1
|
Hu A, Schmidt MHH, Heinig N. Microglia in retinal angiogenesis and diabetic retinopathy. Angiogenesis 2024; 27:311-331. [PMID: 38564108 PMCID: PMC11303477 DOI: 10.1007/s10456-024-09911-1] [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: 11/16/2023] [Accepted: 02/18/2024] [Indexed: 04/04/2024]
Abstract
Diabetic retinopathy has a high probability of causing visual impairment or blindness throughout the disease progression and is characterized by the growth of new blood vessels in the retina at an advanced, proliferative stage. Microglia are a resident immune population in the central nervous system, known to play a crucial role in regulating retinal angiogenesis in both physiological and pathological conditions, including diabetic retinopathy. Physiologically, they are located close to blood vessels and are essential for forming new blood vessels (neovascularization). In diabetic retinopathy, microglia become widely activated, showing a distinct polarization phenotype that leads to their accumulation around neovascular tufts. These activated microglia induce pathogenic angiogenesis through the secretion of various angiogenic factors and by regulating the status of endothelial cells. Interestingly, some subtypes of microglia simultaneously promote the regression of neovascularization tufts and normal angiogenesis in neovascularization lesions. Modulating the state of microglial activation to ameliorate neovascularization thus appears as a promising potential therapeutic approach for managing diabetic retinopathy.
Collapse
Affiliation(s)
- Aiyan Hu
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, Fetscherstr 74, 01307, Dresden, Germany
| | - Mirko H H Schmidt
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, Fetscherstr 74, 01307, Dresden, Germany.
| | - Nora Heinig
- Institute of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden School of Medicine, Fetscherstr 74, 01307, Dresden, Germany.
| |
Collapse
|
2
|
Zhang Y, Zhou A. Macrophage activation contributes to diabetic retinopathy. J Mol Med (Berl) 2024; 102:585-597. [PMID: 38429382 DOI: 10.1007/s00109-024-02437-5] [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: 12/04/2023] [Revised: 02/16/2024] [Accepted: 02/20/2024] [Indexed: 03/03/2024]
Abstract
Diabetic retinopathy (DR) is recognized as a neurovascular complication of diabetes, and emerging evidence underscores the pivotal role of inflammation in its pathophysiology. Macrophage activation is increasingly acknowledged as a key contributor to the onset and progression of DR. Different populations of macrophages originating from distinct sources contribute to DR-associated inflammation. Retinal macrophages can be broadly categorized into two main groups based on their origin: intrinsic macrophages situated within the retina and vitreoretinal interface and macrophages derived from infiltrating monocytes. The former comprises microglia (MG), perivascular macrophages, and macrophage-like hyalocytes. Retinal MG, as the principal population of tissue-resident population of mononuclear phagocytes, exhibits high heterogeneity and plasticity while serving as a crucial connector between retinal capillaries and synapses. This makes MG actively involved in the pathological processes across various stages of DR. Activated hyalocytes also contribute to the pathological progression of advanced DR. Additionally, recruited monocytes, displaying rapid turnover in circulation, augment the population of retinal macrophages during DR pathogenesis, exerting pathogenic or protective effect based on different subtypes. In this review, we examine novel perspectives on macrophage biology based on recent studies elucidating the diversity of macrophage identity and function, as well as the mechanisms influencing macrophage behavior. These insights may pave the way for innovative therapeutic strategies in the management of DR.
Collapse
Affiliation(s)
- Yi Zhang
- Department of Ophthalmology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710004, China
| | - Aiyi Zhou
- Department of Ophthalmology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, 710004, China.
