Early changes in lapine menisci during osteoarthritis development: Part I:Cellular and matrix alterations

Objective: Osteoarthritis (OA) is the most common form of arthritis and pat ients with meniscal and ligament injuries of the knee are at high risk to d evelop the disease. The purpose of this study was to evaluate changes occur ring in both medial and lateral menisci from the knees of anterior cruciate ligament (ACL) transected rabbits during the early stages of OA developmen t. Design: Meniscal tissues from control and experimental rabbits were process ed for histology and immunohistochemistry for assessment of matrix organiza tion and composition. Results: At 3 and 8 weeks following ACL transection, histological examinati on demonstrated extensive extracellular matrix deterioration. Altered cell distribution, areas depleted of cells, and areas of cell clusters were foun d within the medial but fiat in the lateral meniscus. Immunohistochemistry of both medial and lateral menisci demonstrated significant changes in coll agen distribution. Type I and III collagen staining was increased in both m edial and lateral menisci. In contrast, type II collagen staining was overt ly increased only in the medial meniscus. Conclusion: These results demonstrate that after ACL transection, extracell ular matrix deposition as well as altered matrix organization and altered c ell distribution occur early in the medial meniscus. (C) 2001 OsteoArthriti s Research Society international.