Tissue engineering for total meniscal substitution: animal study in sheep model

Objective: The aim of the study was to investigate the use of a novel hyaluronic acid/polycaprolactone material for meniscal tissue engineering and to evaluate the tissue regeneration after the augmentation of the implant with expanded autologous chondrocytes. Two different surgical implantation techniques in a sheep model were evaluated. Methods: Twenty six skeletally mature sheep were treated with total medial meniscus replacements while 2 meniscectomies served as empty controls. The animals were divided in two groups: cell free scaffold or scaffold seeded with autologous chondrocytes. Two different surgical techniques were compared: in 12 animals the implant was sutured to the capsule and to the meniscal ligament and in the other 12 animals also a transtibial fixation of the horns was used. The animals were euthanized after 4 months. The specimens were assessed by gross inspection and histology. Results: All implants showed excellent capsular ingrowth at the periphery. Marcoscopically, no difference was observed between Cell Seeded and Cell Free group. Better implant appearance and integrity was observed in the group without trans-osseous horns fixation. Using the latter implantation technique, lower joint degeneration was observed in the cell-seeded group with respect to cell-free implants. The histological analysis indicated cellular infiltration and vascularisation throughout the implanted constructs. Cartilaginous tissue formation was significantly more frequent in the cell-seeded constructs.