Diabetes Metab J.  2018 Oct;42(5):364-376. 10.4093/dmj.2018.0182.

Pathophysiology of Diabetic Retinopathy: The Old and the New

• Kusuhara S
• Fukushima
• Ogura S
• Inoue N
• Uemura A

• KMID: 2422781
• DOI: http://doi.org/10.4093/dmj.2018.0182

Abstract

Vision loss in diabetic retinopathy (DR) is ascribed primarily to retinal vascular abnormalities"”including hyperpermeability, hypoperfusion, and neoangiogenesis"”that eventually lead to anatomical and functional alterations in retinal neurons and glial cells. Recent advances in retinal imaging systems using optical coherence tomography technologies and pharmacological treatments using anti-vascular endothelial growth factor drugs and corticosteroids have revolutionized the clinical management of DR. However, the cellular and molecular mechanisms underlying the pathophysiology of DR are not fully determined, largely because hyperglycemic animal models only reproduce limited aspects of subclinical and early DR. Conversely, non-diabetic mouse models that represent the hallmark vascular disorders in DR, such as pericyte deficiency and retinal ischemia, have provided clues toward an understanding of the sequential events that are responsible for vision-impairing conditions. In this review, we summarize the clinical manifestations and treatment modalities of DR, discuss current and emerging concepts with regard to the pathophysiology of DR, and introduce perspectives on the development of new drugs, emphasizing the breakdown of the blood-retina barrier and retinal neovascularization.

Keyword

Angiopoietins; Blood-retina barrier; Diabetic retinopathy; Endothelial cells; Macular edema; Pericytes; Retinal neovascularization; Vascular endothelial growth factors

MeSH Terms

Adrenal Cortex Hormones
Angiopoietins
Animals
Diabetic Retinopathy*
Endothelial Cells
Endothelial Growth Factors
Ischemia
Macular Edema
Mice
Models, Animal
Neuroglia
Pericytes
Retinal Neovascularization
Retinal Neurons
Retinaldehyde
Tomography, Optical Coherence
Vascular Endothelial Growth Factors
Adrenal Cortex Hormones
Angiopoietins
Endothelial Growth Factors
Retinaldehyde
Vascular Endothelial Growth Factors

Figure

• 

  Fig. 1 Clinical features of diabetic retinopathy (DR). (A) Pseudo-colored fundus (left) and fluorescein angiography (right) images from ultra-widefield ophthalmoscopy. Note the elevated leakage of fluorescein dye in the macular area in non-proliferative DR (NPDR) and from aberrant neovascularization (NV) in proliferative DR (PDR). Dark areas in fluorescein angiography represent vascular non-perfusion (NP). (B) Cross-sectional macular images from optical coherence tomography (OCT). Note the recurrence of diabetic macular edema (DME) at 3 months after intravitreal anti-vascular endothelial growth factor injection. (C) Superficial and deep retinal vessel images from OCT angiography. Note the microaneurysms and enlargement of the foveal avascular zone in NPDR. HE, hard exudate; VH, vitreous hemorrhage.

• 

  Fig. 2 Schematic of key cellular and molecular events in the progression of diabetic retinopathy. Hyperglycemia initiates oxidative stress, epigenetic modifications, and inflammation in vascular endothelial cells (ECs). Neuroglial degeneration precedes microvascular changes. Pericyte loss from vessel walls sensitizes ECs to microenvironmental stimuli. Infiltrating macrophages secrete vascular endothelial growth factor (VEGF) A and placental growth factor (PlGF). A positive feedback loop between angiopoietin-2 (Ang2) and a forkhead box transcription factor, forkhead Box O1 (FOXO1), in ECs further destabilizes vessel integrity. These events form a cycle of vessel damage, leading to the breakdown of the blood-retina barrier. Retinal hypoxia resulting from vessel occlusion induces extra-retinal neoangiogenesis accompanied by fibrovascular membrane formation. Throughout these processes, signal transduction via the mitogen-activated protein kinase (MAPK) and the phosphatidyl inositol 3-kinase (PI3K)/Akt pathways downstream of VEGF receptor (VEGFR) 2 in ECs is pivotal in retinal angiogenesis and vascular leakage. Tie2, tyrosine kinase with immunoglobulin-like loops and epidermal growth factor homology domains 2.

