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Bedggood P, Ding Y, Metha A. Changes to the shape, orientation and packing of red cells as a function of retinal capillary size. BIOMEDICAL OPTICS EXPRESS 2024; 15:558-578. [PMID: 38404337 PMCID: PMC10890884 DOI: 10.1364/boe.511093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 12/13/2023] [Accepted: 12/18/2023] [Indexed: 02/27/2024]
Abstract
The free diameter of a red blood cell exceeds the lumen diameter of capillaries in the central nervous system, requiring significant deformation of cells. However the deformations undertaken in vivo are not well established due to the difficulty in observing cellular capillary flow in living human tissue. Here, we used high resolution adaptive optics imaging to non-invasively track 17,842 red blood cells in transit through 121 unique capillary segments of diameter 8 µm or less in the retina of 3 healthy human subjects. Within each vessel, a 2D en face profile was generated for the "average cell", whose shape was then inferred in 3D based on the key assumption of a circular capillary cross-section. From this we estimated the average volume, surface area, orientation, and separation between red cells within each capillary tube. Our results showed a network filtration effect, whereby narrower vessels were more likely to contain smaller cells (defined by surface area, which is thought not to vary during a cell's passage through the vascular system). A bivariate linear model showed that for larger cells in narrower vessels: cells re-orient themselves to align with the flow axis, their shape becomes more elongated, there are longer gaps between successive cells, and remarkably, that cell volume is less which implies the ejection of water from cells to facilitate capillary transit. Taken together, these findings suggest that red cells pass through retinal capillaries with some reluctance. A biphasic distribution for cell orientation and separation was evident, indicating a "tipping point" for vessels narrower than approx. 5 µm. This corresponds closely to the typical capillary lumen diameter, and may maximize sensitivity of cellular flow to small changes in diameter. We suggest that the minimization of unnecessary oxygen exchange, and hence of damage via reactive oxygen pathways, may have provided evolutionary pressure to ensure that capillary lumens are generally narrower than red blood cells.
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Affiliation(s)
- Phillip Bedggood
- Department of Optometry and Vision Sciences, The University of Melbourne, 3010, Australia
| | - Yifu Ding
- Department of Optometry and Vision Sciences, The University of Melbourne, 3010, Australia
| | - Andrew Metha
- Department of Optometry and Vision Sciences, The University of Melbourne, 3010, Australia
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Rodriguez D, Church KA, Smith CT, Vanegas D, Cardona SM, Muzzio IA, Nash KR, Cardona AE. Therapeutic Delivery of Soluble Fractalkine Ameliorates Vascular Dysfunction in the Diabetic Retina. Int J Mol Sci 2024; 25:1727. [PMID: 38339005 PMCID: PMC10855319 DOI: 10.3390/ijms25031727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 01/20/2024] [Accepted: 01/27/2024] [Indexed: 02/12/2024] Open
Abstract
Diabetic retinopathy (DR)-associated vision loss is a devastating disease affecting the working-age population. Retinal pathology is due to leakage of serum components into retinal tissues, activation of resident phagocytes (microglia), and vascular and neuronal damage. While short-term interventions are available, they do not revert visual function or halt disease progression. The impact of microglial inflammatory responses on the neurovascular unit remains unknown. In this study, we characterized microglia-vascular interactions in an experimental model of DR. Early diabetes presents activated retinal microglia, vascular permeability, and vascular abnormalities coupled with vascular tortuosity and diminished astrocyte and endothelial cell-associated tight-junction (TJ) and gap-junction (GJ) proteins. Microglia exclusively bind to the neuronal-derived chemokine fractalkine (FKN) via the CX3CR1 receptor to ameliorate microglial activation. Using neuron-specific recombinant adeno-associated viruses (rAAVs), we therapeutically overexpressed soluble (sFKN) or membrane-bound (mFKN) FKN using intra-vitreal delivery at the onset of diabetes. This study highlights the neuroprotective role of rAAV-sFKN, reducing microglial activation, vascular tortuosity, fibrin(ogen) deposition, and astrogliosis and supporting the maintenance of the GJ connexin-43 (Cx43) and TJ zonula occludens-1 (ZO-1) molecules. The results also show that microglia-vascular interactions influence the vascular width upon administration of rAAV-sFKN and rAAV-mFKN. Administration of rAAV-sFKN improved visual function without affecting peripheral immune responses. These findings suggest that overexpression of rAAV-sFKN can mitigate vascular abnormalities by promoting glia-neural signaling. sFKN gene therapy is a promising translational approach to reverse vision loss driven by vascular dysfunction.
