Abstract: Objective To investigate the effects of local transplantation of autologous adipose-derived mesenchymal stem cells (ADSCs) on the formation of hyperplastic scar on rabbit ears. Methods ADSCs were isolated from inguinal fat of six New Zealand rabbits and then sub-cultured. ADSCs of the third passage of each rabbit were used in the following experiments. Six full-thickness skin defect wounds with diameter of 6 mm on the ventral surface of every rabbit ear were made. Wound healing and local-tissue proliferation were observed, and complete epithelization time of wounds and formation time of hyperplastic scar were recorded. The wounds on left ears were selected as group ADSCs, and the wounds on right ears were selected as control group, with 36 wounds in each group. After the complete epithelization of wounds (post injury day 25), 0.2 mL bromodeoxyuridine (BrdU) labeled autologous ADSCs with the concentration of 5×10⁶ per milliliter were injected into each wound of the rabbit of group ADSCs, while the same amount of phosphate buffer solution was injected into each wound of the rabbit of control group. The frequency of injection was once every 5 days, totally for 3 times, and the latter 2 times were injected into scars generated from healed wound. Hyperplastic scars of rabbits of two groups were harvested on the fifth day after the third injection, then the morphology was observed by HE staining, and the arrangement of collagen in hyperplastic scar was observed by VG staining. The distribution of BrdU-labeled ADSCs in the hyperplastic scar was observed with fluorescence microscope. The protein content of type Ⅰ collagen, type Ⅲ collagen, transforming growth factor β₁ (TGF-β₁), and decorin in hyperplastic scar were detected by enzyme-linked immunosorbent assay, and the mRNA expression of decorin and TGF-β₁ in hyperplastic scar were tested by real-time fluorescent quantitative reverse transcription-polymerase chain reaction. Data were processed with paired t test. Results (1) The complete epithelization time of wounds of rabbits' ears was (20.0±2.0) d post injury, and hyperplastic scars were formed on post injury day 35.0±2.2. On post injury day 40, hyperplastic scars of rabbits of control group were still obvious, while those of group ADSCs became smaller, flat, soft, and light colored. (2) Compared with those in control group, epithelial cell layers and the number of nucleated cells in corium layer of hyperplastic scars of rabbits of group ADSCs were increased, and epithelium foot like and dermal papilla like structures were observed. The collagen density of hyperplastic scars of rabbits of control group was tight and arranged disorderly, while that of group ADSCs were decreased significantly and arranged regularly as compared with that of control group. (3) On post injury day 40, BrdU-labeled ADSCs were still observed in the hyperplastic scars of rabbits of group ADSCs. (4) The protein content of type Ⅰ collagen, type Ⅲ collagen, TGF-β₁, and decorin in hyperplastic scars of rabbits of group ADSCs were respectively (1.40±0.04) and (8.18±0.23) μg/L, (25.1±0.7) ng/L, and (4.872±0.101) ng/mL, and those in hyperplastic scars of rabbits of control group were respectively (2.29±0.05) and (12.20±0.38) μg/L, (37.2±1.1) ng/L, and (4.143±0.024) ng/mL. Compared with those in control group, the protein content of type Ⅰ collagen, type Ⅲ collagen, and TGF-β₁ in hyperplastic scars of rabbit of group ADSCs were significantly decreased (with t values from -33.66 to -22.84, P values below 0.001), while the protein content of decorin were significantly increased (t=10.41, P<0.001). (5) Compared with those in control group, the mRNA expression of TGF-β₁ in hyperplastic scars of rabbits of group ADSCs was significantly decreased (t=4.45, P<0.01), while the mRNA expression of decorin was significantly increased (t=5.61, P<0.01). Conclusions Autologous transplantation of ADSCs into scar of rabbit at the early stage can inhibit the formation of hyperplastic scar, promote the quality of wound healing, and the mechanism may relate to the down-regulation of TGF-β₁, type Ⅰ collagen, and type Ⅲ collagen and the up-regulation of decorin induced by ADSCs.