Reference

1. Yau JW, Rogers SL, Kawasaki R, Lamoureux EL, Kowalski JW, Bek T, Chen SJ, Dekker JM, Fletcher A, Grauslund J, Haffner S, Hamman RF, Ikram MK, Kayama T, Klein BE, Klein R, Krishnaiah S, Mayurasakorn K, O'Hare JP, Orchard TJ, Porta M, Rema M, Roy MS, Sharma T, Shaw J, Taylor H, Tielsch JM, Varma R, Wang JJ, Wang N, West S, Xu L, Yasuda M, Zhang X, Mitchell P, Wong TY. Meta-Analysis for Eye Disease (META-EYE) Study Group. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care. 2012; 35:556–564.

2. Wong TY, Sun J, Kawasaki R, Ruamviboonsuk P, Gupta N, Lansingh VC, Maia M, Mathenge W, Moreker S, Muqit MMK, Resnikoff S, Verdaguer J, Zhao P, Ferris F, Aiello LP, Taylor HR. Guidelines on diabetic eye care: the International Council of Ophthalmology Recommendations for screening, follow-up, referral, and treatment based on resource settings. Ophthalmology. 2018; 125:1608–1622.

3. Solomon SD, Chew E, Duh EJ, Sobrin L, Sun JK, VanderBeek BL, Wykoff CC, Gardner TW. Diabetic retinopathy: a position statement by the American Diabetes Association. Diabetes Care. 2017; 40:412–418.

4. Arichika S, Uji A, Murakami T, Unoki N, Yoshitake S, Dodo Y, Ooto S, Miyamoto K, Yoshimura N. Retinal hemorheologic characterization of early-stage diabetic retinopathy using adaptive optics scanning laser ophthalmoscopy. Invest Ophthalmol Vis Sci. 2014; 55:8513–8522.

5. Lammer J, Prager SG, Cheney MC, Ahmed A, Radwan SH, Burns SA, Silva PS, Sun JK. Cone photoreceptor irregularity on adaptive optics scanning laser ophthalmoscopy correlates with severity of diabetic retinopathy and macular edema. Invest Ophthalmol Vis Sci. 2016; 57:6624–6632.

6. Bearse MA Jr, Adams AJ, Han Y, Schneck ME, Ng J, Bronson-Castain K, Barez S. A multifocal electroretinogram model predicting the development of diabetic retinopathy. Prog Retin Eye Res. 2006; 25:425–448.

7. Schmidt-Erfurth U, Sadeghipour A, Gerendas BS, Waldstein SM, Bogunovic H. Artificial intelligence in retina. Prog Retin Eye Res. 2018; 08. 01. [Epub]. DOI: 10.1016/j.preteyeres.2018.07.004.

8. Feldman-Billard S, Larger E, Massin P. Standards for screeningand surveillance of ocular complications in people with diabetes SFD study group. Early worsening of diabetic retinopathy after rapid improvement of blood glucose control in patients with diabetes. Diabetes Metab. 2018; 44:4–14.

9. Bressler NM, Beck RW, Ferris FL 3rd. Panretinal photocoagulation for proliferative diabetic retinopathy. N Engl J Med. 2011; 365:1520–1526.

10. Unoki N, Nishijima K, Kita M, Suzuma K, Watanabe D, Oh H, Kimura T, Sakamoto A, Yoshimura N. Randomised controlled trial of posterior sub-Tenon triamcinolone as adjunct to panretinal photocoagulation for treatment of diabetic retinopathy. Br J Ophthalmol. 2009; 93:765–770.

11. Das A, McGuire PG, Rangasamy S. Diabetic macular edema: pathophysiology and novel therapeutic targets. Ophthalmology. 2015; 122:1375–1394.

