Transcriptional Profiling of Human Hyalocytes

Abstract

Purpose : To characterize the transcriptional profile of human hyalocytes and compare it with profiles of other myeloid cell populations including human brain microglia, blood-derived monocytes and macrophages.

Methods : This study involved a total of 13 patients with disorders of the vitreoretinal interface (seven patients with macular hole and six patients with macular pucker) who underwent vitrectomy at the University Eye Center Freiburg between 2018 and 2019. Vitreal hyalocytes were defined as CD45+, CD11b+, CX3CR1+ and Mat-Mac+ cells and isolated using a FACS-based sorting protocol. RNA extraction, library preparation and RNA sequencing were performed and the sequencing data was analyzed on the Galaxy web platform. The human hyalocyte transcriptome was compared to the transcriptional profile of human brain microglia, blood-derived monocytes and macrophages obtained from the literature.

Results : On average, we isolated 383 ± 233 hyalocytes per patient, resulting in 128 pg/µl ± 76 pg/µl total RNA per sample. RNA sequencing revealed SPP1 (secreted phosphoprotein 1), FTL (ferritin light chain) and CD74 (differentiation cluster 74) as most abundantly expressed genes in hyalocytes. GO enrichment analysis of the 100 most strongly expressed genes showed that biological processes such as humoral immune response (p-adjust<0.00001), leukocyte migration (p-adjust<0.00001) and antigen processing and presentation (p-adjust<0.00005) are dominating in vitreal hyalocytes. The comparison of hyalocytes with other myeloid cell populations showed a strong similarity, whereby the similarity between hyalocytes and macrophages was most pronounced (R²=0.75, p<0.0001).

Conclusions : This study deciphers the transcriptional profile of human hyalocytes which represent a distinct myeloid cell subtype in the eye. Vitreal hyalocytes are characterized by a strong expression of genes related to antigen processing and presentation as well as leucocyte migration. Hyalocytes may represent an overlooked mediator of vitreoretinal disease and the ocular immune privilege.

This is a 2020 ARVO Annual Meeting abstract.