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Affiliation(s)
- Derek Rodriguez
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, TX 78249, USA; (D.R.); (K.A.C.); (C.T.S.); (D.V.); (S.M.C.)
| | - Kaira A. Church
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, TX 78249, USA; (D.R.); (K.A.C.); (C.T.S.); (D.V.); (S.M.C.)
| | - Chelsea T. Smith
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, TX 78249, USA; (D.R.); (K.A.C.); (C.T.S.); (D.V.); (S.M.C.)
| | - Difernando Vanegas
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, TX 78249, USA; (D.R.); (K.A.C.); (C.T.S.); (D.V.); (S.M.C.)
| | - Sandra M. Cardona
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, TX 78249, USA; (D.R.); (K.A.C.); (C.T.S.); (D.V.); (S.M.C.)
| | - Isabel A. Muzzio
- Department of Psychological and Brain Sciences, University of Iowa, Iowa City, IA 52242, USA;
| | - Kevin R. Nash
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL 33612, USA;
| | - Astrid E. Cardona
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, TX 78249, USA; (D.R.); (K.A.C.); (C.T.S.); (D.V.); (S.M.C.)
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Li B, Leng J, Şencan-Eğilmez I, Takase H, Alfadhel MAH, Fu B, Shahidi M, Lo EH, Arai K, Sakadžić S. Differential reductions in the capillary red-blood-cell flux between retina and brain under chronic global hypoperfusion. NEUROPHOTONICS 2023; 10:035001. [PMID: 37323511 PMCID: PMC10266089 DOI: 10.1117/1.nph.10.3.035001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 04/13/2023] [Accepted: 04/26/2023] [Indexed: 06/17/2023]
Abstract
Significance It has been hypothesized that abnormal microcirculation in the retina might predict the risk of ischemic damages in the brain. Direct comparison between the retinal and the cerebral microcirculation using similar animal preparation and under similar experimental conditions would help test this hypothesis. Aim We investigated capillary red-blood-cell (RBC) flux changes under controlled conditions and bilateral-carotid-artery-stenosis (BCAS)-induced hypoperfusion, and then compared them with our previous measurements performed in the brain. Approach We measured capillary RBC flux in mouse retina with two-photon microscopy using a fluorescence-labeled RBC-passage approach. Key physiological parameters were monitored during experiments to ensure stable physiology. Results We found that under the controlled conditions, capillary RBC flux in the retina was much higher than in the brain (i.e., cerebral cortical gray matter and subcortical white matter), and that BCAS induced a much larger decrease in capillary RBC flux in the retina than in the brain. Conclusions We demonstrated a two-photon microscopy-based technique to efficiently measure capillary RBC flux in the retina. Since cerebral subcortical white matter often exhibits early pathological developments due to global hypoperfusion, our results suggest that retinal microcirculation may be utilized as an early marker of brain diseases involving global hypoperfusion.
