Pullulan enhanced MSC retention on OA cartilage. (A) PKH26 labelled MSCs (red) bound to fibrillations on DAPI stained human explanted OA cartilage (blue). MSC retention was increased in (B) 2% or (C) 5% pullulan coated explants. (D) Stereological quantification of MSC retention indicated an increase in cell number on 2% and 5% pullulan coated explants as compared to untreated controls. Magnification bars = 100 μm. DAPI, 4′,6-diamidino-2-phenylindole; MSCs, mesenchymal stem cells; OA, osteoarthritis.