IMPC: Investigating the role of Trichoplein (TCHP) in post-ischaemic vascular repair

Critical limb ischaemia is a severe reduction of the blood flow caused by the blockage of vessels of lower extremities. Complications due to poor circulation can include sores and non-healing wounds in the legs and feet of patients, which if left untreated, result in leg amputation. The blood vessels in the human body are lined with a thin layer of endothelial cells. In healthy people, endothelial cells help to form new vessels by migrating and dividing. Risk factors such as diabetes and obesity make the endothelial cells faulty and weak, which can lead to vessel-related problems like ischaemia, atherosclerosis and delayed healing of wounds. The main priority and an immediate treatment for this condition are to re-grow the vessels and re-establish the circulation to preserve the leg. Surgery can help but is difficult in elderly patients and works less well in those with diabetes and obesity. There is a pressing need for understanding how to restore blood flow to the affected limbs.
We know that a well-defined class of small genes, microRNAs, have the potential to regulate vessel growth and effect leg amputation. We have already discovered that from the endothelial cells a specific microRNA-503 promotes critical limb ischaemia. Moreover, our group has identified that miR-503 inhibits a protein called trichoplein (TCHP), which helps endothelial cells to migrate, and cells without TCHP are more easily damaged or killed.
In this study, we will use a mouse model lacking TCHP in the endothelium to understand the importance of TCHP when blood supply is reduced due to damage. Moreover, by an advance imaging analysis approaches, we will be able to understand the role of TCHP in blood vessel growth and repair.
We believe that understanding how TCHP is regulated and whether it has a role in growing the vessels could help to control vessel related problem like ischaemia, hence TCHP can be an imminent target for developing novel therapies in critical limb ischaemia.
If successful, this pump priming grant would also allow me to generate pilot data to strengthen my application for Senior Fellowship.

After the onset of ischaemia, hypoxia-related pathways, immunoinflammatory balance, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis which act in concert to establish a functional vascular network in ischaemic zones. In patients with ischemic diseases, most of the cellular and molecular mechanisms involved in the activation of vessel growth and vascular remodelling are markedly compromised. Moreover, impaired endothelial function due to cardiovascular risk factors such as obesity and diabetes leads to development and rapid progression of severe vascular diseases.
Thus, the identification and characterization of novel genes/regulatory pathways to better understand the process behind vascular repair is therefore crucial.
Based on prior work, we have demonstrated that microRNA-503 (miR-503) has a prominent role in the diabetes-induced impairment of post-ischemic neovascularization. Leading on from the characterization of miR-503 targets, we have identified a novel regulator of endothelial cells (ECs) function - Trichoplein (TCHP). Our preliminary data reveal that loss of TCHP function in ECs led to an impaired EC functions such as migration and angiogenesis. Accordingly, disruption of TCHP gene expression in zebrafish using morpholinos results in defective blood vessel formation. Finally, we see a decreased expression of TCHP in ECs of type 1 diabetic mice and ECs from patients with vascular dysfunction and premature coronary artery disease. However, very little is still known on the role of TCHP during post-ischaemic angiogenesis, how it regulates vessel dynamics, and whether it plays a role in blood vessel growth.
We will therefore generate an endothelial lineage-specific TCHP knockout mouse, to determine the basal cardiovascular phenotype in these mice and to analyse the importance of TCHP during vascular injury.