Stem cell-derived astrocytes: are they physiologically credible?

Astrocytes are now increasingly acknowledged as having fundamental and sophisticated roles in brain function and dysfunction. Unravelling the complex mechanisms that underlie human brain astrocyte-neuron interactions is therefore an essential step on the way to understanding how the brain operates. Insights into astrocyte function to date have almost exclusively been derived from studies conducted using murine or rodent models. Whilst these have led to significant discoveries, preliminary work with human astrocytes has revealed a hitherto unknown range of astrocyte types with potentially greater functional complexity and increased neuronal interaction with respect to animal astrocytes. It is becoming apparent, therefore, that many important functions of astrocytes will only be discovered by direct physiological interrogation of human astrocytes. Recent advancements in the field of stem cell biology have provided a source of human-based models. These will provide a platform to facilitate our understanding of normal astrocyte functions as well as their role in CNS pathology. A number of recent studies have demonstrated that stem cell-derived astrocytes exhibit a range of properties, suggesting that they may be functionally equivalent to their in vivo counterparts. Further validation against in vivo models will ultimately confirm the future utility of these stem cell-based approaches in fulfilling the need for human-based cellular models for basic and clinical research. In this review we discuss the roles of astrocytes in the brain and highlight the extent to which human stem cell-derived astrocytes have demonstrated functional activities that are equivalent to those observed in vivo.

First Organoid Intelligence (OI) workshop to form an OI community.

The brain is arguably the most powerful computation system known. It is extremely efficient in processing large amounts of information and can discern signals from noise, adapt, and filter faulty information all while running on only 20 watts of power. The human brain's processing efficiency, progressive learning, and plasticity are unmatched by any computer system. Recent advances in stem cell technology have elevated the field of cell culture to higher levels of complexity, such as the development of three-dimensional (3D) brain organoids that recapitulate human brain functionality better than traditional monolayer cell systems. Organoid Intelligence (OI) aims to harness the innate biological capabilities of brain organoids for biocomputing and synthetic intelligence by interfacing them with computer technology. With the latest strides in stem cell technology, bioengineering, and machine learning, we can explore the ability of brain organoids to compute, and store given information (input), execute a task (output), and study how this affects the structural and functional connections in the organoids themselves. Furthermore, understanding how learning generates and changes patterns of connectivity in organoids can shed light on the early stages of cognition in the human brain. Investigating and understanding these concepts is an enormous, multidisciplinary endeavor that necessitates the engagement of both the scientific community and the public. Thus, on Feb 22-24 of 2022, the Johns Hopkins University held the first Organoid Intelligence Workshop to form an OI Community and to lay out the groundwork for the establishment of OI as a new scientific discipline. The potential of OI to revolutionize computing, neurological research, and drug development was discussed, along with a vision and roadmap for its development over the coming decade.

Novel, Fully Characterised Bovine Taste Bud Cells of Fungiform Papillae.

Current understanding of functional characteristics and biochemical pathways in taste bud cells have been hindered due the lack of long-term cultured cells. To address this, we developed a holistic approach to fully characterise long term cultured bovine taste bud cells (BTBCs). Initially, cultured BTBCs were characterised using RT-PCR gene expression profiling, immunocytochemistry, flowcytometry and calcium imaging, that confirmed the cells were mature TBCs that express taste receptor genes, taste specific protein markers and capable of responding to taste stimuli, i.e., denatonium (2 mM) and quinine (462.30 µM). Gene expression analysis of forty-two genes implicated in taste transduction pathway (map04742) using custom-made RT-qPCR array revealed high and low expressed genes in BTBCs. Preliminary datamining and bioinformatics demonstrated that the bovine α-gustducin, gustatory G-protein, have higher sequence similarity to the human orthologue compared to rodents. Therefore, results from this work will replace animal experimentation and provide surrogate cell-based throughput system to study human taste transduction.

Modulation of interleukin-6 and matrix metalloproteinase 2 expression in human fibroblast-like synoviocytes by functional ionotropic glutamate receptors.

OBJECTIVE: Patients with rheumatoid arthritis (RA) have increased concentrations of the amino acid glutamate in synovial fluid. This study was undertaken to determine whether glutamate receptors are expressed in the synovial joint, and to determine whether activation of glutamate receptors on human synoviocytes contributes to RA disease pathology. METHODS: Glutamate receptor expression was examined in tissue samples from rat knee joints and in human fibroblast-like synoviocytes (FLS). FLS from 5 RA patients and 1 normal control were used to determine whether a range of glutamate receptor antagonists influenced expression of the proinflammatory cytokine interleukin-6 (IL-6), enzymes involved in matrix degradation and cytokine processing (matrix metalloproteinase 2 [MMP-2] and MMP-9), and the inhibitors of these enzymes (tissue inhibitor of metalloproteinases 1 [TIMP-1] and TIMP-2). IL-6 concentrations were determined by enzyme-linked immunosorbent assay, MMP activity was measured by gelatin zymography, and TIMP activity was determined by reverse zymography. Fluorescence imaging of intracellular calcium concentrations in live RA FLS stimulated with specific antagonists was used to reveal functional activation of glutamate receptors that modulated IL-6 or MMP-2. RESULTS: Ionotropic and metabotropic glutamate receptor subunit mRNA were expressed in the patella, fat pad, and meniscus of the rat knee and in human articular cartilage. Inhibition of N-methyl-D-aspartate (NMDA) receptors in RA FLS increased proMMP-2 release, whereas non-NMDA ionotropic glutamate receptor antagonists reduced IL-6 production by these cells. Stimulation with glutamate, NMDA, or kainate (KA) increased intracellular calcium concentrations in RA FLS, demonstrating functional activation of specific ionotropic glutamate receptors. CONCLUSION: Our findings indicate that activation of NMDA and KA glutamate receptors on human synoviocytes may contribute to joint destruction by increasing IL-6 expression.