4 5Purpose: To evaluate the therapeutic effect of adipose-derived regenerative cell (ADRC) 6 administration on tendon-bone healing in a rabbit ACL reconstruction model. 7Methods: Anterior cruciate ligament (ACL) reconstruction with semitendinosus tendon autograft 8 was performed on the right knees of adult white rabbits. Eighty rabbits were divided into 2 groups: 9 a treatment group, in which the graft was coated with ADRCs mixed in fibrin glue carrier during 10 surgery, and a control group, in which the graft was coated with fibrin glue only. At 2, 4, 6, 8, and 12 11 weeks postoperatively, 8 rabbits were sacrificed in each group. Three were used for histological 12 evaluation at the tendon-bone interface, and 5 for biomechanical examination. 13Results: In histological analysis, chondroid cells appeared more orderly and more regular in size 14 and shape, and Sharpey-like fibers, which connected the tendon graft and bone tissue, appeared 15 earlier in ADRC-treated tissues than in control tissues. In biomechanical analysis, the ultimate 16 failure load in the ADRC-treated group was significantly greater than that in the control group at 2 17 and 4 weeks (29.5 ± 7.2 N vs. 20.9 ± 2.7 N; P = .016 and 32.3 ± 3.9 N vs 22.8 ± 5.4 N; P = .016, 18 respectively). Stiffness was significantly higher in the ADRC-treated group than in the control 19 group at 6 weeks (21.7 ± 5.9 N/mm vs. 12.6 ± 4.9 N/mm; P = .037). Although the ultimate failure 20 load and stiffness of the ADRC-treated limb was higher than that of the limb in the control group at 21 8 and 12 weeks, these differences were not significant. 22Conclusions: Local administration of ADRCs promoted the early healing process at the tendon-bone 23 junction, both histologically and mechanically, in the rabbit ACL reconstruction model. 24Clinical Relevance: ADRCs could be used to enhance graft healing in ACL reconstruction. 25 26