A regenerative approach for partial tracheal defects, an in vivo canine model

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

The treatment of long-tracheal lesion is difficult because there are currently no viable grafts for tracheal replacement. To solve this problem, we have developed an autologous Tissue-Engineered Trachea (aTET), which is made up of collagenous tissues and cartilage-like structures derived from rat chondrocytes. This graft induced successful long-term survival in a small-animal experiment in our previous study. In this study, we investigated the regeneration process of an aTET to attain reproducible success. We prepared an aTET by using a specially designed mold and performed patch tracheoplasty with an aTET. We assigned twenty-seven rats to three groups according to the three types of patch grafts used: aTET patches (the aTET group), fresh tracheal autograft patches (the Ag group), or polylactic acid and polycaprolactone copolymer sheets (the PPc group). In each group, gross and histological evaluations were performed at 1 month (n = 3), 3 months (n = 3), and 6 months (n = 3) after implantation. We obtained high survival rates in all groups, but only the PPc group attained thick tracheal walls with granular tissues and no tracheal regeneration. On the other hand, the aTET and Ag groups reproducibly achieved complete tracheal regeneration in 6 months. So, an aTET could be a promising candidate for tracheal regeneration grafts.

Human lung microvascular endothelial cells as potential alternatives to human umbilical vein endothelial cells in bio-3D-printed trachea-like structures

BACKGROUND

We have been trying to produce scaffold-free structures for airway regeneration using a bio-3D-printer with spheroids, to avoid scaffold-associated risks such as infection. Previous studies have shown that human umbilical vein endothelial cells (HUVECs) play an important role in such structures, but HUVECs cannot be isolated from adult humans. The aim of this study was to identify alternatives to HUVECs for use in scaffold-free structures.

METHODS

Three types of structure were compared, made of chondrocytes and mesenchymal stem cells with HUVECs, human lung microvascular endothelial cells (HMVEC-Ls), and induced pluripotent stem cell (iPSC)-derived endothelial cells.

RESULTS

No significant difference in tensile strength was observed between the three groups. Histologically, some small capillary-like tube formations comprising CD31-positive cells were observed in all groups. The number and diameters of such formations were significantly lower in the iPSC-derived endothelial cell group than in other groups. Glycosaminoglycan content was significantly lower in the iPSC-derived endothelial cell group than in the HUVEC group, while no significant difference was observed between the HUVEC and HMVEC-L groups.

CONCLUSIONS

HMVEC-Ls can replace HUVECs as a cell source for scaffold-free trachea-like structures. However, some limitations were associated with iPSC-derived endothelial cells.