Can Arthroscopically Harvested Synovial Stem Cells Be Preferentially Sorted Using Stage-Specific Embryonic Antigen 4 Antibody for Cartilage, Bone, and Adipose Regeneration?

PurposeThe aim of this study was to investigate the relation between stage-specific embryonic antigen 4 (SSEA4) expression and synovium-derived stem cell (SDSC) lineage differentiation.MethodsHuman SDSCs were collected during arthroscopic surgery from 4 young patients with anterior cruciate ligament injuries. Passage 2 SDSCs were sorted by fluorescence-activated cell sorting using phycoerythrin-conjugated monoclonal antibody against SSEA4 into 3 groups: SSEA4(+) cells, SSEA4(−) cells, and unsorted control cells. After 1 more passage, expanded cells from each group were evaluated for SSEA4 expression by use of flow cytometry as well as multilineage differentiation capacities, including chondrogenesis, adipogenesis, and osteogenesis, using biochemical analysis, histologic analysis, immunostaining, and real-time polymerase chain reaction.ResultsAfter cell sorting, 1 more passage expansion decreased SSEA4(+) cells from 99.8% to 79.2% and increased SSEA4(−) cells from 4.4% to 53.3% compared with 70.3% in the unsorted cell population. SSEA4(−) SDSCs with a lower cell proliferation exhibited higher chondrogenic potential (in terms of the ratio of glycosaminoglycan to DNA [P < .001] and COL2A1 [type II collagen] messenger RNA [mRNA] [P < .001]) and adipogenic potential (in terms of oil red O staining and quantitative assay [P = .007], LPL [lipoprotein lipase] mRNA [P = .005], and CEBP [CCAAT/enhancer-binding protein alpha] mRNA [P = .010]). In contrast, SSEA4(+) SDSCs retained cell expansion and enhanced osteogenic capacity, as evidenced by intense calcium deposition stained by alizarin red S and a significantly elevated expression of OPN (osteopontin) mRNA (P = .007).ConclusionsIn this study, for the first time, we showed the benefit of using the surface marker SSEA4 in SDSCs to preferentially sort a mixed population of cells. SSEA4(+) SDSCs indicated a strong potential for osteogenesis rather than chondrogenesis and adipogenesis.Clinical RelevanceSDSC-based mesenchymal tissue regeneration can be easily achieved by arthroscopic harvesting followed by quick cell sorting.