Biology subjects

Read, A. T.

Publications and source records attributed to Read, A. T..

8 recordsLinked to original sources

bioRxiv2026

Transcriptomic Profiling of High vs. Low Flow Regions of Mouse and Human Trabecular Meshwork

PurposeAqueous humor outflow through the trabecular meshwork (TM) is segmental, demonstrating high flow (HF) and low flow (LF) regions. Here, we investigate transcriptomic differences between flow regions in naive mouse and non-glaucomatous human TM tissue to better understand intraocular pressure (IOP) regulation. MethodsHuman eyes (<6 hours postmortem) from two donors were perfused with a fluorescent tracer to identify HF and LF regions and fixed. In parallel, one pair of 8-month-old C57Bl/6J mouse eyes were similarly processed. Sagittal sections from HF and LF regions underwent whole-transcriptome spatial profiling. Differential expression and gene set variation analysis were conducted to identify transcript and pathway-level differences between HF vs. LF TM. Selected targets were validated by immunolabeling. ResultsGenes with relevance to TM outflow were identified as significantly differentially expressed in the human dataset, including ADAM metallopeptidase domain 15 (ADAM15), vimentin (VIM), chitinase 3-like 1 (CHI3L1), and several transcription factors (e.g., FOS, JUNB, ESR1). Pathways related to epigenetic modifications were also differentially enriched in human eyes. In both human and mouse eyes, myocilin was significantly upregulated in HF regions, despite greater protein labeling in LF regions of human eyes. In both species, rho-kinase signaling pathways showed increased enrichment in LF regions, while cell stress pathways, and TNF- signaling were increased in HF TM. ConclusionsHF regions maintain a more active stress response that facilitates greater outflow, whereas LF regions exhibit more matrix accumulation and contractility. This characterization of segmental flow regions can inform future studies to target trabecular outflow and lower IOP.

bioengineering↗

bioRxiv2026

Segmental outflow and trabecular meshwork stiffness in an ocular hypertensive mouse model

PurposeElevated intraocular pressure (IOP) due to increased outflow resistance through the trabecular meshwork (TM) is a major risk factor for primary open-angle glaucoma. Outflow through the TM is segmental, consisting of high flow (HF) and low flow (LF) regions. Here, we investigate how ocular hypertension impacts segmental outflow using a dexamethasone (DEX) mouse model and compare TM stiffness between HF and LF regions. MethodsNanoparticles containing DEX or vehicle were injected twice weekly in 2-4-month-old C57BL/6J mice (n=14), and IOP was measured weekly. At week 4, mouse eyes were perfused in vivo with fluorescent nanospheres to assess flow patterns and the circumferential percentage of high, intermediate, and low flow regions in each eye. Sagittal sections were collected from HF and LF regions, and atomic force microscopy (AFM) was used to measure tissue stiffness. Immunofluorescent labeling was used to compare fibronectin and -SMA protein levels. ResultsDEX treatment significantly elevated IOP by an average of 33.3% and altered tracer distribution but not the percentage of HF and LF regions around the circumference. No significant differences in TM stiffness were detected between DEX-treated and control mice, or between HF and LF regions. Increased fibronectin in LF regions of DEX-treated eyes suggested subtle TM structural changes that were not detected by AFM. ConclusionsDexamethasone alters segmental flow distribution and may impact cell contractility rather than ECM stiffness to cause IOP elevation in young mice. These findings better characterize the nature of segmental outflow and TM mechanics in this model of steroid-induced glaucoma.

bioengineering↗

bioRxiv2025

Studies of all-trans retinoic acid transport in myopigenesis

PurposeMyopia incidence is increasing globally. All-trans retinoic acid (atRA) is important in myopigenic retinoscleral signaling, motivating research on its ocular transport. However, atRAs weak autofluorescence limits its direct visualization in tissues. Further, atRA is hydrophobic and must bind to protein carriers for transport. We assessed a fluorescent analog of atRA (LightOxTM14, CAS:198696-03-6, referred as floRA), as an experimentally accessible atRA surrogate by: (i) evaluating its binding to carrier proteins and (ii) visualizing its distribution in ocular tissues. MethodsO_ST_ABSBindingC_ST_ABSWe assessed atRA-carrier protein binding using fluorescence quenching assays with bovine serum albumin (BSA), high density lipoprotein (HDL), apolipoprotein A-I (Apo A-I) and retinol binding protein 4 (RBP4). Direct visualizationWild-type C57BL/6J mice were euthanized, eyes enucleated, and wedges containing sclera and choroid incubated for specific durations in 50 M floRA+BSA. The wedge centers were cryo-sectioned and counterstained for nuclei. Fluorescent micrographs were acquired and analyzed using ImageJ. ResultsAssociation constants (Ka) for atRA and floRA binding to carrier proteins were similar and ranged from 2-13 x 105 M-1, indicating non-specific binding. floRA could be visualized in sclera and choroid, yet showed significant spatial heterogeneity (enhanced fluorescence often colocalizing with nuclei). ConclusionsfloRA is a reasonable surrogate for atRA binding to BSA, HDL, Apo A-I and RBP4. Considering these proteins relative serum and extravascular abundances, and their similar binding affinity to atRA, we predict that serum albumin is an important atRA carrier. Use of floRA in whole tissue tracer studies shows promise but requires further refinement.

biochemistry↗

bioRxiv2024

Endothelial cell stiffness and type drive the formation of biomechanically-induced transcellular pores

