Therapeutic Targeting of Pathogenic Scar-associated Macrophages in the Fibrotic Niche of Chronic Liver Disease

Liver disease is a major global healthcare problem, with 844 million people thought to be affected worldwide resulting in 2 million deaths each year. Worryingly case numbers continue to rise, and liver disease is soon predicted to become the commonest cause of premature death in the UK. There are many different causes of liver disease. Irrespective of the underlying cause, long-term damage to the liver leads to the development of liver scarring, called fibrosis. The amount of fibrosis gets progressively worse over time, meaning that the liver eventually stops functioning properly and starts to fail. Due to the important role of progressive scarring in promoting liver failure and the development of clinical complications, there is a lot of interest in trying to find new treatments to block this scarring process. These antifibrotic therapies would be a very important step forward in the treatment of patients, but unfortunately no such therapies are currently available.

Macrophages are immune cells present throughout the body. We have previously shown that macrophages in the liver play a crucial role in regulating the scarring process. Trying to block the function of these liver macrophages is therefore an attractive strategy to try and reduce fibrosis. Our recent work has studied macrophages in the diseased human liver using a new technology called single-cell RNA-sequencing. We were able to identify a unique type of macrophage in the scarred liver which is important for promoting fibrosis. We now intend to study these macrophages in more detail, with the aim of finding ways of inhibiting the function of these particular cells and ultimately developing new antifibrotic therapies.

In order to achieve this, we will perform a series of experiments using modern scientific techniques. Firstly, in order to get more precise information on how the fibrosis-promoting macrophages function during the progression of liver disease, we will invite patients who are undergoing a biopsy of their liver as part of their planned hospital investigations, to donate a small excess portion of this biopsy to our research study. We will use this tissue to perform single-cell RNA-sequencing to understand how macrophages behave during the development of fibrosis. We will also use another new scientific technique called spatial transcriptomics on these biopsies, to tell us how these macrophages might be talking to neighbouring cells in the liver to regulate the scarring process and help us to identify potential ways these functions can be inhibited. Secondly, we intend to better understand how these macrophages change over time, comparing how they behave when they are exposed to further liver damage or when the damage is stopped. In order to do this, we will use mouse models of liver scarring where the macrophages are very similar to those found in patients, but we are able to study these cells on a more day-to-day basis. This information will enable us to determine how the macrophages which promote progressive scarring differ from other macrophages in the liver and therefore how we might specifically target them. Finally, having identified the specific genes and proteins made by these macrophages, we will use this new information to try and block the function of these cells and inhibit scarring in the liver. Initially this will be done using a technology called CRISPR, which will enable us to rapidly and simultaneously assess the functions of numerous genes in liver macrophages. We will then focus on the specific genes which we show to be important, using both mouse models and human cells to test whether blocking these molecules will be useful to reduce fibrosis.

Ultimately, in completing this project we expect to identify new strategies to inhibit the function of fibrosis-promoting macrophages in the liver, which can then be developed as badly-needed antifibrotic therapies for patients with liver disease.

Liver disease affects 844 million people worldwide resulting in 2 million deaths per year. With a rising incidence and a lack of new effective treatments in most cases, it is predicted that liver disease will soon become the commonest cause of premature death in the UK. Irrespective of the cause of liver disease, chronic damage to the liver results in fibrosis. The degree of fibrosis is the best predictor of adverse clinical outcomes, meaning there is great interest in developing novel antifibrotic therapies to prevent disease progression. Our previous work has shown that a specific subpopulation of scar-associated macrophages (SAMac) are key regulators of liver fibrosis. Hence, therapeutic targeting of SAMac represents an attractive novel therapeutic strategy.
In this Fellowship, we will couple cutting-edge mutiomic data and computational approaches with new experimental models, to dissect the biology of SAMac at previously unprecedented resolution and enable the identification and functional testing of candidate antifibrotic therapeutic strategies.
This will be achieved by completing 3 main aims:
1) Dissect the phenotype and microenvironmental niche of SAMac during early-stage human liver disease
2) Define phenotypic differences in SAMac between progressive and resolving liver fibrosis
3) Functionally assess candidate antifibrotic therapeutic targets to modulate SAMac
The proposed experiments will harness the power of single-cell RNA-sequencing and spatial transcriptomics on fibrotic liver tissue from both humans and mice, to resolve the phenotype of SAMac and interrogate intercellular signalling networks during progressive fibrosis. Candidate target molecules will be functionally assessed using high-throughput in vivo CRISPR screens and antifibrotic efficacy tested using mouse models and human liver organoid cultures. Ultimately, I anticipate identifying new antifibrotic therapeutic strategies which can then be tested in patients with chronic liver disease