Objective: Lubricin expression in the superficial cartilage will be a crucial factor in the success of carti-lage regeneration. Mesenchymal stem cells (MSCs) are an attractive cell source and theuse of aggregates of MSCs has some advantages in terms of chondrogenic potential andefficiency of cell adhesion. Lubricin expression in transplanted MSCs has not been fully elu-cidated so far. Our goals were to determine (1) whether cartilage pellets of human MSCs expressed lubricinin vitro chondrogenesis, (2) whether aggregates of human MSCs pro-moted lubricin expression, and (3) whether aggregates of MSCs expressed lubricin in the superficial cartilage after transplantation into osteochondral defects in rats.
Methods: For in vitro analysis, human bone marrow (BM) MSCs were differentiated into cartilage by pellet culture, and also aggregated using the hanging drop technique. For an animal study, aggregates of BM MSCs derived from GFP transgenic rats were transplanted to the osteo- chondral defect in the trochlear groove of wild type rat knee joints. Lubricin expression was mainly evaluated in differentiated and regenerated cartilages.
Results: In in vitro analysis, lubricin was detected in the superficial zone of the pellets and condi-tioned medium. mRNA expression of Proteoglycan4 (Prg4), which encodes lubricin, in pel-lets was significantly higher than that of undifferentiated MSCs. Aggregates showed different morphological features between the superficial and deep zone, and the Prg4 mRNA expression increased after aggregate formation. Lubricin was also found in the aggregate. In a rat study, articular cartilage regeneration was significantly better in the MSC group than in the control group as shown by macroscopical and histological analysis.Read More