Adult ADHD-linked PARK2 variants subtly reshape lab-grown blood-brain barrier cells

Scientists have grown blood-brain barrier cells from adults with attention-deficit/hyperactivity disorder (ADHD) and uncovered a methodological twist that could matter for anyone modelling the barrier in a dish: how long the cells stay in culture changes their metabolism more than the patients’ genetics do. The study, published in Fluids and Barriers of the CNS, examined whether adult ADHD and rare copy number variations (CNVs) in the PARK2 gene are accompanied by alterations in blood-brain barrier phenotype, mitochondrial properties and cellular metabolism.

PARK2 encodes parkin, a key regulator of mitochondrial quality control, and PARK2 copy number variations constitute a rare genetic risk factor for ADHD, a multifactorial neurodevelopmental disorder. Because mitochondrial dysfunction is implicated in ADHD pathophysiology and can contribute to blood-brain barrier disruption, the team set out to test whether these genetic backgrounds leave a measurable fingerprint on barrier-forming cells. Blood-brain barrier disruption in ADHD remains insufficiently understood, making donor-specific models an attractive route into the underlying mechanisms.

The researchers generated brain capillary endothelial-like cells (BCECs) from ten donor-specific human induced pluripotent stem cell (hiPSC) lines. The donors included adults with ADHD carrying PARK2 CNVs, as well as PARK2 wild type adults with and without ADHD. Each line was analysed at two time points: day 10, the end of differentiation, and day 17, after prolonged culture. This design allowed the team to separate group-associated phenotypes from changes driven simply by how long the cells had been sitting in the culture dish.

At day 10, the cells across all groups looked convincingly barrier-like: they expressed brain endothelial markers, showed high transendothelial electrical resistance (TEER), and displayed low permeability to sodium fluorescein. After prolonged culture to day 17, sodium fluorescein permeability remained low, but TEER-based barrier integrity declined. In other words, one standard readout of barrier quality eroded with time even as the cells kept their tightness to a small tracer molecule.

The metabolic story was equally time-dependent. Prolonged culture reduced glycolytic ATP production rates while increasing mitochondrial ATP production and its relative share of total ATP production, reflecting a shift from glycolysis toward oxidative phosphorylation. Despite a decrease in total ATP production after prolonged culture, the cells’ overall energy status was largely preserved, alongside generally lower intracellular reactive oxygen species (ROS) and a lower mitochondrial membrane potential.

Against this culture-duration backdrop, the genotype-linked differences were comparatively modest. At day 10, BCECs from ADHD donors carrying PARK2 duplications showed greater mitochondrial abundance, the highest basal and oxidative stress-induced intracellular ROS levels, and reduced TEER-based barrier integrity. By day 17, the picture shifted again: BCECs from ADHD donors with PARK2 deletions exhibited the least glycolysis-dependent ATP production profile, although absolute mitochondrial ATP production remained comparable between groups.

The authors conclude that prolonged culture was associated with broad metabolic remodeling that was independent of ADHD status and PARK2 genotype, whereas the mitochondrial and metabolic alterations associated with ADHD and PARK2 CNVs were overall small. That distinction carries practical weight: if culture duration can swamp genotype effects, experiments comparing patient-derived barrier cells must control carefully for when measurements are taken.

On the constructive side, the study identifies culture duration as a critical parameter for characterising hiPSC-derived blood-brain barrier in vitro models, and supports the feasibility of using donor-specific BCECs at the end of differentiation, at day 10, to investigate barrier-associated mechanisms in adult ADHD and PARK2 copy number variations. For a rare genetic risk factor that is difficult to study in patients directly, a reproducible, donor-specific window into the blood-brain barrier is a meaningful step forward, provided researchers keep one eye firmly on the calendar.

Subject of Research: Blood-brain barrier models derived from stem cells of adults with ADHD and PARK2 copy number variations

Article Title: Adult ADHD, PARK2 copy number variations and the blood-brain barrier: Culture duration-dependent metabolic alterations in human induced pluripotent stem cell-derived in vitro models

Article References: Glaser, M., Dieterich, L., Ceslik, L., Schickardt, Z., Gätzner, S., Schmitt, L., Oberwinkler, H., Reining, J., Friedrich, M., Hemmen, K., Schmitz, W., McNeill, R. V., Kittel-Schneider, S., & Appelt-Menzel, A. (2026). Adult ADHD, PARK2 copy number variations and the blood-brain barrier: Culture duration-dependent metabolic alterations in human induced pluripotent stem cell-derived in vitro models. Fluids and Barriers of the CNS, 23(1), Article 123. https://doi.org/10.1186/s12987-026-00892-5

Image Credits: AI Generated

DOI: 10.1186/s12987-026-00892-5

Keywords: ADHD, PARK2, copy number variations, blood-brain barrier, induced pluripotent stem cells, mitochondria, glycolysis, oxidative phosphorylation, TEER, reactive oxygen species, in vitro models, brain endothelial cells