Heat transfer simulation in laser irradiated retinal tissues

2021 ◽  
Author(s):  
Linh Thai Dieu Truong ◽  
Peter J Lesniewski ◽  
Bruce Wedding
Keyword(s):  
Heat Transfer ◽  
Treatment Effectiveness ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Pulse Length ◽  
Realistic Model ◽  
Therapeutic Benefit ◽  
Element Analysis ◽  
Retinal Tissue ◽  
Heat Transfer Theory

Abstract A realistic model of human retinal tissues to simulate thermal performance of optical laser photocoagulation therapy is presented. The key criteria to validate the treatment effectiveness is to ensure the photocoagulation temperature between 60 and 70°C is reached in the treatment region of interest. The model presented consists of truncated volumes of the retinal pigment epithelium (RPE) and adjacent retinal tissues. Two cases of choroid pigmentation are modelled to signify extreme cases of human eye difference: albino and dark colour choroid pigmentation. Conditions for consistent heating over the irradiated treatment spot is modelled for laser beams with different intensity profiles: ‘top-hat’, Gaussian and ‘donut’ modes. The simulation considers both uniform heating within retinal tissue layers and spatial intensity decay due to absorption along the direction of laser propagation. For a 500 m spot, pulse length 100 ms and incident power to the cornea of 200 mW, realistic spatial variation in heating results in peak temperatures increasing within the RPE and shifting towards the choroid in the case of choroidal pigmentation. Finite element analysis methodology, where heat transfer theory governs the temperature evolution throughout tissues peripheral to the irradiated RPE is used to determine the zone of therapeutic benefit. While a TEM01 donut mode beam produces lower peak temperatures in the RPE for a given incident laser power, it reduces the volume of retinal tissue reaching excessive temperatures and maximises the zone of therapeutic benefit. Described are simulation limitations, boundary conditions, grid size and mesh growth factor required for realistic simulation.

scholarly journals Dietary Supplementation with Beta-Cryptoxanthin (BCX) Protects Against Light-Induced Retinal Damage

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 126-126
Author(s):  
Deshanie Rai ◽  
Kazim Sahin ◽  
Kazim Sahin ◽  
Emre Sahin ◽  
Mehmet Tuzcu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Angiogenic Factor ◽  
Retinal Damage ◽  
Waste Products ◽  
Health Technologies ◽  
Retinal Tissue ◽  
Age Related ◽  
Markers Of Oxidative Stress

Abstract Objectives The retinal pigment epithelium (RPE) regulates the transport of nutrients and waste products to and from the retina and protects against light and oxidative stress. Structural or physiological dysfunction of RPE leads to retinal conditions such as age-related eye disease (ARED). It is well-established that artificial and natural light is an important factor in the progression of ARED as it can induce oxidative damage and photochemical lesions. Recently, the use of LED in general lighting has raised concerns regarding the effects of this light source on the RPE. The goal was to investigate whether beta-cryptoxanthin, an efficient pro-vitamin A carotenoid can exert protective effects against LED-induced RPE cell damage. Methods Rats were fed with BCX for 4 weeks at a dose of 2 and 4 mg/kg body weight followed by retinal damage by exposing the eye to bright LED light for 48 hrs. Commercially available white LED sources, which are widely used in rat housing studies was used to induce retinal damage. Animals were sacrificed at the end of the study and retinal tissue and blood samples were collected and evaluated for retinal damage and markers of oxidative stress. Results BCX supplementation significantly reduced retinal damage as demonstrated by histopathology measurements including total retinal thickness, outer nuclear layer thickness, and swelling. Similarly, markers of oxidative stress including serum and retinal tissue levels of malondialdehyde, superoxide dismutase, glutathione peroxidase, and catalase were beneficially modulated by BCX supplementation. In parallel, BCX supplementation reduced inflammatory markers (IL-1β, IL-6, NF-κB), angiogenic factor VEGF, apoptotic proteins (Caspase-3, GAP43, GFAP, NCAM, HO-1) and mitochondrial stress markers (ATF4, ATF6, Grp78, Grp97) in retinal tissue. Conclusions Our study supports that oral supplementation of BCX dose-dependently exerts a protective effect against retinal damage induced by high-intensity light in a rat model by reducing oxidative stress, inflammation, angigogenesis and protection against mitochondrial DNA damage. BCX dietary intakes and supplementation throughout all stages of life can help protect against ARED that may start early in life. Funding Sources OmniActive Health Technologies.

scholarly journals Monocarboxylate Transporter 1 (MCT1) mediates succinate export in the retina

