Chondrocyte-based Cartilage Regeneration Core Technology And Clinical Transformation

Cartilage defect repair for auricle,nose,and thyroid with special three-dimensional structures is one of the main issues in the field of rehabilitative surgery.At present,repair is achieved through either autologous cartilage transplantation or non-degradable stent.The former is derived from the patients themselves,which will lead to secondary trauma of the body.The latter is extremely prone to tissue adhesion and immune rejection due to lack of biological activity for the material.In this case,both methods make the patients suffer.The rapid development of cartilage tissue engineering technology has brought new hope to patients.In previous studies,we considered autologous auricular chondrocytes as an ideal source of seed cells,whether they are residual ear chondrocytes(MCs)in patients with small ear malformations or normal ear chondrocytes(NCs)in healthy people.In a culture system supplemented with basic fibroblast growth factor(b FGF),they can proliferate into a large amount and meanwhile maintain strong cartilage regeneration ability.At the same time,we have also established a chondrocyte-based induction system,which can regenerate mature homogeneous cartilage tissues in vitro under the combined action of various factors.Therefore,we believe that successful clinical transformation can be achieved by finding the ideal scaffold material.At present,the commonly used stents for cartilage tissue engineering are divided into two categories: synthetic materials and natural materials,with both have their own advantages and disadvantages.It is difficult to meet the construction needs in vitro and in vivo using a single material,especially for repairing cartilage with complex three-dimensional morphologies.Therefore,the preparation of composite scaffolds by combining the advantages of various materials is currently the main research trend.PGA non-woven fiber is a suitable scaffold material for cartilage regeneration among all synthetic materials.The coating modification of PGA fiber by PLA can both shape and improve the mechanical strength of the stent.However,too high of a PLA concentration will reduce the cell adhesion rate on the stent complex.PCL is a slow-degrading scaffold with good biocompatibility.However,because its surface is too smooth,it is difficult for cells to adhere and proliferate on the scaffold.we conducted a detailed study of this issue in the first chapter.By fine-tuning the 3D printing parameters,we achieved precise control of the mechanical strength of the PCL bracket(through adjusting the mesh aperture size and thickness).We used PGA/PLA to wrap PCL to prepare a composite scaffold with a "sandwich structure".The PGA/PLA fiber on the surface of the scaffold is beneficial to the adhesion,proliferation,and formation of extracellularmatrix of chondrocytes.Meanwhile,the thermoformed PCL core can be helpful in maintaining the three-dimensional morphology during the process of ex vivo culture.Because of the advantages above,we believe that it is an ideal scaffold for the reconstruction of complex-shaped cartilages such as auricle.In order to improve the preclinical research,we have reconstructed the human ear cartilage in nude mice,rabbits,and sheep,and achieved satisfactory results.Based on the these results,we carried out clinical transformation of tissue-engineered ear reconstruction and performed ear reconstruction on 5 patients.Among them,4 patients experienced obvious cartilage regeneration.The shape and recovery effect of the postoperative auricles were slightly different due to different surgical modes.We chose to use the low-immunogenic natural material of type I cattle collagen in the second chapter in order to achieve precise control of the shape of the auricle and improve the quality of cartilage formation.We combined the 3D model design and 3D printing technology to make a PCL core in the shape of a grid-like auricle.By freeze-drying the collagen gel and PCL together in a special auricle mold,a collagen-PCL composite auricle-shaped scaffold with a "reinforced concrete structure" was formed and a large animal model was established.Based on the results above,weprepared a complete nasal reconstruction stent in the same model and started clinical trials.Using the unsupported cartilage diaphragm technique,we can also construct a cartilage piece with a certain mechanical strength in vitro.By stacking multiple layers,a cartilage piece with a certain elasticity and thickness can be formed in the body,which can be carved into complex shapes such as a auricle.Therefore,in the third chapter,we carried out detailed research on the in vitro film formation of different chondrocytes and implanted the multiple-layered cartilage piece into the body to observe its maturation in vivo.This provides a research base for the clinical transformation of the cartilage piece-constructed auricular.In this dissertation,three methods of tissue-engineered ear reconstruction are proposed,with some research results already achieving clinical transformation.With the advancement of science and technology,we believe that tissue-engineered cartilage can become the main treatment for cartilage defect in the near future.