The Effect of the Addition of Adipose-Derived Mesenchymal Stem Cells to a Meniscal Repair in the Avascular Zone: An Experimental Study in Rabbits

Purpose: To determine whether adipose-derived mesenchymal stem cells (ASCs) affect the healing rate of meniscal lesions sutured in the avascular zone in rabbits. Methods: Four groups were used. In group A (n = 12) a short, 5-mm-long longitudinal lesion in the avascular zone of the anterior horn of the medial meniscus was created and immediately sutured. In group B (n = 8) the same short lesion was created but suture was delayed 3 weeks. In group C (n = 12) a larger, 15-mm-long lesion that spanned the whole meniscus was created and sutured immediately. In group D (n = 8) the same large lesion was sutured 3 weeks later. Both knees in each rabbit were used: 1 served as the control, and in the other, 1 x 10(5) allogeneic ASCs marked with bromodeoxyuridine were placed in the lesion immediately before suturing. The animals were killed at 12 weeks. Results: In group A (short lesion, acute repair) 6 of 12 ASC-treated menisci and 0 of 12 controls had some healing (P = .014). In group B (short lesion, delayed repair) 2 of 8 ASC-treated menisci and 1 of 8 controls had some healing (P = .5). In group C (long lesion, acute repair) 6 of 12 ASC-treated menisci and 0 of 12 controls had some healing (P = .014). In group D (long lesion, delayed repair) 4 of 8 ASC-treated menisci and 0 of 8 controls had some healing (P = .07). The addition of ASCs increased the healing rate (odds ratio, 32 [range, 3.69 to 277]; P = .002). The histologic analysis of the healed zones identified well-formed meniscal fibrocartilage with persistence of cells derived from the ASCs (immunolocated with anti-bromodeoxyuridine antibodies). Conclusions: Adding ASCs to a repair in the avascular zone of rabbit menisci increases the chances of healing. Healing is improved in small and larger lesions. When suture is delayed, the effect is not as evident. Clinical Relevance: In the future, ASCs might help in meniscal repair in the avascular zone.