FIG. 1.

Mesenchymal stem cell (MSC) size. (A–C) Microscopic images of human MSCs (hMSCs) from monolayer (A) or three-dimensional (3D) spheroids after trypsinization (B). A mixture of single-cell suspensions of monolayer hMSCs expressing enhanced green fluorescent protein (green) and spheroid hMSCs labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI; red) (C). (D) Analysis of hMSC size by flow cytometry. The size of hMSCs derived from monolayer (mono) or 3D spheroids (3D) in passage (P) 3 or 7 was estimated by flow cytometry. (E) Embolism following hMSC injection. One million hMSCs derived from monolayer or spheroids were injected into the left carotid artery. Some rats injected with monolayer hMSCs developed blindness with the left eye. The upper left panel showed a blind eye at 3 days post-cell injection. Similarly injected spheroid hMSCs did not cause visible abnormalities in the eyes (upper right panel). Whole-mount preparations of the retina were examined under fluorescence microscope for the presence of DiI-positive cells 24 h after intra-carotid injection of 1 million DiI-labeled hMSCs. In rats injected with monolayer hMSCs, a substantial amount of DiI-positive cells was found in blood vessels of the retina (lower left panel), while in rats injected with spheroid hMSCs, a few DiI-positive cells were detected (lower right panel). Color images available online at www.liebertpub.com/scd