Fig. 4.

The construction strategy of bone and cartilage organoids. The pyramid outlines the stepwise strategy for constructing bone and cartilage organoids, starting from the base and progressing to the top. Cell Selection: The foundation of the strategy includes choosing appropriate cell types, such as BMSCs, osteoblasts, osteoclasts, chondrocytes, iPSCs, and endothelial cells. Matrix Gel Selection: The next tier involves selecting the proper matrix materials to support cell growth and differentiation. Commonly used matrices include Matrigel, collagen, silk fibroin, PEG, and DNA hydrogels. Construction Techniques: Key techniques such as stepwise induction, 3D bioprinting, and the use of bioreactors are employed to guide the development of complex organoid structures. Cytokines and Inducers Selection: Specific cytokines and chemical inducers are critical for driving cell differentiation and tissue development within the organoids. At the apex, fully developed bone or cartilage organoids are formed, representing the culmination of coordinated cellular interactions, matrix scaffolding, construction techniques, and biochemical signals