Category Archives: Publications

Impact of Retinal Degeneration on Response of ON and OFF Cone Bipolar Cells to Electrical Stimulation

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We have a new manuscript from the lab in IEEE, Impact of Retinal Degeneration on Response of ON and OFF Cone Bipolar Cells to Electrical Stimulation. This manuscript is in collaboration with the Lazzi lab out of USC.  The first author, Shayan Farzad, Pragya Kosta, Ege Iseri, Steven T Walston, Jean-Marie C. Bouteiller,  Rebecca L. Pfeiffer @BeccaPfeiffer19, Crystal L. Sigulinsky @CSigulinsky, Jia-Hui Yang, Jessica C. Garcia, James R. Anderson, Bryan W. Jones @BWJones, and Gianluca Lazzi. The PDF is here.

Abstract: In retinal degenerative diseases, such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD), the photoreceptors become stressed and start to degenerate in the early stages of the disease. Retinal prosthetic devices have been developed to restore vision in patients by applying electrical stimulation to the surviving retinal cells. However, these devices provide limited visual perception as the therapeutic interventions are generally considered in the later stages of the disease when only inner retinal layer cells are left. A potential treatment option for retinal degenerative diseases in the early stages can be stimulating bipolar cells, which receive presynaptic signals from photoreceptors. In this work, we constructed computational models of healthy and degenerated (both ON and OFF-type) cone bipolar cells (CBCs) with realistic morphologies extracted from connectomes of the healthy and early-stage degenerated rabbit retina. We examined these cells’ membrane potential and axon terminal calcium current differences when subjected to electrical stimulation. In addition, we investigated how differently healthy and degenerated cells behave with respect to various stimulation parameters, including pulse duration and cells’ distance from the stimulating electrode. The results suggested that regardless of the position of the OFF CBCs in the retina model, there is not a significant difference between the membrane potential of healthy and degenerate cells when electrically stimulated. However, the healthy ON CBC axon terminal membrane potential rising time-constant is shorter (0.29 ± 0.03 ms) than the degenerated cells (0.8 ± 0.07 ms). Moreover, the ionic calcium channels at the axon terminals of the cells have a higher concentration and higher current in degenerated cells (32.24 ± 6.12 pA) than the healthy cells (13.64 ± 2.88 pA) independently of the cell’s position.

Distinctive Synaptic Structural Motifs Link Excitatory Retinal Interneurons To Diverse Postsynaptic Partner Types

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We have a new manuscript from the lab in Cell Reports, Distinctive Synaptic Structural Motifs Link Excitatory Retinal Interneurons To Diverse Postsynaptic Partner Types. This manuscript is in collaboration with the first author, Wan-Qing Yu @wanqing_yu, then co-authors Rachael Swanstrom, Crystal L. Sigulinsky @CSigulinsky, Richard M. Ahlquist, along with Sharm Knecht, myself Bryan W. Jones @BWJones. David M. Berson, and Rachel O. Wong. The PDF is here.

Abstract:
Neurons make converging and diverging synaptic connections with distinct partner types. Whether synapses involving separate partners demonstrate similar or distinct structural motifs is not yet well understood. We thus used serial electron microscopy in mouse retina to map output synapses of cone bipolar cells (CBCs) and compare their structural arrangements across bipolar types and postsynaptic partners. Three presynaptic configurations emerge—single-ribbon, ribbonless, and multiribbon synapses. Each CBC type exploits these arrangements in a unique combination, a feature also found among rabbit ON CBCs. Though most synapses are dyads, monads and triads are also seen. Altogether, mouse CBCs exhibit at least six motifs, and each CBC type uses these in a stereotypic pattern. Moreover, synapses between CBCs and particular partner types appear biased toward certain motifs. Our observations reveal synaptic strategies that diversify the output within and across CBC types, potentially shaping the distinct functions of retinal microcircuits.

Current Perspective on Retinal Remodeling: Implications for Therapeutics

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We have a new paper out of the lab, a perspectives paper on Retinal Remodeling: Implications for Therapeutics. (pdf here).

Authors are Rebecca L. Pfeiffer @BeccaPfeiffer19, and Bryan W. Jones @BWJones.

Abstract: The retinal degenerative diseases retinitis pigmentosa and age-related macular degeneration are a leading cause of irreversible vision loss. Both present with progressive photoreceptor degeneration that is further complicated by processes of retinal remodeling. In this perspective, we discuss the current state of the field of retinal remodeling and its implications for vision-restoring therapeutics currently in development. Here, we discuss the challenges and pitfalls retinal remodeling poses for each therapeutic strategy under the premise that understanding the features of retinal remodeling in totality will provide a basic framework with which therapeutics can interface. Additionally, we discuss the potential for approaching therapeutics using a combined strategy of using diffusible molecules in tandem with other vision-restoring therapeutics. We end by discussing the potential of the retina and retinal remodeling as a model system for more broadly understanding the progression of neurodegeneration across the central nervous system.

