Putative Biomarkers in Tears for Diabetic Retinopathy Diagnosis

Madania Amorim; Beatriz Martins; Francisco Caramelo; Conceição Gonçalves; Grimalde Trindade; Jorge Simão; Patrícia Barreto; Inês Marques; Ermelindo Carreira Leal; Eugénia Carvalho; Flávio Reis; Teresa Ribeiro-Rodrigues; Henrique Girão; Paulo Rodrigues-Santos; Cláudia Farinha; António Francisco Ambrósio; Rufino Silva; Rosa Fernandes

doi:10.3389/fmed.2022.873483

Putative Biomarkers in Tears for Diabetic Retinopathy Diagnosis

Front Med (Lausanne). 2022 May 25:9:873483. doi: 10.3389/fmed.2022.873483. eCollection 2022.

Authors

Madania Amorim^{1

2}, Beatriz Martins^{1

2}, Francisco Caramelo^{1

2}, Conceição Gonçalves³, Grimalde Trindade³, Jorge Simão³, Patrícia Barreto⁴, Inês Marques⁴, Ermelindo Carreira Leal^{2

5}, Eugénia Carvalho^{2

5}, Flávio Reis^{1

2

6}, Teresa Ribeiro-Rodrigues^{1

2

6}, Henrique Girão^{1

2

6}, Paulo Rodrigues-Santos^{1

2

5

6}, Cláudia Farinha^{1

3

4

6}, António Francisco Ambrósio^{1

2

4

6}, Rufino Silva^{1

2

3

4

6}, Rosa Fernandes^{1

2

4

6}

Affiliations

¹ Coimbra Institute for Clinical and Biomedical Research, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
² Center for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.
³ Coimbra University Hospital, Coimbra, Portugal.
⁴ Association for Innovation and Biomedical Research on Light and Image, Coimbra, Portugal.
⁵ Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
⁶ Clinical Academic Center of Coimbra, Coimbra, Portugal.

Abstract

Purpose: Tear fluid biomarkers may offer a non-invasive strategy for detecting diabetic patients with increased risk of developing diabetic retinopathy (DR) or increased disease progression, thus helping both improving diagnostic accuracy and understanding the pathophysiology of the disease. Here, we assessed the tear fluid of nondiabetic individuals, diabetic patients with no DR, and diabetic patients with nonproliferative DR (NPDR) or with proliferative DR (PDR) to find putative biomarkers for the diagnosis and staging of DR.

Methods: Tear fluid samples were collected using Schirmer test strips from a cohort with 12 controls and 54 Type 2 Diabetes (T2D) patients, and then analyzed using mass spectrometry (MS)-based shotgun proteomics and bead-based multiplex assay. Tear fluid-derived small extracellular vesicles (EVs) were analyzed by transmission electron microscopy, Western Blotting, and nano tracking.

Results: Proteomics analysis revealed that among the 682 reliably quantified proteins in tear fluid, 42 and 26 were differentially expressed in NPDR and PDR, respectively, comparing to the control group. Data are available via ProteomeXchange with identifier PXD033101. By multicomparison analyses, we also found significant changes in 32 proteins. Gene ontology (GO) annotations showed that most of these proteins are associated with oxidative stress and small EVs. Indeed, we also found that tear fluid is particularly enriched in small EVs. T2D patients with NPDR have higher IL-2/-5/-18, TNF, MMP-2/-3/-9 concentrations than the controls. In the PDR group, IL-5/-18 and MMP-3/-9 concentrations were significantly higher, whereas IL-13 was lower, compared to the controls.

Conclusions: Overall, the results show alterations in tear fluid proteins profile in diabetic patients with retinopathy. Promising candidate biomarkers identified need to be validated in a large sample cohort.

Keywords: diabetic retinopathy; exosomes; inflammatory cytokines; metalloproteinases; proteome; tear fluid.