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Scientists grow ‘mini-lungs’ to aid the study of cystic fibrosis

cjb250 — Fri, 20 Mar 2015 10:00:10 +0000

̽��ֱ��research is one of a number of studies that have used stem cells – the body’s master cells – to grow ‘organoids’, 3D clusters of cells that mimic the behaviour and function of specific organs within the body. Other recent examples have been ‘mini-brains’ to study Alzheimer’s disease and ‘mini-livers’ to model liver disease. Scientists use the technique to model how diseases occur and to screen for potential drugs; they are an alternative to the use of animals in research.

Cystic fibrosis is a monogenic condition – in other words, it is caused by a single genetic mutation in patients, though in some cases the mutation responsible may differ between patients. One of the main features of cystic fibrosis is the lungs become overwhelmed with thickened mucus causing difficulty breathing and increasing the incidence of respiratory infection. Although patients have a shorter than average lifespan, advances in treatment mean the outlook has improved significantly in recent years.

Researchers at the Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute used skin cells from patients with the most common form of cystic fibrosis caused by a mutation in the CFTR gene referred to as the delta-F508 mutation. Approximately three in four cystic fibrosis patients in the UK have this particular mutation. They then reprogrammed the skin cells to an induced pluripotent state, the state at which the cells can develop into any type of cell within the body.

Using these cells – known as induced pluripotent stem cells, or iPS cells – the researchers were able to recreate embryonic lung development in the lab by activating a process known as gastrulation, in which the cells form distinct layers including the endoderm and then the foregut, from which the lung ‘grows’, and then pushed these cells further to develop into distal airway tissue. ̽��ֱ��distal airway is the part of the lung responsible for gas exchange and is often implicated in disease, such as cystic fibrosis, some forms of lung cancer and emphysema.

̽��ֱ��results of the study are published in the journal Stem Cells and Development.

“In a sense, what we’ve created are ‘mini-lungs’,” explains Dr Nick Hannan, who led the study. “While they only represent the distal part of lung tissue, they are grown from human cells and so can be more reliable than using traditional animal models, such as mice. We can use them to learn more about key aspects of serious diseases – in our case, cystic fibrosis.”

̽��ֱ��genetic mutation delta-F508 causes the CFTR protein found in distal airway tissue to misfold and malfunction, meaning it is not appropriately expressed on the surface of the cell, where its purpose is to facilitate the movement of chloride in and out of the cells. This in turn reduces the movement of water to the inside of the lung; as a consequence, the mucus becomes particular thick and prone to bacterial infection, which over time leads to scarring – the ‘fibrosis’ in the disease’s name.

Using a fluorescent dye that is sensitive to the presence of chloride, the researchers were able to see whether the ‘mini-lungs’ were functioning correctly. If they were, they would allow passage of the chloride and hence changes in fluorescence; malfunctioning cells from cystic fibrosis patients would not allow such passage and the fluorescence would not change. This technique allowed the researchers to show that the ‘mini-lungs’ could be used in principle to test potential new drugs: when a small molecule currently the subject of clinical trials was added to the cystic fibrosis ‘mini lungs’, the fluorescence changed – a sign that the cells were now functioning when compared to the same cells not treated with the small molecule.

“We’re confident this process could be scaled up to enable us to screen tens of thousands of compounds and develop mini-lungs with other diseases such as lung cancer and idiopathic pulmonary fibrosis,” adds Dr Hannan. “This is far more practical, should provide more reliable data and is also more ethical than using large numbers of mice for such research.”

̽��ֱ��research was primarily funded by the European Research Council, the National Institute for Health Research Cambridge Biomedical Research Centre and the Evelyn Trust.

Inset image: Branching mini-lung. Credit: Nick Hannan, ̽��ֱ�� of Cambridge

Reference
Hannan, NR et al. Generation of Distal Airway Epithelium from Multipotent Human Foregut Stem Cells. Stem Cells and Development; 10 March 2015.

Scientists at the ̽��ֱ�� of Cambridge have successfully created ‘mini-lungs’ using stem cells derived from skin cells of patients with cystic fibrosis, and have shown that these can be used to test potential new drugs for this debilitating lung disease.

We can use these 'mini-lungs' to learn more about key aspects of serious diseases – in our case, cystic fibrosis

Nick Hannan

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Testing time for stem cells

lw355 — Thu, 23 Oct 2014 09:27:30 +0000

Much has been written about the promise of stem cells for modern medicine, and cell-based therapies to treat diseases are now being developed by commercial companies in Europe and across the world. But it is their use both to screen medicinal drugs for toxicity and to identify potential new therapies which is increasingly being viewed as one that could have an immediate and far-reaching impact.

Cambridge-based company DefiniGEN supplies the pharmaceutical industry with liver and pancreatic cells that have been reprogrammed from human skin cells. These cells, known as induced pluripotent stem (IPS) cells, are used to test potential new drugs, and can also be used as in vitro models for disease.

