Scaffold-Free Tissue-Engineered Allogenic Adipose-Derived Stem Cells Promote Meniscus Healing

Purpose: To determine whether meniscal tissue could be healed histologically by the implantation of allogenic threedimensional formed adipose-derived stem cells (ADSCs) in a rabbit model of partial meniscectomy. Methods: Forty Japanese white rabbits (aged 15-17 weeks) were assigned to 2 groups. Defects 1.5 mm in diameter were created in the anterior horn of the medial menisci. The defects were left empty in the control group and were filled with cylindrical plugs of allogenic ADSCs extracted from adipose tissue in the experimental group. Macroscopic scoring (range, 0-3), histological scoring (range, 0-12), and immunohistological stainability of type I collagen were evaluated at 2, 4, 8, and 12 weeks postoperatively (n=5 rabbits for each week). Results: Macroscopically, the height of the healing tissue in the experimental group was significantly greater than that of the control group at 2 weeks (3 vs 0, P=.01), 4 weeks (3 vs 1, P=.01), and 8 weeks (3 vs 2, P=.02). Histologically, safranin-O staining was noted at 2 weeks and increased gradually over time in the experimental group. In contrast, the intensity of staining was lower in controls at all weeks. Tissue quality scores were significantly higher in the experimental group than in the controls at all weeks (3 vs 0 at 2 weeks [P=.00009], 4.5 vs 2 at 4 weeks [P=.00023], 9 vs 5 at 8 weeks [P=.0047], 10.5 vs 6 at 12 weeks [P=.00026]). The implanted tissue was positive for type I collagen, and stainability was increased gradually over time. Conclusions: Three-dimensional scaffoldfree allogenic ADSCs implanted into a 1.5-mm avascular meniscal defect survived, adhered to the defect, and promoted histological meniscus healing in a rabbit model. Clinical Relevance: ADSC implantation designed to promote meniscal healing may play an important role as a tool for meniscus healing.