In vitro CNS tissue analogues formed by self-organisation of reaggregated post-natal brain tissue

IL-1β and HMGB1 are anti-neurogenic to endogenous neural stem cells in the sclerotic epileptic human hippocampus

BACKGROUND

The dentate gyrus exhibits life-long neurogenesis of granule-cell neurons, supporting hippocampal dependent learning and memory. Both temporal lobe epilepsy patients and animal models frequently have hippocampal-dependent learning and memory difficulties and show evidence of reduced neurogenesis. Animal and human temporal lobe epilepsy studies have also shown strong innate immune system activation, which in animal models reduces hippocampal neurogenesis. We sought to determine if and how neuroinflammation signals reduced neurogenesis in the epileptic human hippocampus and its potential reversibility.

METHODS

We isolated endogenous neural stem cells from surgically resected hippocampal tissue in 15 patients with unilateral hippocampal sclerosis. We examined resultant neurogenesis after growing them either as neurospheres in an ideal environment, in 3D cultures which preserved the inflammatory microenvironment and/or in 2D cultures which mimicked it.

RESULTS

3D human hippocampal cultures largely replicated the cellular composition and inflammatory environment of the epileptic hippocampus. The microenvironment of sclerotic human epileptic hippocampal tissue is strongly anti-neurogenic, with sustained release of the proinflammatory proteins HMGB1 and IL-1β. IL-1β and HMGB1 significantly reduce human hippocampal neurogenesis and blockade of their IL-1R and TLR 2/4 receptors by IL1Ra and Box-A respectively, significantly restores neurogenesis in 2D and 3D culture.

CONCLUSION

Our results demonstrate a HMGB1 and IL-1β-mediated environmental anti-neurogenic effect in human TLE, identifying both the IL-1R and TLR 2/4 receptors as potential drug targets for restoring human hippocampal neurogenesis in temporal lobe epilepsy.

Monitoring neuron and astrocyte interactions with a 3D cell culture system

Methods are described for the generation and analysis of 3D co-culture models in which astrocyte and neuronal behavior can be studied. Cells may be obtained from a variety of sources, then cultured within collagen hydrogels to explore cellular responses and interactions in response to substances under test or under conditions that mimic physiological or pathological environments. Cell populations are labelled then either mixed within gels or arranged as separate adjacent populations, with further options including directing the self-alignment of cells to form anisotropic 3D cultures. Immunofluorescence staining and confocal microscopy can be used to capture image data from 3D structures and detailed protocols are provided for obtaining reliable results. Finally, 3D image analysis of confocal microscopy data is discussed, providing guidance on how astrocyte and neuronal features can be quantified.

Dissociated neurons and glial cells derived from rat inferior colliculi after digestion with papain

The formation of gliosis around implant electrodes for deep brain stimulation impairs electrode–tissue interaction. Unspecific growth of glial tissue around the electrodes can be hindered by altering physicochemical material properties. However, in vitro screening of neural tissue–material interaction requires an adequate cell culture system. No adequate model for cells dissociated from the inferior colliculus (IC) has been described and was thus the aim of this study. Therefore, IC were isolated from neonatal rats (P3_5) and a dissociated cell culture was established. In screening experiments using four dissociation methods (Neural Tissue Dissociation Kit [NTDK] T, NTDK P; NTDK PN, and a validated protocol for the dissociation of spiral ganglion neurons [SGN]), the optimal media, and seeding densities were identified. Thereafter, a dissociation protocol containing only the proteolytic enzymes of interest (trypsin or papain) was tested. For analysis, cells were fixed and immunolabeled using glial- and neuron-specific antibodies. Adhesion and survival of dissociated neurons and glial cells isolated from the IC were demonstrated in all experimental settings. Hence, preservation of type-specific cytoarchitecture with sufficient neuronal networks only occurred in cultures dissociated with NTDK P, NTDK PN, and fresh prepared papain solution. However, cultures obtained after dissociation with papain, seeded at a density of 2×10⁴ cells/well and cultivated with Neuro Medium for 6 days reliably revealed the highest neuronal yield with excellent cytoarchitecture of neurons and glial cells. The herein described dissociated culture can be utilized as in vitro model to screen interactions between cells of the IC and surface modifications of the electrode.

OrganDots--an organotypic 3D tissue culture platform for drug development

INTRODUCTION

There is an urgent need for preclinical testing systems that more accurately reflect responses in human target organs. The use of ex vivo tissues taken out of the human body and kept alive for sufficient time to perform testing has until recently been limited by tissue availability and by the length of time tissues can be kept alive outside the body, however, recent advances in tissue handling and tissue culture techniques have now made it possible to envisage using such tissues for drug discovery on a scale that is of value for the evaluation of compounds prior to testing in humans.

AREAS COVERED

The article presents a method for generating 3D microtissues at the air-liquid interface 'OrganDots' which are formed by reaggregating primary tissues or stem cell-based material which may be useful in drug discovery and development. The article compares this method with other methods for obtaining ex vivo tissues and looks at their uses as surrogates to testing compounds in humans.

EXPERT OPINION

Reconstituting tissues in vitro has now reached a point where they can be used to profile the activity of compounds prior to in vivo testing. The ability to reconstitute tissues from primary material and the ability to synthesize new tissues in vitro from stem cells may lead to new testing systems that better reflect human pathophysiology and may allow individual differences to be expressed in vitro. These new drug testing systems should lead to more predictable in vitro drug testing systems in the near future.