Lymphangiogenesis in tissue-engineered small intestine

Background. Lymphangiogenesis, the formation of lymphatic vessels, has not been reported in engineered tissue. The purpose of this study was to characterize lymphangiogenesis in tissue-engineered small intestine. Methods. Biodegradable polymer scaffolds seeded with intestinal organoid units were implanted into syngenic recipient rats. Twenty-three neointestinal grafts were harvested from adult rat recipients 1 to 8 weeks postimplantation. Cells expressing the lymphatic endothelial marker vascular endothelial growth factor receptor (VEGFR)-3 were detected immunohistochemically. The lymphangiogenic growth factor VEGF-C was quantified by enzyme-linked immunoadsorbent assay. Results. Between the first and eighth weeks, neointestinal cysts increased in volume and mass. Muscular and mucosal layers increased in thickness and developed to resemble normal intestine histologically. The proportion of neointestinal VEGFR-3-positive cells increased and ultimately, tubular structures developed that resembled lymphatics architecturally, were distinct from CD34-positive blood vessels, and lacked luminal erythrocytes. Conclusion. Lymphangiogenesis occurs in tissue-engineered small intestine. This is the first demonstration of lymphatic vessels in an engineered tissue.