THE IMPACT OF CELLULAR CHARACTERISTICS IN AUTOLOGOUS CHONDROCYTE TRANSPLANTATION

Abstract

Introduction: Autologous chondrocyte transplantation (ACT) has been shown to be a promising method for restoring hyaline cartilage defects. Since it was first reported by Brittberg et al nine years worth of clinical follow up studies indicate that ACT has provided an excellent outcome in the restoration of hyaline cartilage. As ACT relies on the use of cultured cells and the biosynthetic profile of cultured chondrocytes has been shown to be altered during in vitro expansion, cultivation of chondrocytes for ACT has presented many technical and quality control challenges.

Aim: To perform an assessment of the cellular phenotype of cultured chondrocytes, consistent with differentiation of articular hyaline cartilage, to ensure the delivery of ACT for restoration of hyaline cartilage.

Methods: Using RT-PCR and flow cytometry analyses, we characterised the cellular phenotype of culture chondrocytes used for ACT. We examined several transcriptional factors, cytokines and matrix proteins necessary for the differentiation of chondrocytes in a total of 15 cases of ACT. These included SOX9, Cbfa1, Indian Hedgehog (Ihh), TGF-b3, BMP-2, PTHrP, type I and type II collagen, aggrecan and alkaline phosphatase.

Results: The results demonstrated that there is a variety in the expression of these genetic makers but cultured cells used for ACT were within the programme of chondrocyte differentiation. Furthermore, there is variation in the level of apoptosis of chondrocytes between patients as evidenced by annexin V flow cytometry. As evidenced by MRI in two patient samples, apoptosis of chondrocytes greater than 8% was coincident with cases that could not restore hyaline cartilage three months after ACT.

Conclusions: Given that there is a medical need for ACT in the treatment of articular cartilage injury, a process for monitoring the quality of culture chondrocyte prior to implantation may provide a better clinical outcome of ACT.