Abstract
An in‐depth knowledge of the native meniscus morphology and biomechanics in its different areas is essential to develop an engineered tissue. Meniscus is characterized by a great regional variation in extracellular matrix components and in vascularization. Then, the aim of this work was to characterize the expression of factors involved in angiogenesis in different areas during meniscus maturation in pigs. The menisci were removed from the knee joints of neonatal, young and adult pigs, and they were divided into the inner, intermediate and outer areas. Vascular characterization and meniscal maturation were evaluated by immunohistochemistry and Western blot analysis. In particular, expression of the angiogenic factor Vascular Endothelial Growth Factor (VEGF) and the anti‐angiogenic marker Endostatin (ENDO) was analysed, as well as the vascular endothelial cadherin (Ve‐CAD). In addition, expression of Collagen II (COLL II) and SOX9 was examined, as markers of the fibro‐cartilaginous differentiation. Expression of VEGF and Ve‐CAD had a similar pattern in all animals, with a significant increase from the inner to the outer part of the meniscus. Pooling the zones, expression of both proteins was significantly higher in the neonatal meniscus than in young and adult menisci. Conversely, the young meniscus revealed a significantly higher expression of ENDO compared to the neonatal and adult ones. Analysis of tissue maturation markers showed an increase in COLL II and a decrease in SOX9 expression with age. These preliminary data highlight some of the changes that occur in the swine meniscus during growth, in particular the ensemble of regulatory factors involved in angiogenesis.
Highlights
Paired menisci are intracapsular semilunar structures aimed at providing congruence of incompatible articular surfaces of the knee joint
The samples were analysed by immunofluorescent analysis to contemporary detect the distribution of angiogenesis-regulating factors and collagen II fibres [7]
Western blot analysis—In neonatal, ENDO showed a trend of expression, characterized by a significant increase from the inner to outer part of the meniscus (Fig. 3, P < 0.01), while young and adult animals revealed no quantitative differences among the different meniscal areas (Fig. 3, P > 0.05); pooling the three zones, the young meniscus revealed a significantly higher expression of ENDO in comparison with neonatal and adult ones (P < 0.01)
Summary
Paired menisci are intracapsular semilunar structures aimed at providing congruence of incompatible articular surfaces (namely the femoral condyles and tibial plateau) of the knee joint. The well-known meniscus functions of load bearing, shock absorption and joint stability against tension and torsion rely on its specific structural composition, which is characterized by a specialized network of different collagen isoforms, proteoglycans and vascular supply. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.
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