Biology subjects

Smith, N. I.

Publications and source records attributed to Smith, N. I..

6 recordsLinked to original sources

bioRxiv2025

A lipid-driven, microbe-independent mechanism of acne via Lrig1+ follicular progenitor cells

Long-chain saturated fatty acids (lcSFAs) are abundant in the skin, but their pathogenic roles in acne remain unclear. In human sebum profiling, C16:0, the most abundant lcSFA, was the only fatty acid significantly elevated in acne and correlated with inflammatory comedone counts. We then established a mouse model that faithfully recapitulates human acne phenotypes, in which topical C16:0 penetrated the epidermis and induced sebocyte hyperplasia, comedogenesis, and follicular inflammation. Mechanistically, C16:0 activated keratinization and inflammatory pathways and drove sebocyte-lineage differentiation from Lrig1+progenitor cells, which function as cutaneous lipid sensors. These effects persisted in germ-free mice and were unaffected by fatty acid transporter modulation, while MyD88 signaling was partially required for inflammatory cell recruitment. Together, our findings identified C16:0 as a human acne-associated lipid that recapitulates disease hallmarks through a microbe-independent, lipid-driven pathway, highlighting Lrig1+cells as central hubs in remodeling of the pilosebaceous unit.

cell biology↗

bioRxiv2025

Accelerated plastic aging in suspension (APAS): A simple, reproducible approach for the generation of model micro- and nanoplastics through simulated environmental forces

The environmental fragmentation of plastic waste leads to the formation of micro- and nanoplastics (MNPs), which pose serious ecological and human health concerns. Despite increasing interest in their biological effects, many studies rely on artificial, uniform particles that fail to mimic the diverse physical and chemical characteristics of real-world MNPs. To address this limitation, we developed the Accelerated Plastic Aging in Suspension (APAS) system--a scalable, reproducible method that mimics natural aging processes by combining ultraviolet (UV) radiation, thermal stress, and mechanical shear to generate environmentally relevant MNPs from commonly used polymers. We used APAS to fragment polyethylene terephthalate (PET), polyamide 6 (Nylon), and polyacrylonitrile (PAN), and observed time-dependent degradation, including the spontaneous formation of nanoplastics (<100 nm). Flow cytometry revealed substantial increases in particle number and reductions in average particle size over 12 weeks. Imaging flow cytometry confirmed consistent generation of heterogeneous, irregular particles across replicate batches. High-resolution imaging via AFM, TEM, and SEM confirmed the presence of nanoplastics with textured and irregular morphologies. Chemical characterization showed APAS aging altered particle surface charge and induced polymer-specific changes in autofluorescence and Raman spectral profiles, consistent with oxidative surface modifications. Laser Direct Infrared (LDIR) imaging further confirmed structural and chemical changes in polymer spectra post-aging. Functionally, under physiologically relevant shear flow conditions, endothelial cells internalized APAS-generated PET MNPs at significantly higher levels than polystyrene (PS) beads of similar size. Uptake was enhanced particularly under oscillatory flow, highlighting the influence of particle physicochemical properties on cellular interactions. Together, these findings demonstrate the ability of the APAS system to produce complex and realistic MNPs for use in environmental and toxicological studies. The system enables generation of nanoplastics and supports more accurate modelling of biological exposure scenarios compared to conventional synthetic particles.

pharmacology and toxicology↗

bioRxiv2023

Raman microscopy of cryofixed biological specimens for high-resolution and high-sensitivity chemical imaging

