The knee menisci are fibro-cartilaginous tissue located between tibial plateau and femoral condyles in each knee joint, and have important roles in biomechanics of the knee joint including load bearing and shock absorption, secondary stabiliser of the joint and joint lubrication and nutrient distribution [1]. In clinics, complete healing of meniscus still remains as a challenge. Several tissue engineering and other regenerative medicine strategies have been attempting to repair or regenerate the meniscus tissue [2]. Cellularity is one of the important characteristics that should be considered in tissue engineering and regenerative medicine strategies. The aim of this study is to investigate the 3D cellularity of human meniscus. Six lateral meniscus tissues obtained from human donors were prepared into sequential 30 lm-thick histological slices and stained with Giemsa. Cells were counted in an in-depth fashion as either fibrochondrocytes or as fibroblast-like cells respectively based on their roundish or elongated morphology (Fig. 1) in a total of 432 regions using Olympus BX51 Microscope and Stereo Investigator software from MBF Bioscience. 3D cell densities were obtained by calculating the number of the cells found in unit volume in the vascular and avascular parts of the anterior, central and posterior segments of the meniscus. Cellularity varies within the human meniscus (Fig. 2), specifically between avascular and vascular regions of the meniscus by having the mean values of respectively 12820 cells/mm3 and 27199 cells/mm3. In average, the abundance of fibrochondrocytes (14,705 cells/ mm3) is more than two-and-a-half times as that of fibroblast-like cells (5,539 cells/mm3).The clinical phenomena of very poor healing of avascular region and relatively higher healing ability of vascular region could be explained by high cellularity difference in these regions. This work reveals the knowledge of 3D cellularity of human meniscus and provides information to be used in the development of advanced tissue engineering strategies for meniscus regeneration.

References
1. McDermott ID, Masouros SD, Amis AA (2008) Biomechanics of the
menisci of the knee. Current Orthopaedics 22 (3):193–201.
2. Pereira H, Frias AM, Oliveira JM, Espregueira-Mendes J, Reis RL
(2011) Tissue engineering and regenerative medicine strategies in
meniscus lesions. Arthroscopy: The Journal of Arthroscopic & Related
Surgery 27 (12):1706–1719.