4D-BIOPRINTED MULTIPHASIC MULTICELLULAR SCAFFOLD FOR PERSONALIZED OSTEOCHONDRAL TISSUE ENGINEERING

Articular cartilage defects cannot heal on their own, due to the lack of blood supply and regenerative potential. Tissue engineering technology has been showing some promise in overcoming this challenge. In recent years, advances in 3D and 4D printing technology have further enriched the structural design and composition of tissue engineering scaffolds, which also provided convenience for cell loading and cell delivery of living cells, enabling precise control of seeding cells in vivo, achieving better mimicking of tissues. When delivering the cells onto the scaffold, the cell type, cell distribution and cell retention should be fully considered. In general, cells should be delivered with its composition and arrangement similar to natural tissues, in terms of spatial-temporal relationship, in order to serve their original function. In Hong Kong, we designed a bone marrow-derived mesenchymalstem cell (BMSC)-laden 3D-bioprinted multilayer scaffold with methacrylated hyaluronic acid (MeHA)/polycaprolactone incorporating kartogenin and β-TCP for osteochondral defect repair within each region. BMSC-laden MeHA was designed to actively introduce BMSCs in situ, and diclofenac sodium (DC)-incorporated matrix metalloproteinase-sensitive peptide-modified MeHA was induced on the BMSC-laden scaffold as an anti-inflammatory strategy. BMSCs in the scaffolds survived, proliferated, and produced large amounts of cartilage-specific extracellular matrix in vitro. BMSC- laden scaffolds facilitated chondrogenesis by promoting collagen II and suppressed interleukin 1β in osteochondral defects of the femoral trochlea. Congruently, BMSC-laden scaffolds significantly improved joint function of the injured leg. In Shanghai, through assembling cell-laden modules, the macrophage-mesenchymal stem cell (MSC), endothelial cell-MSC, and chondrocyte-MSC co-culture models are successfully established. The in vitro results indicate that the intercellular cross-talk can promote the proliferation and differentiation of each cell type in the system. Moreover, MSCs in the modular scaffolds may regulate the behavior of chondrocytes through the nuclear factor of activated T-Cells (NFAT) signaling pathway. Furthermore, the modular scaffolds loaded with co-cultured chondrocyte-MSC exhibit enhanced regeneration ability of osteochondral tissue, compared with other groups. Overall, this work offers a promising strategy to construct a multicellular tissue engineering scaffold for the systematic investigation of intercellular cross-talk and complex tissue engineering. The scaffold modules could be easily sterilized, transported, and stored. It would not be difficult for inexperienced staff to assemble these modules into a customized scaffold. In addition, these modular scaffolds loaded with varying cell types could be easily stacked and disassembled, benefiting the construction of multicellular tissue engineering scaffolds, enabling desirable intercellular cross-talk.