Single-cell analysis of the progeric vascular wall reveals progressive cell-type specific dysfunction and accumulation of somatic mutations

Background: The premature aging disorder Hutchinson-Gilford Progeria Syndrome (HGPS) is caused by de novo LMNA mutations producing the aberrant Lamin A isoform progerin. HGPS patients die from cardiovascular disease, with their arteries showing extensive cellular and structural remodeling, but the mechanisms driving vascular dysfunction are not fully understood. Methods: To characterize the molecular processes underlying vascular degeneration in HGPS, we used LmnaG609G/G609G mice, which carry the mouse equivalent of the HGPS-causing mutation and recapitulate the vascular phenotype without atheroprone stimuli. We performed single-cell RNA-sequencing on aortic arch cells from wild-type and LmnaG609G/G609G at different ages to capture time-dependent transcriptional changes. The Smart-seq2 protocol was used for sequencing, as it has high sensitivity and provides full-length transcript coverage. Results: We identified transcriptionally distinct VSMC and fibroblast populations that evolved over time. Disease-enriched VSMCs displayed high levels of endoplasmic reticulum (ER) stress and underwent phenotypic switching towards a fibroblast-like state, potentially expanding through intercellular communication. ER stress inhibition with TUDCA showed the ER stress and phenotypic switch develop independently. In addition, we observed increased DNA damage and somatic mutation accumulation in progeria VSMCs, correlating with high ER stress, a ROS response, and eventually increased expression of p53-related genes. Lastly, VSMC apoptosis occurred by 12 weeks of age. Progeria-enriched fibroblasts either became activated or increased cartilage production and accumulated somatic mutations, but to a lesser extent than VSMCs, suggesting cell-type somatic mutation susceptibility. Conclusions: We provide a detailed cellular and molecular atlas of VSMCs and fibroblasts with HGPS progression. We have developed a user-friendly searchable database for the research community to access the expression data, which will be of high relevance in preclinical research to ameliorate vascular aging.