Biology subjects

Li, T. L.

Publications and source records attributed to Li, T. L..

4 recordsLinked to original sources

bioRxiv2022

Stretchable mesh microelectronics for the biointegration and stimulation of neural organoids

Advances in tridimensional (3D) culture approaches have led to the generation of organoids that recapitulate cellular and physiological features of domains of the human nervous system. Although microelectrodes have been developed for long-term electrophysiological interfaces with neural tissue, studies of long-term interfaces between microelectrodes and free-floating organoids remain limited. In this study, we report a stretchable, soft mesh electrode system that establishes an intimate in vitro electrical interface with human neurons in 3D organoids. Our mesh is constructed with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) based electrically conductive hydrogel electrode arrays and an elastomeric poly(styrene-ethylene-butadiene-styrene) (SEBS) as the substrate and encapsulation materials. This mesh electrode can maintain stable electrochemical impedance in buffer solution under 50% compressive and 50% tensile strain. We have successfully cultured pluripotent stem cell-derived human cortical organoids (hCO) on this polymeric mesh for more than 3 months and demonstrated that organoids readily integrate with the mesh. Using simultaneous stimulation and calcium imaging, we show that electrical stimulation through the mesh can elicit intensity-dependent calcium signals comparable to stimulation from a bipolar stereotrode. This platform may serve as a tool for monitoring and modulating the electrical activity of in vitro models of neuropsychiatric diseases.

neuroscience↗

bioRxiv2021

mRNA-1273 vaccination protects against SARS-CoV-2 elicited lung inflammation in non-human primates

Vaccine-elicited SARS-CoV-2 antibody responses are an established correlate of protection against viral infection in humans and non-human primates. However, it is less clear that vaccine-induced immunity is able to limit infection-elicited inflammation in the lower respiratory tract. To assess this, we collected bronchoalveolar lavage fluid samples post-SARS-CoV-2 strain USA-WA1/2020 challenge from rhesus macaques vaccinated with mRNA-1273 in a dose-reduction study. Single-cell transcriptomic profiling revealed a broad cellular landscape 48 hours post-challenge with distinct inflammatory signatures that correlated with viral RNA burden in the lower respiratory tract. These inflammatory signatures included phagocyte-restricted expression of chemokines such as CXCL10 (IP10) and CCL3 (MIP-1A) and the broad expression of interferon-induced genes such as MX1, ISG15, and IFIT1. Induction of these inflammatory profiles was suppressed by prior mRNA-1273 vaccination in a dose-dependent manner, and negatively correlated with pre-challenge serum and lung antibody titers against SARS-CoV-2 spike. These observations were replicated and validated in a second independent macaque challenge study using the B.1.351/beta-variant of SARS-CoV-2. These data support a model wherein vaccine-elicited antibody responses restrict viral replication following SARS-CoV-2 exposure, including limiting viral dissemination to the lower respiratory tract and infection-mediated inflammation and pathogenesis. One Sentence SummarySingle cell RNA sequencing analysis demonstrates that mRNA-1273 vaccination limits the development of lower respiratory tract inflammation in SARS-CoV-2 challenged rhesus macaques

immunology↗

bioRxiv2021

Nanoscale surface topography reduces focal adhesions and cell stiffness by enhancing integrin endocytosis

Both substrate stiffness and surface topography regulate cell behavior through mechanotransduction signaling pathways. Such intertwined effects suggest that engineered surface topographies might substitute or cancel the effects of substrate stiffness in biomedical applications. However, the mechanisms by which cells recognize topographical features are not fully understood. Here we demonstrate that the presence of nanotopography drastically alters cell behavior such that neurons and stem cells cultured on rigid glass substrates behave as if they were on soft hydrogels. We further show that rigid nanotopography resembles the effect of soft hydrogels in reducing cell stiffness and membrane tension as measured by atomic force microscopy. Finally, we demonstrate that nanotopography reduces focal adhesions and cell stiffness by enhancing the endocytosis and the subsequent removal of integrin receptors. This mechanistic understanding will support the rational design of nanotopography that directs cells on rigid materials to behave as if they were on soft ones. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/448920v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1599ab1org.highwire.dtl.DTLVardef@1bade3corg.highwire.dtl.DTLVardef@1543b28org.highwire.dtl.DTLVardef@f7cc15_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Listeria monocytogenes MenI encodes a DHNA-CoA thioesterase necessary for menaquinone biosynthesis, cytosolic survival, and virulence

Listeria monocytogenes is a Gram-positive intracellular pathogen that is highly adapted to invade and replicate in the cytosol of eukaryotic cells. Intermediate metabolites in the menaquinone biosynthesis pathway are essential for the cytosolic survival and virulence of L. monocytogenes, independent of the production of MK and aerobic respiration. Determining which specific intermediate metabolite(s) are essential for cytosolic survival and virulence has been hindered by the lack of an identified DHNA-CoA thioesterase essential for converting DHNA-CoA to DHNA in the MK synthesis pathway. Using the recently identified Escherichia coli DHNA-CoA thioesterase as a query, homology sequence analysis revealed a single homolog in L. monocytogenes, LMRG_02730. Genetic deletion of LMRG_02730 resulted in an ablated membrane potential, indicative of a non-functional electron transport chain (ETC) and an inability to aerobically respire. Biochemical kinetic analysis of LMRG_02730 revealed strong activity towards DHNA-CoA, similar to its E. coli homolog, further demonstrating that LMRG_02730 is a DHNA-CoA thioesterase. Functional analyses in vitro, ex vivo, and in vivo using mutants directly downstream and upstream of LMRG_02730 revealed that DHNA-CoA is sufficient to facilitate in vitro growth in minimal media, intracellular replication, and plaque formation in fibroblasts. In contrast, protection against bacteriolysis in the cytosol of macrophages and tissue specific virulence in vivo requires the production of DHNA. Taken together, these data implicate LMRG_02730 (renamed MenI) as a DHNA-CoA thioesterase and suggest that while DHNA protects the bacteria from killing in the macrophage cytosol, DHNA-CoA is necessary for intracellular bacterial replication.

microbiology↗