Investigating lung regeneration and repair pathways in Cystic Fibrosis

Cystic Fibrosis (CF) is a lethal inherited condition affecting over 10,000 people in the UK and 70,000 people worldwide. It is caused by having two mutations in the Cystic Fibrosis gene which affects a channel called CFTR that controls the flow of salt and water in and out of cells in most organs of the body. This faulty salt channel creates thick, sticky mucus and causes blockages in multiple organs such as the lungs, the bowel and the pancreas. Lung disease is the main cause of ill health in CF and it remains a deadly condition, such that a child born today with CF is only expected to live until the age of 47. The only present cure for advanced CF lung disease is a life-saving lung transplant, but this option isn't available to many, and often CF patients die whilst awaiting a lung transplant.

The development of a new class of CF drugs called CFTR modulators now offers hope to many patients. These drugs open up the faulty CFTR channel allowing salt and water transport and an improvement in mucus blockage in the lungs. Newer modulators have now been shown to improve lung function in people with CF, but they do not reverse the lung damage that has already been suffered. Therefore, treatments focused on repairing damaged lungs are required for people with CF.

The airway contains its own stem cells, called basal cells, that respond to injury and help to repair damaged tissue. Basal cells are present throughout the airway, from the nose all the way to the small airways of the lungs. When the surface of the airway is damaged, basal cells move to cover the area and then transform a variety of cells that line the airway and promote healing.

When people with CF get an infection, their immune system responds excessively, releasing harsh chemicals that damage the airways, and their white blood cells are less effective at killing the bacteria than someone without CF, leading to increased damage within their lungs. Even when treated with antibiotics we know that the CF airways don't repair in the same way as people without CF. Their basal cells transform into more mucus secreting cells and fewer cells to move the mucus, known as cilliated cells. This means more mucus collects in their airways, leaving them more prone to chest infections, and a vicious circle of infection and faulty repair continues.

We can now take basal cells from the nose and grow these in 3 dimensional gels to form tiny balls of cells called organoids. These structures can show how the airways would repair when damaged. They even create their own mucus on the inside.

Aims:
We plan to use organoids made from basal cells that we have sampled from people with CF and use these to figure out why the process of repair is different in the CF lung. We will also take cells from the nose before and after treatment with modulator therapy, to see if this changes the way basal cells behave, and hopefully learn new ways by which we can help the CF lung repair.

Potential applications:
In time, we hope this will allow us to develop treatments that will allow the CF lung to "heal itself from within" by harnessing the power of the lungs own stem cells and avoid the progression of people with CF to severe lung disease and lung transplant.

Cystic Fibrosis (CF) is a lethal genetic condition affecting over 10,000 people in the UK. It is caused by mutations in the cystic fibrosis transmembrane conductance regulator(CFTR) gene leading to decreased function of the CFTR chloride channel. CF patients develop a destructive lung disease as a consequence of this, associated with significant morbidity and mortality. Despite advances in care, the median age of death is 32, and the only cure for advanced lung disease is transplantation.
Novel CFTR modulators partially correct the abnormal chloride transport in CF and have significant effects on mucus clearance and lung function, but leave patients with residual lung damage.
Basal cells are present throughout the human airways and migrate and proliferate in response to injury, acting as stem cells. They produce different progeny cells in steady state and repair, so may be an excellent target to develop strategies that augment lung repair.

Aims:
1. To phenotype basal cells from people with CF compared to healthy controls in terms of gene expression, proliferation and migration.
2. To assess proliferation and differentiation of CF 3D organoid culture compared to healthy controls and assess regenerative capacity after injury
3. To test whether CFTR modulators affect basal cells and can promote repair in 3D organoid culture.
4. To compare clinical outcomes following CFTR modulator therapy in people with CF with novel outcomes of repair and established measurements of inflammation.

Methods: I will undertake basal cell culture and 3D organoid culture of patients with CF and healthy controls. These will then be characterised with RNAseq, qPCR, and immunohistochemistry. Migration and proliferation assays will be performed. Basal cells and organoids will be co-cultured with CFTR modulators to compare with clinical outcomes in vivo.

The potential of lung tissue to regenerate and repair is accepted but has not been extensively studied, particularly in CF.