Revival Of Light Signalling In The Postmortem Mouse And Human Retina

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We have a new collaborative manuscript out in Nature, Revival of light signalling in the postmortem mouse and human retina. Full paper (here).

Authors: Fatima Abbas @neurofim, Silke Becker, Bryan W. Jones @BWJones, Ludovic S. Mure, Satchidananda Panda @SatchinPanda, Anne Hanneken & Frans Vinberg @fvinberg.

Abstract:
Death is defined as the irreversible cessation of circulatory, respiratory or brain activity. Many peripheral human organs can be transplanted from deceased donors using protocols to optimize viability. However, tissues from the central nervous system rapidly lose viability after circulation ceases, impeding their potential for transplantation. However, the time course and mechanisms causing neuronal death and the potential for revival remain poorly defined. Here, using the retina as a model of the central nervous system, we systemically examine the kinetics of death and neuronal revival. We demonstrate the swift decline of neuronal signalling and identify conditions for reviving synchronous in vivo-like trans-synaptic transmission in postmortem mouse and human retina. We measure light-evoked responses in human macular photoreceptors in eyes removed up to 5 h after death and identify modifiable factors that drive reversible and irreversible loss of light signalling after death. Finally, we quantify the rate-limiting deactivation reaction of phototransduction, a model G protein signalling cascade, in peripheral and macular human and macaque retina. Our approach will have broad applications and impact by enabling transformative studies in the human central nervous system, raising questions about the irreversibility of neuronal cell death, and providing new avenues for visual rehabilitation.

Peptide-Based Immunotherapy Against Oxidized Elastin Ameliorates Pathology In Mouse Model Of Smoke-Induced Ocular Injury

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We have a new collaborative manuscript out in iOVS, Peptide-Based Immunotherapy Against Oxidized Elastin Ameliorates Pathology In Mouse Model Of Smoke-Induced Ocular Injury. (pdf here)

Authors: Bärbel Rohrer, Nathaniel Parsons , Balasubramaniam Annamalai , Crystal Nicholson , Elisabeth Obert , Bryan Jones @BWJones, and Andrew D Dick.

Abstract:

Purpose: Age-related macular degeneration (AMD), the leading cause of blindness in western populations, is associated with an overactive complement system, and an increase in circulating antibodies against certain epitopes, including elastin. As loss of the elastin layer of Bruch’s membrane (BrM) has been reported in aging and AMD, we previously showed that immunization with elastin peptide oxidatively modified by cigarette smoke (ox-elastin), exacerbated ocular pathology in the smoke-induced ocular pathology (SIOP) model. Here we asked whether ox-elastin peptide-based immunotherapy (PIT) ameliorates damage.

Methods: C57BL/6J mice were injected with ox-elastin peptide at two doses via weekly subcutaneous administration, while exposed to cigarette smoke for 6 months. FcγR-/- and uninjected C57BL/6J mice served as controls. Retinal morphology was assessed by by electron microscopy, and complement activation, antibody deposition and mechanisms of immunological tolerance were assessed by Western blotting and ELISA.

Results: Elimination of Fcγ receptors, preventing antigen/antibody-dependent cytotoxicity, protected against SIOP. Mice receiving PIT with low dose ox-elastin (LD-PIT) exhibited reduced humoral immunity, reduced complement activation and IgG/IgM deposition in the RPE/choroid, and largely a preserved BrM. While there is no direct evidence of ox-elastin pathogenicity, LD-PIT reduced IFNγ and increased IL-4 within RPE/choroid. High dose PIT was not protective.

Conclusions: These data further support ox-elastin role in ocular damage in in part via elastin-specific antibodies, and support the corollary that PIT with ox-elastin attenuates ocular pathology. Overall, damage is associated with complement activation, antibody-dependent cell-mediated cytotoxicity, and altered cytokine signature.

Keywords: Age-related macular degeneration; Complement; Elastin; Peptide-based immunotherapy; Smoking.

Primary Cilia in Amacrine Cells in Retinal Development

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We have a new collaborative manuscript out in iOVS, Primary Cilia in Amacrine Cells in Retinal Development. (pdf here)

Authors: Ke Ning; Brent E. Sendayen; Tia J. Kowal; Biao Wang; Bryan W. Jones @BWJones; Yang Hu; and Yang Sun.