12. Daruich A, Matet A, Moulin A, Kowalczuk L, Nicolas M, Sellam A, Rothschild PR, Omri S, Gelize E, Jonet L, Delaunay K, De Kozak Y, Berdugo M, Zhao M, Crisanti P, Behar-Cohen F. Mechanisms of macular edema: beyond the surface. Prog Retin Eye Res. 2018; 63:20–68.

13. Klaassen I, Van Noorden CJ, Schlingemann RO. Molecular basis of the inner blood-retinal barrier and its breakdown in diabetic macular edema and other pathological conditions. Prog Retin Eye Res. 2013; 34:19–48.

14. Early Treatment Diabetic Retinopathy Study report number 1. Early Treatment Diabetic Retinopathy Study research group. Photocoagulation for diabetic macular edema. Arch Ophthalmol. 1985; 103:1796–1806.

15. Early Treatment Diabetic Retinopathy Study Report Number 2. Early Treatment Diabetic Retinopathy Study Research Group. Treatment techniques and clinical guidelines for photocoagulation of diabetic macular edema. Ophthalmology. 1987; 94:761–774.

16. Ferrara N, Adamis AP. Ten years of anti-vascular endothelial growth factor therapy. Nat Rev Drug Discov. 2016; 15:385–403.

17. van Asten F, Michels CTJ, Hoyng CB, van der Wilt GJ, Klevering BJ, Rovers MM, Grutters JPC. The cost-effectiveness of bevacizumab, ranibizumab and aflibercept for the treatment of age-related macular degeneration: a cost-effectiveness analysis from a societal perspective. PLoS One. 2018; 13:e0197670.

18. Lally DR, Shah CP, Heier JS. Vascular endothelial growth factor and diabetic macular edema. Surv Ophthalmol. 2016; 61:759–768.

19. Bolinger MT, Antonetti DA. Moving past anti-VEGF: novel therapies for treating diabetic retinopathy. Int J Mol Sci. 2016; 17:E1498.

20. Diabetic Retinopathy Clinical Research Network Writing Committee. Haller JA, Qin H, Apte RS, Beck RR, Bressler NM, Browning DJ, Danis RP, Glassman AR, Googe JM, Kollman C, Lauer AK, Peters MA, Stockman ME. Vitrectomy outcomes in eyes with diabetic macular edema and vitreomacular traction. Ophthalmology. 2010; 117:1087–1093.

21. Cheung N, Mitchell P, Wong TY. Diabetic retinopathy. Lancet. 2010; 376:124–136.

22. Shu DY, Lovicu FJ. Myofibroblast transdifferentiation: the dark force in ocular wound healing and fibrosis. Prog Retin Eye Res. 2017; 60:44–65.

23. Nguyen QD, Brown DM, Marcus DM, Boyer DS, Patel S, Feiner L, Gibson A, Sy J, Rundle AC, Hopkins JJ, Rubio RG, Ehrlich JS. RISE and RIDE Research Group. Ranibizumab for diabetic macular edema: results from 2 phase III randomized trials: RISE and RIDE. Ophthalmology. 2012; 119:789–801.

24. Mitchell P, McAllister I, Larsen M, Staurenghi G, Korobelnik JF, Boyer DS, Do DV, Brown DM, Katz TA, Berliner A, Vitti R, Zeitz O, Metzig C, Lu C, Holz FG. Evaluating the impact of intravitreal aflibercept on diabetic retinopathy progression in the VIVID-DME and VISTA-DME studies. Ophthalmol Retina. 2018; 2:988–996.

25. Krick TW, Bressler NM. Recent clinically relevant highlights from the Diabetic Retinopathy Clinical Research Network. Curr Opin Ophthalmol. 2018; 29:199–205.

26. Writing Committee for the Diabetic Retinopathy Clinical Research Network. Gross JG, Glassman AR, Jampol LM, Inusah S, Aiello LP, Antoszyk AN, Baker CW, Berger BB, Bressler NM, Browning D, Elman MJ, Ferris FL 3rd, Friedman SM, Marcus DM, Melia M, Stockdale CR, Sun JK, Beck RW. Panretinal photocoagulation vs intravitreous ranibizumab for proliferative diabetic retinopathy: a randomized clinical trial. JAMA. 2015; 314:2137–2146.