Formation of transcellular pores facilitates the transport of materials across endothelial barriers. In Schlemms canal (SC) endothelium, impaired pore formation is associated with glaucoma. However, our understanding of the cellular processes responsible for pore formation is limited by lack of in vitro assays. Here, we present a novel platform for studying transcellular pore formation in human endothelial cells. We induced pores in SC cells by seeding them atop micron-sized magnetic beads followed by application of a magnetic field to subject cells to a basal to apical force, mimicking in vivo biomechanical forces. The pore formation process was dynamic, with pores opening and closing. Glaucomatous cells exhibited impaired pore formation that correlated with their increased stiffness. We further discovered that application of forces from the apical to basal direction did not induce pores in SC cells but resulted in formation of pores in other types of endothelial cells. Our studies reveal the central role of cell mechanics in formation of transcellular pores in endothelial cells, and provide a new approach for investigating their associated underlying mechanism/s.

bioengineering↗

bioRxiv2024

Magnetically Steered Cell Therapy For Functional Restoration Of Intraocular Pressure Control In Open-Angle Glaucoma

Trabecular meshwork (TM) cell therapy has been proposed as a next-generation treatment for elevated intraocular pressure (IOP) in glaucoma, the most common cause of irreversible blindness. Using a magnetic cell steering technique with excellent efficiency and tissue-specific targeting, we delivered two types of cells into a mouse model of glaucoma: either human adipose-derived mesenchymal stem cells (hAMSCs) or induced pluripotent cell derivatives (iPSC-TM cells). We observed a 4.5 [3.1, 6.0] mmHg or 27% reduction in intraocular pressure (IOP) for nine months after a single dose of only 1500 magnetically-steered hAMSCs, explained by increased outflow through the conventional pathway and associated with an higher TM cellularity. iPSC-TM cells were also effective, but less so, showing only a 1.9 [0.4, 3.3] mmHg or 13% IOP reduction and increased risk of tumorigenicity. In both cases, injected cells remained detectable in the iridocorneal angle three weeks post-transplantation. Based on the locations of the delivered cells, the mechanism of IOP lowering is most likely paracrine signaling. We conclude that magnetically-steered hAMSC cell therapy has potential for long-term treatment of ocular hypertension in glaucoma. One Sentence SummaryA novel magnetic cell therapy provided effective intraocular pressure reduction in a mouse model, motivating future translational studies.

bioengineering↗

bioRxiv2023

A Method for Analyzing AFM Force Mapping Data Obtained from Soft Tissue Cryosections

Atomic force microscopy (AFM) is a valuable tool for assessing mechanical properties of biological samples, but interpretations of measurements on whole tissues can be difficult due to the tissues highly heterogeneous nature. To overcome such difficulties and obtain more robust estimates of tissue mechanical properties, we describe an AFM force mapping and data analysis pipeline to characterize the mechanical properties of cryosectioned soft tissues. We assessed this approach on mouse optic nerve head and rat trabecular meshwork, cornea, and sclera. Our data show that the use of repeated measurements, outlier exclusion, and log-normal data transformation increases confidence in AFM mechanical measurements, and we propose that this methodology can be broadly applied to measuring soft tissue properties from cryosections.

bioengineering↗

bioRxiv2021

Assessment of the Viscoelastic Mechanical Properties of the Porcine Optic Nerve Head using Micromechanical Testing and Finite Element Modeling

Optic nerve head (ONH) biomechanics is centrally involved in the pathogenesis of glaucoma, a blinding ocular condition often characterized by elevation and fluctuation of the intraocular pressure and resulting loads on the ONH. Further, tissue viscoelasticity is expected to strongly influence the mechanical response of the ONH to mechanical loading, yet the viscoelastic mechanical properties of the ONH remain unknown. To determine these properties, we conducted micromechanical testing on porcine ONH tissue samples, coupled with finite element modeling based on a mixture model consisting of a biphasic material with a viscoelastic solid matrix. Our results provide a detailed description of the viscoelastic properties of the porcine ONH at each of its four anatomical quadrants (i.e., nasal, superior, temporal, and inferior). We showed that the ONHs viscoelastic mechanical response can be explained by a dual mechanism of fluid flow and solid matrix viscoelasticity, as is common in other soft tissues. We obtained porcine ONH properties as follows: matrix Youngs modulus E=1.895 [1.056,2 .391] kPa (median [min., max.]), Poissons ratio{nu} =0.142 [0.060,0 .312], kinetic time-constant{tau} =214 [89,921] sec, and hydraulic permeability k=3.854 x 10-1 [3.457 x 10-2,9.994 x 10-1] mm4/(N sec). These values can be used to design and fabricate physiologically appropriate ex vivo test environments (e.g., 3D cell culture) to further understand glaucoma pathophysiology.

bioengineering↗

bioRxiv2020

Antifibrotic activity of a rho-kinase inhibitor restores outflow function and intraocular pressure homeostasis

Glucocorticoids are widely used as an ophthalmic medication. A common, sight-threatening adverse event of glucocorticoid usage is ocular hypertension, caused by dysfunction of the conventional outflow pathway. We report that netarsudil, a rho-kinase inhibitor, rapidly reversed glucocorticoid-induced ocular hypertension in patients whose intraocular pressures were uncontrolled by standard medications. Mechanistic studies in our established mouse model of glucocorticoid-induced ocular hypertension show that netarsudil both prevented and reversed intraocular pressure elevation. Further, netarsudil reversed characteristic steroid-induced pathologies as assessed by quantification of outflow function and tissue stiffness, and morphological and immunohistochemical indicators of tissue fibrosis. Thus, rho-kinase inhibitors act directly on conventional outflow cells to efficaciously prevent or reverse fibrotic disease processes in glucocorticoid-induced ocular hypertension. These data motivate a novel indication for these agents to prevent or treat ocular hypertension secondary to glucocorticoid administration, and demonstrate the antifibrotic effects of rho-kinase inhibitors in an immune-privileged environment.

physiology↗