The range of cancers for which radiotherapy is being used is ever expanding. There is an unavoidable dose exposure that occurs in surrounding normal cells. This radiation exposure does not have the effect of simply killing normal cells, but elicits a permanent damage or injury profile that not only persists, but continues to evolve throughout the life of the patient. This is known as Radiation Injury Bystander Effect (RIBE). These changes result in ongoing tissue contracture, immense pain, soft tissue swelling, and tissue breakdown; in turn leading to significant disability, recurrent infection, impairment of quality of life, and potentially life-threatening exposure of vital structures such as the heart.
Lymphodema is a debilitating soft tissue disease caused by an impairment of the lymphatic system, which leads to fluid build up in the surrounding interstitial tissue. The lymphatic system is a network of thin-walled vessels - comprised of lymphatic endothelial cells-that is integral to fluid homeostasis, immune cell surveillance and absorption of dietary fat. Lymphodema can be an inherited disorder such as Milroy’s disease but in some individuals, it is acquired following a trauma such as surgery, infection or radiation therapy. Approximately 20% of breast cancer patients undergoing radiotherapy and/or surgical resection of lymph nodes will develop Lymphodema. Currently, there are no therapeutic treatments available.
To understand the genetic basis and signalling pathways activated in individuals with trauma induced lymphodema, we have developed in-vitro and in vivo models of lymphodema that mimic clinical radiation dosage regimes and surgical treatments, specifically focussing on the cell types that occur in the affected lymphodematous tissue: adipocytes, endothelial cells, immune cells and adipose-derived mesenchymal stem cells that comprise the skin architecture. We performed a raft of functional bioassays to specifically interrogate the key functions of each cell type during the course of radiation induced lymphodema and have developed genomic, proteomic and metabolic platforms to understand the key signalling and communication pathways between lymphatic endothelial cells and other key cells within their microenvironment. This knowledge will enable development of therapeutic agents that may treat aspects of this disease such as tissue swelling, tissue fibrosis and pain, as well as agents that promote tissue regeneration.
While radiation therapy is common in treatment of cancer patients, the consequences of RIBE in target tissues can cause severe side effects such as lymphodema. We wish to understand this phenomenon at the cellular and genetic level by interrogating the effects that sub-lethal doses of radiation has on cells that comprise local tissue such as lymphatic and blood endothelial cells, fibroblasts, adipocytes, immune cells and adipose derived mesochymal stem cells. We have performed microarray analysis to obtain gene signatures of these cell types that are unique to the process of radiation injury and have established in vitro and in vivo lymphodema and other injury models to interrogate the leading signalling pathways activated during this process. Our data has allowed us to explore novel mechanisms by which cells communicate during RIBE that will enable the design of novel therapeutics to target side effects of radiation injury such as tissue contracture, pain, lymphodema and cardiac disease.
It is estimated that approximately ~20% of women with breast cancer undergoing radiation and/or surgical resection of affected lymph nodes will develop lymphodema. We would like to understand the genetic basis of these individuals and are in the process of a long-term genetic screen of patients that have begun to develop early signs of lymphodema with the view of identifying any genes that are mutated. This knowledge will assist in developing alternative treatment regimes and management of women with breast cancer, thereby preventing the onset of lymphodema in those individuals genetically predisposed to developing secondary lymphodema.
It has been previously shown in plastic surgery that fat grafting has the ability to promote lymphangiogenesis in vitro and in vivo and ameliorate some of the chronic tissue effects of radiation injury. These effects are largely attributed to the presence of adipose-derived stem cells (ADSC) (Shukla et al., 2015). We wish to understand the mechanism by which ADSC confer their regenerative properties during radiation induced injury in local tissue. We have developed genetic, proteomics, metabolomics and cell function screens to understand what the key molecular components are critical for the process of ADSC rescue during radiation injury.
Lipidema is an alternative form of soft tissue swelling of the lower limbs, most common in females after the onset of puberty. Patients with lipidema develop bilateral limb swelling secondary to adipose tissue deposits, with the feet generally spared (Rockson et al., 2000). Patients develop an immense amount of pain, brusing, immobility and can suffer from depression. There is some evidence to suggest that there is a lymphatic dysfunction component to this disease, however the link has not been clearly defined. There is very little, if any, literature pertaining to the genetics or mechansism of lipidema and there are no current therapies. We are in the process of recruiting a large patient cohort to perform a genetic and tissue analysis of patients affected with lipidema. We would like to understand the molecular basis of this disease with the view of developing therapeutic agents.