Human Amniotic Mesenchymal Stem Cell Sheets Encapsulating Cartilage Particles Facilitate Repair of Rabbit Osteochondral Defects

Background: Human amniotic mesenchymal stem cells (hAMSCs) are being widely applied in various fields. Therefore, hAMSCs represent a promising candidate to facilitate cartilage regeneration. Nonetheless, no studies have investigated the application of hAMSC sheets to repair cartilage defects in vivo. Purpose: To evaluate hAMSC sheets encapsulating cartilage particles to promote repair of rabbit osteochondral defects. Study Design: Controlled laboratory study. Methods: hAMSC sheets were constructed with passage 3 hAMSCs. The phenotypic and structural characteristics of hAMSC sheets were evaluated by flow cytometry and scanning electron microscopy, respectively. The potential for chondrogenic differentiation of hAMSC sheets was assessed by cartilage-specific marker staining, immunohistochemistry, and mRNA and protein expression (SOX9, COLII, and ACAN). Osteochondral defects (diameter, 3.5 mm; depth, 3 mm) were created in the left patellar grooves of 20 New Zealand White rabbits (female or male). The defects were treated with hAMSC sheet/cartilage particles (n = 5), cartilage particles (n = 5), hAMSC sheets (n = 5), or fibrin glue (n = 5). Macroscopic and histological evaluations of the regenerated tissue were conducted after 3 months. The survival time and differentiation of transplanted hAMSCs in the defect area were evaluated by immunofluorescence. Results: hAMSC sheets had a multilayered structure, with cells stacked layer by layer. Importantly, hAMSC sheets highly expressed phenotypic markers of mesenchymal stem cells. Cartilage-specific marker staining and immunohistochemistry were positive, and mRNA and protein expression was higher in the chondrogenically induced hAMSC sheet group than in the hAMSC sheet group ( P < .05). hAMSC sheet/cartilage particles formed a large amount of hyaline-like cartilage in the defect area. In addition, macroscopic and histological scores were significantly higher than those in the other groups. Integration with surrounding normal cartilage and subchondral bone regeneration in the hAMSC sheet/cartilage particles group were better when compared with the other groups. A large number of human nuclear-specific antigen-positive cells were observed in the defect area of hAMSC sheet/cartilage particles and hAMSC sheet groups. Moreover, some positive cells expressed SOX9. Conclusion: hAMSC sheets encapsulating cartilage particles facilitate osteochondral defect repair. Clinical Relevance: Delivery of cells in the form of a cell sheet in conjunction with cartilage particles provides a novel approach for cell-based cartilage regeneration.