27. Sivaprasad S, Prevost AT, Vasconcelos JC, Riddell A, Murphy C, Kelly J, Bainbridge J, Tudor-Edwards R, Hopkins D, Hykin P. CLARITY Study Group. Clinical efficacy of intravitreal aflibercept versus panretinal photocoagulation for best corrected visual acuity in patients with proliferative diabetic retinopathy at 52 weeks (CLARITY): a multicentre, single-blinded, randomised, controlled, phase 2b, non-inferiority trial. Lancet. 2017; 389:2193–2203.

28. Bressler SB, Beaulieu WT, Glassman AR, Gross JG, Jampol LM, Melia M, Peters MA, Rauser ME. Diabetic Retinopathy Clinical Research Network. Factors associated with worsening proliferative diabetic retinopathy in eyes treated with panretinal photocoagulation or ranibizumab. Ophthalmology. 2017; 124:431–439.

29. Robinson R, Barathi VA, Chaurasia SS, Wong TY, Kern TS. Update on animal models of diabetic retinopathy: from molecular approaches to mice and higher mammals. Dis Model Mech. 2012; 5:444–456.

30. Nakao S, Arita R, Nakama T, Yoshikawa H, Yoshida S, Enaida H, Hafezi-Moghadam A, Matsui T, Ishibashi T. Wide-field laser ophthalmoscopy for mice: a novel evaluation system for retinal/choroidal angiogenesis in mice. Invest Ophthalmol Vis Sci. 2013; 54:5288–5293.

31. Park JR, Choi W, Hong HK, Kim Y, Jun Park S, Hwang Y, Kim P, Woo SJ, Park KH, Oh WY. Imaging laser-induced choroidal neovascularization in the rodent retina using optical coherence tomography angiography. Invest Ophthalmol Vis Sci. 2016; 57:OCT331–OCT340.

32. Ikeda W, Nakatani T, Uemura A. Cataract-preventing contact lens for in vivo imaging of mouse retina. Biotechniques. 2018; 65:101–104.

33. Ruberte J, Ayuso E, Navarro M, Carretero A, Nacher V, Haurigot V, George M, Llombart C, Casellas A, Costa C, Bosch A, Bosch F. Increased ocular levels of IGF-1 in transgenic mice lead to diabetes-like eye disease. J Clin Invest. 2004; 113:1149–1157.

34. Ran FA, Hsu PD, Wright J, Agarwala V, Scott DA, Zhang F. Genome engineering using the CRISPR-Cas9 system. Nat Protoc. 2013; 8:2281–2308.

35. Giacco F, Brownlee M. Oxidative stress and diabetic complications. Circ Res. 2010; 107:1058–1070.

36. Reddy MA, Zhang E, Natarajan R. Epigenetic mechanisms in diabetic complications and metabolic memory. Diabetologia. 2015; 58:443–455.

37. Friedrichs P, Schlotterer A, Sticht C, Kolibabka M, Wohlfart P, Dietrich A, Linn T, Molema G, Hammes HP. Hyperglycaemic memory affects the neurovascular unit of the retina in a diabetic mouse model. Diabetologia. 2017; 60:1354–1358.

38. Aiello LP. DCCT/EDIC Research Group. Diabetic retinopathy and other ocular findings in the diabetes control and complications trial/epidemiology of diabetes interventions and complications study. Diabetes Care. 2014; 37:17–23.

39. El-Osta A, Brasacchio D, Yao D, Pocai A, Jones PL, Roeder RG, Cooper ME, Brownlee M. Transient high glucose causes persistent epigenetic changes and altered gene expression during subsequent normoglycemia. J Exp Med. 2008; 205:2409–2417.

40. Rubsam A, Parikh S, Fort PE. Role of inflammation in diabetic retinopathy. Int J Mol Sci. 2018; 19:E942.

41. Wykoff CC. Impact of intravitreal pharmacotherapies including antivascular endothelial growth factor and corticosteroid agents on diabetic retinopathy. Curr Opin Ophthalmol. 2017; 28:213–218.

