Cystic fibrosis is an optimal disease for gene therapy. It’s a single gene disorder which is autosomal and recessive. The protein associated with the disease, CFTR, is extremely well-characterised with a plethora of studies investigating it. It’s a channel for anions including chloride and bicarbonate; losing this channel leads to cystic fibrosis. The protein is expressed in many organs that have a secretary epithelium, but the highest morbidity is when the disease affects the lung.
Of the many mutations that cause cystic fibrosis, approximately 10% will cause a complete loss of the CFTR protein. It’s this patient group, over 1000 people in the UK alone, that Hart’s group are targeting with their therapy. The team have developed an in house nanoparticle delivery system in order to target cells that are supposed to express CFTR with gene therapy.
There are many challenges with delivering gene therapies to the lung. Inhaled therapies are limited by shearing forces which affect the nanoparticles. While in the lung, the respiratory epithelium does a good job at quenching the lung of contaminants, which includes therapeutic nanoparticles. Furthermore, cystic fibrosis in the lung is characterised by thick sticky mucus which adds another barrier.
After that, nanoparticles also need to navigate the cilia, periciliary liquid, and tethered mucins. Once in the right location, the particles also need to find and affect the CFTR-expressing cells. Unfortunately, this is difficult as the main sites of CFTR expression are very rare cell type called ionocytes and not the abundant ciliated cells.
Their in-house lipid and peptide-based system is used to deliver RNA or RNP-based gene therapies. These nanoparticles are designed to overcome delivery challenges, such as endosomal barriers, and efficiently package therapeutic molecules like Cas9, which in this case uses RNP delivery.
Hart's group’s gene editing strategy involves using two guide RNAs to target specific intronic regions and excise mutations in the CFTR gene. This approach has been demonstrated to correct splicing and produce functional CFTR protein in primary cells, showing potential for therapeutic applications.
The research aims to assess in vivo efficacy using transgenic models and improve nanoparticle delivery efficiency. Hart's team is working on further characterising the edited cells and exploring the potential of their nanoparticles in animal models.