2021 ◽  
Author(s):  
Celia M Bisbach ◽  
Daniel T Hass ◽  
James B Hurley
Keyword(s):  
Plasma Membranes ◽  
Ex Vivo ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Monocarboxylate Transporter ◽  
Gas Chromatography Mass Spectrometry ◽  
Short Term ◽  
Monocarboxylate Transporter 1 ◽  
Retinal Tissue ◽  
Ex Vivo Culture

Purpose: Succinate is exported by the retina and imported by eyecup tissue. The transporter(s) mediating this process have not yet been identified. Recent studies showed that Monocarboxylate Transporter 1 (MCT1) can transport succinate across plasma membranes in cardiac and skeletal muscle. Retina and retinal pigment epithelium (RPE) both express multiple MCT isoforms including MCT1. We tested the hypothesis that MCTs facilitate retinal succinate export and RPE succinate import. Methods: We assessed retinal succinate export and eyecup succinate import in short term ex vivo culture using gas chromatography-mass spectrometry. We test the dependence of succinate export and import on pH, proton ionophores, conventional MCT substrates, and the MCT inhibitors AZD3965, AR-C155858, and diclofenac. Results: Succinate exits retinal tissue through MCT1 but does not enter RPE through MCT1 or any other MCT. Intracellular succinate levels are a contributing factor that determines if an MCT1-expressing tissue will export succinate. Conclusions: MCT1 facilitates export of succinate from retinas. An unidentified, non-MCT transporter facilitates import of succinate into RPE.

scholarly journals Cell Therapy for Retinal Dystrophies: From Cell Suspension Formulation to Complex Retinal Tissue Bioengineering

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Karim Ben M’Barek ◽  
Christelle Monville
Keyword(s):  
Cell Therapy ◽  
Current Knowledge ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Age Related Macular Degeneration ◽  
Future Research ◽  
Therapeutic Effects ◽  
Primary Defect ◽  
Retinal Tissue ◽  
Age Related

Retinal degeneration is an irreversible phenomenon caused by various disease conditions including age-related macular degeneration (AMD) and retinitis pigmentosa (RP). During the course of these diseases, photoreceptors (PRs) are susceptible to degeneration due to their malfunctions or to a primary dysfunction of the retinal pigment epithelium (RPE). Once lost, these cells could not be endogenously regenerated in humans, and cell therapy to replace the lost cells is one of the promising strategies to recover vision. Depending on the nature of the primary defect and the stage of the disease, RPE cells, PRs, or both might be transplanted to achieve therapeutic effects. We describe in this review the current knowledge and recent progress to develop such approaches. The different cell sources proposed for cell therapy including human pluripotent stem cells are presented with their advantages and limits. Another critical aspect described herein is the pharmaceutical formulation of the end product to be delivered into the eye of patients. Finally, we also outline the future research directions in order to develop a complex multilayered retinal tissue for end-stage patients.

scholarly journals The Role of Oxidative Stress and Autophagy in Blue-Light-Induced Damage to the Retinal Pigment Epithelium in Zebrafish In Vitro and In Vivo

2021 ◽  
Vol 22 (3) ◽  
pp. 1338
Author(s):  
Kai-Chun Cheng ◽  
Yun-Tzu Hsu ◽  
Wangta Liu ◽  
Huey-Lan Huang ◽  
Liang-Yu Chen ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Blue Light ◽  
Light Exposure ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Dependent Manner ◽  
Tissue Development ◽  
Retinal Tissue ◽  
Zebrafish Larvae

Age-related macular degeneration (AMD) is the progressive degeneration of the retinal pigment epithelium (RPE), retina, and choriocapillaris among elderly individuals and is the leading cause of blindness worldwide. Thus, a better understanding of the underlying mechanisms in retinal tissue activated by blue light exposure is important for developing novel treatment and intervention strategies. In this study, blue-light-emitting diodes with a wavelength of 440 nm were applied to RPE cells at a dose of 3.7 ± 0.75 mW/cm2 for 24 h. ARPE-19 cells were used to investigate the underlying mechanism induced by blue light exposure. A trypan blue exclusion assay was used for the cell viability determination. Flow cytometry was used for apoptosis rate detection and autophagy analysis. An immunofluorescence microscopy analysis was used to investigate cellular oxidative stress and DNA damage using DCFDA fluorescence staining and an anti-γH2AX antibody. Blue light exposure of zebrafish larvae was established to investigate the effect on retinal tissue development in vivo. To further demonstrate the comprehensive effect of blue light on ARPE-19 cells, next-generation sequencing (NGS) was performed for an ingenuity pathway analysis (IPA) to reveal additional related mechanisms. The results showed that blue light exposure caused a decrease in cell proliferation and an increase in apoptosis in ARPE-19 cells in a time-dependent manner. Oxidative stress increased during the early stage of 2 h of exposure and activated DNA damage in ARPE-19 cells after 8 h. Furthermore, autophagy was activated in response to blue light exposure at 24–48 h. The zebrafish larvae model showed the unfavorable effect of blue light in prohibiting retinal tissue development. The RNA-Seq results confirmed that blue light induced cell death and participated in tissue growth inhibition and maturation. The current study reveals the mechanisms by which blue light induces cell death in a time-dependent manner. Moreover, both the in vivo and NGS data uncovered blue light’s effect on retinal tissue development, suggesting that exposing children to blue light could be relatively dangerous. These results could benefit the development of preventive strategies utilizing herbal medicine-based treatments for eye diseases or degeneration in the future.

