Pulmonary fibrosis (PF) is a complex, age-related lung disease. The exact cause of PF is unknown, but short telomere length in alveolar epithelial type 2 (AT2) cells have been implicated in its pathogenesis. Around 25% of patients with PF have a familial form of PF, with the majority of mutations identified in telomere related genes (TRG) such as RTEL1.

We hypothesise that AT2 cells generated from induced pluripotent stem cells (iPSCs) (iAT2) derived from patients with a TRG mutation can be used as a model to explore telomere biology and determine its role in PF, identifying new treatments.

We describe a large sibship of 15 people, 5 of whom carry a heterozygous RTEL1 mutation identified via exome sequencing. Peripheral blood mononuclear cells were isolated from members carrying the RTEL1 mutation, were reprogrammed to iPSCs, characterised for pluripotency via immunostaining, and karyotyped. Subsequently, these iPSCs were differentiated towards iAT2 spheroids via a directed differentiation protocol and were interrogated for telomere length, gene and protein expression.

2 iPSC lines were successfully generated from patients with an RTEL1 mutation. iPSCs expressed SSEA-4, TRA-1-60, and TRA-1-81, markers for pluripotency and were found to be karyotypically normal. These patient-derived iPSCs were differentiated to iAT2 spheroids and used to explore telomere length, TERT expression, and telomerase activity. CRISPR-Cas9 gene editing to produce syngeneic pairs is planned.

We have generated a novel model of PF from patients with a TRG mutation in RTEL1. This tool will allow us to further explore telomere biology and its role in PF.