Investigating metabolic pathways that drive tissue remodelling and fibrosis in Tuberculosis

Tuberculosis (TB) is still one of the most prevalent infectious diseases we currently face, resulting in 1.2 million deaths annually around the world. The pathogen, Mycobacterium tuberculosis (M.tb) is responsible for the onset of TB in patients by entering through the airways and activating the body's primary defence mechanisms known as the innate immune system. This involves the recruitment of many immune cells, of which include macrophages to impede the spread of the M.tb infection. Fibroblasts, a cell found in the lung also contribute to the pathogenesis of TB by secreting enzymes called matrix metalloproteinases (MMPs). MMPs are responsible for the breakdown of structural components of the lung called extracellular matrix (ECM) and in TB, there is an elevated expression of MMPs, which leads to extensive tissue remodelling and the formation of scar tissue in the lungs of patients. There is increasing evidence to suggest that immune cells such as macrophages can interact with fibroblasts to alter their function. Previous studies from my group demonstrated that M.tb infected macrophages can indirectly affect fibroblasts to enhance MMP-1 secretion, to drive the tissue destruction seen in the lungs of TB patients.
One of the symptoms of TB often reported is a significant weight loss in patients, indicating that their regular metabolism is affected following M.tb infection. Furthermore, patients who are diagnosed with metabolic associated syndromes such as malnutrition or diabetes, are often linked to an increased risk of developing severe cases of TB. This highlights that M.tb heavily impacts metabolic pathways in cells during infection. Studies conducted by my group and others showed that a shift in metabolism is detected in macrophages that are infected with M.tb. However, the metabolic status of fibroblasts in TB disease or how interactions with the innate immune system regulate these underlying metabolic pathways in fibroblasts to contribute to lung tissue damage in TB is still unknown.
Therefore, the main aims of my PhD project are to investigate the interface between the innate immune system and fibroblasts within the context of M.tb infection and which metabolic pathways in fibroblasts drive MMP production and hence excessive tissue remodelling seen in TB patients. To address these aims, I will use various laboratory techniques including tissue culture of human fibroblasts and immune cells such as macrophages, western blot, quantitative PCR (qPCR) and ELISA to define whether the interaction between macrophages and fibroblasts within the context of M.tb infection leads to enhanced MMP production and identify which metabolic pathway regulates these effects. I will also utilise CRISPR-Cas9 technology to block specific metabolic pathways in fibroblasts to examine the importance of these pathways in driving tissue destruction.
This project will allow us to gain a deeper understanding about how metabolism and the innate immune system crosslink with lung cells such as fibroblasts during M.tb infection to drive lung tissue damage. As there are currently no treatments available to prevent the formation of scar tissue in the lung, this research could be used to develop novel therapeutic targets to stop excessive tissue remodelling and aid patient recovery.