Abstract:

Purpose: Primary cilia are conserved organelles found in polarized cells within the eye that regulate cell growth, migration, and differentiation. Although the role of cilia in photoreceptors is well-studied, the formation of cilia in other retinal cell types has received little attention. In this study, we examined the ciliary profile focused on the inner nuclear layer of retinas in mice and rhesus macaque primates.

Methods: Retinal sections or flatmounts from Arl13b-Cetn2 tg transgenic mice were immunostained for cell markers (Pax6, Sox9, Chx10, Calbindin, Calretinin, ChaT, GAD67, Prox1, TH, and vGluT3) and analyzed by confocal microscopy. Primate retinal sections were immunostained for ciliary and cell markers (Pax6 and Arl13b). Optical coherence tomography (OCT) and ERGs were used to assess visual function of Vift88 mice.

Results: During different stages of mouse postnatal eye development, we found that cilia are present in Pax6-positive amacrine cells, which were also observed in primate retinas. The cilia of subtypes of amacrine cells in mice were shown by immunostaining and electron microscopy. We also removed primary cilia from vGluT3 amacrine cells in mouse and found no significant vision defects. In addition, cilia were present in the outer limiting membrane, suggesting that a population of Müller glial cells forms cilia.

Conclusions: We report that several subpopulations of amacrine cells in inner nuclear layers of the retina form cilia during early retinal development in mice and primates.

 

Natural Immunoglobulin M-based Delivery of a Complement Alternative Pathway Inhibitor in Mouse Models of Retinal Degeneration

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We have a new manuscript out in Experimental Eye Research, Natural Immunoglobulin M-based Delivery of a Complement Alternative Pathway Inhibitor in Mouse Models of Retinal Degeneration. (pdf here)

Authors: Balasubramaniam Annamalai, Nathaniel Parsons, Crystal Nicholson, Kusumam Joseph, Beth Coughlin, Xiaofeng Yang, Bryan W. Jones @BWJones, Stephen Tomlinson, and Bärbel Rohrer.

Abstract:

Purpose: Age-related macular degeneration is a slowly progressing disease. Studies have tied disease risk to an overactive complement system. We have previously demonstrated that pathology in two mouse models, the choroidal neovascularization (CNV) model and the smoke-induced ocular pathology (SIOP) model, can be reduced by specifically inhibiting the alternative complement pathway (AP). Here we report on the development of a novel injury-site targeted inhibitor of the alternative pathway, and its characterization in models of retinal degeneration.

Methods: Expression of the danger associated molecular pattern, a modified annexin IV, in injured ARPE-19 cells was confirmed by immunohistochemistry and complementation assays using B4 IgM mAb. Subsequently, a construct was prepared consisting of B4 single chain antibody (scFv) linked to a fragment of the alternative pathway inhibitor, fH (B4-scFv-fH). ARPE-19 cells stably expressing B4-scFv-fH were microencapsulated and administered intravitreally or subcutaneously into C57BL/6 J mice, followed by CNV induction or smoke exposure. Progression of CNV was analyzed using optical coherence tomography, and SIOP using structure-function analyses. B4-scFv-fH targeting and AP specificity was assessed by Western blot and binding experiments.

Results: B4-scFv-fH was secreted from encapsulated RPE and inhibited complement in RPE monolayers. B4-scFv-fH capsules reduced CNV and SIOP, and western blotting for C3a, C3d, IgM and IgG confirmed a reduction in complement activation and antibody binding in RPE/choroid.

Conclusions: Data supports a role for natural antibodies and neoepitope expression in ocular disease, and describes a novel strategy to target AP-specific complement inhibition to diseased tissue in the eye.

Precis: AMD risk is tied to an overactive complement system, and ocular injury is reduced by alternative pathway (AP) inhibition in experimental models. We developed a novel inhibitor of the AP that targets an injury-specific danger associated molecular pattern, and characterized it in disease models.

Keywords: Alternative pathway inhibitor; Choroidal neovascularization; Complement system; Encapsulated ARPE-19 cells; Natural antibody-mediated targeting; Smoke-induced ocular pathology.

Subretinal Rather Than Intravitreal Adeno-Associated Virus–Mediated Delivery of a Complement Alternative Pathway Inhibitor Is Effective in a Mouse Model of RPE Damage

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We have a new manuscript out in iOVS, Subretinal Rather Than Intravitreal Adeno-Associated Virus–Mediated Delivery of a Complement Alternative Pathway Inhibitor Is Effective in a Mouse Model of RPE Damage. (pdf here)

Authors: Balasubramaniam Annamalai; Nathaniel Parsons; Crystal Nicholson; Elisabeth Obert; Bryan W. Jones @BWJones; and Bärbel Rohrer.