42. Miyamoto K, Khosrof S, Bursell SE, Rohan R, Murata T, Clermont AC, Aiello LP, Ogura Y, Adamis AP. Prevention of leukostasis and vascular leakage in streptozotocin-induced diabetic retinopathy via intercellular adhesion molecule-1 inhibition. Proc Natl Acad Sci U S A. 1999; 96:10836–10841.

43. Sohn EH, van Dijk HW, Jiao C, Kok PH, Jeong W, Demirkaya N, Garmager A, Wit F, Kucukevcilioglu M, van Velthoven ME, DeVries JH, Mullins RF, Kuehn MH, Schlingemann RO, Sonka M, Verbraak FD, Abramoff MD. Retinal neurodegeneration may precede microvascular changes characteristic of diabetic retinopathy in diabetes mellitus. Proc Natl Acad Sci U S A. 2016; 113:E2655–E2664.

44. van Dijk HW, Kok PH, Garvin M, Sonka M, Devries JH, Michels RP, van Velthoven ME, Schlingemann RO, Verbraak FD, Abramoff MD. Selective loss of inner retinal layer thickness in type 1 diabetic patients with minimal diabetic retinopathy. Invest Ophthalmol Vis Sci. 2009; 50:3404–3409.

45. Santos AR, Ribeiro L, Bandello F, Lattanzio R, Egan C, Frydkjaer-Olsen U, Garcia-Arumi J, Gibson J, Grauslund J, Harding SP, Lang GE, Massin P, Midena E, Scanlon P, Aldington SJ, Simao S, Schwartz C, Ponsati B, Porta M, Costa MA, Hernandez C, Cunha-Vaz J, Simo R. European Consortium for the Early Treatment of Diabetic Retinopathy (EUROCONDOR). Functional and structural findings of neurodegeneration in early stages of diabetic retinopathy: cross-sectional analyses of baseline data of the EUROCONDOR project. Diabetes. 2017; 66:2503–2510.

46. Barber AJ, Lieth E, Khin SA, Antonetti DA, Buchanan AG, Gardner TW. Neural apoptosis in the retina during experimental and human diabetes. Early onset and effect of insulin. J Clin Invest. 1998; 102:783–791.

47. Simo R, Hernandez C. European Consortium for the Early Treatment of Diabetic Retinopathy (EUROCONDOR). Neurodegeneration in the diabetic eye: new insights and therapeutic perspectives. Trends Endocrinol Metab. 2014; 25:23–33.

48. Barber AJ, Baccouche B. Neurodegeneration in diabetic retinopathy: potential for novel therapies. Vision Res. 2017; 139:82–92.

49. Campochiaro PA, Aiello LP, Rosenfeld PJ. Anti-vascular endothelial growth factor agents in the treatment of retinal disease: from bench to bedside. Ophthalmology. 2016; 123:S78–S88.

50. Senger DR, Galli SJ, Dvorak AM, Perruzzi CA, Harvey VS, Dvorak HF. Tumor cells secrete a vascular permeability factor that promotes accumulation of ascites fluid. Science. 1983; 219:983–985.

51. Leung DW, Cachianes G, Kuang WJ, Goeddel DV, Ferrara N. Vascular endothelial growth factor is a secreted angiogenic mitogen. Science. 1989; 246:1306–1309.

52. Aiello LP, Avery RL, Arrigg PG, Keyt BA, Jampel HD, Shah ST, Pasquale LR, Thieme H, Iwamoto MA, Park JE, Nguyen HV, Aiello LM, Ferrara N, King GL. Vascular endothelial growth factor in ocular fluid of patients with diabetic retinopathy and other retinal disorders. N Engl J Med. 1994; 331:1480–1487.

53. Tolentino MJ, Miller JW, Gragoudas ES, Jakobiec FA, Flynn E, Chatzistefanou K, Ferrara N, Adamis AP. Intravitreous injections of vascular endothelial growth factor produce retinal ischemia and microangiopathy in an adult primate. Ophthalmology. 1996; 103:1820–1828.

