Effect and potential mechanism of modified citrus pectin in 3D printing-based cartilage tissue engineering

Modified citrus pectin (MCP) is widely used as a dietary supplement in the food and pharmaceutical industries with pleiotropic bioactivities. Particularly, MCP has effects on chondroprotection and phenotype maintenance of chondrocyte. Here, after confirming its chondroprotective effect in a partial-thickness articular cartilage (AC) defect, the distributions of MCP in cartilage and chondrocytes were investigated using fluorescence labeled-MCP. Then the potential of it in cartilage tissue engineering (CTE) was studied using 3D-printed scaffolds of hybrid hydrogel (GelMA/HAMA/MCP) of MCP, methacryloydylated-gelatin (GelMA) and hyaluronic acid (HAMA). Finally, the mechanism of the scaffolds on chondrogenesis were analyzed through transcriptome sequencing. It was found that MCP could penetrate cartilage, enter chondrocytes and accumulate in lysosome by binding with Gal-3. MCP could promote the proliferation and maintain the phenotype of chondrocytes in continuous passage culture. Mechanistically, MCP-based scaffold could upregulate the expression of genes of chondrogenic markers and growth factors, downregulate genes related to inflammation or degeneration mediators, and modulate autophagy pathways to maintain homeostasis of chondrocytes. Ultimately, MCP-based scaffolds could support chondrocytes adhesion, proliferation, ECM deposition, and enhance the chondrogenesis of the engineered cartilage. Together, our results demonstrate that MCP has great potential in three-dimensional bioprinting (3DBP)-based CTE to enhance the cartilage regeneration.