Gene expression in menisci from the knees of skeletally immature and mature female rabbits.

This study, using the sensitive molecular technique of semiquantitative reverse transcription-polymerase chain reaction, evaluated mRNA levels for several molecules in medial and lateral menisci from the knees of skeletally mature and immature rabbits. Total RNA was extracted from the medial and lateral menisci of New Zealand White rabbits with the TRIspin method. Total RNA and DNA were similar in the two menisci of both immature and mature rabbits. The total RNA was reverse-transcribed and analyzed by semiquantitative polymerase chain reaction using rabbit-specific primer sets; levels of mRNA for a subset of molecules differed between the medial and lateral menisci. These variations in mRNA levels were also influenced by the degree of skeletal maturity of the rabbits. For most of the genes, mRNA levels were generally higher in the medial than in the lateral meniscus. The medial meniscus from immature and mature rabbits had significantly increased levels of mRNA for molecules such as transforming growth factor-beta, cyclooxygenase-2, and tissue inhibitor of metalloprotease-1. In contrast, compared with mRNA in the lateral meniscus, that for types II and III collagen, biglycan, insulin-like growth factor-2, plasminogen activator inhibitor-1, and matrix metalloprotease-1 was significantly increased in the medial meniscus of mature rabbits only and that for versican and type-I collagen was significantly increased in the medial meniscus of immature rabbits only. Levels of mRNA for inducible nitric oxide synthase and basic fibroblast growth factor were similar in both menisci for both age groups. The present study demonstrates that regulation of mRNA levels in medial and lateral menisci is tissue-specific and influenced by the skeletal maturity of the animals.