Dissecting the sex-specific contribution of astrocytes and endothelial cells at the leaky blood-brain barrier in major depressive disorder (MDD)

• Applicant: Privatdozentin Dr. Barbara Di Benedetto
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 534915660

Interactions among astrocytes and endothelial cells (EC) forming blood vessels are essential to building a properly functional blood-brain barrier (BBB). Astrocyte-specific signaling molecules modulate tight junctions (TJ) between EC, thereby controlling BBB sealing properties and thus the trans-endothelial blood-brain trafficking of various substances. Any disruption in these events may lead to the onset of brain disorders. Indeed, an impaired morphology of astrocytes and reduced TJ proteins expression characterizes the leaky BBB in postmortem brains of major depressive disorder (MDD) patients. Epidemiological data also revealed sex differences in MDD prevalence, with women twice more affected as men. Intriguingly, the disruption of the BBB in female mice induces depression-like behaviors. Thus, there is a high need to investigate sex-dependent cellular and molecular mechanisms which link a leaky BBB with the etiopathogenesis of MDD to identify alternative disease trajectories, which might be targeted by personalized treatments. Hypotheses/research questions/ objectives: This proposal aims to: 1. Profile molecular differences of astrocytes and EC between healthy and MDD rat/human samples, which might serve as diagnostic markers. 2. Isolate sex-dependent differences in cell-type-specific (dys)functions at the BBB in MDD. The proposed experimental and theoretical work is highly interconnected and we will gain much more insights by combining in vitro, in vivo, and in silico studies. For the wet-lab experiments, we will use 2D primary cell culture models prepared from either healthy MDD-like rats and a 3D cell culture system to specifically study the BBB (SynBBB). Using a combination of biomolecular, biochemical, histological, pharmacogenetic, and behavioral tools, we will identify and manipulate cell-type-specific properties to investigate their contribution to MDD. For the computational modeling, we will analyze the experimental data and use the results to develop multi-compartment astrocyte models, including BBB and EC. Specifically, we will develop a single-cell astrocyte model extended by an endfoot and attached blood vessel to include TJ to study the diffusion of molecules between one astrocyte and the blood vessel. Size and geometry of the cells will be acquired from brain images and used to model drug effects. Overall, we will heavily exchange data between labs; the experimental data will be used to fit parameters for the computational models and the results from the simulations will be used to refine the experiments. Level of originality innovation: Presently, it is unknown whether and how dysfunctional astrocytes, dysfunctional ECs or both contribute to the onset of MDD, how they may influence BBB formation and the exact ell types targeted by therapeutic drugs.

• DFG Programme: Research Grants
• International Connection: Austria
• Cooperation Partner: Professorin Dr. Kerstin Lenk, Ph.D.