Abstract
Summary Statement
Re-biopsies of five patients after spheroid-based, scaffold-free autologous chondrocyte transplantation revealed regeneration of cartilage with immunohistochemical characteristics of articular cartilage.
Introduction
Traumatic lesions of articular cartilage represent a crucial risk-factor for cartilage degradation and osteoarthritis, because the regenerative capacity of articular cartilage is highly limited. Even if there exist several strategies to treat traumatic cartilage damages such as the classical autologous chondrocyte transplantation (ACT) or matrix assisted ACT, the optimal solution is not yet been found since transplantation errors are known. A relatively new strategy represents the scaffold-free spheroid based autologous chondrocyte transplantation. After harvesting articular cartilage in this strategy spheroids of chondrocytes will be synthesised after chondrocyte isolation and expansion. The spheroids will be implanted and rest at the transplantation site by adhesion.
Patients & Methods
During the last two years 5 patients, which underwent spheroid-based ACT, gave reason for a second look arthroscopy due to clinical problems independent from the initial damage (e.g. meniscus lesion). In these patients a biopsy after informed consent was taken by help of a Jamshidi-needle (1,5 mm) which underwent histological analyses after haematoxilin-eosin and alcian blue staining as well as immunohistological analyses for Coll-II, Coll-X, Aggrecan, SOX-9 and lubricin via standardised automated staining methods. Furthermore, from one patient a surplus spheroid was analyzed by scanning and transmission electron microscopical methods after standard processing of the specimen.
Results
The re-biopsies were taken after different time-points after ACT according to the clinical indication for arthroscopy. The histological analyses revealed in all patients the typical feature of hyaline chondroid tissue with high alcian-blue staining. The apical zone of the regenerated tissue demonstrated flattened chondrocytes, immunohistochemically positive for lubricine, a typical feature for normal articular chondrocytes. The middle and the deep zone revealed round shaped chondrocytes, which were positive for Coll-II, Sox-9 and aggrecan, the typical pattern for articular cartilage, but negative for Coll-X, which is typical for hypertrophic chondrocytes. In the surplus spheroid of one patient we could demonstrate collagen fibers between the round-shaped chondrocytes, which indicates collagen syntheses by the cells in the spheroid.
Discussion/Conclusion
The present date represents the first histomorphological data after spheroid-based ACT. The findings indicate a proper regeneration of cartilage with immunohistological characteristics typical for articular cartilage. One explanation for these positive results even after 6 months of ACT could be a smooth phenotypic re-differentiation of the chondrocytes within the spheroid, which is given by the round shaped phenotype of the cells within the spheroid and the ultrastructural detection of collagen fibers. Finally, our findings demonstrate the need for further re-biopsy based analyses. To reach this goal a registry of ACT-Patients with an integrated alert-system by further Arthroscopy could give a chance to get more biopsies for histological and immunohistological data.