| |
Collapse
|
3
|
Chen L, Cao Y, Shen Y, Li H, Ye R, Yao J. Downregulation of PIK3IP1 in retinal microglia promotes retinal pathological neovascularization via PI3K-AKT pathway activation. Sci Rep 2023; 13:12754. [PMID: 37550343 PMCID: PMC10406944 DOI: 10.1038/s41598-023-39473-z] [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: 03/30/2023] [Accepted: 07/26/2023] [Indexed: 08/09/2023] Open
Abstract
Retinal pathological neovascularization involves endothelial cells, pericytes, photoreceptor cells, ganglion cells, and glial cells, whose roles remain unclear. Using the Scissor algorithm, we found that microglia are associated with formation of fibrovascular membranes and can promote pathological neovascularization. GO and KEGG results showed that PI3K-AKT pathway activation in retinal microglia was associated with pathological neovascularization, and PIK3IP1 was associated with retinal microglia activation. Then we used PCR, Western blot and Elisa techniques to confirm that the expression of VEGFA, FGF2, HGFα and MMP9 was increased in microglia after Lipopolysaccharide (LPS) induction. We also used cell flow cytometry and OIR models to verify the role of PI3K-AKT pathway and PIK3IP1 in microglia. Targeting of PIK3IP1 regulated the activation of the PI3K-AKT pathway in microglia, microglia function activation, and pro-angiogenic effects. These findings reveal the role of M1-type microglia in pathological neovascularization and suggests that targeting the PI3K-AKT pathway in microglia may be a new strategy for treating retinal pathological neovascularization.
Collapse
Affiliation(s)
- Lushu Chen
- The Fourth School of Clinical Medicine, Nanjing Medical University, Nanjing, China
- The Affiliated Eye Hospital, Nanjing Medical University, 138 Han Zhong Road, Nanjing, 210029, China
| | - Yuan Cao
- The Fourth School of Clinical Medicine, Nanjing Medical University, Nanjing, China
- The Affiliated Eye Hospital, Nanjing Medical University, 138 Han Zhong Road, Nanjing, 210029, China
| | - Yaming Shen
- The Fourth School of Clinical Medicine, Nanjing Medical University, Nanjing, China
- The Affiliated Eye Hospital, Nanjing Medical University, 138 Han Zhong Road, Nanjing, 210029, China
| | - Huan Li
- The Fourth School of Clinical Medicine, Nanjing Medical University, Nanjing, China
- The Affiliated Eye Hospital, Nanjing Medical University, 138 Han Zhong Road, Nanjing, 210029, China
| | - Rong Ye
- The Fourth School of Clinical Medicine, Nanjing Medical University, Nanjing, China
- The Affiliated Eye Hospital, Nanjing Medical University, 138 Han Zhong Road, Nanjing, 210029, China
| | - Jin Yao
- The Fourth School of Clinical Medicine, Nanjing Medical University, Nanjing, China.
- The Affiliated Eye Hospital, Nanjing Medical University, 138 Han Zhong Road, Nanjing, 210029, China.
| |
Collapse
|
4
|
Wang X, Wang T, Lam E, Alvarez D, Sun Y. Ocular Vascular Diseases: From Retinal Immune Privilege to Inflammation. Int J Mol Sci 2023; 24:12090. [PMID: 37569464 PMCID: PMC10418793 DOI: 10.3390/ijms241512090] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/21/2023] [Accepted: 07/26/2023] [Indexed: 08/13/2023] Open
Abstract
The eye is an immune privileged tissue that insulates the visual system from local and systemic immune provocation to preserve homeostatic functions of highly specialized retinal neural cells. If immune privilege is breached, immune stimuli will invade the eye and subsequently trigger acute inflammatory responses. Local resident microglia become active and release numerous immunological factors to protect the integrity of retinal neural cells. Although acute inflammatory responses are necessary to control and eradicate insults to the eye, chronic inflammation can cause retinal tissue damage and cell dysfunction, leading to ocular disease and vision loss. In this review, we summarized features of immune privilege in the retina and the key inflammatory responses, factors, and intracellular pathways activated when retinal immune privilege fails, as well as a highlight of the recent clinical and research advances in ocular immunity and ocular vascular diseases including retinopathy of prematurity, age-related macular degeneration, and diabetic retinopathy.
Collapse
Affiliation(s)
- Xudong Wang
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| | - Tianxi Wang
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| | - Enton Lam
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| | - David Alvarez
- Department of Immunology, Harvard Medical School, Boston, MA 02115, USA
| | - Ye Sun
- Department of Ophthalmology, Harvard Medical School, Boston Children’s Hospital, Boston, MA 02115, USA; (X.W.)
