Mechanical Reinforcement and Growth Factor Delivery Strategies for In Situ Cartilage Repair

In situ cartilage engineering aims to repair damaged cartilage within the body by using biomaterials
such as hydrogels, often loaded with regenerative cells to support tissue formation at the injury
site. Hydrogels are promising candidates for in situ cartilage repair due to their biocompatibility
and tunable properties. Two major strategies have been explored to enhance their performance:
mechanical reinforcement, through the incorporation of secondary structures to improve mechanical
behavior and structural integrity; and growth factor delivery, to stimulate cell proliferation,
differentiation, and extracellular matrix synthesis. This review first analyzes mechanical reinforcement
and growth factor delivery separate, discussing their advantages, limitations, and gaps in the
context of in situ applications. It then highlights the emerging opportunity to combine these strategies
within composite, cell-laden hydrogels, and critically examines the current studies, alongside
the additional challenges in clinical translation that arises. Finally, future directions are proposed
to guide the design and testing of composite hydrogels for more effective and translatable in situ
cartilage repair therapies.
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