Biology subjects

Gravanis, A.

Publications and source records attributed to Gravanis, A..

3 recordsLinked to original sources

bioRxiv2023

Comprehensive characterization of the neurogenic and neuroprotective action of a novel TrkB agonist using mouse and human stem cell models of Alzheimer's Disease

Neural stem cell (NSC) proliferation and differentiation in the mammalian brain decreases to minimal levels postnatally. Nevertheless, neurogenic niches persist in the adult cortex and hippocampus in rodents, primates and humans, with adult NSC differentiation sharing key regulatory mechanisms with development. Adult neurogenesis impairments have been linked to Alzheimers Disease (AD) pathology. Addressing these impairments is a promising new avenue for therapeutic intervention based on neurogenesis. However, this possibility has been hindered by technical difficulties of using in-vivo models to conduct screens, including working with scarce NSCs in the adult brain and differences between human and mouse models or ethical limitations. In our study, we use a combination of mouse and human stem cell models to circumvent these issues and perform comprehensive characterization of a novel neurogenic compound using in vitro screening. Our work focuses on the brain-derived neurotrophic factor (BDNF) pathway, a pivotal neurotrophin in the regulation of neuronal growth and differentiation via its receptor tyrosine receptor kinase B (TrkB). We describe the design, chemical synthesis and biological characterization of ENT-A011, a steroidal dehydroepiandrosterone (DHEA) derivative and BDNF mimetic with neuroprotective and neurogenic actions. The compound is able to increase proliferation of mouse primary adult hippocampal NSCs and embryonic cortical NSCs, in the absence of EGF/FGF, while reducing Amyloid-{beta} (A{beta}) induced cell death, acting specifically through TrkB activation. The compound is also able to increase astrocytic gene markers involved in NSC maintenance, protect hippocampal neurons from A{beta} toxicity and prevent synapse loss after A{beta} treatment. To provide a translational link to human cells, we also used neural progenitor cells (NPCs) differentiated from three human induced pluripotent stem cell lines from healthy and AD donors. Our findings suggest that ENT-A011 successfully induces proliferation and prevents cell death after A{beta} toxicity of human NPCs. Additionally, using RNAseq profiling, we demonstrate that the compound acts through a core gene network shared with BDNF. Our work characterizes a novel synthetic BDNF mimetic with potential neurogenic and neuroprotective actions in Alzheimers disease via stem cell-based screening, demonstrating the promise of stem cell systems for short-listing competitive candidates for further testing.

pharmacology and toxicology↗

bioRxiv2022

A Microengineered Brain-Chip to Model Neuroinflammation in Humans

Species differences in the brain and the blood-brain barrier (BBB) biology hamper the translation from animal models to humans and impede the development of specific therapeutics for brain diseases. Here we present a human Brain-Chip engineered to recapitulate critical aspects of the complex brain cell-cell interactions that mediate neuroinflammation development. Our human organotypic microphysiological system (MPS) includes endothelial-like cells, pericytes, glia, and cortical neurons and maintains BBB permeability at in vivo relevant levels, providing a significant improvement in complexity and clinical mimicry compared to previous MPS models. This is the first report of a Brain-Chip with an RNA expression profile close to that of the adult human cortex and that demonstrates advantages over Transwell culture. Through perfusion of TNF-, we recreated key inflammatory features, such as glia activation, the release of proinflammatory cytokines, and increased barrier permeability. Our model may provide a reliable tool for mechanistic studies in neuron-glial interactions and dysregulation of BBB function during neuroinflammation.

bioengineering↗

bioRxiv2020

A novel Organ-Chip system emulates three-dimensional architecture of the human epithelia and allows fine control of mechanical forces acting on it.

Successful translation of in vivo experimental data to human patients is an unmet need and a bottleneck in the development of effective therapeutics. micro technology aims to address this need with significant advancements reported recently that enable modeling of organ level function. These microengineered chips enable researcher to recreate critical elements such as in vivo relevant tissue-tissue interface, air-liquid interface, and mechanical forces, such as mechanical stretch and fluidic shear stress, are crucial in emulating tissue level functions. Here, we present the development of a new, comprehensive 3D cell-culture system, where we combined our proprietary Organ-Chip technology with recent advantages in three-dimensional organotypic culture. Leveraging microfabrication techniques, we engineered a flexible chip that consists of a channel containing an organotypic epithelium surrounded by two vacuum channels that can be actuated to stretch the hydrogel throughout its thickness. Furthermore, the ceiling of this channel is a removable lid with a built-in microchannel that can be perfused with liquid or air and removed as needed for direct access to the tissue. The floor of this channel is a porous flexible membrane in contact with a microfluidic channel that provides diffusive mass transport to and from the channel. This additional microfluidic channel can be coated with endothelial cells to emulate a blood vessel and capture endothelial interactions. Our results show that the Open-Top Chip design successfully addresses common challenges associated with the Organs-on-Chips technology, including the capability to incorporate a tissue-specific extracellular matrix gel seeded with primary stromal cells, to reproduce the architectural complexity of tissues by micropatterning the gel, that can be extracted for H&E staining. We provide proof-of-concept data on the feasibility of the system using skin and alveolar epithelial primary cells and by simulating alveolar inflammation.

bioengineering↗