Collagen Meniscus Implant (CMI): ultrastructure, biochemistry and gene expression before and after implantation

Collagen meniscus implant (CMI) is a tissue engineering technique for the management of irreparable meniscal lesions. In this study we evaluate morphological and biochemical changes occurring in CMI after implantation. Gene expression technique was also adopted to characterize the phenotype of the invading cells. Light microscopy, immunohistochemistry (type I and II collagen), SEM and TEM analysis was performed on 5 biopsy specimens, harvested from 5 different patients (range, 6 to 16 months after surgery). Flurophore Assisted Carbohydrate Electrophoresis (FACE) and Real Time PCR evaluation was carried out on 2 biopsy specimens, harvested respectively 6 and 16 months after implantation. All these investigations were also applied on non implanted scaffolds for comparison. Scaffold sections appeared composed by parallel connective laminae, connected by smaller connective bundles, surrounding elongated lacunae. In the biopsies specimens, the lacunae were filled by connective tissue with newly formed vessels and fibroblast-like cells. Immunohistochemistry revealed exclusively type I collagen in the scaffold, while type II collagen appeared in the biopsies specimens. FACE analysis carried out in the scaffold did not detect any GAG disaccharides. Conversely, disaccharides were detected in the implants. Real Time PCR showed signal only for Collagen type I. In the scaffolds no gene expression was recorded. The morphological findings demonstrate that CMI is a biocompatible scaffold available for colonization by connective cells and vessels. Biochemical data show an specific production of extracellular matrix after implantation. The absence of signal for type II collagen gene can be attributed to different maturation stages of the ingrowing tissue.