| |
Collapse
|
5
|
Padovani-Claudio DA, Ramos CJ, Capozzi ME, Penn JS. Elucidating glial responses to products of diabetes-associated systemic dyshomeostasis. Prog Retin Eye Res 2023; 94:101151. [PMID: 37028118 PMCID: PMC10683564 DOI: 10.1016/j.preteyeres.2022.101151] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 11/21/2022] [Accepted: 11/22/2022] [Indexed: 04/08/2023]
Abstract
Diabetic retinopathy (DR) is a leading cause of blindness in working age adults. DR has non-proliferative stages, characterized in part by retinal neuroinflammation and ischemia, and proliferative stages, characterized by retinal angiogenesis. Several systemic factors, including poor glycemic control, hypertension, and hyperlipidemia, increase the risk of DR progression to vision-threatening stages. Identification of cellular or molecular targets in early DR events could allow more prompt interventions pre-empting DR progression to vision-threatening stages. Glia mediate homeostasis and repair. They contribute to immune surveillance and defense, cytokine and growth factor production and secretion, ion and neurotransmitter balance, neuroprotection, and, potentially, regeneration. Therefore, it is likely that glia orchestrate events throughout the development and progression of retinopathy. Understanding glial responses to products of diabetes-associated systemic dyshomeostasis may reveal novel insights into the pathophysiology of DR and guide the development of novel therapies for this potentially blinding condition. In this article, first, we review normal glial functions and their putative roles in the development of DR. We then describe glial transcriptome alterations in response to systemic circulating factors that are upregulated in patients with diabetes and diabetes-related comorbidities; namely glucose in hyperglycemia, angiotensin II in hypertension, and the free fatty acid palmitic acid in hyperlipidemia. Finally, we discuss potential benefits and challenges associated with studying glia as targets of DR therapeutic interventions. In vitro stimulation of glia with glucose, angiotensin II and palmitic acid suggests that: 1) astrocytes may be more responsive than other glia to these products of systemic dyshomeostasis; 2) the effects of hyperglycemia on glia are likely to be largely osmotic; 3) fatty acid accumulation may compound DR pathophysiology by promoting predominantly proinflammatory and proangiogenic transcriptional alterations of macro and microglia; and 4) cell-targeted therapies may offer safer and more effective avenues for DR treatment as they may circumvent the complication of pleiotropism in retinal cell responses. Although several molecules previously implicated in DR pathophysiology are validated in this review, some less explored molecules emerge as potential therapeutic targets. Whereas much is known regarding glial cell activation, future studies characterizing the role of glia in DR and how their activation is regulated and sustained (independently or as part of retinal cell networks) may help elucidate mechanisms of DR pathogenesis and identify novel drug targets for this blinding disease.
Collapse
Affiliation(s)
- Dolly Ann Padovani-Claudio
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, B3321A Medical Center North, 1161 21st Avenue South, Nashville, TN, 37232-0011, USA.
| | - Carla J Ramos
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, AA1324 Medical Center North, 1161 21st Avenue South, Nashville, TN, 37232-0011, USA.
| | - Megan E Capozzi
- Duke Molecular Physiology Institute, Duke University School of Medicine, 300 North Duke Street, Durham, NC, 27701, USA.
| | - John S Penn
- Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, B3307 Medical Center North, 1161 21st Avenue South, Nashville, TN, 37232-0011, USA.
| |
Collapse
|
6
|
Goyal M, Bordt AS, Neitz J, Marshak DW. Trogocytosis of neurons and glial cells by microglia in a healthy adult macaque retina. Sci Rep 2023; 13:633. [PMID: 36635325 PMCID: PMC9837165 DOI: 10.1038/s41598-023-27453-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 01/02/2023] [Indexed: 01/13/2023] Open
Abstract
Microglial cells are the primary resident immune cells in the retina. In healthy adults, they are ramified; that is, they have extensive processes that move continually. In adult retinas, microglia maintain the normal structure and function of neurons and other glial cells, but the mechanism underlying this process is not well-understood. In the mouse hippocampus, microglia engulf small pieces of axons and presynaptic terminals via a process called trogocytosis. Here we report that microglia in the adult macaque retina also engulf pieces of neurons and glial cells, but not at sites of synapses. We analyzed microglia in a volume of serial, ultrathin sections of central macaque retina in which many neurons that ramify in the inner plexiform layer (IPL) had been reconstructed previously. We surveyed the IPL and identified the somas of microglia by their small size and scant cytoplasm. We then reconstructed the microglia and studied their interactions with other cells. We found that ramified microglia frequently ingested small pieces of each major type of inner retinal neuron and Müller glial cells via trogocytosis. There were a few instances where the interactions took place near synapses, but the synapses, themselves, were never engulfed. If trogocytosis by retinal microglia plays a role in synaptic remodeling, it was not apparent from the ultrastructure. Instead, we propose that trogocytosis enables these microglia to present antigens derived from normal inner retinal cells and, when activated, they would promote antigen-specific tolerance.
