Endoplasmic reticulum stress contributes to the development of ocular graft-vs-host disease in the eyelids and the ocular surface

Background

While endoplasmic reticulum (ER) stress has been implicated in various aspects of graft-versus-host disease (GVHD), its effects on the eyelids and ocular surface in patients with chronic GVHD (cGVHD) remains poorly understood. We aimed to investigate the relationship between ER stress and ocular GVHD using the ER stress suppressor, 4-phenylbutyric acid (PBA).

Methods

The study used allogeneic bone marrow transplantation (BMT) and syngeneic BMT to establish a cGVHD mouse model. cGVHD mice were treated with either intraperitoneal administration of PBA or 2 % PBA eye drops following BMT.

Results

The Intraperitoneal PBA-treated (PBAip) group retained a larger meibomian gland (MG) area and corneal epithelial damage and inflammatory and fibrotic cell infiltration in the ocular surface was attenuated compared to vehicle-treated cGVHD mice. The expression of unfolded protein response markers was significantly elevated in the vehicle group compared to the syngeneic control and the PBAip group. Electron microscopy and immunohistochemistry revealed that fibroblasts and macrophages infiltrated the eyelids and ocular surface of cGVHD mice under ER stress. The corneal fluorescein staining score was significantly lower in the PBA eye drop-treated group than in the vehicle-treated group. The numbers of leukocyte marker CD45-, T cell marker CD4-, and macrophage marker F4/80-positive cells were significantly reduced in the PBA eye drop-treated group compared to the vehicle group.

Conclusions

The study suggests that the ER stress response, which is triggered by cGVHD in ocular surface tissues, can be suppressed by PBA, an ER stress suppressor, potentially offering therapeutic benefits in ocular GVHD.