Biology subjects

Curcio, C. A.

Publications and source records attributed to Curcio, C. A..

6 recordsLinked to original sources

bioRxiv2026

Visible Light Optical Coherence Tomography Reveals Aging at the RetinalPigment Epithelium-Bruch's Membrane Interface

Landmark histological studies have shown that as the retina ages, lipids and other debris accumulate within Bruchs membrane (BM) and in spaces introduced between BM and the retinal pigment epithelium (RPE). These deposits grow with age, increasing the risk of age-related macular degeneration (AMD), the leading cause of irreversible vision loss for older adults globally. Current in vivo imaging lacks specificity to study BM and the important spaces at the RPE/BM interface in living human eyes, while histological techniques suffer from processing artifacts that distort photoreceptors. Here we employ visible light Optical Coherence Tomography (OCT), with 1 micrometer depth resolution, to quantitatively analyze these tissues in living eyes. We identify age-related changes in a human cohort without retinal pathology: thickening and loss of contrast of the hyper-reflective BM band, and thickening of the RPE together with the sub-RPE basal laminar space (RPE+sBL). Both forms of thickening were locally coupled depending on eccentricity, suggesting related biosynthetic mechanisms. A thicker BM and RPE+sBL were locally associated with anomalies in the overlying photoreceptors. Thus, sub-clinical changes in aging eyes detected by visible light OCT resemble early versions of deposits found in AMD. Visible light OCT depicts the relationship between RPE+sBL, BM, and photoreceptors in aging, holding promise to precisely and non-invasively grade ocular phenotypes ranging from normal aging to early AMD. Significance StatementAs humans age, lipids and other debris deposit in Bruchs membrane (BM) of the human eye (1) and spaces introduced between the retinal pigment epithelium (RPE) and BM. These deposition processes are linked to the eventual development of age-related macular degeneration (AMD), the leading blinding disease amongst older adults. Here we investigate these deposits with visible light OCT imaging in living human subjects without overt retinal pathology. Whereas early RPE/BM deposits were previously assessed only in donor eyes postmortem via preparations that distort photoreceptors, our results shed light on these AMD precursors and overlying photoreceptor changes in living human eyes.

biophysics↗

bioRxiv2025

Visual pathway origins: an electron microscopic volume for connectomic analysis of the human foveal retina

The fovea is a unique specialization of the primate retina and is a promising site for obtaining the first complete connectome of a human central nervous system (CNS) structure. Within the fovea, neural cells and circuits have been miniaturized and compressed during evolution to sample the visual image at highest spatial resolution and begin the neural processing that serves human form, color, and motion perception. Here we present a comprehensive analysis of a sample of human foveal retina using deep learning-based segmentation to reconstruct all cells and synaptic connections at nanoscale resolution. We classified [~]3,000 cells into 51 distinct morphological types based on their structural features and connectivity patterns. Our observations reveal novel synaptic pathways absent in non-human primates, suggesting specialized circuits contribute uniquely to human trichromatic color vision. A biophysical model of the distinct connectomes made by gap junctions (electrical synapses) between short- (S) and medium-long- (ML) wavelength-sensitive cone photoreceptors, suggests chromatic interactions between S and ML cones prior to the first chemical synapse. Segmentation of retinal ganglion cells (RGCs) suggests the presence of only 11 visual pathways, with 5 high-density RGC pathways accounting for over 95% of foveal output to the brain: a dramatic contrast to the 40+ ganglion cell types recognized in mouse retina. Our connectomic analysis reveals distinctive features of human neural circuitry and demonstrates how AI-based computational approaches can advance understanding of human brain structure and function. Significant statementVision begins in the retina, an accessible outpost of the brain located at the back of the eye. When we directly view an object, we use the fovea--a tiny region containing over 50 distinct, densely packed neuron types. How these diverse cells interconnect through synapses to transmit visual information has been difficult to determine. Here, we used artificial intelligence-based computational methods to create a complete wiring diagram--a connectome--mapping every neuron and synapse in a sample of human fovea. This connectomic resource will be freely available to researchers worldwide. Discoveries so far include synaptic circuits linked to human color vision, demonstrating how connectomics can reveal what makes the human nervous system unique.

neuroscience↗

bioRxiv2023

Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function

Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or to age-related disease triggers lipid accumulation within the RPE, on Bruchs membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (apoB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPE{Delta}Mttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic deletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor -associated cholesterol deposits and photoreceptor cell death, and loss of rod but not cone function. RPE-specific ablation of Mttp had no significant effect on plasma lipids and lipoproteins. While, apoB was decreased in the RPE, ocular retinoid concentrations remained unchanged. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but not directly involved in ocular retinoid and plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.

cell biology↗

bioRxiv2021

Tissue fixation effects on human retinal lipid analysis by MALDI imaging and LC-MS/MS technologies

