Human polymer-based cartilage grafts for the regeneration of articular cartilage defects.

The use of autologous chondrocyte implantation (ACI) and its further development combining autologous chondrocytes with bioresorbable matrices may represent a promising new technology for cartilage regeneration in orthopaedic research. Aim of our study was to evaluate the applicability of a resorbable three-dimensional polymer of pure polyglycolic acid (PGA) for the use in human cartilage tissue engineering under autologous conditions. Adult human chondrocytes were expanded in vitro using human serum and were rearranged three-dimensionally in human fibrin and PGA. The capacity of dedifferentiated chondrocytes to re-differentiate was evaluated after two weeks of tissue culture in vitro and after subcutaneous transplantation into nude mice by propidium iodide/fluorescein diacetate (PI/FDA) staining, scanning electron microscopy (SEM), gene expression analysis of typical chondrocyte marker genes and histological staining of proteoglycans and type II collagen. PI/FDA staining and SEM documented that vital human chondrocytes are evenly distributed within the polymer-based cartilage tissue engineering graft. The induction of the typical chondrocyte marker genes including cartilage oligomeric matrix protein (COMP) and cartilage link protein after two weeks of tissue culture indicates the initiation of chondrocyte re-differentiation by three-dimensional assembly in fibrin and PGA. Histological analysis of human cartilage tissue engineering grafts after 6 weeks of subcutaneous transplantation demonstrates the development of the graft towards hyaline cartilage with formation of a cartilaginous matrix comprising type II collagen and proteoglycan. These results suggest that human polymer-based cartilage tissue engineering grafts made of human chondrocytes, human fibrin and PGA are clinically suited for the regeneration of articular cartilage defects.

[Molecular characterization of tissue-engineered articular chondrocyte transplants based on resorbable polymer fleece]. / Molekulare Charakterisierung von gezüchteten humanen dreidimensionalen Chondrozytentransplantaten.

Three-dimensional arrangement and subsequent transplantation of chondrocytic cells in resorbable polymers has been shown to be a promising technique for the treatment of cartilaginous defects. Engineering of artificial cartilage tissue includes dedifferentiation of chondrocytes in monolayer culture, the use of biodegradable matrices and polymer scaffolds, and re-expression of chondrocytic marker genes in three-dimensional culture. The aim of this study was to characterize molecularly the phenotypic changes occurring with autologous cartilage tissue engineering. Human articular chondrocytes were isolated, cultured in medium containing human serum, and expanded up to passage 3. Chondrocytes were embedded in human fibrinogen and in polyglactin-polydioxanon fleeces and cultured three-dimensionally up to 4 weeks. Dedifferentiation of chondrocytes in monolayers and formation of cartilage tissue in vitro or after subcutaneous transplantation into nude mice was assessed by gene expression analysis of typical chondrocytic genes, histology, and immunohistochemistry. The expansion of chondrocytes with human serum resulted in the induction of type I and type III collagens, whereas cartilage-specific type II collagen, cartilage oligomeric matrix protein, cartilage link protein, and aggrecan were repressed and induced again after three-dimensional arrangement of chondrocytes in polyglactin-polydioxanon. Transplantation experiments documented the synthesis of proteoglycan and cartilage-specific type II collagen in vivo. Three-dimensional arrangement of human articular chondrocytes in resorbable polyglactin-polydioxanon fleeces supports chondrogenic differentiation and the formation of a hyaline-like cartilaginous matrix in vitro and in vivo.