Addition Of Collagen To 3D Bioprinted Meniscus Model Increases Elastic Modulus And Preserves Metabolic Activity

The menisci play a vital role in the knee joint through shock absorption and efficient distribution of load across the tibiofemoral joint. Meniscal tears are amongst the most prevalent sports-related injuries in orthopedics, with most cases requiring arthroscopic partial meniscectomy. The damage of meniscal tissue, especially in younger patients, increases the risk of onset of knee osteoarthritis (OA). Past studies have collectively suggested alterations in collagen content and organization in menisci affected by injury or OA. Tissue engineered models can serve as a platform for understanding the composition, biomechanics, and regenerative potential of the human meniscus. PURPOSE: Leverage 3D bioprinting technology to characterize the biological response and mechanical properties of meniscal constructs with varying extracellular matrix bioinks. METHODS: A 3D digital meniscus model was developed by performing microcomputed tomography of a human meniscus. Inner and outer zone meniscus cells from porcine knees were expanded in culture. Groups of five replicate cell-laden Alginate or Alginate + Type I Collagen constructs consisting of 500,000 cells/mL were bioprinted. Constructs were cross-linked with 100 mM, 250 mM, or 500 mM CaCl2 immediately after bioprinting. The MTT assay was performed to assess metabolic activity after 72 hours in culture. Compression testing was performed to compare the elastic modulus of cylindrical specimens printed with and without Type I collagen after 24 hours in culture. RESULTS: The addition of Type I collagen to alginate-based bioinks improved mechanical strength of printed constructs. Crosslinking with 500 mM CaCl2 caused an increase in the elastic modulus of collagen-alginate bioprinted constructs compared to 100 mM and 250 nM CaCl2 (17 kPa vs. 7 and 5 kPa, respectively). Metabolic activity was observed to be statistically similar (p > 0.05) across all concentrations of crosslinking agent and bioink compositions. CONCLUSION: While alginate bioinks provide satisfactory biocompatibility and tunable stiffness, the incorporation of collagen enhances mechanical strength. Hence, the addition of collagen to an alginate bioink may be a promising candidate for applications in meniscal tissue engineering.