The lymphatic system isn’t an easy concept to grasp, not even for a medical student. Suffice to say it’s a network of vessels that branch throughout the body, and play an important role in the draining of excess fluid from tissues, clearing out waste, and supporting the immune system.

For some reason, in the past we assumed the brain and the eye were excluded from the lymphatic system, as was bone, but it’s not true.

Oxford scientists have revealed there are lymphatic vessels in bone, and have even demonstrated their role in regenerating bone and blood cells (blood cells are manufactured in bone marrow as are stem cells), and how bones change with age.

Scientists not only discovered an active network of lymph vessels within bone, but also identified some of the key signals that pass between lymph vessels, blood stem cells, and bone stem cells.

Dr Lincoln Biswas of the MRC Human Immunology Unit at Oxford’s MRC Weatherall Institute for Molecular Medicine and co-first author of this study, said: “Interestingly after injury, lymphatic vessels in bone show dynamic crosstalk with blood stem cells and with specialised perivascular cells in order to accelerate bone healing.

“Such interactions between lymphatics and bone stem cells can be harnessed to promote bone healing such as in fracture repair.”

Dr Junyu Chen, a co-first author of the first study, now based at Sichuan University, China, said: “Ageing is associated with diminished capacity for bone repair, and our findings show that lymphatic signalling is impaired in aged bones. Remarkably, the administration of young lymphatic endothelial cells [which line lymphatic vessels] restores healing of aged bones, thus providing a future direction to promote bone healing in the elderly.”

Dr Anjali Kusumbe, who led the research, said: “I am very excited as these findings not only demonstrate that lymphatic vessels do exist in bone, but also reveal their critical interactions with blood stem cells and perivascular bone stem cells after injury to promote healing, thereby presenting lymphatics as a therapeutic avenue to stimulate bone and blood regeneration.

“Further, these findings are very fundamental, opening doors for understanding the impact of bone lymphatics on the immune system and their role in bone and blood diseases.”

This is a huge step forward, giving an insight into the powerful role of the lymphatic system in bones, blood cell growth, and healing.

The researchers now aim to explore the role of lymphatic vessels in bone-based diseases such as rheumatoid arthritis, and to explore the potential for new treatments for bone and blood diseases.