Tissue engineering-based cartilage repair with allogenous chondrocytes and gelatin–chondroitin–hyaluronan tri-copolymer scaffold: A porcine model assessed at 18, 24, and 36 weeks

Abstract

We previously showed that cartilage tissue can be engineered in vitro with porcine chondrocytes and gelatin/chondoitin-6-sulfate/hyaluronan tri-copolymer which mimic natural cartilage matrix for use as a scaffold. In this animal study, 15 miniature pigs were used in a randomized control study to compare tissue engineering with allogenous chondrocytes, autogenous osteochondral (OC) transplantation, and spontaneous repair for OC articular defects. In another study, 6 pigs were used as external controls in which full thickness (FT) and OC defects were either allowed to heal spontaneously or were filled with scaffold alone. After exclusion of cases with infection and secondary arthritis, the best results were obtained with autogenous OC transplantation, except that integration into host cartilage was poor. The results for the tissue engineering-treated group were satisfactory, the repair tissue being hyaline cartilage and/or fibrocartilage. Spontaneous healing and filling with scaffold alone did not result in good repair. With OC defects, the subchondral bone plate was not restored by cartilage tissue engineering. These results show that tri-copolymer can be used in in vivo cartilage tissue engineering for the treatment of FT articular defects.

Introduction

Although articular cartilage is a metabolically active tissue, the chondrocytes in the matrix have a relatively slow rate of turnover and the tissue itself lacks a blood supply to support repair and remodeling. Because of the limited capacity for spontaneous repair, minor injury to articular cartilage can lead to progressive damage and degeneration. Recently, tissue engineering has emerged as a new method in which a combination of cells, scaffold, and bioactive agents is used to fabricate functional new tissue to replace damaged cartilage [1]. Many kinds of scaffold, both natural and synthetic, have been proposed for use in cartilage tissue engineering [2].

The mechanism by which the cell synthesizes and secretes extracellular matrix (ECM) and is then, in turn, regulated by the ECM is termed dynamic reciprocity [3]. In our previous in vitro study [4], we hypothesized that a tri-copolymer formed from gelatin, chondroitin, and hyaluronan might mimic cartilage matrix and provide the necessary information for cell attachment to meet the requirement for dynamic reciprocity for cartilage tissue engineering. When this system was tested, chondrocytes were found to be uniformly distributed in the scaffold in spinner flask cultures, but less so in Petri dish cultures, ECM formation was seen on histological examination, and, in spinner flask cultures, chondrocytes retained their phenotype for at least 5 weeks and synthesized type II collagen, showing that gelatin/chondroitin sulfate/hyaluronan tri-copolymer has potential for use as a cartilage tissue engineering scaffold.

In the present study, miniature pigs were used to test the therapeutic effect of tissue engineering-based cartilage repair with allogenous chondrocyte-seeded tri-copolymer scaffold. Many treatment modalities, such as autogenous chondrocyte implantation, mosaicplasty, or marrow stimulating techniques, have been introduced to treat focal articular cartilage injury in young patients, but the results have been variable and the techniques have some limitations [5], [6], [7], [8]. For tissue engineering to be considered as a realistic treatment for focal articular injury, it should be at least as good as the current treatment modalities. In this study, 15 sexually mature miniature pigs were used in a randomized control study to compare tissue engineering, autogenous osteochondral (OC) transplantation, and spontaneous healing for full thickness (FT) articular defects and OC defects.

Only a few studies on cartilage repair using tissue engineering have tested the effect of scaffold alone (without cell seeding) [8], although this is an absolute requirement. In addition, currently available scaffold matrices generally have suboptimal biocompatibility and biodegradability properties, and may therefore be expected to cause adverse reactions, which will need to be overcome during the course of healing. Transplanted cells may help in such a situation, but this needs to be proved experimentally [8]. Another six sexually mature pigs were therefore used in our study to check the biocompatibility and repair capacity of scaffold alone and to examine spontaneous repair of FT and OC defects.