Inner Meniscus Cells Maintain Higher Chondrogenic Phenotype Compared with Outer Meniscus Cells

Abstract

Meniscus cells have several distinct properties in cellular morphology and extracellular matrix production. Inner meniscus cells are considered to have more chondrocytic phenotype compared with outer meniscus cells. However, the chondrogenic property of each meniscus cell has not been elucidated in detail. In this study, we investigated the difference between human inner and outer meniscus-derived cells in extracellular matrix deposition and chondrogenic potential. Monolayer-cultured inner meniscus cells showed small and ovoid shapes though slender and fibroblastic cells were obtained from outer half of human meniscus. The syntheses of type II collagen and safranin O-stained proteoglycans were increased in chondrogenic pellets derived from inner meniscus cells, rather than in outer meniscus cell-derived pellets. On the other hand, adipogenic lipid vacuoles were equally accumulated in both inner and outer meniscus cells after adipogenic treatment. Chondrogenic treatments also enhanced the expression of chondrogenic marker genes, such as Sry-type HMG box (SOX) 9, Scleraxis, and α1(II) collagen, in inner meniscus cells. However, SOX9 expression was not increased in outer meniscus cells even after chondrogenic treatment. This study demonstrated that inner meniscus cells maintained higher chondrogenic potential compared with outer meniscus cells. Our results suggest that the difference between inner and outer meniscus cells in chondrogenic property might have an essential role in preserving a zone-specific meniscal feature.

• meniscus
• chondrogenic potential
• SOX9
• type II collagen

ACKNOWLEDGMENTS

We thank Ms. Motomi Hachioji and Dr. Aki Yoshida for their kind cooperation. This work was supported by Japan Society for the Promotion of Science (No. 20791040), the Japanese Foundation for Research and Promotion of Endoscopy, Ryobi Teien Memory Foundation, Okayama Medical Foundation, and Child Health and Development from the Ministry of Health, Labor and Welfare (T.F.).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.