RESUMO
In several animal models of osteoarthritis induced by cruciate ligament transection, a dense, scar-like tissue mass forms rapidly on the medial side of the knee joint. This mass mimics clinical fibrosis that sometimes occurs after joint surgery. It is unknown exactly why this medial tissue mass forms and what cells are involved in its formation. This study characterizes this medial mass by histology, biochemistry, and the expression of types I and III collagen mRNA. The medial mass is compared with the medial collateral ligament (MCL) and the MCL epiligament in anterior cruciate-transected and unoperated joints, and to normal skin and skin scar. The morphology of the medial mass resembled the epiligament and skin scar more than the MCL. The concentration of DNA and RNA and the RNA-DNA ratio were elevated dramatically in the medial mass compared with all other tissues including skin scar. However, the mRNA copy number and ratio of collagen types I and III mRNAs did not differ significantly among the medial mass, MCL, epiligament, and skin in either the control or the operated joints. The response of the medial mass, MCL, and MCL epiligament to cruciate transaction involves both hyperplasia and hypertrophy, but without a dramatic shift in cell phenotype. The medial mass may be a useful mimic or model of intraarticular adhesions, hypertrophic scars, ligament sprains, and arthrofibrosis.
Assuntos
Ligamento Cruzado Anterior/patologia , Cicatriz/patologia , Ligamento Colateral Médio do Joelho/patologia , Osteoartrite do Joelho , Joelho de Quadrúpedes/patologia , Ferimentos e Lesões/patologia , Adaptação Fisiológica , Animais , Ligamento Cruzado Anterior/química , Ligamento Cruzado Anterior/metabolismo , Lesões do Ligamento Cruzado Anterior , Cicatriz/metabolismo , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Colágeno Tipo III/genética , Colágeno Tipo III/metabolismo , DNA/análise , Modelos Animais de Doenças , Cães , Hiperplasia/metabolismo , Hiperplasia/patologia , Hipertrofia/metabolismo , Hipertrofia/patologia , Ligamento Colateral Médio do Joelho/química , Ligamento Colateral Médio do Joelho/metabolismo , RNA/análise , RNA Mensageiro/metabolismo , Joelho de Quadrúpedes/lesões , Joelho de Quadrúpedes/metabolismo , Ferimentos e Lesões/metabolismoRESUMO
We analyzed the neuronal occurrence of autonomic transmitters; noradrenaline (NA), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP), in the Achilles tendon, medial and lateral collateral ligaments and knee joint capsule in the rat--by immunohistochemistry (IHC). In addition, the tissue concentrations of the sympathetic neuropeptide, NPY, and the parasympathetic peptide, VIP, were determined by radioimmunoassay (RIA). IHC demonstrated nerve fibers containing sympathetic vasoconstrictors--NA and NPY--and the parasympathetic vasodilator, VIP, in all tissues. NPY- and NA-positive nerve fibers were predominantly observed in larger blood vessels, whereas, nerve fibers immunoreactive to VIP were found in smaller vessels. In many nerve fibers a co-localization of the transmitters was seen. RIA showed that the concentration of NPY compared to VIP was 15-times higher in ligaments and twice as high in tendons and capsules. The differences noted may reflect a difference in vulnerability to degenerative conditions. In pathological conditions, dysregulation of autonomic transmitters in hypovascularized tissues subjected to repetitive mechanical load may contribute to tissue hypoxia leading to degeneration and rupture of tendons and ligaments.