Defining lymphatic microstructure and the genetic basis of lipolymphedema

The lymphatic system regulates tissue fluid homeostasis, intestinal fat absorption, and immune cell trafficing. Lymphedema is soft tissue swelling secondary to lymphatic dysfunction, which results in the accumulation of tissue fluid in the interstitial space. This might occur as a primary disorder of the developing lymphatic system, or alternatively lymphedema might be an acquired disorder secondary to lymphatic injury. For example, secondary lymphedema is a common problem following cancer and cancer treatments such as lymph node surgery and radiotherapy, resulting in significant morbidity. Radiotherapy is an established risk factor for lymphedema, and in addition to causing direct injury to the lymphatic vessel, it is possible that alternative mechanisms might also contribute to radiation-induced lymphatic dysfunction, such as localized ischemia of the lymphatic wall. It is also likely that predisposing genetic risk factors are at play, as not all individuals exposed to the same risk factors will develop secondary lymphedema. Lipoedema is a different form of soft tissue swelling due to the abnormal accumulation of adipose tissue. Lipoedema and lymphatic dysfunction appear to be linked, as individuals frequently develop a degree of lymphedema, particularly as the condition progresses in severity, where it may be decribed as lipo-lymphedema. The cause of lipoedema and the genetic basis of the condition are currently unknown. This thesis aims to discover and define alternative mechanisms for lymphtic dysfunction in the context of secondary lymphedema, particularly focussing on the supply of oxygenated blood to the lymphatic vessel wall. We also aim to describe inheritance patterns and the genetic factors involved in lipoedema and lipo-lymphedema. Such knowledge might uncover therapeutic targets and facilitate the development of treatments for lymphedema and lipoedema, including gene therapy.