Abstract 41

MATRIX-INDUCED AUTOLOGOUS CHONDROCYTE IMPLANTATION: INFLUENCE OF SEEDING DENSITY.

Craig Willers, Ming-Hao Zheng

School of Surgery and Pathology (Orthopaedics), University of Western Australia

Osteochondral injury accounts for approximately 20% of arthroscopic diagnoses of the knee, mainly located on the medial femoral condyles. Conventional treatment is generally symptomatic and/or characterized by inferior fibrocartilage repair. Matrix-induced Autologous Chondrocyte Implantation (MACI) was implemented to encourage regeneration in osteochondral defects in this study. Twenty rabbits were randomly divided into five equal groups to assess their regenerative outcome following untreated injury, membrane-only MACI treatment, MACI at 10⁴ cells/ml, MACI at 10⁵ cells/ml, and MACI at 10⁶ cells/ml after 8 weeks. During primary surgery, 3x3mm defects were established in the medial femoral condyles and autologous chondrocytes for cultivation and re-implantation. After integration of chondrocytes into the type I/III collagen ACI-Maix membrane, treatment was administered by packing fibrin glue into the osseous compartment and introducing seeded ACI-Maix into the articular cartilage void. Upon sacrifice and processing, regenerative tissues were investigated by H&E, polarised light LM, Alcian Blue (proteoglycan), and type II collagen immunohistochemistry, then scored using a modified ICRS scoring system. Untreated defects could only manage an inferior fibrocartilaginous repair with no restoration of osteochondral architecture at all time points. Membrane-only MACI regeneration was characterised by cartilage of reduced thickness and matrix synthesis. MACI treatment produced regenerative tissue nearly identical across the three seeding densities and at all three time points, with reliable hyaline-like morphology and healthy matrix production. This project suggests that seeding densities below the commercially accepted density of 10⁶ cells/ml are capable of regenerating tissue of the same calibre. This may be clinically significant in reducing perioperative cultivation times.

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