Sumi Choi1
Dong-A University1
Cartilage bears the load distributed in the joint and plays a pivotal role in stabilizing the joint through lubrication and shock absorption. Damage to the articular cartilage can accelerate joint degeneration and cause other joint diseases. Due to the nature of cartilage insufficient vascularization and lack of nerves and lymphatic vessels, the self-renewal process of articular cartilage rarely occurs after injury. Because non-human vertebrates have the potential to regenerate tissues such as bone, cartilage, muscle, nerve, and blood vessels, their signaling pathways and reprogramming factors have been investigated to induce chondrocyte differentiation from human stem cells. In this study, we specified chondrogenic factors in lizards capable of regenerating amputated tails. We identified the target molecule endoplasmin protein (ENPL, heat shock protein 90 kDa beta member 1) as a chondrogenic factor in 2D human tonsil-derived mesenchymal stem cells (hTMSC). Additionally, we designed a cartilage-mimetic hydrogel composed of hyaluronic acid and chondroitin sulfate for delivering ENPL and hTMSCs to damaged cartilage tissue. ECM-based 3D hydrogels can provide a mechanical and biochemical tissue microenvironment suitable for cartilage growth. The hTMSCs in the 3D hydrogel structure were successfully differentiated into chondrogenic cells. Additionally, a mouse osteoarthritis model confirmed the synergistic effect of cartilage regeneration of ENPL protein and bioactive hydrogels. This study demonstrates that ECM-based ENPL-equipped hydrogels can provide a therapeutic option for cartilage tissue engineering.<br/><br/>In this study, we present options for cartilage therapy of bioactive hydrogel-based scaffolds that induce in situ implantation, systems capable of forming cross-links, and stem cell chondrogenesis. Injectable hydrogels can provide a system for repairing and repairing damaged cartilage by delivering cells with minimal invasiveness to target sites of damaged tissues, including delivery of irregularly shaped areas. Here, we introduce an enzyme-mediated cross-linking method to fabricate injectable hydrogels. These enzyme-based reactions are suitable under cell-friendly physiological conditions. Natural proteins and tissues are rich in primary amines and imidazole groups and thiol groups that can bind phenolic moieties. Oxidation of phenol to ortho-quinone is the main function of tyrosinase (Ty). Because ortho-quinone is highly electrophilic, it can participate in various reactions such as Schiff-base reaction, Michael addition, and coupling reactions. In this regard, we designed a Ty-cross-linkable hydrogel by modifying hyaluronic acid (HA) and chondroitin sulfate (CS) with tyramine (TA). HA and CS are the components of the extracellular matrix (ECM), commonly used in tissue engineering, and can provide a biological and chemical environment for cartilage tissue. TA was conjugated to HA and CS using EDC/NHS chemistry for hydrogel crosslinking of HA and CS. Here, HA-TA and CS-TA generated by conjugating TA are advantageous for Ty-mediated crosslinking. Ty oxidizes the phenolic group of TA to form a quinone group. These reactive groups readily form covalent bonds with other chemical moieties such as amines, thiols, and imidazole groups. In this study, we show that TA-based hydrogels composed of ECM can provide cells and tissues with biocompatibility, cell compatibility, and a biomimetic environment. In addition, we targeted HSP90b1, which is related to the survival and proliferation of chondrocytes, by paying attention to the mechanism of lizard tail regeneration in which cartilage is regenerated instead of bone to induce cartilage differentiation. We demonstrate that Ty-based hydrogels incorporating the target protein ENPL can serve as strong candidates for cartilage regeneration with the added benefit of the biochemical response of ECM.