Repair of chondral defects with allogenous chondrocyte-seeded hyaluronan/collagen II microspheres in a rabbit model

Using a recently established method to prepare hyaluronan/collagen II (HA/Col II) microspheres for a novel biomaterial to couple with living cells/tissues, this animal model study evaluated the effects on a 4-week healing process of chondral defects by the implantation of allogenous chondrocyte-seeded HA/Col II microspheres that had been cultured in vitro for 7 days prior to implantation compared with unseeded HA/Col II microspheres or an untreated wound. Four weeks postsurgery, the untreated group's defect was filled with translucent soft tissue. At the same time, the edges and demarcation lines of the healing defects that were implanted with either HA/Col II microspheres or chondrocyte-seeded HA/Col II microspheres were infused yet recognizable. Furthermore, the new tissues were well integrated into the surrounding articular cartilage. Less glycosaminoglycan (GAG) staining was observed in the defects implanted with HA/Col II microspheres, which indicated that most of the repair tissues were derived from fibrocartilage formation. Conversely, more GAG staining appeared in the defect implanted with chondrocyte-seeded HA/Col II microspheres, which demonstrated a higher level of hyaline cartilage regeneration. Due to the short healing period assigned to this study, the repaired cartilage showed limited incorporation into the surrounding host cartilage and some loose connection to the subchondral bone.