54. Simons M, Gordon E, Claesson-Welsh L. Mechanisms and regulation of endothelial VEGF receptor signalling. Nat Rev Mol Cell Biol. 2016; 17:611–625.

55. Koch S, Claesson-Welsh L. Signal transduction by vascular endothelial growth factor receptors. Cold Spring Harb Perspect Med. 2012; 2:a006502.

56. Miller JW, Le Couter J, Strauss EC, Ferrara N. Vascular endothelial growth factor a in intraocular vascular disease. Ophthalmology. 2013; 120:106–114.

57. Hiratsuka S, Minowa O, Kuno J, Noda T, Shibuya M. Flt-1 lacking the tyrosine kinase domain is sufficient for normal development and angiogenesis in mice. Proc Natl Acad Sci U S A. 1998; 95:9349–9354.

58. Murakami M, Iwai S, Hiratsuka S, Yamauchi M, Nakamura K, Iwakura Y, Shibuya M. Signaling of vascular endothelial growth factor receptor-1 tyrosine kinase promotes rheumatoid arthritis through activation of monocytes/macrophages. Blood. 2006; 108:1849–1856.

59. Mesquita J, Castro-de-Sousa JP, Vaz-Pereira S, Neves A, Passarinha LA, Tomaz CT. Vascular endothelial growth factors and placenta growth factor in retinal vasculopathies: current research and future perspectives. Cytokine Growth Factor Rev. 2018; 39:102–115.

60. Saint-Geniez M, Maharaj AS, Walshe TE, Tucker BA, Sekiyama E, Kurihara T, Darland DC, Young MJ, D'Amore PA. Endogenous VEGF is required for visual function: evidence for a survival role on muller cells and photoreceptors. PLoS One. 2008; 3:e3554.

61. Saint-Geniez M, Kurihara T, Sekiyama E, Maldonado AE, D'Amore PA. An essential role for RPE-derived soluble VEGF in the maintenance of the choriocapillaris. Proc Natl Acad Sci U S A. 2009; 106:18751–18756.

62. Kurihara T, Westenskow PD, Bravo S, Aguilar E, Friedlander M. Targeted deletion of VEGFA in adult mice induces vision loss. J Clin Invest. 2012; 122:4213–4217.

63. Holz FG, Dugel PU, Weissgerber G, Hamilton R, Silva R, Bandello F, Larsen M, Weichselberger A, Wenzel A, Schmidt A, Escher D, Sararols L, Souied E. Single-chain antibody fragment VEGF inhibitor rth258 for neovascular age-related macular degeneration: a randomized controlled study. Ophthalmology. 2016; 123:1080–1089.

64. Davis S, Aldrich TH, Jones PF, Acheson A, Compton DL, Jain V, Ryan TE, Bruno J, Radziejewski C, Maisonpierre PC, Yancopoulos GD. Isolation of angiopoietin-1, a ligand for the TIE2 receptor, by secretion-trap expression cloning. Cell. 1996; 87:1161–1169.

65. Augustin HG, Koh GY, Thurston G, Alitalo K. Control of vascular morphogenesis and homeostasis through the angiopoietin-Tie system. Nat Rev Mol Cell Biol. 2009; 10:165–177.

66. Maisonpierre PC, Suri C, Jones PF, Bartunkova S, Wiegand SJ, Radziejewski C, Compton D, McClain J, Aldrich TH, Papadopoulos N, Daly TJ, Davis S, Sato TN, Yancopoulos GD. Angiopoietin-2, a natural antagonist for Tie2 that disrupts in vivo angiogenesis. Science. 1997; 277:55–60.

67. Oh H, Takagi H, Suzuma K, Otani A, Matsumura M, Honda Y. Hypoxia and vascular endothelial growth factor selectively up-regulate angiopoietin-2 in bovine microvascular endothelial cells. J Biol Chem. 1999; 274:15732–15739.

