Collagen hydrogels loaded with fibroblast growth factor-2 as a bridge to repair brain vessels in organotypic brain slices

Buket Ucar,Sedef Yusufogullari,Christian Humpel

doi:10.1007/s00221-020-05907-7

Abstract

Vessel damage is a general pathological process in many neurodegenerative disorders, as well as spinal cord injury, stroke, or trauma. Biomaterials can present novel tools to repair and regenerate damaged vessels. The aim of the present study is to test collagen hydrogels loaded with different angiogenic factors to study vessel repair in organotypic brain slice cultures. In the experimental set up I, we made a cut on the organotypic brain slice and tested re-growth of laminin + vessels. In the experimental set up II, we cultured two half brain slices with a gap with a collagen hydrogel placed in between to study endothelial cell migration. In the experimental set up I, we showed that the number of vessels crossing the cut was tendencially increased with the addition of fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor, or platelet-derived growth factor-BB compared to the control group. In the experimental set up II, we demonstrated that a collagen hydrogel loaded with FGF-2 resulted in a significantly increased number of migrated laminin + cells in the gap between the slices compared to the control hydrogel. Co-administration of several growth factors did not further potentiate the effects. Taken together, we show that organotypic brain slices are good models to study brain vessels and FGF-2 is a potent angiogenic factor for endothelial cell proliferation and migration. Our results provide evidence that the collagen hydrogels can be used as an extracellular matrix for the vascular endothelial cells.

Highlights

The human brain contains approximately 650 km-long capillaries, so much that it is estimated that each neuron is perfused by its own capillary (Zlokovic 2005; Cipolla 2009)
We explore the potential use of collagen hydrogels as an extracellular matrix environment for endothelial cell proliferation, migration, and possible new vessel formation in organotypic brain slices by loading the hydrogels with angiogenic factors fibroblast growth factor-2 (FGF-2), Vascular endothelial growth factor (VEGF), and platelet-derived growth factor-BB (PDGF-BB)
Experimental set up I: vessel crossings after a cut Organotypic brain slices incubated for 2 weeks attached and flattened on the membrane insert (Fig. 1a) and cresyl violet staining showed homogeneous cell layers (Fig. 1b)

Summary

Introduction

The human brain contains approximately 650 km-long capillaries, so much that it is estimated that each neuron is perfused by its own capillary (Zlokovic 2005; Cipolla 2009). The brain capillary network includes primarily endothelial cells and pericytes, which are surrounded by astrocytic endfeet, forming a neurovascular unit (Cipolla 2009). Endothelial cells line all the vessels from big arteries and veins to the smallest capillaries in the whole body, regulating the Communicated by Thomas Deller. Endothelial cells under normal circumstances proliferate very slowly, for a mouse brain once a couple of years (Alberts et al 2002). In case of injury or other external stimuli such as angiogenic factors and inflammatory molecules, proliferation of endothelial cells accelerates. After sustaining a vessel injury, angiogenic mechanisms take action which, mostly fail to restore the previous function. To study endothelial cell proliferation and migration, aortic ring models are one of the most common methods, in which a ring of the aorta is embedded in extracellular

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