Chemo- and radiotherapy promote cerebromicrovascular pathology in a preclinical model of pediatric medulloblastoma

Objective: Pediatric medulloblastoma survivors treated with cranial radiotherapy and combination chemotherapy frequently develop late-onset cerebrovascular complications, including cerebral microhemorrhages, white-matter injury and elevated risk of stroke. However, why these cerebrovascular pathologies arise only years after cancer therapy remain poorly understood. Growing evidence suggests that the key driver might be the chronic, gradual accumulation of senescent cells within the cerebral microvasculature. Hypothesis: We hypothesized that combined chemo- and radiotherapy (CCT+CRT) synergistically promote endothelial senescence, leading to heightened vascular fragility and delayed-onset cerebrovascular dysfunction (e.g., blood-brain-barrier (BBB) breakdown, increased cerebral microhemorrhage (CMH) burden). Methods: Transgenic p16-3MR mice, which express red fluorescent protein to enable identification of senescent cells, received clinically relevant fractionated CRT (5 Gy, twice weekly for 2.5 weeks) and CCT (cisplatin, vincristine, cyclophosphamide) treatment. Endothelial senescence in the brain was quantified by flow cytometry. BBB permeability was assessed via intravital two-photon imaging following the injection of 40 kDa, 3 kDa, and 0.3 kDa fluorescent dextrans. CMHs were induced via a hypertension-based vascular stress model using angiotensin II delivered by osmotic minipumps and L-NAME administered in drinking water. Motor performance was evaluated with the CatWalk XT® gait analysis system. CMH number and area were quantified histologically using diaminobenzidine and hematoxylin staining. Results: Flow cytometry results confirmed that CCT+CRT induced endothelial senescence in the brain. BBB assessment showed sustained, therapy-induced increases in permeability. CCT+CRT also accelerated the onset of neurological signs associated with CMHs, and caused detectable impairments in motor coordination (e.g., reduced regularity index). Moreover, both the number and total area of CMHs were significantly elevated in treated mice compared with controls. Conclusion: Our findings demonstrate that CCT+CRT-induced endothelial senescence contributes to increased cerebrovascular fragility, characterized by BBB disruption and higher CMH burden. These CCT+CRT therapy-induced changes may underlie the delayed cerebrovascular impairments observed in pediatric medulloblastoma survivors. Targeting senescent cells may therefore offer a promising therapeutic strategy to mitigate cancer therapy-induced vascular injury and support long-term brain health. Funds: NCIR01CA255840 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.