Tissue Engineered Meniscus Repair: Influence of Cell Passage Number, Tissue Origin, and Biomaterial Carrier

Objective. Studies have shown that meniscal repairs have better outcomes over both partial and total meniscectomies. Tissue engineering strategies to repair meniscus tears have been explored using cell sources that involve a donor as well as a period of in vitro cell expansion before use. This study explored cell sources that could be easily harvested and rapidly isolated by enzymatic digestion and cannulated delivery. Methods. Bovine menisci were used to create a bucket handle tear. Cell lines were established from meniscus, synovium, and adipose tissue and fluorescently labeled. At passages P2, P4, and P8, cells were added to the defect from the following experimental groups: cells alone, collagen gel, collagen scaffold, or hyaluronic acid. Menisci constructs were xenografted subcutaneously onto the dorsum of athymic rats and incubated for 3, 6, and 9 weeks, at which time they were retrieved and processed for histology. Results. Meniscal cells were able to repair defects faster and significantly better than adipose or synovium derived cells. Adipose cells were the least effective in comparison. Repair was significantly better at 9 weeks compared with 6 and 3 weeks. Macroscopic examination of menisci that received cell implants showed the thickest tissue in menisci that had collagen implants, and the thinnest fill occurred in menisci treated with cells alone. Histology confirmed no cells or integrative repair in the control specimens. Conclusions. Delivery of cells alone outperformed the additional use of biomaterials. Our results suggest a strategy that would use both meniscus and synovial cells for arthroscopic meniscal repair.