68. Yao D, Taguchi T, Matsumura T, Pestell R, Edelstein D, Giardino I, Suske G, Rabbani N, Thornalley PJ, Sarthy VP, Hammes HP, Brownlee M. High glucose increases angiopoietin-2 transcription in microvascular endothelial cells through methylglyoxal modification of mSin3A. J Biol Chem. 2007; 282:31038–31045.

69. Regula JT, Lundh von Leithner P, Foxton R, Barathi VA, Cheung CM, Bo Tun SB, Wey YS, Iwata D, Dostalek M, Moelleken J, Stubenrauch KG, Nogoceke E, Widmer G, Strassburger P, Koss MJ, Klein C, Shima DT, Hartmann G. Targeting key angiogenic pathways with a bispecific CrossMAb optimized for neovascular eye diseases. EMBO Mol Med. 2016; 8:1265–1288.

70. Watanabe D, Suzuma K, Suzuma I, Ohashi H, Ojima T, Kurimoto M, Murakami T, Kimura T, Takagi H. Vitreous levels of angiopoietin 2 and vascular endothelial growth factor in patients with proliferative diabetic retinopathy. Am J Ophthalmol. 2005; 139:476–481.

71. Saharinen P, Eklund L, Alitalo K. Therapeutic targeting of the angiopoietin-TIE pathway. Nat Rev Drug Discov. 2017; 16:635–661.

72. Shen J, Frye M, Lee BL, Reinardy JL, McClung JM, Ding K, Kojima M, Xia H, Seidel C, Lima e Silva R, Dong A, Hackett SF, Wang J, Howard BW, Vestweber D, Kontos CD, Peters KG, Campochiaro PA. Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature. J Clin Invest. 2014; 124:4564–4576.

73. Papadopoulos KP, Kelley RK, Tolcher AW, Razak AR, Van Loon K, Patnaik A, Bedard PL, Alfaro AA, Beeram M, Adriaens L, Brownstein CM, Lowy I, Kostic A, Trail PA, Gao B, DiCioccio AT, Siu LL. A phase I first-in-human study of nesvacumab (REGN910), a fully human anti-angiopoietin-2 (Ang2) monoclonal antibody, in patients with advanced solid tumors. Clin Cancer Res. 2016; 22:1348–1355.

74. Campochiaro PA, Khanani A, Singer M, Patel S, Boyer D, Dugel P, Kherani S, Withers B, Gambino L, Peters K, Brigell M. TIME-2 Study Group. Enhanced benefit in diabetic macular edema from AKB-9778 Tie2 activation combined with vascular endothelial growth factor suppression. Ophthalmology. 2016; 123:1722–1730.

75. Korhonen EA, Lampinen A, Giri H, Anisimov A, Kim M, Allen B, Fang S, D'Amico G, Sipila TJ, Lohela M, Strandin T, Vaheri A, Ylä-Herttuala S, Koh GY, McDonald DM, Alitalo K, Saharinen P. Tie1 controls angiopoietin function in vascular remodeling and inflammation. J Clin Invest. 2016; 126:3495–3510.

76. Kim M, Allen B, Korhonen EA, Nitschke M, Yang HW, Baluk P, Saharinen P, Alitalo K, Daly C, Thurston G, McDonald DM. Opposing actions of angiopoietin-2 on Tie2 signaling and FOXO1 activation. J Clin Invest. 2016; 126:3511–3525.

77. Cogan DG, Toussaint D, Kuwabara T. Retinal vascular patterns. IV. Diabetic retinopathy. Arch Ophthalmol. 1961; 66:366–378.

78. Armulik A, Genove G, Betsholtz C. Pericytes: developmental, physiological, and pathological perspectives, problems, and promises. Dev Cell. 2011; 21:193–215.

79. Uemura A, Ogawa M, Hirashima M, Fujiwara T, Koyama S, Takagi H, Honda Y, Wiegand SJ, Yancopoulos GD, Nishikawa S. Recombinant angiopoietin-1 restores higher-order architecture of growing blood vessels in mice in the absence of mural cells. J Clin Invest. 2002; 110:1619–1628.

