The choroid plexus (CP), which is located in the brain ventricles, is essential for maintaining brain homeostasis. The epithelial cells of the CP create the blood-cerebrospinal fluid barrier (B-CSF), which serves as an interface between the circulating blood and CSF (Figure 1A) [1]. The B-CSF barrier is crucial in the spread of inflammatory reactions from the periphery to the central nervous system (CNS) and contributes to the pathogenesis and progression of different neurological diseases [2]. Despite its clinical significance, the B-CSF barrier is one of the least investigated parts of the CNS. Its role has often been underestimated in favor of the blood-brain barrier; therefore, no extensive studies have been made on the 3D development of the B-CSF barrier in vitro. In this study, we present 3D modeling of the B-CSF using collagen-based hydrogels in vitro.
In this study, the Z310 rat choroid plexus epithelial cells were encapsulated in the blend hydrogel of modified gelatin (GelMA)-Collagen type I for a duration of 15 days, and the cell behavior was investigated by measuring the cell viability, proliferation, formation of the barrier in 3D and the expression of the transthyretin (TTR) marker. Furthermore, we performed an intensive investigation on analyzing the physical, chemical, and mechanical properties of the hydrogel blend composition after varying the ratios of the GelMA to collagen (50 mg/ml GelMA-0.2, 0.3, 2, 3 mg/ml collagen). After 15 days culture of encapsulated Z310 cells in the hydrogel (GelMA+3 mg/ml collagen) a dense monolayer of cells was visisble(Figure 1B). it was confirmed by scanning electron microscopy and confocal laser scanning microscopy that the combination of the porous structure of GelMA and the fibrillar organization of collagen provided a suitable structural support for cells to grow, secrete their own ECM and transport proteins needed for barrier integrity and functionality. The cells exhibited an expression of the TTR marker (Figure 1C), which acts as the primary transport protein for thyroxine and retinol (vitamin A) and neuroprotector against Aβ peptide, a central agent in the development of Alzheimer’s disease [3,4]. These findings suggest that GelMA-collagen blend hydrogels could be used as suitable 3D matrices for in vitro modeling the B-CSF barrier. This model can be tested for in vitro drug delivery, studying the disease mechanisms and tissue regeneration.
The study was supported by the Mobility Activity 8J21DE001 & Specific research - support for student projects MUNI/A/1331/2021 and Bundesministerium für Bildung und Forschung (BMBF) Projekt-ID: 57561119.
References
[1] B.Engelhardt et al., Seminars in Immunopathology, 2009, 31, 497-511.
[2] P. Solár et al., Fluids and Barriers of the CNS, 2020, 17, 35.
[3] Y. Sekijima et al., 2005, 121, 73-85.
[4] T. Gião et al., International Journal of Molecular Sciences, 2020, 6, 2075.