Transplantation of artificial human lymphatic vascular tissues fabricated using a cell-accumulation technique and their engraftment in mouse tissue with vascular remodelling.

Transplantation of engineered tissues with microvascular structure is advancing towards therapeutic application to improve the flow of blood and/or lymphatic fluids. In lymphatic disorders, transplantation of tissue-engineered lymphatic grafts can be an ideal treatment for draining excessive lymphatic fluid. In this study, we examined the transplantation of 3-dimensional artificial human lymphatic network tissue (AHLT) fabricated by the cell accumulation technique into the subcutaneous tissue and fascia of mice. At 2 weeks after transplantation, the AHLT showed engraftment of artificial lymphatic vessels immunopositive for human CD31 and human podoplanin. Notably, we also observed the generation of blood vessel-like structure comprising endothelial cells immunopositive for human CD34 and mural-like cells immunopositive for human CD90 and αSMA, which were considered as myofibroblasts. In the fabrication of AHLT in vitro, the sporadic emergence of human CD34-positive/Prox-1-negative sites was observed, followed by the formation of blood vessel-like structure in the graft within 7 days after transplantation. The fine structure of engrafted AHLT observed by transmission electron microscopy showed that the engrafted artificial lymphatic vessels possess the specific structures of native lymphatic capillaries such as loose interendothelial connections and anchoring filaments. In contrast, blood vessel-like structure showed tight interendothelial connections, thick basement membranes, and layers of mural-like cells, which resemble small blood vessels. These results suggested the remodelling of artificial lymphatic network to form blood vessel-like structure associated with mural-like cells along with AHLT fabrication and engraftment.