Mesenchymal progenitor cells derived from synovium and infrapatellar fat pad as a source for superficial zone cartilage tissue engineering: analysis of superficial zone protein/lubricin expression.

Superficial zone protein (SZP) is a boundary lubricant of articular cartilage in joints. As SZP at the surface of articular cartilage plays an important role in the normal function of synovial joints, the localization of SZP-secreting cells at the surface of tissue-engineered cartilage is prerequisite. The aim of this study was to identify suitable progenitor cell sources for tissue engineering of superficial zone cartilage. We investigated whether mesenchymal progenitor cells (MPCs) from synovium and infrapatellar fat pad (IFP) have the potential for secretion of SZP after chondrogenic differentiation in an aggregate pellet culture system. SZP was immunolocalized in pellets from synovium-MPCs and IFP-MPCs. The enzyme-linked immunosorbent assay analysis of SZP demonstrated that chondrogenically differentiated synovium-MPC and IFP-MPC pellets secreted SZP into media. Real-time polymerase chain reaction analysis showed significant upregulation of SZP mRNA in synovium-MPC and IFP-MPC pellets after chondrogenic differentiation. The synovium-MPCs demonstrated the higher colony-forming, proliferative, and chondrogenic potential, and exhibited greater SZP secretion after chondrogenic induction compared with IFP-MPCs. In conclusion, both synovium and IFP are promising cell sources for tissue engineering of superficial zone cartilage.