Abstract:

Purpose: The risk for age-related macular degeneration has been tied to an overactive complement system. Despite combined attempts by academia and industry to develop therapeutics that modulate the complement response, particularly in the late geographic atrophy form of advanced AMD, to date, there is no effective treatment. We have previously demonstrated that pathology in the smoke-induced ocular pathology (SIOP) model, a model with similarities to dry AMD, is dependent on activation of the alternative complement pathway and that a novel complement activation site targeted inhibitor of the alternative pathway can be delivered to ocular tissues via an adeno-associated virus (AAV).

Methods: Two different viral vectors for specific tissue targeting were compared: AAV5-VMD2-CR2-fH for delivery to the retinal pigment epithelium (RPE) and AAV2YF-smCBA-CR2-fH for delivery to retinal ganglion cells (RGCs). Efficacy was tested in SIOP (6 months of passive smoke inhalation), assessing visual function (optokinetic responses), retinal structure (optical coherence tomography), and integrity of the RPE and Bruch’s membrane (electron microscopy). Protein chemistry was used to assess complement activation, CR2-fH tissue distribution, and CR2-fH transport across the RPE.

Results: RPE- but not RGC-mediated secretion of CR2-fH was found to reduce SIOP and complement activation in RPE/choroid. Bioavailability of CR2-fH in RPE/choroid could be confirmed only after AAV5-VMD2-CR2-fH treatment, and inefficient, adenosine triphosphate–dependent transport of CR2-fH across the RPE was identified.

Conclusions: Our results suggest that complement inhibition for AMD-like pathology is required basal to the RPE and argues in favor of AAV vector delivery to the RPE or outside the blood-retina barrier.

Model-Based Comparison of Current Flow in Rod Bipolar Cells of Healthy and Early-Stage Degenerated Retina

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We have a new manuscript out in Experimental Eye Research, Model-Based Comparison of Current Flow in Rod Bipolar Cells of Healthy and Early-Stage Degenerated Retina. (pdf here)

Authors: Pragya Kosta, Ege Iseri, Kyle Loizos, Javad Paknahad, Rebecca L. Pfeiffer @BeccaPfeiffer19, Crystal L. Sigulinsky @CLSigulinsky, James R. Anderson, Bryan W. Jones @BWJones, and Gianluca Lazzi.

Abstract: Retinal degenerative diseases, such as retinitis pigmentosa, are generally thought to initiate with the loss of photoreceptors, though recent work suggests that plasticity and remodeling occurs prior to photoreceptor cell loss. This degeneration subsequently leads to death of other retinal neurons, creating functional alterations and extensive remodeling of retinal networks. Retinal prosthetic devices stimulate the surviving retinal cells by applying external current using implanted electrodes. Although these devices restore partial vision, the quality of restored vision is limited. Further knowledge about the precise changes in degenerated retina as the disease progresses is essential to understand how current flows in retinas undergoing degenerative disease and to improve the performance of retinal prostheses. We developed computational models that describe current flow from rod photoreceptors to rod bipolar cells

 

Model-based Comparison of Current Flow in Rod Bipolar Cells of Healthy and Early-Stage Degenerated Retina

Chapter: Retinal Connectomics

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We have a new chapter out in the Elsevier book series The Senses, 2021.

Authors are myself, Bryan W. Jones @BWJones and Robert E. Marc @robertmarc60.

Abstract: The retina is both a light sensor and a highly complex image-processing device – like supercomputers at the backs of eyes. The retina is also wonderfully compact with all circuitry (glia, neurons, synapses and gap junctions) required to compute sensory input, making it a convenient model for understanding the rest of the nervous system. This is also true for disease, with early evidence indicating retina may be a good model for studying progressive neural degenerative diseases. Modern ultrastructural approaches to the study of neural connections is a relatively new !eld has been termed “connectomics”. Connectomics approaches applied to the retina is termed retinal connectomics. These approaches are relatively new !elds that leverage modern technologies in light and ultrastructural imaging, computational storage, and data management to allow tracking of neuronal identity and connectivity, delivering a robust edge/node network map of circuit topologies. Understanding circuit topologies is critical to understanding how retinas process information, and how information processing is corrupted in disease. This chapter summarizes early history, discusses technical aspects of imaging connectomes, justi!es the importance of why connectomics approaches are important, particularly in retina, discusses what has been learned from early efforts in connectomics, and points the way to the next steps.

Please email me: bryan.jones@m.cc.utah.edu if you would like a pdf of the chapter.