2020 Evidence in forming neocartilage. Trachea Research Update

 Table 2. Principal tracheal reconstruction attempts from 1994 to current.

Authors	Methods	Results
Vacanti et al. [91], 1994	Tubular scaffold from sheets of fibrous polyglycolic acid cellularized with chondrocytes.	Implanted in four rats, as substitutes for 4–6 tracheal rings. The animals died soon after surgery.
Kanzaki et al. [92], 2006	Prevascularized Dacron support covered by a layer of rabbit tracheal epithelial cells.	Four weeks after transplantation, the tracheal grafts were covered by a mature, pseudostratified columnar epithelium.
Macchiarini et al. [62], 2008	A tissue engineered tracheal graft (TETG) was implanted in a patient with severe bronchial stenosis following treatment for tuberculosis.	Most patients died after the implantation of tissue-engineered airways.
Weidenbecher et al. [18], 2009	Sheets of cartilage obtained from the auricular cartilage of New Zealand white rabbits used in combination to a muscle/silicone.	Demonstrated mechanical stability without degradation but all rabbits expired due to obstruction/stenosis between 1 and 39 days after surgery.
Naito et al. [94], 2011	Fibroblast and collagen hydrogels, mechanically supported by osteogenically induced mesenchymal stem cells (MSC) in ring-shaped 3D-hydrogel cultures.	Six of the nine animals died during implantation, while three of them survived for 24 h and died the day after.
Jungebluth et al. [68], 2011	Polymer in POSS-PCU [polyhedral oligomericsilsesqui-oxane (POSS) covalently linked to poly (-carbonate-urea) urethane (PCU)], cellularized with stem cells by dynamic culture in a bioreactor carried out urgently on a 37-year-old man.	Partial epithelial colonization of the polymer.
Hinderer et al. [14], 2012	Composite PCL–gelatin–decorine scaffold with a three-dimensional structure and pores of an average size of 14.4 ± 6.4 μm.	Uniform composition of the scaffold, but a poor mechanical resistance and the presence of cells only at the outer surface of the construct.
Gustafsson et al. [89], 2012	Rat mesenchymal stromal cells cultured on a polyethylene terephthalate [PET] and polyurethane [PU] scaffold and coated with adhesion proteins.	Similar cell densities and MSC proliferating cells; no advantages with adhesion proteins.
Shi et al. [90], 2012	Copolymer of N-carboxyethylchitosan/nanohydroxyapatite chitosan/nanohydroxyapatite composites for tissue-engineered trachea.	Satisfactory tensile strength.
Huang et al. [16], 2016	PCL-based scaffold coated with an artificial pleura patch on a 47-year-old woman affected by tracheomalacia after tubercular disease.	Progressive improvement of the tracheal respiratory space (from 0.3 to 1 cm in maximum diameter).
Johnson et al. [101], 2016	In vitro characterization of design and compressive property of 3D-biofabricated/decellularized hybrid grafts for tracheal tissue engineering.	Decellularized swine trachea was reinforced with a PCL scaffold, using a 3D printer.
Tan et al. [83], 2017	Stent of Nitinol coated with porcine dermis, continuously irrigated with a solution of Ringer’s lactate with added neoangiogenic factors and antibiotics.	Patient survived and was discharged on month after implantation.
Ikeda et al. [106], 2017	Implantation of induced pluripotent stem cell-derived tracheal epithelial cells.	Survival of tracheal epithelial tissues in rat.
Hsieh et al. [108], 2018	3D printing of tubular scaffolds with elasticity and complex structure from multiple waterborne polyurethanes for tracheal tissue engineering	Stability and cartilage growth.
Chan DS [109], 2019	3D-printed polycaprolactone implants to reconstruct circumferential tracheal defects in rabbits.	Feasibility but overgrowth of granulation tissue.
Kim et al. [107], 2020	Transplantation of a 3D-printed tracheal graft combined with iPS cell-derived MSCs and chondrocytes.	Evidence in forming neocartilage.