Building the basis for human meniscus regeneration

Objectives: Total or partial meniscectomy have been the gold standard for the treatment of degenerated/diseased menisci. Despite meniscal regeneration represents a recent trend in tissue engineering, fundamental studies related to human meniscus biochemistry and biomechanics are still scarce. This work aims to contribute in the knowledge of this tissue aiming future clinical applications namely, the aspects dealing with the cellular phenotypes and density, biomechanics and extracellular matrix composition. Methods: Human tissue was obtained from Clínica Saúde Atlântica by means of surgery or biopsy, in accordance with local ethical committee guidelines. The HMC´s were isolated from different donor (sex and age) explants or using an enzymatic standard protocol. Micro-computed tomography (Micro-CT) of freeze-dried meniscus was carried out. Histological (haematoxylin and eosin - H&E, trichrome stain and toluidine blue stainings) analysis was performed for segmental characterization of ECM and cells density. Dynamic mechanical analysis was carried out for medial, anterior and posterior segments of meniscus (in PBS at pH 7.4). Results and Discussion: Micro-CT analysis revealed that meniscus (freeze-dried) possessed a mean porosity of 53%, a mean pore size and trabeculae thickness of 85 μm and 80 μm, respectively. The cells isolated from meniscus are a mixed population of cells, i.e. fibrochondrocyte-like and MSCs. The histological evaluation has shown that meniscus ECM is composed of collagen-type I. This tissue is fibrocartilagineous in nature and presented a higher cell density in the periphery as compared to meniscus core. Cellular density among the different segments (anterior, medial, posterior) of meniscus was quantified using the H&E 2-D histological images. Conclusions: This study has contributed to improve the knowledge on meniscus biology and mechanical properties. It is believed that these important issues should be considered to develop adequate acellular and cellular strategies for tissue engineer meniscus.