Characterizing a hallmark of glymphatic insufficiency: Wasteosomes accumulate in periventricular white matter hyperintensities and exhibit complex relationships with mixed pathology, sclerotic index and perivascular space

The glymphatic system is a recently elucidated waste clearance system in the brain, thought to be critical for the maintenance of homeostasis. Corpora amylacea or "wasteosomes", are discontinuous lipid labyrinth structures that are polyglucosan rich, retain cellular waste and are thought to be of astrocytic origin. Wasteosomes have been proposed as a hallmark of glymphatic insufficiency predominantly due to: 1) their spatial localization around glymphatic drainage points including periventricular (PV) regions, perivascular spaces (PVS), and sub-pial regions; and, 2) their correlation with aging, vascular disorders, neurodegenerative diseases, and conditions that impair sleep. White matter hyperintensities (WMHs) are diffuse hyperintense areas seen on T2-weighted or fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) scans that represent damage to white matter. PV WMHs and are known predictors of mild cognitive impairment, stroke, dementia and death. The relationship between wasteosome accumulation, PV WMHs, vascular pathology and PVS is currently unknown. For the first time, in a mixed diagnostic cohort of pathologically diagnosed: Alzheimers disease (AD), cerebrovascular disease (CVD), mixed AD/CVD, and control tissue with no pathological diagnosis, we connected the histopathological wasteosome profile in periventricular brain sections in relation to 7T FLAIR-MRI confirmed PV WMHs, vascular stenosis and PVS. Our results reveal wasteosomes accumulate in PV WMHs, are increased in proximity to large PV venules, and exhibit complex relationships with WMH severity, mixed pathology, sclerotic index and PVS. These findings suggest wasteosomes may serve as histological markers of impaired glymphatic drainage and provide new insights into the pathophysiology underlying white matter injury.