Tissue-engineered 3D human lymphatic microvascular network for in vitro studies of lymphangiogenesis

This protocol describes how to generate a human 3D lymphatic capillary network from primary cells without the use of synthetic scaffolds or exogenous factors. The tissue is stable over many weeks and accurately recapitulates in vivo human dermal lymphatic microvasculature. This protocol describes a unique in vitro method for the generation of a 3D human lymphatic network within native connective tissue devoid of any exogenous material such as scaffolds or growth factors. In this five-stage protocol, human lymphatic endothelial cells (LECs) cocultured with dermal fibroblasts spontaneously organize into a stable 3D lymphatic capillary network. Stage 1 involves the isolation of primary fibroblasts and LECs from human skin. Fibroblasts are then cultured to produce connective tissue rich in extracellular matrix (stage 2), onto which LECs are seeded to form a network (stage 3). After stacking of tissue layers and tissue maturation at the air–liquid interface (stage 4), the 3D construct containing the lymphatic microvascular network can be analyzed by microscopy (stage 5). Lymphatic vasculature generated by this approach exhibits the major cellular and ultrastructural features of native in vivo human dermal lymphatic microvasculature and is stable over many weeks. The protocol for generating a 3D construct takes 6 weeks to complete, and it requires experience in cell culture techniques. The system described here offers a unique opportunity to study the mechanisms underlying lymphatic vessel formation, remodeling and function in a human cell context.