2015 ISAKOS Biennial Congress ePoster #403

Tissue Engineering of Knee Menisci With Cell Co-Cultures Without the Use of Scaffold.

Nikolaos K. Paschos, MD, PhD, Jamaica Plain, MA UNITED STATES
Pasha Hadidi, PhD, Davis, CA UNITED STATES
Jerry Hu, PhD, Davis, CA UNITED STATES
Kyriacos Athanasiou, PhD, PE, Houston, TX UNITED STATES

University of California, Davis, Davis, CA, USA

FDA Status Not Applicable

Summary: Different cell-type co-culture systems were successful in engineering scaffold-less tissue-engineered menisci with mechanical and biochemical properties comparable to native tissue.

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Abstract:

Introduction.

Treatment of menisci injuries represents one of the most challenging problems in sports medicine, due to the poor healing potential of the menisci and the association between menisci degeneration and osteoarthritis. Tissue engineering of menisci that could be used for transplantation is a promising approach. Current tissue engineering methods have certain limitations and have not been able to reach values close to native tissue. One of the reasons for this drawback is the limited regeneration potential of menisci cells, thus, current techniques use menisci cells in combination with articular cartilage cells. In contrast, certain fibroblasts have better healing and regeneration potential. Another limitation is the presence of scaffold that is associated with degradation and cell phenotype alteration and toxicity. The purpose of this study was to engineer scaffold-less tissue-engineered menisci with functional properties comparable to native tissue, with the use of different cell-type co-culture systems.

Methods.

Menisci cells (MC), ligament fibroblasts (FC) and articular cartilage cells (AC) were isolated from knee cadaveric specimens. Direct co-culture systems from the above cell types were used, i.e. 50:50 cell ratio for MC:AC, and FC:AC. These cells combinations were seeded in shape-specific agarose wells to form 12 menisci constructs per group using the self-assembling technique. Constructs generated from meniscus cells alone were used as a control. All constructs were grown in culture media for 4 weeks and subsequently were evaluated for their macroscopic appearance, from two independent researchers, blinded to the groups using a scoring system evaluating size, uniformity, and shape, in comparison to native tissue. Histological morphology and biochemical content (collagen, glycosaminoglycan) were evaluated. The biomechanical properties of the engineered menisci were evaluated using the confined compression creep test for compression and shear properties and tensile testing for tensile strength.

Results.

All co-culture cell combinations were able to form shape specific engineered menisci. Macroscopically, the best score was obtained for FC:AC co-cultures (92±4), with MC:AC (84±5) and MC constructs (71±7) having inferior scores (p=0.0003, p<0.0001 respectively). Histologically, FC:AC constructs showed zonal arrangement of cells with collagen I being predominant in red-red region and collagen II being predominant in white-white region. Compressive relaxation and instantaneous moduli were 238±24kPa and 543±42kPa for FC:AC constructs, 198±34kPa and 458±32kPa for MC:AC constructs and 46±11kPa and 127±16kPa for MC constructs (p<0.001, for all comparisons). Aggregate Modulus was 188±12kPa, 120±10kPa and 74±7kPa for FC:AC, MC:AC, and MC constructs respectively (p<0.0001 for all comparisons). The values of FC:AC constructs were comparable to those of native tissue (compressive relaxation moduli, instantaneous and aggregate moduli 228±15kPa, 553±21kPa and 184±8kPa) (p=0.23, p=0.46 and p=0.34 respectively). Ultimate Tensile Strength (UTS) and Young’s modulus were 1.7±0.2MPa and 5.2±0.3MPa for FC:AC constructs, 1.1±0.1MPa and 3.9±0.4MPa for MC:AC constructs (p<0.0001 for all comparisons) and 0.5±0.1MPa and 1.9±0.2MPa for MC constructs.

Conclusions.

A direct co-culture system without the use of scaffold was successful in engineering menisci that could be used for menisci transplantation. The use of ligament fibroblasts in co-culture was proven beneficial for the biomechanical properties of engineered tissue, which was comparable to native tissue values. Co-cultures were also successful in replicating the morphological characteristics of menisci as well as zonal and regional arrangement of cells and collagen component.