multiparous animals were not significantly depressed. DNA yields were not affected by pregnancy. Type I collagen mRNA levels were significantly depressed in both menisci only in primigravida rabbits. Versican mRNA levels were significantly elevated in both menisci only in multiparous rabbits. None of the transcripts for the other matrix molecules assessed were influenced by pregnancy. Collagenase mRNA levels were unaffected by pregnancy, but TIMP-1 mRNA levels were significantly decreased in the medial meniscus of primigravida rabbits and in the lateral meniscus of multiparous rabbits. Complex changes in the pattern of mRNA expression were observed for growth factors (TGF-beta bFGF, and IGF2). Inducible nitric oxide synthase mRNA expression was not altered during pregnancy. Transcripts for cyclooxygenase-2 were 61 and 50% of control values in the medial meniscus of primigravida and multiparous animals, respectively, while cyclooxygenase-2 mRNA levels were 150 and 188% of control values in the lateral meniscus from primigravida and multiparous animals, respectively. Such results indicate that pregnancy-induced changes in the pattern of mRNA expression are meniscus specific. Furthermore, the results support the hypothesis that different connective tissues of the knee respond to pregnancy in a unique manner.