Morphological and gene expression analysis of matrix-induced autologous chondrocyte implantation (MACI)

Introduction: Matrix-induced autologous chondrocyte implantation (MACI) is a tissue engineering technique for treatment of deep articular cartilage lesions. Cultured chondrocytes seeded on a type I/II collagen membrane are implanted in the chondral lesion using fibrin glue. Several authors have evaluated biopsies of the regenerates by light microscopy, while only few results have been obtained from ultrastructural and gene expression analysis after MACI. The aim of this study is to study both structural and molecular evolution of MACI. Materials and Methods: 3 biopsy harvested from 3 different patients at 2-year follow-up were evaluated. In order to define cell phenotype, gene expression and biochemical methods were employed. Biochemical evaluation was performed with Fluorophore Assisted Carbohydrate Electrophoresis (FACE), which studies the composition of the extracellular matrix disaccharide GAG units. On the other hand, type I and II collagen gene expression analysis was performed by Real Time PCR (RT-PCR), which observes the activation of a specific gene during the different polymerization phases. Risultati: FACE demonstrated the presence of glycosaminoglycanes with a pattern resembling hyaline cartilage. QRT-PCR recorded type II collagen gene expression in all samples. In only one case, type I collagen gene expression was observed as well. Histological analysis revealed hyaline-like tissue formation (with type II collagen, condroitinsulfate and tidemark formation) in all cases. In one sample concomitant type I collagen expression was identified at the superficial layer. At ultrastructural evaluation, an hyaline-like cartilage collagen fibrillary network riorganization and cell cluster arrangement were observed. Discussion: Ultrastructural and gene expression analysis of MACI reveal hyaline-like cartilage tissue reorganization at 2-year follow-up. Conclusions: The present study demonstrates that type I/II collagen membrane is an ideal scaffold for chondroblast growth, allowing hyaline cartilage-like tissue formation once implanted on the chondral defect.