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Affiliation(s)
- Baoqiang Li
- Chinese Academy of Sciences, Shenzhen Institute of Advanced Technology, Brain Cognition and Brain Disease Institute; Shenzhen Fundamental Research Institutions, Shenzhen–Hong Kong Institute of Brain Science, Shenzhen, Guangdong, China
- Harvard Medical School, Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States
| | - Ji Leng
- Chinese Academy of Sciences, Shenzhen Institute of Advanced Technology, Brain Cognition and Brain Disease Institute; Shenzhen Fundamental Research Institutions, Shenzhen–Hong Kong Institute of Brain Science, Shenzhen, Guangdong, China
| | - Ikbal Şencan-Eğilmez
- Harvard Medical School, Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States
| | - Hajime Takase
- Harvard Medical School, Massachusetts General Hospital, Department of Radiology, Charlestown, Massachusetts, United States
- Harvard Medical School, Massachusetts General Hospital, Department of Neurology, Charlestown, Massachusetts, United States
| | - Mohammed Ali H. Alfadhel
- Harvard Medical School, Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States
| | - Buyin Fu
- Harvard Medical School, Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States
| | - Mahnaz Shahidi
- University of Southern California, Department of Ophthalmology, Los Angeles, California, United States
| | - Eng H. Lo
- Harvard Medical School, Massachusetts General Hospital, Department of Radiology, Charlestown, Massachusetts, United States
- Harvard Medical School, Massachusetts General Hospital, Department of Neurology, Charlestown, Massachusetts, United States
| | - Ken Arai
- Harvard Medical School, Massachusetts General Hospital, Department of Radiology, Charlestown, Massachusetts, United States
- Harvard Medical School, Massachusetts General Hospital, Department of Neurology, Charlestown, Massachusetts, United States
| | - Sava Sakadžić
- Harvard Medical School, Massachusetts General Hospital, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States
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Liu R, Wang X, Hoshi S, Zhang Y. High-speed measurement of retinal arterial blood flow in the living human eye with adaptive optics ophthalmoscopy. OPTICS LETTERS 2023; 48:1994-1997. [PMID: 37058625 PMCID: PMC11185870 DOI: 10.1364/ol.480896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 03/06/2023] [Indexed: 06/19/2023]
Abstract
We present a technique to measure the rapid blood velocity in large retinal vessels with high spatiotemporal resolution. Red blood cell motion traces in the vessels were non-invasively imaged using an adaptive optics near-confocal scanning ophthalmoscope at a frame rate of 200 fps. We developed software to measure blood velocity automatically. We demonstrated the ability to measure the spatiotemporal profiles of the pulsatile blood flow with a maximum velocity of 95-156 mm/s in retinal arterioles with a diameter >100 µm. High-speed and high-resolution imaging increased the dynamic range, enhanced sensitivity, and improved the accuracy when studying retinal hemodynamics.
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Affiliation(s)
- Ruixue Liu
- Doheny Eye Institute, 150 N Orange Grove Blvd, Pasadena, CA 91103
| | - Xiaolin Wang
- Doheny Eye Institute, 150 N Orange Grove Blvd, Pasadena, CA 91103
| | - Sujin Hoshi
- Doheny Eye Institute, 150 N Orange Grove Blvd, Pasadena, CA 91103
- Department of Ophthalmology, University of California - Los Angeles, 100 Stein Plaza Driveway, Los Angeles, CA 90024
- Department of Ophthalmology, University of Tsukuba, Ibaraki, Japan
| | - Yuhua Zhang
- Doheny Eye Institute, 150 N Orange Grove Blvd, Pasadena, CA 91103
- Department of Ophthalmology, University of California - Los Angeles, 100 Stein Plaza Driveway, Los Angeles, CA 90024
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Bedggood P, Ding Y, Metha A. Measuring red blood cell shape in the human retina. OPTICS LETTERS 2023; 48:1554-1557. [PMID: 37221708 DOI: 10.1364/ol.483062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/11/2023] [Indexed: 05/25/2023]
Abstract
The free diameter of a red blood cell generally exceeds the lumen diameter of capillaries in the central nervous system, requiring significant cellular deformation. However, the deformations undertaken are not well established under natural conditions due to the difficulty in observing corpuscular flow in vivo. Here we describe a novel, to the best of our knowledge, method to noninvasively study the shape of red blood cells as they traverse the narrow capillary networks of the living human retina, using high-speed adaptive optics. One hundred and twenty-three capillary vessels were analyzed in three healthy subjects. For each capillary, image data were motion-compensated and then averaged over time to reveal the appearance of the blood column. Data from hundreds of red blood cells were used to profile the average cell in each vessel. Diverse cellular geometries were observed across lumens ranging from 3.2 to 8.4 µm in diameter. As capillaries narrowed, cells transitioned from rounder to more elongated shapes and from being counter-aligned to aligned with the axis of flow. Remarkably, in many vessels the red blood cells maintained an oblique orientation relative to the axis of flow.
