The Lymph System is revealing more of its secrets
In research published this year, it seems that the Lymph System directly supports bone regeneration after injury.
According to current teaching, bones lack lymphatic vessels, however this new research has demonstrated that, in both human and mouse bones, lymphatic vessels are present. This is partly due to the difficulty of imaging calcified tissues.
“Lymphatic vessels not only connect secondary lymphoid organs with tissue sites throughout the body but are also now shown directly irrigating bones and participating in their regeneration” say the authors of this new study.
In the illustration below, lymphatic vessels are shown actively working in sites of injury/stress.
The full pdf is openly available and contains numerous imaging scans taken during the research.
They conclude: “Lymphatic vessels play a vital role in facilitating the transport of essential fluids, macromolecules, and immune cells.16,17,67–73 Recent work suggests an even broader array of functions. For instance, lymphatic vessels support cardiac development, and homeostasis, and help restore heart tissue following injury via secretion of the LEC-derived extracellular protein, relin. In the skin, lymphatic vessel-stem cell crosstalk drives wound repair. Specifically, in the skin context, stem cells support lymphatic drainage and wound repair through secretion of the lymphangiocrine factor, angiopoietin-like protein 7 (Angptl7). LECs (Lymphatic endothelial cells) have also been implicated in cancer metastasis, where the LEC-derived ETS domain-containing protein 2 (ELK2) facilitates communication between the tumor and its surrounding microenvironment. Here, we identify a fundamental role for LECs in mediating bone and hematopoietic regeneration after genotoxic stress. Finally, our findings show that cell-intrinsic changes in the bone lymphatic endothelium during aging underlie their lack of response to genotoxic stress in aged bones, thereby impacting bone and hematopoietic regeneration in aged animals. These findings raise further questions regarding LEC function, and it would be particularly interesting to examine the potential crosstalk between lymphatic vessels and bone-resident immune cells, for instance in the context of inflammatory diseases of the bone such as rheumatoid arthritis and osteoarthritis.”
Link to full article: Biswas L, Chen J, De Angelis J, Singh A, Owen-Woods C, Ding Z, Pujol JM, Kumar N, Zeng F, Ramasamy SK, Kusumbe AP. Lymphatic vessels in bone support regeneration after injury. Cell. 2023 Jan 19;186(2):382-397.e24. doi: 10.1016/j.cell.2022.12.031. PMID: 36669473.