Meniscus regeneration combining meniscus and mesenchymal stromal cells in a degradable meniscus implant: an in vitro study.

Meniscus regeneration is an unmet clinical need as damage to the meniscus is common and causes early osteoarthritis. The aim of the present study was to investigate the feasibility of a one-stage cell-based treatment for meniscus regeneration by augmenting a resorbable collagen-based implant with a combination of recycled meniscus cells and mesenchymal stromal cells (MSCs). Cell communication and fate of the different cell types over time in co-culture were evaluated by connexin 43 staining for gap junctions and polymerase chain reaction (PCR) to discriminate between meniscus cells and MSCs, based on a Y-chromosome gene. To define optimal ratios, human meniscus cells and bone-marrow-derived MSCs were cultured in different ratios in cell pellets and type I collagen hydrogels. In addition, cells were seeded on the implant in fibrin glue by static seeding or injection. Cellular communication by gap junctions was shown in co-culture and a decrease in the amount of MSCs over time was demonstrated by PCR. 20 : 80 and 10 : 90 ratios showed significantly highest glycosaminoglycan and collagen content in collagen hydrogels. The same statistical trend was found in pellet cultures. Significantly more cells were present in the injected implant and cell distribution was more homogenous as compared to the statically seeded implant. The study demonstrated the feasibility of a new one-stage cell-based procedure for meniscus regeneration, using 20 % meniscus cells and 80 % MSCs seeded statically on the implant. In addition, the stimulatory effect of MSCs towards meniscus cells was demonstrated by communication through gap junctions.