Successful tracheal regeneration using biofabricated autologous analogues without artificial supports

Abstract

Tracheas have a tubular structure consisting of cartilage rings continuously joined by a connective tissue membrane comprising a capillary network for tissue survival. Several tissue engineering efforts have been devoted to the design of scaffolds to produce complex structures. In this study, we successfully fabricated an artificial materials-free autologous tracheal analogue with engraftment ability by combining in vitro cell self-aggregation technique and in-body tissue architecture. The cartilage rings prepared by aggregating chondrocytes on designated culture grooves that induce cell self-aggregation were alternately connected to the connective tissues to form tubular tracheal analogues by subcutaneous embedding as in-body tissue architecture. The tracheal analogues allogeneically implanted into the rat trachea matured into native-like tracheal tissue by covering of luminal surfaces by the ciliated epithelium with mucus-producing goblet cells within eight months after implantation, while maintaining their structural integrity. Such autologous tracheal analogues would provide a foundation for further clinical research on the application of tissue-engineered tracheas to ensure their long-term functionality.

Regeneration Process of an Autologous Tissue-Engineered Trachea (aTET) in a Rat Patch Tracheoplasty Model

“…As previously reported [ 32 ], we manufactured an original tracheal mimetic tissue of an aTET containing a ring-shaped cartilage-like structure and collagenous tissue with enough strength to maintain the tracheal structure. Briefly, the process of manufacturing the aTET involved three steps.…”

“…Although many grafts have been suggested, very few of them demonstrated long-term survival. In particular, only two reports on long-term survival in small-animal models have been published [ 31 , 32 ], including our previous study, which is the only study on tissue-engineered graft use [ 32 ]. To develop a new tracheal graft with reproducible long-term survival, there are three problems that must be addressed: (1) creating a graft with sufficient strength, (2) minimizing foreign body reactions, and (3) promoting the regeneration of the tracheal structures [ 2 , 3 , 4 , 5 , 6 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ].…”

“…This graft has a tubular structure composed of autologous collagenous tissue and cartilage-like constituents fabricated from rat chondrocytes. When using this aTET for circumferential tracheal implantation in a rat model, it survived for 8 months, with no lethal tracheal collapse or granulation and with the regeneration of tracheal epithelium and the maintenance of cartilaginous tissue [ 32 ]. But approximately 60% of the models died within one postoperative day due to tracheal obstruction [ 32 ], and we have not yet determined the regeneration process of the aTET in detail because of the low survival rates of the models.…”

“…When using this aTET for circumferential tracheal implantation in a rat model, it survived for 8 months, with no lethal tracheal collapse or granulation and with the regeneration of tracheal epithelium and the maintenance of cartilaginous tissue [ 32 ]. But approximately 60% of the models died within one postoperative day due to tracheal obstruction [ 32 ], and we have not yet determined the regeneration process of the aTET in detail because of the low survival rates of the models. So, we conducted this study to clarify the regeneration process of the aTET by performing patch tracheoplasty, for which the survival rate is much higher compared to the circumferential tracheal implantation model.…”

Fabrication of shape-designable cartilage from human induced pluripotent stem cell-derived chondroprogenitors using a cell self-aggregation technique

“…Formation of these aggregates can be induced in specific tissues by incubation in culture medium containing various signals [34]. We further successfully prepared rigid cartilage rings having desired inner diameter by culturing rat costal chondrocytes for 3 weeks maturation in a ringshaped culture groove with a surface coating of CAT polymer [35]. Via self-aggregation and selforganization of ExpLBM cells induced via the CAT, it is possible to control the shape of the engineered cartilage without the use of scaffolds.…”