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Barrasa-Ramos S, Dessalles CA, Hautefeuille M, Barakat AI. Mechanical regulation of the early stages of angiogenesis. J R Soc Interface 2022; 19:20220360. [PMID: 36475392 PMCID: PMC9727679 DOI: 10.1098/rsif.2022.0360] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Favouring or thwarting the development of a vascular network is essential in fields as diverse as oncology, cardiovascular disease or tissue engineering. As a result, understanding and controlling angiogenesis has become a major scientific challenge. Mechanical factors play a fundamental role in angiogenesis and can potentially be exploited for optimizing the architecture of the resulting vascular network. Largely focusing on in vitro systems but also supported by some in vivo evidence, the aim of this Highlight Review is dual. First, we describe the current knowledge with particular focus on the effects of fluid and solid mechanical stimuli on the early stages of the angiogenic process, most notably the destabilization of existing vessels and the initiation and elongation of new vessels. Second, we explore inherent difficulties in the field and propose future perspectives on the use of in vitro and physics-based modelling to overcome these difficulties.
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Affiliation(s)
- Sara Barrasa-Ramos
- LadHyX, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Claire A. Dessalles
- LadHyX, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
| | - Mathieu Hautefeuille
- Laboratoire de Biologie du Développement (UMR7622), Institut de Biologie Paris Seine, Sorbonne Université, Paris, France,Facultad de Ciencias, Universidad Nacional Autónoma de México, CDMX, Mexico
| | - Abdul I. Barakat
- LadHyX, CNRS, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
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Zhang Q, Sampani K, Xu M, Cai S, Deng Y, Li H, Sun JK, Karniadakis GE. AOSLO-net: A Deep Learning-Based Method for Automatic Segmentation of Retinal Microaneurysms From Adaptive Optics Scanning Laser Ophthalmoscopy Images. Transl Vis Sci Technol 2022; 11:7. [PMID: 35938881 PMCID: PMC9366726 DOI: 10.1167/tvst.11.8.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 07/02/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose Accurate segmentation of microaneurysms (MAs) from adaptive optics scanning laser ophthalmoscopy (AOSLO) images is crucial for identifying MA morphologies and assessing the hemodynamics inside the MAs. Herein, we introduce AOSLO-net to perform automatic MA segmentation from AOSLO images of diabetic retinas. Method AOSLO-net is composed of a deep neural network based on UNet with a pretrained EfficientNet as the encoder. We have designed customized preprocessing and postprocessing policies for AOSLO images, including generation of multichannel images, de-noising, contrast enhancement, ensemble and union of model predictions, to optimize the MA segmentation. AOSLO-net is trained and tested using 87 MAs imaged from 28 eyes of 20 subjects with varying severity of diabetic retinopathy (DR), which is the largest available AOSLO dataset for MA detection. To avoid the overfitting in the model training process, we augment the training data by flipping, rotating, scaling the original image to increase the diversity of data available for model training. Results The validity of the model is demonstrated by the good agreement between the predictions of AOSLO-net and the MA masks generated by ophthalmologists and skillful trainees on 87 patient-specific MA images. Our results show that AOSLO-net outperforms the state-of-the-art segmentation model (nnUNet) both in accuracy (e.g., intersection over union and Dice scores), as well as computational cost. Conclusions We demonstrate that AOSLO-net provides high-quality of MA segmentation from AOSLO images that enables correct MA morphological classification. Translational Relevance As the first attempt to automatically segment retinal MAs from AOSLO images, AOSLO-net could facilitate the pathological study of DR and help ophthalmologists make disease prognoses.
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Affiliation(s)
- Qian Zhang
- Division of Applied Mathematics, Brown University, Providence, RI, USA
| | - Konstantina Sampani
- Beetham Eye Institute, Joslin Diabetes Center, Department of Medicine and Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - Mengjia Xu
- Division of Applied Mathematics, Brown University, Providence, RI, USA
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Shengze Cai
- Division of Applied Mathematics, Brown University, Providence, RI, USA
| | - Yixiang Deng
- School of Engineering, Brown University, Providence, RI, USA
| | - He Li
- School of Engineering, Brown University, Providence, RI, USA
| | - Jennifer K. Sun
- Beetham Eye Institute, Joslin Diabetes Center, Department of Medicine and Department of Ophthalmology, Harvard Medical School, Boston, MA, USA
| | - George Em Karniadakis
- Division of Applied Mathematics and School of Engineering, Brown University, Providence, RI, USA
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