  Cranial lymphatic vessels (LVs) are involved in transport of fluids,
macromolecules and CNS immune responses. Little information about spinal LVs is
available, because these delicate structures are embedded within vertebral
tissues and difficult to visualize using traditional histology. Here we reveal
an extended vertebral column LV network using three-dimensional imaging of
decalcified iDISCO-clarified spine segments. Spinal LVs are metameric circuits
exiting along spinal nerve roots and connecting to lymph nodes and the thoracic
duct. They navigate in the epidural space and the dura mater around the spinal
cord, and associate with leukocytes, peripheral dorsal root and sympathetic
ganglia. Spinal LVs are VEGF-C-dependent and remodel extensively after spinal
cord injury. They constitute an extension to cranial circuits for meningeal
fluids, but also a route for perineural fluids and a link with peripheral
immune and nervous circuits. Vertebral column LVs may be potential targets to
improve the maintenance and repair of 32 spinal tissues as well as gatekeepers
of CNS immunity.

Tissues and Organs