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Diabetic Retinopathy: premature cellular senescence and microvascular dysfunction

Diabetic Retinopathy: premature cellular senescence and microvascular dysfunction

By Pietro Maria Bertelli, PhD Candidate, Queens University Belfast

Introduction

Eye complications are very frequent in patients with diabetes, and this can lead to vision impairment and blindness 1,2. A better understanding of the pathophysiology of diabetic vascular complications is needed to facilitate the development of novel treatments. Diabetes has been previously associated with ageing and cellular senescence 3, 4. Retinal blood vessels, composed of endothelial cells and pericytes, are significantly affected by diabetic conditions 5–7. We are evaluating the impact of diabetes on endothelial cell function at the cellular and molecular level in relation to senescence to provide new insights into the biology of diabetic retinopathy.

Diabetic Retinopathy

Diabetic Retinopathy (DR) is considered the most common microvascular complication occurring in the working-age population in western countries 8. The diabetic milieu, such as hyperglycaemia, hyperlipidaemia and hypertension, triggers several pathological pathways, which result in vascular dysfunction associated with deficit in blood perfusion, increased vascular permeability, vessel loss and ischaemia 9. This can lead to diabetic macular oedema (DMO) and/or pre-retinal pathological neovascularisation as two frequent complications of DR that cause visual impairment and blindness 9,10. 

Cellular Senescence

Senescence was firstly defined by Hayflick and colleagues as the limited capability of cells to divide and propagate in culture conditions 11,12. Three subtypes can be described: replicative, stress-induced and oncogene-induced senescence.

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Figure 1: Hallmarks of senescent cells. Senescent cells are characterised by an irreversible growth arrest, resistance to apoptosis, SA-βGal expression, secretion of growth factors, cytokines, chemokines and others (SASP) and changes in the molecular and gene expression profiles. Scale bars=50 μm.

Senescent cells enter a state of permanent cell cycle arrest13 but, they remain metabolically active. Furthermore, they are characterised by a senescence-associated secretory phenotype (SASP)14, increased lysosomal β-galactosidase expression15, morphological changes and a changed molecular and gene expression profile16–18 (Figure 1 and 2).

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Figure 2: Morphological changes and SA- βGal expression in senescent cells. (A) Senescent cells are flat and bigger in size compared to early passage cells. (B) Senescent have an increased expression of SA- β Galactosidase, due to an increase of the lysosomal content. SA- β Galactosidase is detected by a colorimetric assay performed at pH 615. In figure A and B human retinal endothelial cells in a monolayer cell culture are shown. Scale bars =150 μm

Endothelial Cell Senescence and SASP in Diabetic Conditions

Some studies, mainly performed in cultured human endothelial cells exposed to high glucose and diabetic mouse models, have suggested development of premature endothelial senescence under diabetic conditions 19–21. More recently, SASP was further confirmed to be a significant contributor in the pathological aspects of DR22. Our group at Queen’s University Belfast has characterised the senescence programme in human endothelial progenitors and its association with SASP components such as interleukin 823.

My PhD project at Queen’s University Belfast funded by the National Eye Research Centre, and our research group supported by JDRF and the Leverhulme Trust , are investigating the role that cellular senescence plays in the pathogenesis of diabetic retinopathy with a particular interest in endothelial cells for the development of therapeutic strategies for the condition: senotherapies24.

