Tunneling model of lymphatic vessel formation. The model is based on ultrastructural observations performed in in vitro and in vivo models of lymphangiogenesis. (A): LEC alignment. Elongated LEC migrate and extend long cytoplasmic protrusions. (B): Vacuolization and matrix degradation. The continuity of LEC lining is mediated by interdigitations (i). Vesicle invaginations lead to the formation of intracellular vacuoles (v) in the cytoplasm and in protrusions. Matrix degradation (d) occurs intracellularly and extracellularly generating space between cells. (C): Luminogenesis. The lumen (lu) is formed de novo in the intercellular space. The intracellular vacuoles coalesce (cv) and likely fuse with the cytoplasmic membrane to increase the lumen.
Detry et al. BMC Cell Biology 2011 12:29 doi:10.1186/1471-2121-12-29