Collapse
Affiliation(s)
- Megan Goyal
- Department of Neurobiology and Anatomy, McGovern Medical School, Houston, TX, USA
| | - Andrea S Bordt
- Department of Neurobiology and Anatomy, McGovern Medical School, Houston, TX, USA
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - Jay Neitz
- Department of Ophthalmology, University of Washington, Seattle, WA, USA
| | - David W Marshak
- Department of Neurobiology and Anatomy, McGovern Medical School, Houston, TX, USA.
| |
Collapse
|
7
|
Boneva SK, Wolf J, Wieghofer P, Sebag J, Lange CAK. Hyalocyte functions and immunology. EXPERT REVIEW OF OPHTHALMOLOGY 2022. [DOI: 10.1080/17469899.2022.2100763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Stefaniya K Boneva
- Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Julian Wolf
- Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Peter Wieghofer
- Cellular Neuroanatomy, Institute of Theoretical Medicine, Medical Faculty, University of Augsburg, Augsburg, Germany
| | - J Sebag
- Doheny Eye Institute, UCLA, Pasadena, CA, USA
- UCLA Geffen School of Medicine, Los Angeles, CA, USA
- VMR Institute for Vitreous Macula Retina, Huntington Beach, California, USA
| | - Clemens AK Lange
- Eye Center, Medical Center, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Ophtha-Lab, Department of Ophthalmology at St. Franziskus Hospital, Muenster, Germany
| |
Collapse
|
8
|
Rosmus DD, Lange C, Ludwig F, Ajami B, Wieghofer P. The Role of Osteopontin in Microglia Biology: Current Concepts and Future Perspectives. Biomedicines 2022; 10:biomedicines10040840. [PMID: 35453590 PMCID: PMC9027630 DOI: 10.3390/biomedicines10040840] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/26/2022] [Accepted: 03/27/2022] [Indexed: 12/14/2022] Open
Abstract
The innate immune landscape of the central nervous system (CNS), including the brain and the retina, consists of different myeloid cell populations with distinct tasks to fulfill. Whereas the CNS borders harbor extraparenchymal CNS-associated macrophages whose main duty is to build up a defense against invading pathogens and other damaging factors from the periphery, the resident immune cells of the CNS parenchyma and the retina, microglia, are highly dynamic cells with a plethora of functions during homeostasis and disease. Therefore, microglia are constantly sensing their environment and closely interacting with surrounding cells, which is in part mediated by soluble factors. One of these factors is Osteopontin (OPN), a multifunctional protein that is produced by different cell types in the CNS, including microglia, and is upregulated in neurodegenerative and neuroinflammatory conditions. In this review, we discuss the current literature about the interaction between microglia and OPN in homeostasis and several disease entities, including multiple sclerosis (MS), Alzheimer’s and cerebrovascular diseases (AD, CVD), amyotrophic lateral sclerosis (ALS), age-related macular degeneration (AMD) and diabetic retinopathy (DR), in the context of the molecular pathways involved in OPN signaling shaping the function of microglia. As nearly all CNS diseases are characterized by pathological alterations in microglial cells, accompanied by the disturbance of the homeostatic microglia phenotype, the emergence of disease-associated microglia (DAM) states and their interplay with factors shaping the DAM-signature, such as OPN, is of great interest for therapeutical interventions in the future.
Collapse
Affiliation(s)
| | - Clemens Lange
- Eye Center, Freiburg Medical Center, University of Freiburg, 79106 Freiburg, Germany; (C.L.); (F.L.)
- Ophtha-Lab, Department of Ophthalmology, St. Franziskus Hospital, 48145 Muenster, Germany
| | - Franziska Ludwig
- Eye Center, Freiburg Medical Center, University of Freiburg, 79106 Freiburg, Germany; (C.L.); (F.L.)
| | - Bahareh Ajami
- Department of Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA;
| | - Peter Wieghofer
- Institute of Anatomy, Leipzig University, 04103 Leipzig, Germany;
- Cellular Neuroanatomy, Institute of Theoretical Medicine, Medical Faculty, Augsburg University, 86159 Augsburg, Germany
- Correspondence:
| |
Collapse
|