INVESTIGATING SENESCENCE PHENOTYPES IN ASTROCYTES DERIVED FROM A53T Α-SYNUCLEIN PD-PATIENT IPSCS

Cellular senescence is characterized by irreversible cell cycle arrest, resistance to apoptosis, and a senescence-associated secretory phenotype (SASP). Besides aging, environmental and cellular stressors may also trigger senescence. Emerging evidence links senescent astrocytes to neurodegenerative disorders, including Parkinson’s disease (PD). However, whether the PD-associated A53T mutation in alpha-synuclein (αSyn) drives astrocytic senescence remains unclear. We recently reported that astrocytes derived from A53T PD-patient induced pluripotent stem cells (iPSC) exhibit αSyn accumulation, impaired proteostasis, and neurotoxic effects on dopaminergic neurons (Paschou et al, PNAS 2025, 10.1073/pnas.2505240122). Here, we demonstrate that A53T astrocytes impair neuronal health through paracrine signaling associated with a senescent-like phenotype. Healthy neurons exposed to A53T astrocyte-conditioned medium (ACM) showed reduced viability. Conversely, treating A53T neurons with control ACM reduced protein aggregation and improved survival and network integrity. Our comprehensive analysis identified hallmarks of senescence in A53T astrocytes: increased senescence-associated beta-galactosidase activity, elevated levels of the cell cycle inhibitor CDKN1A, upregulated γH2AX, indicative of DNA damage, reduced LaminB1 expression, enlarged cell and nuclear size, lysosomal dysregulation, autofluorescence, and accumulation of multilamellar bodies evidenced by TEM. Proteomic analysis, combined with alignment to the CellAge database, revealed a SASP signature in the A53T astrocytes. Antibody-array profiling of ACM showed dysregulation of factors involved in ECM organization, growth factor signaling, and insulin-related pathways. Our findings indicate that the A53T-αSyn mutation induces astrocytic senescence, promoting early PD progression through SASP. Our ongoing experiments aim to dissect the underlying mechanisms and identify novel astrocyte-targeted therapeutic strategies. Funding: Empeirikeion Foundation; GSRI-TAEDR-0535850-BrainPrecision; H.F.R.I.project 590-3rd Call.