Raman microscopy is an emerging molecular imaging technology, yet its signal-to-noise-ratio (SNR) in measurements of biological specimens is severely limited due to the small cross-section of Raman scattering. Here, we present Raman imaging techniques of cryofixed specimens to overcome SNR limitations by enabling long exposure of specimens under highly stabilized low-temperature conditions. The observation of frozen specimens in a cryostat at a constant low temperature immediately after rapid freezing enabled the improvement of SNR and significantly enhanced spatial and spectral resolution. We also confirmed that the cryofixation can preserve physicochemical states of specimens by observing alkyne-labeled coenzyme Q in cytosol and hemeproteins in acute ischemic myocardium, which cannot be done by fixation using chemical reagents. Finally, we applied the technique for multiplex Raman imaging of label-free endogenous molecules and alkyne-tagged molecules in cryofixed HeLa cells, demonstrating its capability of high-content imaging of complex biological phenomena while maintaining physiological conditions.

biophysics↗

bioRxiv2023

Time-deterministic cryo-optical microscopy

We developed a technique to rapidly freeze biological systems during observation under an optical microscope, which allows for detailed optical observation at a precise time in the biological dynamics at high spatial resolution and quantifiability under low-temperature conditions. Our study further found that ion distributions and molecular conformations can be fixed in space and time, demonstrated by visualization of calcium waves rapid-frozen at an instant using fluorescent ion indicators. These results show that time-deterministic cryo-optical microscopy can suspend cellular dynamics while maintaining molecular and ionic states, allowing us to view cellular dynamics in a way that has not been possible before. One-Sentence SummaryRapid freezing of dynamic biological systems during optical observation presents time information to the fixed samples

biophysics↗

bioRxiv2021

Cellular adhesion is a controlling factor in neutrophil extracellular trap formation induced by antineutrophil cytoplasmic antibodies

Anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is a life-threatening condition characterized by improper activation of neutrophils and release of neutrophil extracellular traps (NETs) in small vessels. This study aimed to explain the role of NETs in AAV pathogenesis by investigating a link between neutrophil adhesion and NET release. We leveraged an imaging flow cytometry-based assay and three-dimensional culture to demonstrate that neutrophil adhesion is essential for ANCA induced NET formation. We confirmed this requirement for cell adhesion using standard microscopy on ultra-low attachment hydrogel surfaces and demonstrate that this depends on the focal adhesion kinase pathway as determined using inhibitors for multiple targets in this process. ANCA increased expression of {beta}2 integrins on neutrophils, and we confirmed that these integrins were required for NET formation using blocking antibodies. Finally, inhibitors for oxidative burst prevented NET formation, and this oxidative burst was mediated by the focal adhesion pathway. Overall, our findings reveal a central role for neutrophil attachment in NET formation in response to ANCA, helping to explain the restricted localization pattern of vessel damage, and suggesting that targeting neutrophil adhesion factors may be beneficial in preventing pathological damage from NETs during AAV.

immunology↗

bioRxiv2021

Deriving accurate molecular indicators of protein synthesis through Raman-based sparse classification

Raman spectroscopy has the ability to retrieve molecular information from live biological samples non-invasively through optical means. Coupled with machine learning, it is possible to use the large amount of information contained in a Raman spectrum to create models that can predict the state of new samples based on statistical analysis from previous measurements. Furthermore, in case of linear models, the separation coefficients can be used to interpret which bands are contributing to the discrimination between experimental conditions, which correspond here to single-cell measurements of macrophages under in vitro immune stimulation. We here evaluate a typical linear method using discriminant analysis and PCA, and compare it to regularized logistic regression (Lasso). We find that the use of PCA is not beneficial to the classification performance. Furthermore, the Lasso approach yields sparse separation vectors, since it suppresses spectral coefficients which do not improve classification, making interpretation easier. To further evaluate the approach, we apply the Lasso technique to a well-defined case where protein synthesis is inhibited, and show that the separating features are consistent with RNA accumulation and protein levels depletion. Surprisingly, when Raman features are selected purely in terms of their classification power (Lasso), the selected coefficients are contained in side bands, while typical strong Raman peaks are not present in the discrimination vector. We propose that this occurs because large Raman bands are representative of a wide variety of cellular molecules and are therefore less suited for accurate classification.

biochemistry↗