80. Park DY, Lee J, Kim J, Kim K, Hong S, Han S, Kubota Y, Augustin HG, Ding L, Kim JW, Kim H, He Y, Adams RH, Koh GY. Plastic roles of pericytes in the blood-retinal barrier. Nat Commun. 2017; 8:15296.

81. Ogura S, Kurata K, Hattori Y, Takase H, Ishiguro-Oonuma T, Hwang Y, Ahn S, Park I, Ikeda W, Kusuhara S, Fukushima Y, Nara H, Sakai H, Fujiwara T, Matsushita J, Ema M, Hirashima M, Minami T, Shibuya M, Takakura N, Kim P, Miyata T, Ogura Y, Uemura A. Sustained inflammation after pericyte depletion induces irreversible blood-retina barrier breakdown. JCI Insight. 2017; 2:e90905.

82. Ehlers JP, Wang K, Singh RP, Babiuch AS, Schachat AP, Yuan A, Reese JL, Stiegel L, Srivastava SK. A prospective randomized comparative dosing trial of ranibizumab in bevacizumab-resistant diabetic macular edema: the REACT study. Ophthalmol Retina. 2018; 2:217–224.

83. Uemura A. Pharmacologic management of diabetic retinopathy. J Biochem. 2018; 163:3–9.

84. Selvam S, Kumar T, Fruttiger M. Retinal vasculature development in health and disease. Prog Retin Eye Res. 2018; 63:1–19.

85. Uemura A, Kusuhara S, Katsuta H, Nishikawa S. Angiogenesis in the mouse retina: a model system for experimental manipulation. Exp Cell Res. 2006; 312:676–683.

86. Uemura A, Kusuhara S, Wiegand SJ, Yu RT, Nishikawa S. Tlx acts as a proangiogenic switch by regulating extracellular assembly of fibronectin matrices in retinal astrocytes. J Clin Invest. 2006; 116:369–377.

87. Gerhardt H, Golding M, Fruttiger M, Ruhrberg C, Lundkvist A, Abramsson A, Jeltsch M, Mitchell C, Alitalo K, Shima D, Betsholtz C. VEGF guides angiogenic sprouting utilizing endothelial tip cell filopodia. J Cell Biol. 2003; 161:1163–1177.

88. Fukushima Y, Okada M, Kataoka H, Hirashima M, Yoshida Y, Mann F, Gomi F, Nishida K, Nishikawa S, Uemura A. Sema3E-PlexinD1 signaling selectively suppresses disoriented angiogenesis in ischemic retinopathy in mice. J Clin Invest. 2011; 121:1974–1985.

89. Kim J, Oh WJ, Gaiano N, Yoshida Y, Gu C. Semaphorin 3E-Plexin-D1 signaling regulates VEGF function in developmental angiogenesis via a feedback mechanism. Genes Dev. 2011; 25:1399–1411.

90. Smith LE, Wesolowski E, McLellan A, Kostyk SK, D'Amato R, Sullivan R, D'Amore PA. Oxygen-induced retinopathy in the mouse. Invest Ophthalmol Vis Sci. 1994; 35:101–111.

91. Kwon SH, Shin JP, Kim IT, Park DH. Aqueous levels of angiopoietin-like 4 and semaphorin 3E correlate with nonperfusion area and macular volume in diabetic retinopathy. Ophthalmology. 2015; 122:968–975.

92. Klaassen I, van Geest RJ, Kuiper EJ, van Noorden CJ, Schlingemann RO. The role of CTGF in diabetic retinopathy. Exp Eye Res. 2015; 133:37–48.

93. Di Carlo SE, Peduto L. The perivascular origin of pathological fibroblasts. J Clin Invest. 2018; 128:54–63.

94. Arevalo JF, Maia M, Flynn HW Jr, Saravia M, Avery RL, Wu L, Eid Farah M, Pieramici DJ, Berrocal MH, Sanchez JG. Tractional retinal detachment following intravitreal bevacizumab (Avastin) in patients with severe proliferative diabetic retinopathy. Br J Ophthalmol. 2008; 92:213–216.