New research has discovered how the lymphatic system could help metabolic syndrome, as well as a new component of tissue regeneration that might provide therapies for conditions such as hair loss.
Given the amount of wear and tear the skin is subjected to on a daily basis, it has a phenomenal ability to replenish itself.
Spread throughout the skin are small reservoirs of stem cells, nested within supportive micro-environments called ‘niches’, which keep a tight rein on this repair process. Too much tissue might cause problems like cancer, while too little might accelerate ageing.
Until now, scientists were uncertain whether the stem cells themselves could instruct other stem cells to form new skin by reshaping their niche. However, new research published in the journal Science, and led by Elaine Fuchs, the Rebecca C. Lancefield Professor, indicates that stem cells can indeed influence tissue regeneration.
The study identifies a molecular co-ordination tool used by stem cells to signal across niches.
The researchers also discovered a new component of the niche: a specialised type of vessel called lymphatic capillaries, which transport immune cells and drain excess fluids and toxins from tissues. These capillaries form an intimate network around the stem cell niche within each hair follicle, the study showed, thereby interconnecting all its niches.
Postdoctoral fellow, Shiri Gur-Cohen, said: “By turning the skin completely transparent. We were able to reveal the complex architecture of this network of tubes.”
Hair-follicle stem cells control the behaviour of lymphatic capillaries by secreting molecules that act as an ‘on-off switch’ for drainage, the scientists found, enabling them to control the composition of fluids and cells in the surrounding locale and ultimately synchronise regeneration across the tissue.
Fuchs, said: “The involvement of the lymphatic system in this process is a new concept,and might potentially provide new therapeutic targets for lymph-related conditions such as wound-healing defects and hair loss.”
The Lymphatic system and obesity
Research that was published earlier this year also shows how mobilising the lymphatic system may help combat obesity-induced metabolic syndrome.
In obesity, adipose tissue expands and becomes dysfunctional, leading to the appearance of a cluster of medical issues known as “the metabolic syndrome,” which includes increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels. The adipose tissue found in obesity exhibits symptoms of chronic inflammation, including hypoxia, immune cell accumulation, and fibrosis, leading to spilling over of pro-inflammatory substances and excess lipids into the circulation. This allows fat to circulate and be deposited in other tissues that are less well-equipped to safely store it.
Investigators explored whether they can engage the lymphatic system to help regulate obesity-induced inflammation of fat (adipose) tissue and restore systemic metabolic fitness.
Lead investigator Joseph M. Rutkowski of the Division of Lymphatic Biology, Department of Medical Physiology, at Texas A&M College of Medicine, said: “Adipose tissue inflammation is at the root of the epidemic of obesity’s metabolic syndrome. Reducing inflammation in mice has worked to improve metabolism but has not translated well to humans.
“Understanding the mechanisms of adipose inflammation and how to regulate it sheds light on the biology of our current obesity problem. We hypothesised that increasing lymphangiogenesis (formation of lymphatic vessels) in adipose tissue would help to reduce obesity-associated adipose inflammation,”
Normally, the primary function of the lymphatic system is to transport lymph, a fluid containing infection-fighting white blood cells, throughout the body via lymphatic vessels. Lymphatic vessels are similar to the circulatory system’s veins and capillaries.
The lymphatic vasculature and lymphatic endothelial cells in tissues are essential for maintaining tissue balance through the uptake and transport of peripheral fluid, large molecules, and immune cells. Tissue inflammation is often accompanied by the formation of new lymph vessels, a process known as lymphangiogenesis. Although obesity seems to inhibit lymphangiogenesis and reduce lymphatic function in adipose tissue, the goal of this research was to determine whether artificially enhancing the lymph system in obese adipose tissue can be beneficial.