Programmed cell death-1 is expressed in large retinal ganglion cells and is upregulated after optic nerve crush

Abstract

Programmed cell death-1 (PD-1) is a key negative receptor inducibly expressed on T cells, B cells and dendritic cells. It was discovered on T cells undergoing classical programmed cell death. Studies showed that PD-1 ligation promotes retinal ganglion cell (RGC) death during retinal development. The purpose of this present study is to characterize PD-1 regulation in the retina after optic nerve crush (ONC). C57BL/6 mice were subjected to ONC and RGC loss was monitored by immunolabelling with RNA-binding protein with multiple splicing (Rbpms). Time course of PD-1 mRNA expression was determined by real-time PCR. PD-1 expression was detected with anti-PD-1 antibody on whole mount retinas. PD-1 staining intensity was quantitated. Colocalization of PD-1 and cleaved-caspase-3 after ONC was analyzed. Real-time PCR results demonstrated that PD-1 gene expression was significantly upregulated at day 1, 3, 7, 10 and 14 after ONC. Immunofluorescent staining revealed a dramatic increase of PD-1 expression following ONC. In both control and injured retinas, PD-1 tended to be up-expressed in a subtype of RGCs, whose somata size were significantly larger than others. Compared to control, PD-1 intensity in large RGCs was increased by 82% in the injured retina. None of the large RGCs expressed cleaved-caspase-3 at day 5 after ONC. Our work presents the first evidence of PD-1 induction in RGCs after ONC. This observation supports further investigation into the role of PD-1 expression during RGC death or survival following injury.

A novel retinal ganglion cell quantification tool based on deep learning

“…Nevertheless, the observed 6.89 ± 1.90% reduction in RGC density in the microbead-induced OHT paradigm is in agreement with previous reports showing 7–9% RGC loss in CD57Bl/6 mice 4–6 weeks after microbead injection by manual counting of DAPI+ 42 , neurobiotin-traced 43 or Brn3a-immunopositive (Brn3a+) cells 44 . The reported RGC survival rate at 7 days after ONC injury (40.80 ± 1.96%) is also in accordance with studies using RGC recordings 9 , RBPMS immunohistochemistry 9 , 16 , 41 , 45 and FluoroGold tracing 46 – 51 in mice, all showing 20–50% RGC survival 1 week after nerve crush. Theoretically, RBPMS counts should be higher than Brn3a counts, as RBPMS should be expressed in all RGCs, whereas Brn3a is no longer seen as a pan-RGC marker and—at least for injured retinas—its expression diminishes when RGCs are coping with stress (cfr.…”

“…This is in stark contrast to a nuclear RGC staining, which has the advantage of resulting in a more consistent labelling in terms of size as well as circularity and brightness, rendering it more amenable for automatic quantification. Indeed, the majority of research articles studying RBPMS-immunopositive (RBPMS+) RGCs are reporting manual counts 11 , 14 – 16 , still resulting in a lack of a fully automated pipeline that does not require entering user-defined variables, although attempts are being made with classic image analysis techniques 8 , 17 . Fully automated RBPMS labelling requires to go beyond conventional automatic counting methods and look towards artificial intelligence.…”

PD-1 is required to maintain stem cell properties in human dental pulp stem cells

“…As an inhibitory signal, PD-1 may be involved in RGC apoptosis during retinal development through a caspase 3-dependent pathway [28]. PD-1 expression was shown to be significantly increased in RGCs after a crushing injury to the optic nerve [29]. These findings suggest that PD-1 might play a pivotal role in retinal neurodegeneration.…”

In tumor cells, thyroid hormone analogues non-immunologically regulate PD-L1 and PD-1 accumulation that is anti-apoptotic

“…NDAT blocks the action of T 4 on the PD-1 axis in these cancer cells (Figure 1 ). Such preliminary studies provide no functional basis for the PD-1 response in human tumor cells, but it is known that injured, non-tumoral retinal ganglion cells (RGCs) express PD-1 [ 32 ], as do mouse RGCs scheduled to undergo apoptosis [ 33 ]. Thus, elaboration of PD-1 in cells other than lymphocytes and macrophages may be related to self-defense, e.g., apoptosis.…”