Trilineage differentiation of mesenchymal stem cells. Representative microscopic images of von Kossa and Oil-Red-O staining to confirm osteogenic and adipogenic differentiation of plastic adherent bone marrow-derived cell populations (scale bars = 100 μm). Chondrogenic differentiation was confirmed by the formation of dense cell pellets (haematoxylin and eosin (H&E) staining) that were positive for Safranin O (orange–red stain) (scale bars = 1 mm). Upper row: control, non-induced cultures; central row: control, induced (non-injected) cultures. Representative images for cell populations injected through a 23G needle and subsequently induced are shown. No difference was observed between these and populations injected through 20G or 21G needles.