Imaging mass spectrometry (IMS) allows the location and abundance of lipids to be mapped across tissue sections of human retina. For reproducible and accurate information, sample preparation methods need to be optimized. Paraformaldehyde fixation of a delicate multilayer structure like human retina facilitates the preservation of tissue morphology by forming methylene bridge cross-links between formaldehyde and amine/ thiols in biomolecules; however, retina sections analyzed by IMS are typically fresh-frozen. To determine if clinically significant inferences could be reliably based on fixed tissue, we evaluated the effect of fixation on analyte detection, spatial localization, and introduction of artefactual signals. Hence, we assessed the molecular identity of lipids generated by matrix-assisted laser desorption ionization (MALDI-IMS) and liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) for fixed and fresh-frozen retina tissues in positive and negative ion modes. Based on MALDI-IMS analysis, more lipid signals were observed in fixed compared to fresh-frozen retina. More potassium adducts were observed in fresh-frozen tissues than fixed as the fixation process caused displacement of potassium adducts to protonated and sodiated species in ion positive ion mode. LC-MS/MS analysis revealed an overall decrease in lipid signals due to fixation that reduced glycerophospholipids and glycerolipids and conserved most sphingolipids and cholesteryl esters. The high quality and reproducible information from untargeted lipidomics analysis of fixed retina informs on all major lipid classes, similar to fresh-frozen retina, and serves as a steppingstone towards understanding of lipid alterations in retinal diseases.

biochemistry↗

bioRxiv2020

Fluorescence Lifetimes and Spectra of RPE and sub-RPE Deposits in Histology of Normal and AMD Eyes

PurposeTo investigate autofluorescence lifetimes as well as spectral characteristics of drusen and retinal pigment epithelium (RPE) in age-related macular degeneration (AMD). MethodFluorescence lifetimes and spectra of five eyes with AMD and nine control eyes were analyzed in cryosections by means of two-photon excited fluorescence at 960 nm. Spectra were detected at 490 - 647nm. Lifetime was measured using time-correlated single photon counting in two spectral channels: 500-550nm and 550-700nm. The fluorescence decays over time were approximated by a series of three exponential functions and the amplitude-weighted mean fluorescence lifetime {tau}m was determined. Results196 sub-RPE deposits were identified (AMD n=76, healthy n=120) and 230 RPE sites recorded. The peak emission wavelength of drusen was significantly green-shifted compared to RPE (peak at 570nm vs. 610nm), but not different between patients and controls. Drusen showed considerably longer {tau}m than RPE: (ch1: 581 {+/-} 163 ps vs. 177 {+/-} 25 ps, ch2: 541 {+/-} 125 ps vs. 285 {+/-} 31 ps, p < 0.001). Drusen found in AMD eyes had longer lifetimes than drusen of controls (ch1: 650 {+/-} 167 ps vs. 537 {+/-} 145 ps, ch2: 600 {+/-} 125 ps vs. 504 {+/-} 111 ps, p < 0.001). In addition, drusen in AMD eyes showed a more homogenous fluorescence distribution and more drusen were larger than 63{micro}m than in control eyes. ConclusionsEx vivo fluorescence imaging of drusen in cross-sections enables the separation of their autofluorescence from that of over- or underlying structures. Our analysis showed considerable variability of drusen lifetimes but not spectra. This indicates that drusen consist of a variety of different fluorophores or expose the same fluorophores to different microenvironments. Changes in drusen lifetimes could be related to AMD progression.

cell biology↗

bioRxiv2020

Lipid Landscape of the Human Retina and Supporting Tissues Revealed by High Resolution Imaging Mass Spectrometry

The human retina evolved to facilitate complex visual tasks. It supports vision at light levels ranging from starlight to sunlight, and its supporting tissues and vasculature regulate plasma-delivered lipophilic essentials for vision, including retinoids (vitamin A derivatives). The human retina is of particular interest because of its unique anatomic specializations for high-acuity and color vision that are also vulnerable to prevalent blinding diseases. The retinas exquisite cellular architecture is composed of numerous cell types that are aligned horizontally, giving rise to structurally distinct cell, synaptic, and vascular layers that are visible in histology and in diagnostic clinical imaging. Suitable for retinal investigations, MALDI imaging mass spectrometry (IMS) technologies are now capable of providing images at low micrometer spatial resolution with high levels of chemical specificity. In this study, a multimodal imaging approach combined with a recently developed method of high accuracy multi-image registration was used to define the localization of lipids in human retina tissue at laminar, cellular, and sub-cellular levels. Data acquired by IMS combined with autofluorescence and bright-field microscopy of human retina sections in macular and peripheral regions indicate differences in distributions and abundances of lipid species across and within single cell types. Of note is localization of signals within specific layers of macula, localization within different compartments of photoreceptors and RPE, complementarity of signals between macular retina and non-macular RPE, and evidence that lipids differing by a single double bond can have markedly different distributions.

biochemistry↗