MT-Exo-derived miR-4651 and miR-6126 coordinately regulate the SRSF1–progerin and SP1–PrPᶜ axes to attenuate vascular aging in HGPS

Hutchinson-Gilford progeria syndrome (HGPS) is characterized by progressive vascular injury that remains incompletely controlled by therapies targeting progerin-associated pathology. Here, we investigated the therapeutic activity and molecular mechanisms of melatonin-preconditioned mesenchymal stromal cell-derived small extracellular vesicles (MT-Exo) using a patient-anchored translational framework integrating longitudinal vascular phenotyping and serial serum samples from an index patient with HGPS with independently sourced HGPS fibroblasts and endothelial-cell models. Serial HGPS serum samples exhibited increased progerin and cellular prion protein (PrPᶜ) signals, together with elevated troponin I, in the setting of progressive multisite vasculopathy. HGPS serum impaired endothelial morphology and angiogenic network formation, whereas recombinant PrPᶜ induced cellular-stress, inflammatory, chromatin, and nuclear-lamina abnormalities. MT-Exo attenuated HGPS serum-induced endothelial dysfunction and reduced progerin, PrPᶜ, p16, and γH2AX abnormalities and lamin A/C disorganization in HGPS fibroblasts. Mechanistically, MT-Exo-enriched miR-4651 directly targeted SRSF1 and attenuated progerin-associated nuclear-lamina abnormalities, whereas MT-Exo-enriched miR-6126 directly targeted SP1 and reduced PRNP/PrPᶜ expression. These two microRNAs therefore acted through distinct but complementary regulatory pathways involving SRSF1-progerin and SP1-PRNP/PrPᶜ signaling. A prespecified patient-informed virtual-cohort analysis of 15 treatment strategies further prioritized a cluster of lonafarnib-based combinations containing MT-Exo, dual miRNA, or miR-6126 for subsequent experimental evaluation, although no single regimen was consistently top-ranked across models. Collectively, these findings identify complementary miR-4651-SRSF1-progerin and miR-6126-SP1-PRNP/PrPᶜ regulatory axes in HGPS vascular aging and provide a mechanistic rationale for preclinical evaluation of MT-Exo- and miRNA-based combination strategies.