scholarly journals Complement System in Pathogenesis of AMD: Dual Player in Degeneration and Protection of Retinal Tissue

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Milosz P. Kawa ◽  
Anna Machalinska ◽  
Dorota Roginska ◽  
Boguslaw Machalinski
Keyword(s):  
Complement System ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
The Elderly ◽  
Age Related Macular Degeneration ◽  
Complement Components ◽  
Retinal Tissue ◽  
Age Related ◽  
Cellular Debris ◽  
Active Complement

Age-related macular degeneration (AMD) is the most common cause of blindness among the elderly, especially in Western countries. Although the prevalence, risk factors, and clinical course of the disease are well described, its pathogenesis is not entirely elucidated. AMD is associated with a variety of biochemical abnormalities, including complement components deposition in the retinal pigment epithelium-Bruch’s membrane-choriocapillaris complex. Although the complement system (CS) is increasingly recognized as mediating important roles in retinal biology, its particular role in AMD pathogenesis has not been precisely defined. Unrestricted activation of the CS following injury may directly damage retinal tissue and recruit immune cells to the vicinity of active complement cascades, therefore detrimentally causing bystander damage to surrounding cells and tissues. On the other hand, recent evidence supports the notion that an active complement pathway is a necessity for the normal maintenance of the neurosensory retina. In this scenario, complement activation appears to have beneficial effect as it promotes cell survival and tissue remodeling by facilitating the rapid removal of dying cells and resulting cellular debris, thus demonstrating anti-inflammatory and neuroprotective activities. In this review, we discuss both the beneficial and detrimental roles of CS in degenerative retina, focusing on the diverse aspects of CS functions that may promote or inhibit macular disease.

scholarly journals Delivery Systems of Retinoprotective Proteins in the Retina

2021 ◽  
Vol 22 (10) ◽  
pp. 5344
Author(s):  
Ivan T. Rebustini ◽  
Alexandra Bernardo-Colón ◽  
Alejandra Isasi Nalvarte ◽  
S. Patricia Becerra
Keyword(s):  
Endothelial Cells ◽  
Retinal Pigment Epithelium ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Delivery Systems ◽  
Rpe Cells ◽  
Retinal Tissue ◽  
Tissue Integrity ◽  
Pigment Epithelium Derived Factor ◽  
Degenerative Disorders

Retinoprotective proteins play important roles for retinal tissue integrity. They can directly affect the function and the survival of photoreceptors, and/or indirectly target the retinal pigment epithelium (RPE) and endothelial cells that support these tissues. Retinoprotective proteins are used in basic, translational and in clinical studies to prevent and treat human retinal degenerative disorders. In this review, we provide an overview of proteins that protect the retina and focus on pigment epithelium-derived factor (PEDF), and its effects on photoreceptors, RPE cells, and endothelial cells. We also discuss delivery systems such as pharmacologic and genetic administration of proteins to achieve photoreceptor survival and retinal tissue integrity.

Coupled Electro-Thermal-Mechanical Micro-Hotplate-Based for Micro Gas Pressure Sensor

2011 ◽  
Vol 204-210 ◽  
pp. 1086-1089
Author(s):  
Ren Cheng Jin ◽  
Ming Liang Shao ◽  
Li Sha Meng ◽  
Zhe Nan Tang ◽  
Jia Qi Wang
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Pressure Sensor ◽  
Rarefied Gas ◽  
Simulation Analysis ◽  
Theoretical Models ◽  
Gas Pressure ◽  
Coupled Analysis ◽  
Element Analysis ◽  
Heat Transfer Theory

In this paper, electro-thermal-mechanical theoretical analysis of micro-hotplate-based micro gas pressure sensor is carried out, which is on basis of the classical heat transfer theory and rarefied gas dynamics. Combined with micro-hotplate (MHP) theory analysis of heat transfer and thermal-mechanical finite element modeling, electro-thermal-mechanical coupled analysis of theoretical models with regard to the MHP-based micro gas pressure sensor is built. Then, through the ANSYS-one of the finite element analysis software-the simulation analysis of MHP went well. The simulation results show that MHP generates a smaller deformation because of adding the thermal conductivity, and MHP provides a more feasible analysis method in the theoretical study of micro hotplate.

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