̽��ֱ��company spun out of the ̽��ֱ�� in 2012 and is one of the first commercial opportunities to arise from Cambridge’s expertise in stem cell research. Its portfolio of products is based on the research of Dr Ludovic Vallier, Professor Roger Pedersen, Dr Tamir Rashid, Dr Nick Hannan and Dr Candy Cho at the Anne McLaren Laboratory for Regenerative Medicine (LRM) in Cambridge.

“Drug failure in the late phase of clinical development is a major challenge to finding new therapeutics which are urgently needed by a broad number of patients with major health-care problems such as diabetes,” said Vallier. “A great deal of time and money are often lost following these false leads, and this limits the capacity of pharmaceutical companies to explore novel therapies. So, identifying toxic drugs as early as possible is vital to the efficiency and safety of the drug discovery process.

“Because we use human cells, our lab has a specific philosophy that all the data we generate is used not only for fundamental research, but also relates back to the clinic,” added Vallier, who holds a joint appointment at the LRM and the Wellcome Trust Sanger Institute, and is also Chief Scientific Officer at DefiniGEN. “We are interested in how stem cells work but we also always ask how the research we’re doing might have a clinical or translational interest.”

IPS cells can be grown outside the body indefinitely, but can also develop into almost any other cell type, providing the opportunity to have a ready source of human cells for testing new drugs. Vallier’s lab is combining basic knowledge in developmental biology and stem cells to develop methods for differentiating IPS cells into liver and pancreatic cells. Despite being generated in a dish, these cells show many of the same characteristics as those generated through natural development.

In particular, the group uses a mix of IPS cells and human embryonic stem (ES) cells to understand the molecular mechanisms that could govern the onset of various metabolic diseases such as those that affect the liver and pancreas.

̽��ֱ��liver is a large and complex organ and plays a number of important roles in the body, including digestion and the secretion and production of proteins. It is also the key organ for metabolising drugs and removing toxic substances from the body. For this reason, demonstrating that a drug candidate is not toxic to the liver is a crucial stage in the development of new drugs. It is also a test that most new drug candidates fail – increasing the cost and decreasing the efficiency of the drug development process.

A lack of high-quality human liver cells, or primary hepatocytes, means that inferior models are often used for testing potential new drugs. ̽��ֱ��cells generated in Vallier’s lab, however, show many of the same functional characteristics as primary hepatocytes, both for toxicology testing and as models of liver disease, including the most commonly inherited metabolic conditions such as familial hypercholesterolaemia and alpha 1-antitrypsin disorder.

Vallier’s team is also able to use these cells to model a diverse range of inherited liver diseases, offering the potential to accelerate the development of new therapies for these conditions. “There is no cure for end-stage liver disease apart from transplantation,” said Vallier. “Due to an acute shortage of donors, many research groups have been looking at alternative means of treating liver failure, including stem-cell-based therapy.”

Understanding the basic mechanisms behind the genesis and development of liver disease is helping his team develop new ways to generate functional liver cells that could be used to treat these conditions in future.

̽��ֱ��researchers are taking a similar approach to the pancreas, with a particular focus on diabetes. According to Diabetes UK, 3.2 million people in the UK have been diagnosed with diabetes, and an estimated 630,000 people have the condition, but don’t know it.

A promising therapy to treat type 1 diabetes is transplanting the insulin-producing islet cells of the pancreas, but there are only enough donated islets to treat fewer than 1% of diabetic patients who might benefit from this form of treatment.

Vallier’s group is working to generate large numbers of pancreatic islet cells from stem cells, which could be used for transplantation-based therapy. In addition, they are building in vitro models to study the molecular mechanisms that control pancreatic specification in the embryo. Vallier’s group has identified several genes that could be important for pancreatic development and in determining an individual’s resistance to diabetes.

“Using IPS cells, we’re trying to understand how individual genetics can influence development, insulin production capacity and disease onset,” said Vallier. “Essentially, human IPS cells can be used to model human genetics in a dish, which hasn’t been possible until now.

“Thanks to IPS cells, we’re now able to discover things that are not possible to do using animal models or any in vitro system. Not only will this help us understand more about the mechanisms behind human development, such as how cells in the human embryo develop into organs, but it will also help with drug screening and with making more-precise drugs, which is what’s really needed for the liver and pancreas. These types of in vitro applications are possible now, while cell-based treatments are more in the longer term. But you have to walk before you can run.”

DefiniGEN is one of the first commercial opportunities to arise from Cambridge’s expertise in stem cell research. Here, we look at some of the fundamental research that enables it to supply liver and pancreatic cells for drug screening.

Thanks to IPS cells, we’re now able to discover things that are not possible to do using animal models or any in vitro system

Ludovic Vallier

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Testing time for stem cells

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