Fluorescent microscopic findings. Fluorescent microscopy for in vivo tracing of injected mesenchymal stem cells (MSCs) at 1, 3, and 5 weeks. (A to C) PBS + MSC group. (D to F) Hyaluronic acid (HA) + MSC group. Bar = 50 μm. (G) Quantification of the carboxyfluorescein diacetate succinimidyl ester (CFDA-SE)-labeled MSCs. Data are mean ± standard deviation of five guinea pigs in each group. *P < 0.05.