References

  1. Simó-Servat, O., Simó, R. & Hernández, C. Circulating Biomarkers of Diabetic Retinopathy: An Overview Based on Physiopathology. J. Diabetes Res. 2016, (2016).
  2. Ting, D. S. W., Cheung, G. C. M. & Wong, T. Y. Diabetic retinopathy: global prevalence, major risk factors, screening practices and public health challenges: a review. Clin. Experiment. Ophthalmol. n/a-n/a (2015). doi:10.1111/ceo.12696
  3. Palmer, A. K. et al. Cellular senescence in type 2 diabetes: A therapeutic opportunity. Diabetes 64, 2289–2298 (2015).
  4. Tian, X.-L. & Li, Y. Endothelial cell senescence and age-related vascular diseases. J. Genet. genomics 41, 485–95 (2014).
  5. Saker, S., Stewart, E. A., Browning, A. C., Allen, C. L. & Amoaku, W. M. The effect of hyperglycaemia on permeability and the expression of junctional complex molecules in human retinal and choroidal endothelial cells. Exp. Eye Res. 121, 161–167 (2014).
  6. Stitt, A. W. AGEs and diabetic retinopathy. Investig. Ophthalmol. Vis. Sci. 51, 4867–4874 (2010).
  7. Zhang, W., Liu, H., Al-Shabrawey, M., Caldwell, R. W. & Caldwell, R. B. Inflammation and diabetic retinal microvascular complications. J. Cardiovasc. Dis. Res. 2, 96–103 (2011).
  8. Antonetti, D. A., Klein, R. & Gardner, T. W. Diabetic Retinopathy. N. Engl. J. Med. 366:1227-1239 (2012). doi:10.1056/NEJMra1005073
  9. Stitt, A. W. et al. The progress in understanding and treatment of diabetic retinopathy. Prog. Retin. Eye Res. 51, 156–186 (2016).
  10. Shin, E. S., Sorenson, C. M. & Sheibani, N. Diabetes and retinal vascular dysfunction. J. Ophthalmic Vis. Res. 9, 362–73 (2014).
  11. Hayflick, L. & Moorhead, P. S. The serial cultivation of human diploid cell strains. Exp. Cell Res. 25, 585–621 (1961).
  12. Hayflick, L. The limited in vitro lifetime of human diploid cell strains. Exp. Cell Res. 37, 614–636 (1965).
  13. Campisi, J. & d’Adda di Fagagna, F. Cellular senescence: when bad things happen to good cells. Nat. Rev. Mol. Cell Biol. 8, 729–740 (2007).
  14. Tchkonia, T., Zhu, Y., Deursen, J. Van, Campisi, J. & Kirkland, J. L. Cellular senescence and the senescent secretory phenotype : therapeutic opportunities. J. Clin. Invest. 123, 966–972 (2013).
  15. Dimri, G. P. et al. A biomarker that identifies senescent human cells in culture and in aging skin in vivo. Proc. Natl. Acad. Sci. U. S. A. 92, 9363–7 (1995).
  16. Munoz-Espin, D. & Serrano, M. Cellular senescence: from physiology to pathology. Nat. Rev. Mol. Cell Biol. 15, 482–496 (2014).
  17. Chen, J. & Goligorsky, M. S. Premature senescence of endothelial cells: Methusaleh’s dilemma. Am. J. Physiol. Heart Circ. Physiol. 290, H1729–H1739 (2006).
  18. Rodier, F. & Campisi, J. Four faces of cellular senescence. 192, 547–556 (2011).
  19. Chen, J. et al. Glycated collagen I induces premature senescence-like phenotypic changes in endothelial cells. Circ. Res. 90, 1290–1298 (2002).
  20. Blazer, S. et al. High glucose-induced replicative senescence: Point of no return and effect of telomerase. Biochem. Biophys. Res. Commun. 296, 93–101 (2002).
  21. Yokoi, T. et al. Apoptosis signal-regulating kinase 1 mediates cellular senescence induced by high glucose in endothelial cells. Diabetes 55, 1660–1665 (2006).
  22. Oubaha, M. et al. Senescence-associated secretory phenotype contributes to pathological angiogenesis in retinopathy. Sci. Transl. Med. 8, 362ra144-362ra144 (2016).
  23. Medina, R. J. et al. Ex vivo expansion of human outgrowth endothelial cells leads to IL-8-mediated replicative senescence and impaired vasoreparative function. Stem Cells 31, 1657–1668 (2013).
  24. Childs, B. G., Durik, M., Baker, D. J. & van Deursen, J. M. Cellular senescence in aging and age-related disease: from mechanisms to therapy. Nat Med 21(12), 1424–1435 (2015).
11th Mar 2021 Pietro Maria Bertelli, PhD Candidate, Queens University Belfast

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